Ruprecht-Karls-Universität Heidelberg

Königstuhl Kolloquium


Upcoming events


2019-08-30
15:00
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Double stars are trouble stars: Close pairs in Gaia DR2, DR3, DR4
Uli Bastian (ZAH/ARI)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
On the one hand, double stars are a nuisance for data reductions. On the other hand, they are scientifically interesting and important. After all, binaries probably constitute the majority of the overall stellar population. Thus they are crucial e.g. for our understanding of the formation of stars and planets in general. The Gaia mission sees, discovers, measures and parameterizes double stars - both optical pairs and physical binaries - in a surprising multitude of ways. Each of these ways poses an operational challenge as well as a scientific chance. Once fully exploited they will give a strongly revised picture of stellar binarity statistics. And they will remove all the disturbances caused by duplicity in the astrometric and photometric data of Gaia DR2. Gaia DR1 achieved an effective angular resolution (i.e.pair separations) of 2 arcsec, DR2 of 0.4 arcsec. But the actual optical resolution of the Gaia instrument is about 0.15 arcsec, and there are ways to detect and measure pairs down to the milli-arcsec level. All this can be done for hundreds of millions of stars, but it means a few more years of hard work by the Gaia data reduction consortium.

2019-09-06
15:00
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Modeling embedded star formation
Michael Kueffmeier (ITA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Stars are embedded in di?erent environments of Giant Molecular Clouds during their formation phase. Despite this fact, it is common practice to assume an isolated spherical core as the initial condition for models of individual star formation. To avoid the uncertainties of initial and boundary conditions, we use an alternative approach of zoom-in simulations to account for the environment in which protostars form. Our magnetohydrodynamical simulations show that the diversity in protostellar environments is reflected in the accretion process of protostars, as well as in the disk formation process. Regarding protostellar multiples our analysis suggests that companions initially form with wider separations of ~1000 au and afterwards migrate to smaller separations of ~100 au from the primary star. Against the background of observations of bridge-like structures such as seen for e.g. IRAS 16293-2422, we find that similar structures emerge as transient phenomena during protostellar multiple formation. To account for infall events of single stars at later times, we study how encounter events with gas condensations affects the properties of the star and the properties of its disk.

2019-09-13
15:00
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TBA
Sarah Leslie (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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TBA

2019-09-27
15:00
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TBD
Paola Pinilla (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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TBD

2019-10-18
15:00
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Accretion and Feedback in High-Mass Star Formation
Rolf Kuiper (Uni Tuebingen/MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
In the course of their accretion phase, massive (proto)stars impact their natal environment in a variety of feedback effects such as thermal heating, MHD-driven protostellar jets and outflows, radiation forces, and photoionization / HII regions. Here, I present our most recent simulation results in terms of the relative strength of the feedback components and the size of the reservoir from which the forming stars gain their masses. For the first time, these simulations include all of the feedback effects mentioned above which allows us to shed light on the physical reason for the upper mass limit of present-day stars. Furthermore, we predict the fragmentation of massive circumstellar accretion disks as a viable road to the formation of spectroscopic massive binaries and the recently observed strong accretion bursts in high-mass star forming regions.

To advertise our latest code development, I will also overview the most recent results obtained in a variety of other astrophysical research fields from the formation of embedded Super-Earth planets' first atmospheres (Cimerman et al. 2017, MNRAS) to the formation of the progenitors of the first supermassive black holes in the early universe (Hirano et al. 2017, Science).

2019-10-25
15:00
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TBD
Ravit Helled (Zurich)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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TBD

2019-11-08
15:00
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New Light on Standard Candles: Testing Hubble Tension using High-precision Observations of Cepheid Variable Stars
Richard Anderson (ESO Garching)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2019-11-15
15:00
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TBA
Christine Wilson (McMasters)
Königstuhl Kolloquium
MPIA lecture hall,
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TBA

2019-11-22
15:00
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Back-up (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2019-11-29
15:00
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TBA
Patzer Colloquium (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2019-12-06
15:00
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TBD
Anaelle Maury (CEA/Saclay)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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TBD

2020-06-19
15:00
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Sera Markoff (UVA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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KoCo Signature Speaker


Past events


2019-08-02
15:00
The Industrial Revolution of Galactic archaeology
Sven Buder (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
How did the Milky Way form and evolve? Which processes shaped its structure at which times?
Stars as Galactic time capsules are our best tracers to answer these questions and in the recent years we have made revolutionary progress in observing their properties in large samples.
We have come to realise that our traditional picture of the Milky Way as a composite of three main stellar components (halo, disk, and bulge) is too simplistic - the stellar properties overlap and reveal great complexity. In order to confirm or reject formation scenarios of the Milky Way, we have to understand how the stellar properties come about and are interlinked.
I will outline the challenges that come with the collection of big data from stellar spectroscopic surveys, such as the 'Galactic Archaeology with HERMES' (GALAH) survey, and show which efficient and automated techniques we have developed to manage the very large data flow of stellar surveys.
In the course of my PhD, I have used the chemical information from GALAH together with dynamical information and stellar ages to analyse the Galactic disk in the solar neighborhood in order to disentangle the complex nature of the two populations of the disk. One of the big open questions is which role did accretion play in the formation of the disk populations? Could the recently (re-)discovered accreted halo stars of Gaia-Sausage/Gaia-Enceladus have caused the drastic change in the evolution of the disk?
During the KoCo I will guide you through the last 4 years of my journey in exploring the Milky Way and its chemodynamic information with the aim to shed light on the above mentioned questions.

2019-07-26
15:00
How (not) to select targets for a spectroscopic survey
David Hogg (NYU, MPIA)
Königstuhl Kolloquium
HdA auditorium,
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Abstract
The scientific capabilities of a spectroscopic survey depend on the spectroscopic data quality, on how the targets were selected, and on how well that selection can be quantitatively characterized. For many projects, the target selection and its characterization are the biggest sources of uncertainty for important results. There are many large spectroscopic programs in operation and starting in astrophysics. These range from cosmological large-scale structure mapping experiments, to large Galactic archaeology and stellar physics projects, to extreme-precision radial-velocity surveys for exoplanets, to follow-up of real-time events in streams from time-domain imaging surveys. In all of these cases, there will be important long-term scientific goals for these spectroscopic programs that depend on being able to make statistical inferences. For example, what is the distribution in phase space of stars with particular element abundances and ages? Or what is the occurrence rate of exoplanets of certain types at certain periods? In order for these questions to be answerable in the end, projects must be able to produce (at least approximate) selection functions. That requirement, in turn, puts constraints on the possible rules by which targets can be chosen for spectroscopic observation. I will discuss some parts of this, including some simple results?rules to live by?and some open questions.

2019-07-19
15:00
Stellar Radial Velocity Jitter: A model free analysis and an introduction to the RV SPY survey
Stefan Brems (LSW)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2019-07-19
15:00
The Formation and Growth of Supermassive Black Holes at Early Cosmic Epochs
Anna-Christina Eilers (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Quasars are the most luminous objects in the universe and can be observed at the earliest cosmic epochs, providing unique insights into the early phases of black hole, structure, and galaxy formation. Observations of these quasars demonstrate that they host supermassive black holes (SMBHs) at their center, already less than ~1 Gyr after the Big Bang. The formation and growth of these SMBHs in such short amounts of cosmic time is a crucial yet unanswered question in studies of quasar and galaxy evolution. An important piece of the puzzle is the lifetime of quasars ? the time that galaxies shine as active quasars ? but to date its value remains uncertain by several orders of magnitude. I will present a new method to obtain independent constraints on the lifetime of high redshift quasars, based on measurements of the sizes of the ionized regions around quasars, known as proximity zones. The sizes of these proximity zones are sensitive to the lifetime of the quasars, because the intergalactic gas has a finite response time to the quasars' radiation. Applying this method to a data set of high redshift quasar spectra at z>6, we discovered an unexpected population of very young quasars, indicating lifetimes of only ~10,000 years, which significantly challenges all current black hole formation theories. I will highlight the implications and tensions of such short quasar lifetimes on the SMBH formation paradigm, and discuss several potential modifications that could explain our results, for instance super-critical mass accretion rates, obscured quasar growth phases, or flickering quasar light curves. I will show potential ways to disentangle the various scenarios with future observations with the James Webb Space Telescope.

2019-07-12
15:00
Stellar Radial Velocity Jitter: A model free analysis and an introduction to the RV SPY survey
Stefan Brems (LSW)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Stars show various amount of radial velocity (RV) jitter due to varying
stellar activity levels. I will show that by systematically analyzing
archival RV data with the pooled variance technique, one can quantify
this jitter as a function of age and observational timescale (lag). The
results yield a very strong dependence on the stellar age, ranging from
over 800 m/s for 3 Myr old stars down to the instrumental precision of
about 1.5 m/s for several Gyr old stars. Furthermore, the lag influences
the intrinsic stellar RV variation by about a factor of two when
probing a few days instead of weeks or years.
These results can for example be used to plan surveys where the age is a
major selection criterion. Being such a survey targeting young stars, I
will present the observational strategy as well as first results from
ongoing Radial Velocity Survey for Planets around Young stars (RV SPY)
using the FEROS spectrograph at the MPG/ESO 2.2m telescope.

2019-07-05
15:00
The Milky Way Laboratory
Cara Battersby (Uni of Conneticut)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Our own Milky Way Galaxy is a powerful and relatively nearby laboratory in which to study the physical processes that occur throughout the Universe, from the organization of gas on galactic scales to the life cycle of gas and stars under varied environmental conditions. I will present a brief tour of our Milky Way Laboratory, including 1) the connection between long, filamentary molecular clouds and spiral structure, 2) statistical studies of high-mass star formation using surveys of our Galaxy's disk, and 3) how observing our extreme, turbulent Galactic Center (the Central Molecular Zone) can help us learn more about how gas is converted into stars during the peak epoch of cosmic star formation.

2019-06-28
15:00
MPIA space involvement
Oliver Krause & Knud Jahnke (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Space-based observatories have brought a tremendous progress to astronomy over the past decades. From inaccessible wavelength bands in the X-ray, UV or infrared, to much improved sensitivities from lower backgrounds, to diffraction limited imaging above the atmosphere - there are a number of key differences to ground-based observing facilities.

MPIA has been a long-standing contributor to space-based telescopes and their instrumentation, as well as scientific user of space-generated data. We will give an overview of five new upcoming space observatories with MPIA hardware contributions: JWST, Euclid, WFIRST, SPICA, and HabEx. We will present their construction status and timelines, as well as the opportunities for MPIA science exploitation.

2019-06-21
15:00
Characterization of Planetary Atmospheres
Karan Molaverdikhani (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Characterization of planetary atmospheres has always been a challenge. While the next generation of facilities, such as ELT, JWST, and ARIEL, will improve our understanding of planetary atmospheres, the number of well-characterized exoplanet atmospheres is expected to remain limited. Large-scale simulations assist us with this shortcoming by predicting the diversity of the planetary atmospheres, connecting the spare observational measurements, and by pointing toward the regions on the parameter space where a higher chance of the detection of planets with desired properties is expected. I will overview our current understanding of planetary atmospheres and will highlight the results of our hierarchical modelling of planetary atmospheres\; including our newly proposed classification scheme for irradiated gaseous planets and the Methane Valley.

2019-06-14
15:00
Gravitational instabilities: The fastest way to form planets
Hans Baehr (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The early stages of circumstellar disk evolution are likely influenced by the relatively large gas mass, driving gravitational perturbations that result in turbulence and disk fragmentation. Fragmentation of the disk produces dense gaseous objects with masses on the order of a few Jupiter masses an up, and preferentially occurs in the cool distant regions of the disk. This provides a possible formation channel for directly imaged planets which are difficult to account for otherwise. Unfortunately, despite filling in this niche of planet formation, several factors make gravitational instabilites a minor factor in the overall planet formation paradigm. I will discuss the viability of gravitational instabilities as a planet formation theory, including recent developments in both observation and theory. These developments perhaps point away from the formation of massive gaseous planets and towards the early concentration of solid material in the vein of traditional core accretion models, but within the first million years of the lifetime of the disk.

2019-06-07
15:00
New approaches to stellar ages: Chronostar for kinematic ages, and Gaia+interferometric orbits for evolutionary ages
: Michael Ireland (ANU)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
One of the core goals of astrophysics is to determine the evolutionary history of stars, galaxies and the Universe. Unfortunately, there are few accurate determinations of ages of the Universe's constituents. I will describe new takes on two promising techniques for accurate stellar ages into the next decade. Firstly, I will describe the concept of ?traceback ages?, where stars from a common origin can have their ages determined by combining velocities with their distance from a common origin. This technique as largely failed so far, due to a myriad of reasons, including the rarity of unbound, compact clusters, and data where at least one kinematic axis has a large observational uncertainty. We have recently overcome these difficulties by combining the precision of Gaia data with Bayesian techniques and trace-forward of models in the Galactic potential, encompassed by the Chronostar code. We determine an age of beta Pic of 18.3+/-1.3 Myr, with an systematic uncertainty for individual members which is order the birth cluster crossing time of 12 Myr. I will describe the next steps for Chronostar, and where its limits are expected to lie. I will also briefly describe the problem of evolutionary ages for >1Gyr giant stars not part of a cluster. This is intimately connected to the controversy over the reported frequency of planets around ?retired A stars?. The combination of Gaia, long baseline interferometry and asteroseismology promises to significantly enhance our knowledge of these ages in the coming few years.

2019-05-24
15:00
Numerical experiments on star formation: mass functions and angular momenta
Lee Hartmann (UMich)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The initial mass function of stars - the number of stars N formed per interval of mass M - has long been known to be a power law, with d log N/d log M = ? = -1.3. Many explanations of this distribution have been advanced over the years, including fractal dimensions of star-forming molecular clouds and/or self-similar grouping of clouds. I will discuss simplified numerical simulations of star formation which show that gravitational accretion onto initial seed masses generates a power law mass distribution approaching ? ? -1 asymptotically, irrespective of complications of cloud structure. This mechanism can also explain the mass function of young star clusters, which also has a power law distribution with ? = -1. Finally, I will describe preliminary results concerning the origin of protostellar cloud angular momenta, including magnetic fields, with implications for the properties of protoplanetary disks that result from cloud collapse.

2019-05-17
15:00
Early-type galaxies: climbing to the top of the mass ladder
Eric Emsellem (ESO)
Königstuhl Kolloquium
MPIA lecture hall,
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Abstract
Nearby galaxies display a range of morphologies, sizes, masses, which are the results of a complex set of formation and evolution processes. In this talk, I will focus on early-type galaxies which contain about half of all the stars in our local Universe.
I will review our current knowledge of how they form, what are the most important mechanisms which shaped them, and illustrate how our understanding of these objects changed over the last decade via the use of simulations and integral-field spectroscopy. I will then focus on the most massive galaxies, and report on results from numerical simulations and an observational campaign conducted with the MUSE spectrograph, which led to some interesting surprises.

2019-05-10
15:00
What Processes Shape our Milky Way's Disk?
Hans-Walter Rix (MPIA)
Königstuhl Kolloquium
MPIA lecture hall,
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Abstract
It is often said that the Milky Way can serve as a 'model organism' to explore and understand the physical mechanism that shape galaxies from random initial fluctuations into the beautiful island universes we see today. This statement is true, but easily said and much harder to make a reality. Over the last years I have collaborated with a number of students, post-docs and visitors at MPIA combining spectral surveys and now Gaia to turn this Galactic Archeology mantra into astrophysical insights. In this talk I will synthesize some of this effort, focussing on two aspects of our Galaxy's main component, its disk:
what sets the overall radial profile of the disk, and what sets its vertical structure? The answers to both questions are linked to the question of how much dynamical memory loss our Galaxy has incurred -- despite its exceptionally quiescent history. I believe we are now considerably closer to understanding why disk galaxies look the way they do.

2019-05-03
15:00
Exocometary Science
Luca Matrà (CfA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Evidence for exocomets, icy bodies in extrasolar planetary systems, has rapidly increased over the past decade, giving rise to the budding field of exocometary science. Exocomets are detected through the gas and dust they release as they collide and grind down within their natal belts, or as they sublimate once scattered inwards to the regions closest to their host star. Most detections are in young, 10 to a few 100 Myr-old systems that are undergoing the final stages of terrestrial planet formation. This opens the exciting possibility to study exocomets at the epoch of volatile delivery to the inner regions of planetary systems.

In this talk, I will present the different lines of evidence for exocomets from UV to mm wavelengths. In particular, I will show how detection of molecular and atomic gas allows us to estimate molecular ice abundances and elemental abundances in young exocomets, enabling comparison with the Solar Nebula and Solar System comets. Finally, I will link the composition of exocometary belts to their origins in protoplanetary disks, discussing evidence for a preferential belt formation location which is dependent on the host star's luminosity.

2019-04-26
15:00
From dense cores to disk: Following the gas
Jaime Pineda (MPE)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
A detailed understanding of star-formation is important to establish the "micro-physics" involved in the galactic star-formation relations, and also to determine the initial condition for proto-planetary disks. One of the important steps in the star-formation process is the accumulation of material from the molecular cloud with supersonic turbulence into the dense cores, which have subsonic turbulence. The first direct observation of the transition between supersonic and subsonic turbulence in a nearby cloud provided the first direct constraints on this dissipation process. On the other hand, recent observations have shown that large protoplanetary disks in the early stages are relatively rare, and for those that are large, there is compelling evidence for asymmetries related to gravitational instabilities. However, little is known of the connection between the disks and the parental dense core.

In this talk, I will present some of our latest efforts on studying the dense core and molecular cloud connection, thanks to a large program at the Green Bank Telescope (~250hrs, PIs: Jaime Pineda and Rachel Friesen). This survey allows us to more accurately determine the dense core properties in a systematic fashion and across several clouds. Also, I will present interferometric observations of dense cores that will provide new insight into the core formation and the material transport down to the scales relevant for disk formation.

2019-04-12
15:00
The Brightest Stars in the Universe as Extragalactic Probes of Cosmic Abundances and Distances
Rolf-Peter Kudritzki (IFA,USM)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The determination of chemical composition and distance is crucial for investigating the formation and evolution of star-forming galaxies. Stellar absorption line studies based on quantitative spectroscopy provide an attractive alternative to the standard techniques using the strong emission lines of HII regions for chemical composition or stellar photometric methods for distances. I will introduce a number of newly developed methods
- multi-object spectroscopy of individual blue and red supergiant stars, the brightest
stars in the universe at visual and NIR wavelengths,
- NIR spectroscopy of super star clusters,
- optical spectroscopy of the integrated light of stellar populations in the disks of star
forming galaxies,
- the flux-weighted gravity luminosity relationship for distance determinations
and present results accumulated in the last two years. I will then discuss the scientific perspectives and potential of these methods for the use of future Extremely Large Telescopes (ELTs).

2019-04-05
15:00
The multi-phase ISM of radio galaxies: a spectroscopic study of ionised and warm gas
Francesco Santoro (MPIA)
Königstuhl Kolloquium
MPIA lecture hall,
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Abstract
Active galactic nuclei (AGN) are among the most powerful sources of energy in the universe. They usually resides at the centre of massive galaxies and their energy is originated by the accretion of material onto a supermassive black hole. AGN can inject a significant amount of energy in the interstellar medium (ISM) of their host galaxies in the form of radiation and/or jets of relativistic particles. The interaction between the energy emitted by an AGN and the material in the host galaxy is called 'AGN feedback' and, nowadays, is routinely included in cosmological simulations aimed at reproduction the observed properties of the current population of galaxies (e.g. the quenching of the star formation in massive galaxies).

In this talk I will address some of the open questions related to AGN feedback and to the mechanisms involved in the accretion of gas onto a supermassive black hole. This is has been done by studying the ISM of radio galaxies (i.e. AGN showing relativistic jets) spanning different evolutionary stages and by using different observational techniques, mainly in the optical and in the infrared band, to probe the warm ionised and warm molecular gas. In particular, I will focus on the effect that radio jets can have on the gas of the host galaxy and how this allows us to take a look at the many facets of the AGN feedback phenomenon.

2019-03-29
15:00
TBA
Paola Di Matteo (GEPI/Obs. de Paris)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Signature Speaker

2019-03-22
15:00
Paola Di Matteo (GEPI/Obs. de Paris)
: Signature Speaker
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2019-03-22
15:00
Paola Di Matteo (GEPI/Obs. de Paris)
: Signature Speaker
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2019-03-22
15:00
Probing the cold phase of the interstellar medium and star formation in nearby galaxies
Neven Tomicic (MPIA)
Königstuhl Kolloquium
MPIA lecture hall,
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Abstract
Properly measuring the spatial distribution of the star formation rate (SFR) in nearby galaxies helps us to understand the driving forces for the star formation in galaxies, and their effects on the interstellar medium (ISM). Additionally, it can lead to better understanding the physical factors that set the efficiency with which galaxies convert gas into stars (star formation efficiency\; SFE), and their role in galactic evolution. However, this is hindered by the uncertainties in estimating SFRs and calibrating the SFR prescriptions. Furthermore, variations in the star formation efficiency between and within galaxies are difficult to disentangle from uncertainties of their estimated SFRs. The uncertainties in estimating SFRs are caused by not properly measuring the attenuation of light, probing large spatial scales across nearby galaxies, or averaging over a large sample of galaxies.
To bypass these uncertainties, common SFR prescriptions are used, which also have large uncertainties and variations.

In this talk, I will show how we utilize optical integral field unit (IFU) observations of the nearby Andromeda galaxy, in order to properly measure the attenuation of light at high spatial resolution (100 pc), and thus properly estimate the SFRs and the SFR prescriptions. Moreover, by using the results of our optical IFU and sub-mm observations of the interacting galaxy NGC 2276, I will show how the early phase of galactic interaction affects the star formation efficiency of molecular gas across the interacting galaxy.

2019-03-22
09:45
The Milky Way as a dark matter lab
Jorge Penarrubia (ROE)
Königstuhl Kolloquium
MPIA lecture hall,

2019-03-21
09:45
A modern theoretical framework for the cosmic evolution of galactic emission lines
Michaela Hirschmann (U. Vienna, Dark Center)
Königstuhl Kolloquium
MPIA lecture hall,

2019-03-20
10:30
Numerical Structure and Galaxy Formation for Cosmological Insight
Annalisa Pillepich (MPIA)
Königstuhl Kolloquium
MPIA lecture hall (TBC),

2019-03-19
09:45
Intergalactic Signatures of Reionization and the Growth of the First Supermassive Black Holes
Frederick Davies (UC Santa Barbara)
Königstuhl Kolloquium
MPIA lecture hall,

2019-03-18
09:45
The Milky Way as a laboratory on galaxy formation and dark matter
Chervin Laporte (U. Victoria)
Königstuhl Kolloquium
MPIA lecture hall,

2019-03-15
15:00
"Milky Way dust in 3D: from local molecular clouds to the spiral arms"
Sara Rezaei Kh. (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract

Milky Way dust in 3D: from local molecular clouds to the spiral arms

Only a tiny fraction of the mass of the Galaxy is in dust, yet it plays important roles in different processes\; from the formation of stars and planets to the luminosity of the Galaxy. Attempts to map our Milky Way date back to the 18th century, but we are still struggling to find an accurate picture of our Galaxy as a result of our obscured view within the dusty disk. In this talk, I will give you a general introduction to dust and extinction, followed by a summary of the improvements in 3D dust extinction mapping. I will then introduce our new technique in mapping the 3D distribution of dust in the Milky Way using the Gaussian process that allows capturing arbitrary structures and results in smooth maps without artefacts typically seen in most other methods. I will show our results based mainly on data from Gaia and APOGEE for the local molecular clouds as well as the Galactic disk, where we unveil the distribution of the spiral arms of the Milky Way in dust.

2019-03-08
15:00
Science with VLTI+GRAVITY
Woflfgang Brandner (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
GRAVITY is a 4-telescope beam combiner for ESO's Very Large Telescope Interferometer (VLTI), working in the K-band. While the instrument design has been optimized for high-precision observations of the Milky Way's central supermassive black hole Sgr A* and its immediate environment, the unique sensitivity of VLTI+GRAVITY enable a large range of science applications.

In this talk, I will briefly describe the main capabilities and technological innovations of GRAVITY, which includes the four CIAO (one for each of the 8m-Unit Telescopes) infrared adaptive optics systems provided by MPIA, followed by a concise overview of science results obtained during GRAVITY commissioning and the first 1.5 years of regular science operations at the VLTI. The science topics range from the atmosphere of the exoplanet HR 8799e over properties of disks and outflows in the central AU of Young Stellar Objects, multiplicity of stars in the center of the Orion Nebula Cluster, resolution of microlensed images, spectral-imaging of the close environment of Eta Carinae, and observations of Galactic X-ray binaries, to the study of relativistic effects in the Galactic Center, and a direct measurement of the mass of the supermassive blackhole in the center of the quasar 3C 273.

2019-03-01
15:00
TBA
: Sara Rezaei Kh. (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2019-03-01
15:00
TBA
Marcel Neeleman (MPIA)
Königstuhl Kolloquium
MPIA lecture hall,

2019-02-22
15:00
Stellar populations in the densest stellar systems in the Universe
Nikolay Kacharov (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
In this talk I will introduce some of the open questions in the field of globular clusters and nuclear star clusters. As one part of the colloquium, I will talk about the multiple populations phenomenon in globular clusters and focus on our recent discoveries in intermediate age clusters in the Magellanic Clouds. The second part will be dedicated to the much more extended star formation histories in nuclear star clusters. I will discuss our discrete IFU spectroscopic observations of the nucleus of the tidally disrupted Sgr dSph galaxy - the massive globular cluster M54, and also integrated light spectroscopy in the nuclei of yet undisturbed nearby galaxies. I will explore and discuss possible theories for the formation of these very dense objects based on our observations.

2019-02-15
15:00
The Cosmic Evolution of Cold Molecular Gas since Redshift 6 from A3COSMOS
Daizhong Liu (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Determining the cosmic evolution of cold molecular gas in galaxies is fundamental for our understanding of galaxy evolution. However, obtaining such measurements for large samples of galaxies at z~1--6 remains challenging even in the era of ALMA. Recent studies of the cosmic gas evolution focus on redshifts below z=3 reporting conflicting results, and cosmological simulations still struggle to fit the observations. As (sub-)millimeter dust continuum has now been established as a reliable tracer of the cold gas, and it can be much more efficiently observed than line tracers (e.g. CO), we have started a concerted effort to automatically mine the public ALMA archive for the COSMOS field (A3COSMOS). A3COSMOS provides (sub-)millimeter detections and subsequent galaxy properties in a coherent, systematic way that allows us to quantify systematic biases in using dust continuum. Our database currently includes about 2000 ALMA images covering 280 sq. arcmin with over 1500 ALMA detections based on well-characterized statistics. Using rich ancillary data available we identify ~1000 galaxies with bona-fide properties lying at z~1--6. We combine this unique catalog of cold gas measurements with more than 500 local (z~0) and high-redshift (z<3) galaxies with CO and/or dust continuum detections in the literature to explore the correlations between gas mass fraction, molecular gas depletion time, redshift, stellar mass and star formation rate. Our analysis reveals a linear evolution of the gas fraction with cosmic time, in line with the evolution of the ?galaxy main sequence?. This evolution further implies a cosmic molecular gas density evolution consistent with previous works at z<1-3, but higher by a moderate factor at z>5--6 as predicted by cosmological simulations. As ALMA accumulates more observations in the future, the cold molecular gas evolution at z>5--6 will eventually be constrained by A3COSMOS.

2019-02-08
15:00
Dust Spreading in Debris Discs: Do Small Grains Cling on to Their Birth Environment?
Nicole Pawellek (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Debris discs are dusty belts of planetesimals around main-sequence stars, similar to comets and asteroids in the solar system. The planetesimals themselves cannot be observed directly, yet they produce detectable dust in mutual collisions. Observing this debris dust, we can try to infer properties of invisible planetesimals. Here we address the question of what is the best way to measure the location and extent of outer planetesimal belts, i.e., ''Kuiper belts'' that encompass extrasolar planetary systems. A standard method is using resolved images at millimetre wavelengths, which reveal dust grains of comparable sizes. This is because smaller dust particles seen in the infrared or optical are subject to a large array of non-gravitational forces that drag them away from their birth places, and so may not closely trace the parent bodies. In this study, we examine whether imaging of debris discs at shorter, far- or even mid-infrared, wavelengths might enable determining the spatial location of the exo-Kuiper belts with sufficient accuracy. We find that around M-type stars the dust best visible in the mid-infrared is efficiently displaced inward from their birth location by stellar winds, causing the discs to look more compact in the mid-infrared images than they actually are. However, around A-type stars, where the majority of debris discs is found, and even around G-type stars, discs are still the brightest at the location of the birth ring at mid-infrared wavelengths. Thus, sensitive infrared facilities with good angular resolution, such as MIRI on the James Webb Space Telescope, will enable tracing exo-Kuiper belts in nearby debris disc systems.

2019-02-01
15:00
Stellar Interiors as seen from Asteroseismology
Conny Aerts (U. Leuven)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The space age of asteroseismology brought tremendous progress in the
observational probing of stellar interiors. In this seminar, we first explain
for the non expert how asteroseismology allows to deduce the interior physics of
stars at a level that is impossible to reach in any other way. We summarise the
great asset of asteroseismic sizing, weighing, and ageing of low-mass stars,
with applications to exoplanetary science and galactic archeology. Further, we
focus on the capability to derive the interior rotation properties of various
types of stars and discuss the implications for the theory of angular momentum
transport. We also touch upon recent findings on chemical mixing in the deep
interior of single and binary stars with a convective core. We end the talk by
highlighting the major opportunities from combining space asteroseismology and
astrometry with ground-based spectroscopy of large ensembles of stars in the
Milky Way and in the Magellanic Clouds.

2019-01-25
15:00
Giant Molecular Filaments studied in different gas tracers
Yuan Wang (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Observations show that large (~100~pc) and massive (~10^5 Msun) filaments, known as giant molecular filaments (GMFs), may be linked to galactic dynamics and trace the gravitational mid-plane in the Milky Way (MW). They are the largest coherent gas structures and a central building block of the Milky Way. Yet our understanding of GMFs is still poor, limited to estimates of their occurrence, gas masses and lengths. In this talk, I will present our studies of two GMFs (GMF38a and GMF54), which are observed with different gas tracers (atomic and molecular). We studied the cold neutral media of atomic hydrogen via HI self-absorption towards the ~200pc long filament GMF38a, and compared the kinematics and column density distribution of the atomic hydrogen to the molecular gas (CO). The column density probability density functions (N-PDFs) show that the atomic gas is dominated by turbulent motions, whereas the N-PDF of the molecular gas shows a power-law tail that indicates gravitational collapse. We further mapped the dense gas of GMF54 (~45pc) with the IRAM 30m telescope, covering the common dense gas tracers HCN, HNC, HCO+ and their 13C isotopologues, as well as the cold dense gas tracer N2H+. Combining the complementary 13CO data, we studied and compared the kinematics and the density distribution of GMFs over an order of magnitude in density.

2019-01-18
15:00
Star Formation and Galactic Environment
Eva Schinnerer (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
High angular resolution observations of nearby galaxies allow us to sample the star formation process in different galactic environments.This provides insights on the importance and role of galactic components such as bulges, stellar bars, spiral arms and active galactic nuclei (AGN) in the conversion of cold (molecular) gas into stars. New instruments can now regularly image with high quality and sensitivity large field-of-views
at the scale of individual star-forming units, namely Giant Molecular Clouds (GMCs) and HII region (complexes): ALMA is fundamental for imaging of the molecular gas properties in the star-forming disks, while the optical Integral Field Unit MUSE on the VLT is providing detailed information on the ionised gas and stellar population. I will highlight recent progress in the field and present new results from the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) survey that studies a representative sample of nearby massive, normal star-forming galaxies.

2019-01-11
15:00
The Disk Substructures at High Angular Resolution Project (DSHARP)
Kees Dullemond (ITA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Abstract: DSHARP is an ALMA Large Programme aimed at obtaining high-resolution (beam ~ 30 milliarcsec) maps of 20 protoplanetary disks in band 6 (1.3 mm) in the continuum. The data were released about a month ago, along with a first set of papers. I will give an overview of the data and some of the gems hidden in them. I will then focus on the theoretical interpretation that the DSHARP team has done, and many of the still open questions that need to be addressed in the coming months.

2018-12-14
15:00
TBA
Karin Lind (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
TBA

2018-12-14
15:00
Lithium in the Galaxy: To Be or not to Be
Karin Lind (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The astronomical community's interest in Li continues to be vastly disproportional to its small abundance. The Li content of stars in the Galaxy links together several different research fields\; from cosmology and Big Bang nucleosynthesis, to cosmic ray spallation in the interstellar medium, to mixing processes in stellar interiors, and even the presence of exoplanets. I will describe the intricate abundance patterns found for stars in different evolutionary phases and how the fragile nature of this light element makes it an excellent diagnostic tool for late-type stellar evolution all they way from the pre-main sequence to the tip of the asymptotic giant branch. I will further discuss some famous problems related to Li production and depletion and potential solutions in the light of improved models of stars and their spectra.

2018-12-07
15:00
TBD
HHSF18
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
TBD

2018-12-07
15:00
The Square Kilometer Array
Tyler Bourke (SKAO)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The Square Kilometre Array (SKA) is a global effort to build the World's largest radio telescopes, which will transform our understanding in many areas of astrophysics, including the history of our Universe and the emergence of the first stars and galaxies\; the merger of super-massive black-holes and their release of gravitational waves, as tests of General Relativity\; the enigmatic powerful bursts of radio emission (Fast Radio Bursts) whose origin and nature remain controversial\; the formation of planets and search for extraterrestrial life\; and many other areas of great interest to astronomers worldwide.

The past few years have seen great progress toward the realization of the SKA, with construction of Phase 1 (SKA1) to start in 2020 and science operations anticipated to begin in 2026. In this presentation I will provide a status update on SKA activities, with a focus on the science it will enable and the progress toward construction.

2018-11-30
15:00
Patzer Colloquium
TBA (TBA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2018-11-30
15:00
Three award winners
Patzer Colloquium (MPIA+ZAH)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2018-11-23
15:00
TBD
Bertram Bitsch (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
TBD

2018-11-23
15:00
Planet formation in evolving protoplanetary discs
Bertram Bitsch (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Observations of exoplanets have revealed a complex diversity in planetary systems regarding their masses, orbital configurations and number of planets. For example it has been shown that super-Earth planets are the most common planets in our galaxy even though we have no super-Earth in our own solar systems and that these planets are mostly in multiple systems. Hot Jupiters, on the other hand, are easy to detect, but are actually very rare objects. In addition new observations give indications about the chemical compositions of these planets. All these constraints have to be matched by theories of planet formation.

The formation of planetary cores of several Earth masses can be greatly accelerated by accreting objects of mm-cm size, so called pebbles. When the planetary cores have reached masses around 10 Earth masses, they can start to accrete gas from the protoplanetary disc and eventually form gas giants, like Jupiter and Saturn in our own solar system. During their formation, the planetary cores interact gravitationally with the disc and migrate through it. At the same time the protoplanetary disc evolves so that its temperature decreases, resulting in an inward movement of the water ice line. Previous simulations have also mostly followed the evolution of single planets, where multi-body dynamics have been ignored.

I will present here our new framework of planet formation that features a complex interplay between N-body dynamics, pebble accretion, planet migration, disc evolution and planetary instabilities after the gas disc phase. I will highlight the results of our new simulations and point to open questions that need to be answered in order to constrain planet formation theories even further.

2018-11-16
15:00
TBD
Rowan Smith (University of Manchester)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
TBD

2018-11-16
15:00
Filaments all the way down: Simulating molecular gas in the Milky Way
Rowan Smith (University of Manchester)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The process of star formation and galaxy evolution are inseparably linked. Stars feed back energy and momentum into the ISM, but galactic scale forces will help determine where dense star-forming molecular clouds can form. Previously star formation was simulated only in isolation, and galaxy scale models did not resolve star forming clouds, however recent simulation efforts have begun to unite these important physical processes. Observations have also shown us that molecular clouds are far from the abstracted collapsing spherical clouds or periodic turbulent boxes used to model them previously. Instead many clouds take the form of long filaments with extremely coherent velocities.

In this talk I present simulations exploring the morphology and star formation in filamentary molecular clouds from spiral galaxy simulations with AREPO. The clouds are resolved down to sub-parsec scales in the original simulation meaning, uniquely, that both galactic-scale forces and internal cloud substructure can be studied at the same time. The simulations include supernovae feedback, self-gravity, time-dependent chemistry and sinks particles to represent sites of star formation. This allows us to study the evolution of the CNM, where gas will be bright in CII or CO emission, and where there will be CO dark gas.

Using this dataset we can extract filamentary clouds and compare their lengths and widths against observations of arm and inter-arm filaments observed in our Galaxy. Within our simulated clouds we identify networks of dense filaments connecting star forming gas cores. Previous analysis of such networks of filaments in isolated turbulent molecular cloud cores. has shown that the mass flows along filaments play a key role in building up a stellar initial mass function, and in growing massive stars.

2018-11-09
15:00
The base material of terrestrial planets - investigating the dust in the inner region of protoplanetary disks
Lucia Klarmann (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The inner regions of protoplanetary disks are where terrestrial planets and super-Earths form and/or migrate to. The small spatial extend of this region makes direct observations difficult. But interferometric observations and dust modeling can put constraints on the base material of terrestrial planet formation.

We self-consisently calculate the expected rim structure for a wide range of possible dust compositions. Synthetic observations of these radiative transfer models show that the rim position can be well constrained using NIR interferometry. Comparing our rim positions with observations from Lazareff+17, we find that the observed positions can be explained by a power law grain size distribution, but also the presence of highly refractory grains.

Motivated by the low carbon fraction in the Earth, we investigate how to sustain a low fraction of refractory carbon in the inner disk. We find that radial dust transport in the disk must be significantly reduced during parent body formation, possibly by a quickly formed giant planet core. Otherwise grains from the outer disk region will replenish refractory carbon very efficiently within the grain drift timescale.

2018-10-26
15:00
TBD
Mario Flock (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
TBD

2018-10-26
15:00
The Inner Regions of Protoplanetary Disks: 3D Radiation Magneto-Hydrodynamical Models
Mario Flock (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Many planets orbit within an AU of their stars, raising questions about their origins. Particularly puzzling are the planets found near the silicate sublimation front. We investigate conditions near the front in the protostellar disk around a young intermediate-mass star, using the first global 3D radiation non-ideal MHD simulations in this context.

The results show magnetorotational turbulence around the sublimation front at 0.5 AU. Beyond 0.8 AU is the dead zone, cooler than 1000 K and with turbulence orders of magnitude weaker. A local pressure maximum just inside the dead zone concentrates solid particles, allowing for efficient growth. Over many orbits, a vortex develops at the dead zone's inner edge, increasing the disk's thickness locally by around 10%.

We synthetically observe the results using Monte Carlo transfer calculations, finding the sublimation front is bright in the near-infrared. The models with vertical magnetic flux develop extended, magnetically-supported atmospheres that reprocess extra starlight, raising the near infrared flux 20%. The vortex throws a non-axisymmetric shadow on the outer disk.

Radiation-MHD models of the kind we demonstrate open a new window for investigating protoplanetary disks' central regions. They are ideally suited for exploring young planets' formation environment, interactions with the disk, and orbital migration, in order to understand the origins of the close-in exoplanets.

2018-10-19
15:00
TBD
Michael Rugel (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
TBD

2018-10-19
15:00
OH abundance and feedback from star clusters with the THOR survey
Michael Rugel (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
In this colloquium, I present characterizations of molecular cloud properties with the THOR survey (The HI, OH and Radio Recombination Line (RRL) survey of the Milky Way). We analyze OH absorption at 18 cm within THOR and follow-up observations. We derive the abundance with respect to molecular hydrogen and the total number of hydrogen nuclei: 1) We find a decreasing OH abundance with increasing column density of molecular hydrogen. 2) Due to significant column densities of atomic hydrogen at low OH column density, the OH abundance with respect to the column density of hydrogen nuclei is approximately constant. 3) We detect OH components which are associated with gas that is not predominantly molecular or even CO-dark. We conclude that OH is a potential tracer for diffuse gas.
Regarding the impact of star clusters on molecular clouds, we detect signatures of feedback in RRL emission in the star forming region W49A. A comparison to the WARPFIELD models (one-dimensional models of feedback-driven shells) indicates that feedback is not yet strong enough to disperse its molecular cloud and that the shell is either in process of re-collapsing to initiate a new event of star formation or has already re-collapsed. This suggests that at least parts of the star formation in W49A is regulated by feedback.

2018-10-12
15:00
TBD
Fei Yan (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2018-10-12
15:00
Transit spectroscopy of exoplanet atmospheres
Fei Yan (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
With almost 4000 exoplanets been discovered, characterizing their atmospheres becomes a rapidly expanding branch in exoplanet research. In this talk, I will focus on transit spectroscopy ? the most commonly used method for atmosphere observations. This method has been successfully applied to discover various chemical species (e.g. water, carbon monoxide, sodium) as well as to characterize psychical conditions like temperature profile and wind. I will present results of our transit observations with CARMENES and MODS/LBT spectrographs, including probing the atmosphere of the hottest exoplanet - KELT-9b. In addition, I will also talk about how the variation of stellar line profiles during transit will affect exoplanet atmosphere observations.

2018-10-05
15:00
TBA
PSF signature speaker Sarah Hörst (JHU)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)

2018-10-05
15:00
Exploring Planetary Atmospheres in a Lab
PSF signature speaker Sarah Hörst (JHU) : Planets in a Bottle
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
From exoplanets, with their surprising lack of spectral features, to Titan and its characteristic haze layer, numerous planetary atmospheres may possess photochemically produced particles of "haze". With few exceptions, we lack strong observational constraints (in situ or remote sensing) on the size, shape, density, and composition of these particles. Photochemical models, which can generally explain the observed abundances of smaller, gas phase molecules, are not well suited for investigations of much larger, solid phase particles. Laboratory investigations of haze formation in planetary atmospheres therefore play a key role in improving our understanding of the formation and composition of haze particles. I will discuss a series of experiments aimed at improving our understanding of the physical and chemical properties of planetary atmospheric hazes on Titan, Pluto, super-Earths, and mini-Neptunes.

2018-09-28
15:00
The Intricate Role of Cold Gas and Dust in Galaxy Evolution at Early Cosmic Epochs
Dominik Riechers (Cornell, MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Great progress has been made over the past two decades in constraining
the star formation history of the universe, but our understanding of
how cosmic star formation is fuelled by cold gas at high redshift is
currently informed primarily by specific, and potentially biased
samples of galaxies. To overcome these limitations, we have carried
out the CO Luminosity Density at High Redshift (COLDz) survey, a large
blind volume search for cold molecular gas in galaxies at redshifts
2-3 and 5-7 with the Karl G. Jansky Very Large Array (VLA). The
resulting measurement of the "cold gas history of the universe" near
the peak epoch of cosmic star formation and in the first billion years
of cosmic time provides important information on the fuelling
mechanisms that drive cosmic star formation. Surveys like COLDz set
the necessary broader context for targeted in-depth studies of the
physical properties of star formation in different galaxy populations
back to the earliest epochs with the Atacama Large sub/Millimeter
Array (ALMA). Such studies fundamentally enhance our picture of early
galaxy evolution by providing a better understanding of the stellar
mass buildup, and they are a critical pathfinder toward galaxy surveys
in the early universe with upcoming large facilities, in particular
the next generation Very Large Array (ngVLA).

2018-09-28
15:00
Evolution of Gas Content Through Cosmic History
Fabian Walter (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The temporal evolution of the cosmic star formation rate density is now well established out to high redshift. This star formation rate density shows a clear peak at z~1-2 that is about one order of magnitude higher than today. The cause for this behavior must be driven by the properties of the underlying reservoir of molecular gas, the fuel for star formation galaxies. The last decade has seen dramatic progress in quantifying the molecular gas content in galaxies through cosmic times, through various observational camapigns. I will summarize our current view of the molecular gas content in distant galaxies. This will include some of the recent results emerging from ASPECS: The ALMA SPECtroscopic Survey in the Hubble Ultra-Deep Field (UDF). This ALMA large program provides a census of molecular gas in high-redshift galaxies through full frequency scans at approximately uniform line sensitivity. The resulting cosmic molecular gas density as a function of redshift shows a factor 3-10 decrease from z=2 to z=0. The cosmic star formation history therefore appears to be at least partly driven by the increased availability of molecular gas reservoirs at the peak of cosmic star formation (z~2).

2018-09-21
15:00
The World Beyond the Snow Line: Microlensing Comes of Age
Andy Gould (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Microlensing is orthogonal to all other planet-search techniques. First, its sensitivity to planets peaks just beyond the snowline, where planets are thought to be most common. Second, it is roughly equally sensitive to planets around all stars, independent of their luminosity, and even to planets that have no host. Third, it is roughly equally sensitive to planets at a range of distances from 1 to 8 kpc. These features potentially enable microlensing to cast a radically different light on planetary demographics. I discuss how the 10-fold increase in microlensing data provided by the Korea Microlensing Telescope Network (KMTNet) and "microlens parallax" observations with the Spitzer Space Telescope are rapidly unleashing this potential.

2018-09-21
15:00
The World Beyond the Snow Line: Microlensing Comes of Age
Andy Gould (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Microlensing is orthogonal to all other planet-search techniques. First, its sensitivity to planets peaks just beyond the snowline, where planets are thought to be most common. Second, it is roughly equally sensitive to planets around all stars, independent of their luminosity, and even to planets that have no host. Third, it is roughly equally sensitive to planets at a range of distances from 1 to 8 kpc. These features potentially enable microlensing to cast a radically different light on planetary demographics. I discuss how the 10-fold increase in microlensing data provided by the Korea Microlensing Telescope Network (KMTNet) and "microlens parallax" observations with the Spitzer Space Telescope are rapidly unleashing this potential.

2018-09-14
15:00
Quantifying and understanding variations in star formation
Sami Dib (NBI)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Star formation is a multi-physics, multi-scale process. The multiplicity of physical processes and scales can generate a significant amount of scatter in the outcome of star formation, in particular in terms of key quantities such as the stellar initial mass function (IMF), the star formation rate (SFR), and the star formation efficiency (SFE). By analyzing large data sets that are becoming increasingly available, one can now assess whether variations do actually exist, quantify them, and attempt to explain them via a comparison with (a range of) theoretical models. I will illustrate this by presenting examples related to the IMF in young Galactic stellar clusters and to the star formation scaling relations in nearby galaxies. I will show that current data argues against a universal IMF in Galactic stellar clusters. I will also argue that the star formation scaling relations on galactic scales should include a description of the role of several other physical quantities, instead of being understood in terms of a mere dependence of the SFR on the density of the star forming gas.

2018-09-14
15:00
Quantifying and understanding variations in star formation
Sami Dib (NBI)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Star formation is a multi-physics, multi-scale process. The multiplicity of physical processes and scales can generate a significant amount of scatter in the outcome of star formation, in particular in terms of key quantities such as the stellar initial mass function (IMF), the star formation rate (SFR), and the star formation efficiency (SFE). By analyzing large data sets that are becoming increasingly available, one can now assess whether variations do actually exist, quantify them, and attempt to explain them via a comparison with (a range of) theoretical models. I will illustrate this by presenting examples related to the IMF in young Galactic stellar clusters and to the star formation scaling relations in nearby galaxies. I will show that current data argues against a universal IMF in Galactic stellar clusters. I will also argue that the star formation scaling relations on galactic scales should include a description of the role of several other physical quantities, instead of being understood in terms of a mere dependence of the SFR on the density of the star forming gas.

2018-09-07
15:00
Magnetic Fields ? Polarization ? Disks
Gesa Bertrang (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Magnetic fields are predicted to be an important factor for a wide range of physical processes in protoplanetary disks. In the classical picture, (sub-)mm continuum polarization is the tracer for magnetic fields in disks. Aspherical dust grains, whose thermal emission is intrinsically polarized, get aligned by the magnetic field due to radiative torques. In recent years, however, this picture has been challenged. New theoretical studies show that (sub-)mm continuum polarization can also be created by scattering of the thermal dust emission or arise from aspherical grains which are aligned by the radiation field rather than the magnetic field. These three mechanisms trace fundamentally different physics in protoplanetary disks, yet, their polarization predictions are not clearly distinguishable. In this talk, I will highlight the role of magnetic fields in protoplanetary disks, present already achieved (indirect) observational constraints, and give an outlook on how to disentangle the sources of continuum polarimetry with ALMA by applying spectro-polarimetry.

2018-09-07
15:00
Magnetic Fields ? Polarization ? Disks
Gesa Bertrang (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Magnetic fields are predicted to be an important factor for a wide range of physical processes in protoplanetary disks. In the classical picture, (sub-)mm continuum polarization is the tracer for magnetic fields in disks. Aspherical dust grains, whose thermal emission is intrinsically polarized, get aligned by the magnetic field due to radiative torques. In recent years, however, this picture has been challenged. New theoretical studies show that (sub-)mm continuum polarization can also be created by scattering of the thermal dust emission or arise from aspherical grains which are aligned by the radiation field rather than the magnetic field. These three mechanisms trace fundamentally different physics in protoplanetary disks, yet, their polarization predictions are not clearly distinguishable. In this talk, I will highlight the role of magnetic fields in protoplanetary disks, present already achieved (indirect) observational constraints, and give an outlook on how to disentangle the sources of continuum polarimetry with ALMA by applying spectro-polarimetry.

2018-08-10
15:00
Fitting a model to data, 2018 edition
David Hogg (NYU, MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
I use examples from the Gaia Mission to illustrate ideas behind the theory and best practices for fitting a model to data. I will address (a) accounting for noisy data and selection effects, (b) dealing with outliers, and (c) model selection and deciding among models. I use very simple models (like straight lines!) and Gaia data for my examples, but the rules I give ? which are designed to minimize the loss of information ? are applicable at all model complexities and in all domains.

2018-08-10
15:00
Fitting a model to data, 2018 edition
David Hogg (NYU, MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
I use examples from the Gaia Mission to illustrate ideas behind the theory and best practices for fitting a model to data. I will address (a) accounting for noisy data and selection effects, (b) dealing with outliers, and (c) model selection and deciding among models. I use very simple models (like straight lines!) and Gaia data for my examples, but the rules I give ? which are designed to minimize the loss of information ? are applicable at all model complexities and in all domains.

2018-08-03
15:00
Mind the gap: swimming the channels between islands of popular star formation research
Joe Mottram (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Like most sub-fields, star formation research has it's popular topics for research. Current examples include searching for structure in disks around low or high-mass protostars, and studying filaments in molecular clouds. I will present research from three projects, each of which aimed to make progress on our broader understanding of the star formation process and ISM lifecycle by exploring the space between these popular islands of research. First, I will present studies of thermal H2O and CO transitions observed towards a sample of low, intermediate and high-mass young stellar objects in order to explore the differences and similarities between low and high-mass protostars. This project ultimately led to a surprising alternative explanation for the emission in such transitions from external galaxies. Second, I will show observational studies of ionised pillars with CARMA, ALMA and MUSE, and how these are helping to constrain models of how these iconic structures are formed. Finally, I will discuss part of my work here at the MPIA combining single-dish and interferometric data to link sites of high-mass star formation with their surroundings. Taken together, these projects reveal the value of striking our into new territory by exploring the space between our islands of knowledge.

2018-08-03
15:00
Mind the gap: swimming the channels between islands of popular star formation research
Joe Mottram (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
Show/hide abstract

Abstract
Like most sub-fields, star formation research has it's popular topics for research. Current examples include searching for structure in disks around low or high-mass protostars, and studying filaments in molecular clouds. I will present research from three projects, each of which aimed to make progress on our broader understanding of the star formation process and ISM lifecycle by exploring the space between these popular islands of research. First, I will present studies of thermal H2O and CO transitions observed towards a sample of low, intermediate and high-mass young stellar objects in order to explore the differences and similarities between low and high-mass protostars. This project ultimately led to a surprising alternative explanation for the emission in such transitions from external galaxies. Second, I will show observational studies of ionised pillars with CARMA, ALMA and MUSE, and how these are helping to constrain models of how these iconic structures are formed. Finally, I will discuss part of my work here at the MPIA combining single-dish and interferometric data to link sites of high-mass star formation with their surroundings. Taken together, these projects reveal the value of striking our into new territory by exploring the space between our islands of knowledge.

2018-07-27
15:00
Reconstruction of the Milky Way with tidal streams
Ana Bonaca (CfA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The arduous quest of reconstructing the distribution of matter in the Galaxy has been reinvigorated in the months following the second data release from the Gaia mission. Studies of cold stellar streams -- remnants of tidally disrupted globular clusters which trace the underlying gravitational potential -- received a particular boost thanks to the Gaia proper motions. Employing the Fisher information approach, we show that the mean track of a stream's 6D positions and velocities intrinsically constrains the total enclosed mass at the stream's current position. Furthermore, Gaia's view of the longest cold stream, GD-1, uncovered significant density variations along the stream and stars offset from the main track -- likely signatures of a perturbed past. Using multiple streams to measure the enclosed mass in different regions of the Milky Way, and GD-1 to test for the presence of low-mass dark matter subhalos, we should produce a 3D map of the Milky Way halo that can distinguish between competing cosmological models.

2018-07-27
15:00
Reconstruction of the Milky Way with tidal streams
Ana Bonaca (CfA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
Show/hide abstract

Abstract
The arduous quest of reconstructing the distribution of matter in the Galaxy has been reinvigorated in the months following the second data release from the Gaia mission. Studies of cold stellar streams -- remnants of tidally disrupted globular clusters which trace the underlying gravitational potential -- received a particular boost thanks to the Gaia proper motions. Employing the Fisher information approach, we show that the mean track of a stream's 6D positions and velocities intrinsically constrains the total enclosed mass at the stream's current position. Furthermore, Gaia's view of the longest cold stream, GD-1, uncovered significant density variations along the stream and stars offset from the main track -- likely signatures of a perturbed past. Using multiple streams to measure the enclosed mass in different regions of the Milky Way, and GD-1 to test for the presence of low-mass dark matter subhalos, we should produce a 3D map of the Milky Way halo that can distinguish between competing cosmological models.

2018-07-20
15:00
Science with the Stratospheric Observatory for Infrared Astronomy (Sofia)
Maja Kazmierczak-Barthel (DSI)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The infrared is a key part of the electromagnetic spectrum for studying star formation and evolution, galaxies, planets, and the interstellar medium. As most infrared wavelengths are absorbed by the water vapor of our planet's atmosphere, except for a few narrow spectral windows, astronomical infrared observations have been limited to space-, balloon-, or aircraft-observatories. SOFIA is the last remaining observatory from a truly "Golden Age" for Mid- and Far-Infrared Astronomy, that included space missions like IRAS, ISO, Spitzer, and Herschel. At least for another decade or two SOFIA will be the only observatory that can regularly access the Mid-and Far-Infrared sky.

SOFIA consists of a 2.7m telescope (effective 2.5m), that is lifted by a heavily modified Boeing 747-SP into the stratosphere above more than 99% of the atmosphere's water vapor. A full complement of instruments provides imaging, spectroscopic, and polarimetric capabilities, to follow up and extend many discoveries of past infrared space missions that ended due to a limited supply of cryogen. In addition, it provides for more progress, as very new state of the art instrumentation can be used, returned to the lab, and further improved. The mobility of the facility gives rise to even more observational opportunities like stellar occultations and other targets of opportunity.

The presentation will give an overview over the capabilities of the observatory, including a few illustrative scientific applications. We will discuss the wavelength coverage, sensitivities, and observing modes, as well as limitations that arise from the specifics of an observational platform on-board of an aircraft. Particular emphasis will be given to the recently released "Cycle 7 Call for Proposals", the specific tools necessary for proposal generation, and how to successfully compete for observing time on SOFIA.

2018-07-20
15:00
Science with the Stratospheric Observatory for Infrared Astronomy (Sofia)
Maja Kazmierczak-Barthel (DSI)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
Show/hide abstract

Abstract
The infrared is a key part of the electromagnetic spectrum for studying star formation and evolution, galaxies, planets, and the interstellar medium. As most infrared wavelengths are absorbed by the water vapor of our planet's atmosphere, except for a few narrow spectral windows, astronomical infrared observations have been limited to space-, balloon-, or aircraft-observatories. SOFIA is the last remaining observatory from a truly "Golden Age" for Mid- and Far-Infrared Astronomy, that included space missions like IRAS, ISO, Spitzer, and Herschel. At least for another decade or two SOFIA will be the only observatory that can regularly access the Mid-and Far-Infrared sky.

SOFIA consists of a 2.7m telescope (effective 2.5m), that is lifted by a heavily modified Boeing 747-SP into the stratosphere above more than 99% of the atmosphere's water vapor. A full complement of instruments provides imaging, spectroscopic, and polarimetric capabilities, to follow up and extend many discoveries of past infrared space missions that ended due to a limited supply of cryogen. In addition, it provides for more progress, as very new state of the art instrumentation can be used, returned to the lab, and further improved. The mobility of the facility gives rise to even more observational opportunities like stellar occultations and other targets of opportunity.

The presentation will give an overview over the capabilities of the observatory, including a few illustrative scientific applications. We will discuss the wavelength coverage, sensitivities, and observing modes, as well as limitations that arise from the specifics of an observational platform on-board of an aircraft. Particular emphasis will be given to the recently released "Cycle 7 Call for Proposals", the specific tools necessary for proposal generation, and how to successfully compete for observing time on SOFIA.

2018-07-13
15:00
From VLT to ELT
Signature Speaker Michele Cirasuolo (ESO)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
In this presentation I will discuss three topics: some recent results obtained with KMOS on the physics and dynamics of high galaxies\; the current status of the MOONS instrument and the unprecedented capabilities of the new Extremely Large Telescope (ELT).

First I will discuss the latest results we have obtained from a Large Programme with KMOS called KLEVER. The programme is designed to observe and spatially resolve a sample of ~100 galaxies at 1<\;z<\;2.5 with full near-IR wavelength coverage (YJ,H,K) delivering the (nearly) full set of rest-frame optical nebular lines and therefore an extraordinary diagnostic power.

I will then present a scientific and technical overview of the MOONS instrument, a new multi-object spectrograph for the Very Large Telescope. The combination of high multiplex (1000 targets) and wide simultaneous wavelength coverage (0.64 - 1.8 microns) of MOONS will provide the astronomical community with a powerful, world-leading instrument able to serve a wide range of Galactic and Extragalactic studies.

Finally I will highlight the key science drivers of the new ESO's flagship facility: the Extremely Large Telescope.
The E-ELT is now under construction and with its 39-metre primary mirror it will be the largest optical/near-IR telescope in the world. I will present an overview of the E-ELT Programme, focusing on the latest status of the telescope, its instrumentation and the scientific synergies.

2018-07-13
15:00
From VLT to ELT
Signature Speaker Michele Cirasuolo (ESO)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
Show/hide abstract

Abstract
In this presentation I will discuss three topics: some recent results obtained with KMOS on the physics and dynamics of high galaxies\; the current status of the MOONS instrument and the unprecedented capabilities of the new Extremely Large Telescope (ELT).

First I will discuss the latest results we have obtained from a Large Programme with KMOS called KLEVER. The programme is designed to observe and spatially resolve a sample of ~100 galaxies at 1<\;z<\;2.5 with full near-IR wavelength coverage (YJ,H,K) delivering the (nearly) full set of rest-frame optical nebular lines and therefore an extraordinary diagnostic power.

I will then present a scientific and technical overview of the MOONS instrument, a new multi-object spectrograph for the Very Large Telescope. The combination of high multiplex (1000 targets) and wide simultaneous wavelength coverage (0.64 - 1.8 microns) of MOONS will provide the astronomical community with a powerful, world-leading instrument able to serve a wide range of Galactic and Extragalactic studies.

Finally I will highlight the key science drivers of the new ESO's flagship facility: the Extremely Large Telescope.
The E-ELT is now under construction and with its 39-metre primary mirror it will be the largest optical/near-IR telescope in the world. I will present an overview of the E-ELT Programme, focusing on the latest status of the telescope, its instrumentation and the scientific synergies.

2018-07-06
15:00
Gamma Rays from The Galactic Centre - an indirect sign for dark matter?
Johannes King (LSW)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Gamma-ray astronomy is an established tool for studying the most energetic, non-thermal processes in the Universe. These processes are typically linked to the acceleration of cosmic rays, which in turn emit gamma-rays for example via inverse compton scattering or the decay of neutral pions. Another process that potentially yields a detecable gamma-ray signal is the annihilation or decay of dark matter particles. Since such a signal is proportional to the dark matter densitiy the Galactic Centre is the ideal place for indirect dark matter searches.

I will present recent studies of the gamma radiation from the Galactic Centre based on observations with H.E.S.S., an array of five imaging atmospheric Cherenkov telescopes located in Namibia. H.E.S.S. plays a major role in the indirect search for dark matter and will continue to do so in the coming years.

2018-07-06
15:00
Gamma Rays from The Galactic Centre - an indirect sign for dark matter?
Johannes King (LSW)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Gamma-ray astronomy is an established tool for studying the most energetic, non-thermal processes in the Universe. These processes are typically linked to the acceleration of cosmic rays, which in turn emit gamma-rays for example via inverse compton scattering or the decay of neutral pions. Another process that potentially yields a detecable gamma-ray signal is the annihilation or decay of dark matter particles. Since such a signal is proportional to the dark matter densitiy the Galactic Centre is the ideal place for indirect dark matter searches.

I will present recent studies of the gamma radiation from the Galactic Centre based on observations with H.E.S.S., an array of five imaging atmospheric Cherenkov telescopes located in Namibia. H.E.S.S. plays a major role in the indirect search for dark matter and will continue to do so in the coming years.

2018-06-29
15:00
Stellar Forensics with the Most Powerful Explosions in the Universe
Maryam Modjaz (NYU)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Supernovae (SNe) and Gamma-ray Bursts (GRBs) are exploding stars and constitute the most powerful explosions in the universe. Since they are visible over large cosmological distances, release almost all elements heavier than Helium, and leave behind extreme remnants such as black holes, they are fascinating objects, as well as crucial tools for many areas of astrophysics, including cosmology. However, for many years the fundamental question of which stellar systems give rise to which kinds of explosions has remained outstanding, for both Type Ia SNe used for cosmology as well as for Superluminous SNe and long-duration GRBs that must originate from special kinds of massive stars. I will discuss the exciting recent progress that we have made on this question in key areas by publishing and thoroughly analyzing the largest data sets in the world. I will conclude with an outlook on how the most promising venues of research - using the existing and upcoming innovative large time-domain surveys such as ZTF and LSST - will shed new light on the diverse deaths of stars.

2018-06-29
15:00
Stellar Forensics with the Most Powerful Explosions in the Universe
Maryam Modjaz (NYU)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
Show/hide abstract

Abstract
Supernovae (SNe) and Gamma-ray Bursts (GRBs) are exploding stars and constitute the most powerful explosions in the universe. Since they are visible over large cosmological distances, release almost all elements heavier than Helium, and leave behind extreme remnants such as black holes, they are fascinating objects, as well as crucial tools for many areas of astrophysics, including cosmology. However, for many years the fundamental question of which stellar systems give rise to which kinds of explosions has remained outstanding, for both Type Ia SNe used for cosmology as well as for Superluminous SNe and long-duration GRBs that must originate from special kinds of massive stars. I will discuss the exciting recent progress that we have made on this question in key areas by publishing and thoroughly analyzing the largest data sets in the world. I will conclude with an outlook on how the most promising venues of research - using the existing and upcoming innovative large time-domain surveys such as ZTF and LSST - will shed new light on the diverse deaths of stars.

2018-06-22
13:15
The production of dust in galaxies
Ciska Kemper (ASIAA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The evolution of interstellar dust reservoirs, and the evolution of galaxies themselves go hand-in-hand, as the presence of dust alters evolutionary drivers, such as the interstellar radiation field and the star formation history, while at the same time, the dust is being formed and altered by processes taking place in galaxies. Indeed, dust can often even be used as a tracer of physical conditions. The exact mineralogical composition, the size and the shape of dust grains, are all affected by the physical conditions. Due to the more permanent nature of solids, dust grains provide a historical record of its processing history, while interstellar gas will only ever probe the
present conditions.

I will discuss our recent results on the Magellanic Clouds, Local Group galaxies, the Milky Way, AGN tori, and starburst galaxies, and highlight future observational opportunities open to astronomers to continue the study of interstellar dust in galaxies.

2018-06-22
13:15
The production of dust in galaxies
Ciska Kemper (ASIAA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The evolution of interstellar dust reservoirs, and the evolution of galaxies themselves go hand-in-hand, as the presence of dust alters evolutionary drivers, such as the interstellar radiation field and the star formation history, while at the same time, the dust is being formed and altered by processes taking place in galaxies. Indeed, dust can often even be used as a tracer of physical conditions. The exact mineralogical composition, the size and the shape of dust grains, are all affected by the physical conditions. Due to the more permanent nature of solids, dust grains provide a historical record of its processing history, while interstellar gas will only ever probe the
present conditions.

I will discuss our recent results on the Magellanic Clouds, Local Group galaxies, the Milky Way, AGN tori, and starburst galaxies, and highlight future observational opportunities open to astronomers to continue the study of interstellar dust in galaxies.

2018-06-15
15:00
The chemical evolution of the Sculptor dwarf spheroidal galaxy (and what we can learn from it!)
Ása Skuladottir (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
At current date the Milky Way has over 50 known satellite galaxies, each
with unique properties. Sculptor is one of the classical dwarf spheroidal
galaxies, with a total mass on the order of ~3x10^8 Msun, and a relatively
high stellar mass for a Local Group dwarf galaxy system: ~8x10^6 Msun.
This galaxy is dominated by an old stellar population (>10 Gyr) and is
therefore an ideal system to study early chemical evolution. Currently we
have available detailed chemical abundances (up to 20 different elements)
for over 100 stars, covering the large metallicity range -4.0<[Fe/H]<-0.9,
(as well as less detailed abundances for ~400 stars), making this one of
the best chemically studied galaxy outside of the Milky Way. From the
details of Sculptor's chemical evolution history, we can therefore learn
valuable lessons about dwarf galaxies in general, as well as larger
systems.

2018-06-15
15:00
The chemical evolution of the Sculptor dwarf spheroidal galaxy (and what we can learn from it!)
Ása Skuladottir (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
Show/hide abstract

Abstract
At current date the Milky Way has over 50 known satellite galaxies, each
with unique properties. Sculptor is one of the classical dwarf spheroidal
galaxies, with a total mass on the order of ~3x10^8 Msun, and a relatively
high stellar mass for a Local Group dwarf galaxy system: ~8x10^6 Msun.
This galaxy is dominated by an old stellar population (>10 Gyr) and is
therefore an ideal system to study early chemical evolution. Currently we
have available detailed chemical abundances (up to 20 different elements)
for over 100 stars, covering the large metallicity range -4.0<[Fe/H]<-0.9,
(as well as less detailed abundances for ~400 stars), making this one of
the best chemically studied galaxy outside of the Milky Way. From the
details of Sculptor's chemical evolution history, we can therefore learn
valuable lessons about dwarf galaxies in general, as well as larger
systems.

2018-06-08
15:00
Asteroseismology in the Gaia Era
Marc Pinsonneault (OSU)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Stellar oscillations are powerful tools for understanding the structure and evolution of stars. With the advent of time domain space missions they can now be measured for large samples of evolved cool stars. The combination of this asteroseismic data, astrometry from Gaia, and large spectroscopic surveys is transforming our understanding of stellar populations and stellar physics. In this talk I review the current state of the art in red giant asteroseismology: both how well we can measure stellar properties using it and how it has changed our understanding of stellar populations. I will also discuss the powerful combination of asteroseismology and

2018-06-08
15:00
Asteroseismology in the Gaia Era
Marc Pinsonneault (OSU)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Stellar oscillations are powerful tools for understanding the structure and evolution of stars. With the advent of time domain space missions they can now be measured for large samples of evolved cool stars. The combination of this asteroseismic data, astrometry from Gaia, and large spectroscopic surveys is transforming our understanding of stellar populations and stellar physics. In this talk I review the current state of the art in red giant asteroseismology: both how well we can measure stellar properties using it and how it has changed our understanding of stellar populations. I will also discuss the powerful combination of asteroseismology and

2018-06-01
15:00
The Lowest-Mass Galaxies in the Early Universe: Insights from the Local Group
Dan Weisz (UC Berkeley)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The Local Group is home to ~100 galaxies less massive than the Small Magellanic Cloud (10^8 Msun). Such low-mass galaxies have become increasingly relevant to a broad range of astrophysics from cosmic reionization to deciphering the nature of dark matter. Yet, they are simply too faint to be directly detected at any appreciable redshift, compromising our ability to place them into a cosmological context. In this talk, I will describe how observations of resolved stellar populations in Local Group galaxies enable the measurement of detailed star formation histories, which provide the only avenue for tracing the evolution of low-mass galaxies across cosmic time. I will review our current knowledge of low-mass galaxy evolution over 6 decades in stellar mass, with a particular emphasis on the early Universe. I will illustrate how local observations of stars and galaxies can be used in tandem with high-redshift studies to improve our understanding of cosmic reionization. I will conclude by discussing prospects for increased synergy between near-field and far-field galaxy studies in the JWST era.

2018-06-01
15:00
The Lowest-Mass Galaxies in the Early Universe: Insights from the Local Group
Dan Weisz (UC Berkeley)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The Local Group is home to ~100 galaxies less massive than the Small Magellanic Cloud (10^8 Msun). Such low-mass galaxies have become increasingly relevant to a broad range of astrophysics from cosmic reionization to deciphering the nature of dark matter. Yet, they are simply too faint to be directly detected at any appreciable redshift, compromising our ability to place them into a cosmological context. In this talk, I will describe how observations of resolved stellar populations in Local Group galaxies enable the measurement of detailed star formation histories, which provide the only avenue for tracing the evolution of low-mass galaxies across cosmic time. I will review our current knowledge of low-mass galaxy evolution over 6 decades in stellar mass, with a particular emphasis on the early Universe. I will illustrate how local observations of stars and galaxies can be used in tandem with high-redshift studies to improve our understanding of cosmic reionization. I will conclude by discussing prospects for increased synergy between near-field and far-field galaxy studies in the JWST era.

2018-05-18
15:00
detecting optimal targets for characterization & understanding
Nestor Espinoza (MPIA) : Transiting exoplanets
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Transiting exoplanets are exciting objects to study because, with sufficient follow-up, they can be almost completely characterized. From bulk and atmospheric compositions to a plethora of orbital information, these exoplanets can provide key information that, in principle, enable us to build (and test) models to understand how they are shaped to their present-day forms. However, only a handful of transiting exoplanets "optimal" for characterization exist, despite the large number of confirmed transiting exoplanets detected to date\; their detection and characterization is thus an important challenge on its own. In this talk, I will present our on-going efforts with the K2-CL collaboration to find new, interesting characterizable systems with the K2 mission, how and why these have to be followed up after their discovery to keep their ephemerides up to date, and our efforts within the ACCESS survey, with which we are exploring exoplanet atmospheres of interesting targets in the optical window, which is key to unveil what their atmospheres are made of, specially if combined with HST/WFC3 data. Lessons learned and natural transitions of these projects in light of the upcoming TESS and JWST missions will be discussed.

2018-05-18
15:00
detecting optimal targets for characterization & understanding
Nestor Espinoza (MPIA) : Transiting exoplanets
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Transiting exoplanets are exciting objects to study because, with sufficient follow-up, they can be almost completely characterized. From bulk and atmospheric compositions to a plethora of orbital information, these exoplanets can provide key information that, in principle, enable us to build (and test) models to understand how they are shaped to their present-day forms. However, only a handful of transiting exoplanets "optimal" for characterization exist, despite the large number of confirmed transiting exoplanets detected to date\; their detection and characterization is thus an important challenge on its own. In this talk, I will present our on-going efforts with the K2-CL collaboration to find new, interesting characterizable systems with the K2 mission, how and why these have to be followed up after their discovery to keep their ephemerides up to date, and our efforts within the ACCESS survey, with which we are exploring exoplanet atmospheres of interesting targets in the optical window, which is key to unveil what their atmospheres are made of, specially if combined with HST/WFC3 data. Lessons learned and natural transitions of these projects in light of the upcoming TESS and JWST missions will be discussed.

2018-05-11
15:00
Exploring the Evolution of Circumstellar Disks with ALMA
John Carpenter (Joint ALMA Observatory)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
ALMA is providing new opportunities to explore the evolution of circumstellar disks. From snapshot surveys of protoplanetary disks in nearby star forming regions, to sensitive high-resolution images of young disks, and to surveys of old debris disks, ALMA is tracing the structure and properties of disks at all evolutionary stages. This talk will present recent ALMA observations that are contributing to our understanding of the properties of protoplanetary and debris disks. I will first summarize the results from recent ALMA surveys that are establishing the demographics of protoplanetary disks between ages of 1 and 10 Myr. I will also present new high-resolution images of 20 protoplanetary disks from an ALMA Large Program that is designed to determine the prevalence of substructure (e.g., rings, spirals, and gaps) in young protoplanetary disks. Finally, I will present new ALMA data for a debris disk around a ~ 100 Myr old solar analog and discuss the implications for planet formation in this system.

2018-05-11
15:00
Exploring the Evolution of Circumstellar Disks with ALMA
John Carpenter (Joint ALMA Observatory)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
ALMA is providing new opportunities to explore the evolution of circumstellar disks. From snapshot surveys of protoplanetary disks in nearby star forming regions, to sensitive high-resolution images of young disks, and to surveys of old debris disks, ALMA is tracing the structure and properties of disks at all evolutionary stages. This talk will present recent ALMA observations that are contributing to our understanding of the properties of protoplanetary and debris disks. I will first summarize the results from recent ALMA surveys that are establishing the demographics of protoplanetary disks between ages of 1 and 10 Myr. I will also present new high-resolution images of 20 protoplanetary disks from an ALMA Large Program that is designed to determine the prevalence of substructure (e.g., rings, spirals, and gaps) in young protoplanetary disks. Finally, I will present new ALMA data for a debris disk around a ~ 100 Myr old solar analog and discuss the implications for planet formation in this system.

2018-05-04
15:00
Jupiter's Jet-Streams and interior revealed by Juno
Yamila Miguel (Leiden)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract

Giant planets were the first planets to form and the most influential ones. Their interiors and atmospheres have crucial information to understand the origins of the solar system and of our own Earth.  \;

With the aim to reach a deeper understanding of Jupiter's interior and atmosphere, the Juno spacecraft was sent to the biggest giant in the solar system, and its first results have fundamentally changed our understanding of this planet. \;


In this seminar I will show the models we use to understand Jupiter's interior and our latest Juno results -including a much deeper understanding of Jupiter's interior and jet streams-, that will help us to reach a better understanding of Jupiter formation history.


2018-05-04
15:00
Jupiter's Jet-Streams and interior revealed by Juno
Yamila Miguel (Leiden)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract

Giant planets were the first planets to form and the most influential ones. Their interiors and atmospheres have crucial information to understand the origins of the solar system and of our own Earth.  \;

With the aim to reach a deeper understanding of Jupiter's interior and atmosphere, the Juno spacecraft was sent to the biggest giant in the solar system, and its first results have fundamentally changed our understanding of this planet. \;


In this seminar I will show the models we use to understand Jupiter's interior and our latest Juno results -including a much deeper understanding of Jupiter's interior and jet streams-, that will help us to reach a better understanding of Jupiter formation history.


2018-04-27
15:00
Neutron star mergers and the high-density equation of state
Andreas Bauswein (HITS)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
In August 2017 the LIGO-Virgo network detected for the first time gravitational waves from a neutron star merger. The event, dubbed GW170817, was followed by electromagnetic radiation. Various emission mechanisms produced radiation at different wavelengths throughout the electromagnetic spectrum from gamma rays to radio. The gravitational and electromagnetic radiation has provided a wealth of information on the physics of neutron star mergers. In particular, it was possible to infer constraints on stellar properties of neutron stars and the only incompletely known equation of state of high-density matter. Specifically, bounds on neutron star radii have been derived from this very first observation of a neutron star merger. Future detections with increased sensitivity promise accurate and robust measurements of neutron star properties and thus to elucidate properties of high-density matter.

2018-04-27
15:00
Neutron star mergers and the high-density equation of state
Andreas Bauswein (HITS)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
In August 2017 the LIGO-Virgo network detected for the first time gravitational waves from a neutron star merger. The event, dubbed GW170817, was followed by electromagnetic radiation. Various emission mechanisms produced radiation at different wavelengths throughout the electromagnetic spectrum from gamma rays to radio. The gravitational and electromagnetic radiation has provided a wealth of information on the physics of neutron star mergers. In particular, it was possible to infer constraints on stellar properties of neutron stars and the only incompletely known equation of state of high-density matter. Specifically, bounds on neutron star radii have been derived from this very first observation of a neutron star merger. Future detections with increased sensitivity promise accurate and robust measurements of neutron star properties and thus to elucidate properties of high-density matter.

2018-04-20
15:00
10 years of Galaxy Evolution
Arjen van der Wel (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
To conclude my ~10-year stay at MPIA I will give an overview of the progress in understanding the formation and evolution of galaxies that we have made over the past decade. This summary will be broad, ranging from theory and simulations to the observations of distant star-bursting dwarf galaxies, but from the specific perspective provided by large optical/near-IR surveys. I will describe how MPIA has stood at the forefront of the transition from an era of discovery -- which showed where the stars in the universe are and when they formed --  \;to an era of concrete physical insight in to the galaxy evolution process.

2018-04-20
15:00
10 years of Galaxy Evolution
Arjen van der Wel (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
To conclude my ~10-year stay at MPIA I will give an overview of the progress in understanding the formation and evolution of galaxies that we have made over the past decade. This summary will be broad, ranging from theory and simulations to the observations of distant star-bursting dwarf galaxies, but from the specific perspective provided by large optical/near-IR surveys. I will describe how MPIA has stood at the forefront of the transition from an era of discovery -- which showed where the stars in the universe are and when they formed --  \;to an era of concrete physical insight in to the galaxy evolution process.

2018-04-13
15:00
High-resolution cosmological simulations of Milky Way mass galaxies"
Tobias Buck (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The Milky Way and its dwarf galaxy companions are among the most well studied galaxy we know.
Current very high-resolution zoom-in baryonic simulations of the formation of Milky Way mass galaxies are in incredible
agreement with observed properties our Milky Way. First, I will introduce the new high-resolution set of simulations from the NIHAO project and discuss the formation of the Milky Way. I will cover the early phases of violent star formation and the accretion of its satellites providing observational constraints on the effect of environment dwarf galaxy properties. I will further discuss the (kinematic) structure and evolution of the stellar disc and the morphology and abundance patterns of the Milky Way's central region - its bar and boxy/peanut bulge. Using these simulations I am able to provide a theoretical understanding of the formation of the Milky Way in the era of Gaia.

2018-04-13
15:00
High-resolution cosmological simulations of Milky Way mass galaxies"
Tobias Buck (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
The Milky Way and its dwarf galaxy companions are among the most well studied galaxy we know.
Current very high-resolution zoom-in baryonic simulations of the formation of Milky Way mass galaxies are in incredible
agreement with observed properties our Milky Way. First, I will introduce the new high-resolution set of simulations from the NIHAO project and discuss the formation of the Milky Way. I will cover the early phases of violent star formation and the accretion of its satellites providing observational constraints on the effect of environment dwarf galaxy properties. I will further discuss the (kinematic) structure and evolution of the stellar disc and the morphology and abundance patterns of the Milky Way's central region - its bar and boxy/peanut bulge. Using these simulations I am able to provide a theoretical understanding of the formation of the Milky Way in the era of Gaia.

2018-04-06
15:00
The second Gaia data release
Coryn Bailer-Jones (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract

On 25 April the Gaia Consortium will make its second data release based
on 22 months of mission data. The release will contain five-parameter
astrometry and three-band photometry for over 1 billion stars down to
G=20.7, radial velocities for 7 million stars, variability
classification for several hundred thousand stars, plus basic stellar
parameters for up to 160 million stars. I will give an overview of the
content, precision, and coverage of this release plus some tips on how
(not) to use the data.

2018-04-06
15:00
The second Gaia data release
Coryn Bailer-Jones (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
Show/hide abstract

Abstract

On 25 April the Gaia Consortium will make its second data release based
on 22 months of mission data. The release will contain five-parameter
astrometry and three-band photometry for over 1 billion stars down to
G=20.7, radial velocities for 7 million stars, variability
classification for several hundred thousand stars, plus basic stellar
parameters for up to 160 million stars. I will give an overview of the
content, precision, and coverage of this release plus some tips on how
(not) to use the data.

2018-03-23
15:00
The Role of Environment in Shaping Molecular Cloud Structure and Star Formation
Chris Faesi (MPIA)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Giant Molecular Clouds (GMCs) are the cradles of stellar birth across the universe and thus play a key role in the baryon cycle within galaxies. GMCs in the Milky Way show a high degree of uniformity in their physical structure, but recent observations of nearby galaxies have suggested that their properties may vary systematically with environment. To explore the question of universality vs. environment, I have undertaken a series of high-resolution, high-sensitivity studies of molecular gas and star formation in NGC 300, a low mass, star forming spiral galaxy that at a distance of 2 Mpc provides an ideal laboratory for resolved GMC studies and comparison to our own Galaxy. I will describe the results of a campaign of multiwavelength observations of NGC 300 culminating in an ALMA study that achieves 10 pc resolution, fully resolving GMC scales in a sample of 250 clouds. I will show that despite large differences between global properties of the Milky Way and NGC 300, their GMC populations appear to be remarkably similar. Furthermore, the relationship between star formation and molecular gas identified in the Milky Way also holds in NGC 300. I will demonstrate that local physical properties such as midplane disk pressure of the interstellar medium, which is similar between the Milky Way and NGC 300, may explain observed differences in GMC properties in other galaxies such as M51, as well as in more extreme physical environments such as the Galactic Center. I will conclude by describing the ongoing campaign to link small-scale interstellar medium physics with large-scale galaxy properties under the auspices of the PHANGS (Physics at High Angular resolution in Nearby GalaxieS) collaboration. We have in-progress large programs with both ALMA and MUSE to measure molecular gas and tracers of star formation at arcsecond resolution across the disks of tens of galaxies, providing improved statistics and greatly expanding the parameter space for GMC-scale analyses in a range of environments.

2018-03-16
15:00
Crowded field 3D spectroscopy in NGC300 - spectacular details of resolved stellar populations revealed through the combination of ACS with MUSE
Martin Roth (AIP)
Königstuhl Kolloquium
Max-Planck-Institut für Astronomie, Level 3 Lecture Hall (301)
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Abstract
Already a decade ago, the Advanced Camera for Surveys Nearby Galaxy survey Treasury (ANGST) has provided images and photometry of individual stars in nearby galaxies, thus furnishing the hope to provide deep insight into star formation histories and the chemical evolution of galaxies. However, the known limitations of photometry have remained an obstacle to fully exploit the angular resolution of HST in analyzing stellar populations in galaxies such as the sculptor group galaxy NGC300. We have selected NGC300 as the target of our MUSE GTO program at the VLT UT4 to explore the potential of IFUs for crowded field 3D spectroscopy, utilizing PSF-fitting techniques that have become a standard for imaging data in the optical and NIR already for some time (DAOPHOT etc.). With the input of stellar centroids obtained from the ANGST catalogue, we are demonstrating that the PampelMuse PSF-fitting tool is capable to extract more than 500 spectra for individual stars of luminosity class I?III from a single MUSE pointing (1.5 h exposure time). These spectra are well deblended and allow for spectral type classification as well as the measurement of radial velocities. Next to stars of spectral types O?M, we find numerous carbon stars, blue emission line stars, and LBV and symbiotic star candidates. The excellent image quality and sensitivity of MUSE has also enabled the discovery of extremely faint HII regions, planetary nebulae, supernova remnants, and substructure of the diffuse ionized gas (DIG).

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