Ruprecht-Karls-Universität Heidelberg


Upcoming events



Past events


2017-06-21
16:00
The impact of a star-formation efficiency profile on the evolution of open clusters
Bekdaulet Shukirgaliyev (ARI)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to MPIA, LSW, HITS,

2017-06-21
15:15
The history of star cluster formation in the Milky Way disk from MWSC survey data
Anatoly Piskunov & Nina Kharchenko (Institute of Astronomy, Moscow, Russia & Main Astronomical Observatory Kiev, Ukraine)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to MPIA, LSW, HITS,

2017-06-07
16:00
New Perspective on Classical Pulsators
Radek Smolec (Nicolaus Copernicus Astronomical Center)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to MPIA, LSW, HITS,
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Abstract
I will present the recent discoveries of new forms of pulsation in classical pulsators. These include multi-periodic and modulated pulsation. Double-periodic pulsation must be common phenomenon among first overtone pulsators, both Cepheids and RR Lyrae stars. The commonly observed additional variability is of low amplitude and cannot be interpreted as due to radial pulsation. First model which provides the selection mechanism and identification for non-radial modes was proposed and offers the possibility of studying the interiors of classical pulsators. Low-amplitude instabilities in classical pulsators are also more common than previously thought. The recent example I will focus on is quasi-periodic modulation in fundamental mode classical Cepheids.

2017-06-07
15:15
Non-linear effects of a metallicity dependent initial mass function in Milky Way analogues
Thales Gutcke (MPIA)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to MPIA, LSW, HITS,
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Abstract
Cosmological, hydrodynamical simulations commonly assume a universal stellar inital mass function (IMF) when attempting to produce realistic Milky Way analogues. Yet constaints from simulations on stellar-to-halo mass ratios, feedback strength, metallicity evolution and metallicity distributions are all degenerate with the effects of a non-universal, or specifically metallicity-dependent IMF. I will report on the magnitude of uncertainty produced by the assumption of a universal IMF by running simulations of Miky Way analogues using the moving mesh code AREPO run with universal (Salpeter, Kroupa and Chabrier) and varying metallicity-dependent IMFs. Additionally, I will show the non-linear effects on metallicity that an empirical relation between metalllicity and the high mass slope of the IMF can produce and attempt to constrain this relation with mock observations of the predicted alpha abundance patterns.

2017-05-29
11:30
Evolutionary Description of Giant Molecular Cloud Mass Functions in Galactic Disks
Masato Kobayashi (Nagoya University, Japan)
SFB Seminar - The Milky Way System
ARI seminar room 1st floor, special guest seminar (host D. Kruijssen)
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Abstract
Recent radio observations show that giant molecular cloud (GMC) mass functions noticeably vary across galactic disks (e.g., Colombo et al. 2014). High-resolution magnetohydrodynamics simulations show that multiple episodes of compression are required for creating a molecular cloud in the magnetized interstellar medium (e.g., Inoue et al. 2012). To understand time evolution of GMC mass functions, we formulate the evolution equation for the GMC mass function to reproduce the observed profiles, for which multiple compressions are driven by a network of expanding shells due to H II regions and supernova remnants. We also introduce the cloud-cloud collision (CCC) terms in the evolution equation in contrast to previous work. In this seminar, I would like to present computed time evolutions and the following two suggestions: (1) the GMC mass function slope is governed by the ratio of GMC formation timescale to its dispersal timescale whereas the CCC effect is limited only in the massive end of the profile, (2) almost all of the dispersed gas contributes to the mass growth of pre-existing GMCs in arm regions whereas less than 60 percent contributes in inter-arm regions. Our results suggest that measurement of the GMC mass function slope provides a powerful method to constrain those GMC timescales and the gas resurrecting factor in various environments across galactic disks.

2017-05-24
15:15
Modeling the interstellar medium in different environments
Ralf Klessen & Simon Glover (hosts) (ITA)
SFB Seminar - The Milky Way System
Philosophenweg 19, seminar room
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Abstract
Special SFB Seminar and Get-Together at ITA. Talks: (i) Daniel Rahner: Winds and radiation in unison - feedback from young massive clusters; (ii) Robin Tress: Simulations of the Galactic Center: a possible explanation for the CMZ asymmetry; (iii) Mattia Sormani: Periodicity makes galactic shocks unstable

2017-04-26
16:00
Dynamical models of flattened and rotating globular clusters
Sarah Jeffreson (ARI)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to MPIA, LSW, HITS
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Abstract
We present a family of self-consistent axisymmetric rotating globular cluster models which are fitted to spectroscopic data for NGC 362, NGC 1851, NGC 2808, NGC 4372, NGC 5927 and NGC 6752 to provide constraints on their physical and kinematic properties, including their rotation signals. They are constructed by flattening Modified Plummer profiles, which have the same asymptotic behaviour as classical Plummer models, but can provide better fits to young clusters due to a slower turnover. The models are in dynamical equilibrium as they depend solely on the action variables. We employ a fully Bayesian scheme to investigate the uncertainty in our model parameters (including mass-to-light ratios and inclination angles) and evaluate the Bayesian evidence ratio for rotating to non-rotating models. We find convincing levels of rotation only in NGC 2808. In the other clusters, there is only a hint of rotation (in particular, NGC 4372 and NGC 5927), as the data quality does not allow us to draw strong conclusions. Where rotation is present, we find that it is confined to the central regions. As part of this work, we have developed a novel q-Gaussian basis expansion of the line-of-sight velocity distributions, from which general models can be constructed via interpolation on the basis coefficients.

2017-04-26
15:15
The local rotation curve of the Milky Way
Oleksiy Golubov (Kharkiv University)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to MPIA, LSW, HITS
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Abstract
We use a sample of SEGUE G-dwarfs to constrain the local behaviour of the rotation curve of the Milky Way. We find the mean galactocentric rotation velocity of the stars, correct for the asymmetric drift and the vertical gradient of the circular velocity, and construct the rotation curve at the galactocentric radii 7 to 10 kpc. The rotation curve appears flat, with no significant dips in the considered range. Then we use TGAS sample with Gaia parallaxes to constrain the local slope of the rotation curve.

2017-01-25
16:00
Mapping Multiple Stellar Populations of Globular Cluster Origin in the Field
Prof Dr. Eva K. Grebel (ARI)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to HITS, LSW, MPIA,
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Abstract
Essentially all globular clusters contain multiple stellar populations, and their presence has even been proposed to be a defining characteristic of globular clusters. In contrast, the less massive and usually short-lived open clusters do not show evidence for multiple stellar populations. The origin of photometrically or spectroscopically identified multiple populations remains a major unsolved puzzle though. If multiple populations do indeed form exclusively in globulars as our current knowledge suggests, they may be used to trace the globular cluster contribution to the field. Chemically, multiple stellar populations stand out by their light element abundance variations. The search for these chemical signatures among field stars permits us to identify candidates that were likely stripped from globular clusters. An alternative method is the search for stars that are chemically and kinematically consistent with an origin from specific globular clusters (while not necessarily showing light element abundance variations). Mapping such present-day field stars will ultimately allow us to quantify the role of globular clusters in the build-up of field populations.

2017-01-25
15:15
The properties of the Galactic bulge as told by its RR Lyrae stars
Dr. István Dékány (ARI)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to HITS, LSW, MPIA,
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Abstract
The Galactic bulge holds key information on the early formation history of the Milky Way, but efforts aiming to map its detailed present-day structure have not reached a full consensus. Our goal is to accurately map both the space-varying extinction curve in the bulge's foreground, and the 3-dimensional distribution of its oldest stellar population using RR Lyrae stars as tracers. We find non-standard mean optical-infrared extinction ratios and trace large and coherent variations in the reddening curve, in qualitative agreement with independent findings. We employ an unbiased extinction correction to derive an accurate map of the old Galactic bulge. It is remarkably different from the barred structure traced by red clump stars, and shows subtle features requiring further investigation.

2017-01-11
15:15
Simulations of the Milky Way's Formation in a Cosmological Context
Prof. Dr. Volker Springel (HITS/ARI)
SFB Seminar - The Milky Way System
HITS, Konrad Zuse meeting room, 2nd floor, (video broadcast on demand)
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Abstract
This is a special SFB seminar and get-together at the Heidelberg Institute for Theoretical Studies (HITS): * Volker Springel: Simulations of the Milky Way's Formation in a Cosmological Context * Christine Simpson: Galactic Outflows and Cosmic Rays * Martin Sparre: Cosmological Simulations of Galaxy Mergers

2016-11-23
16:00
The Multi-Scale Physics of Star Formation and Feedback in the Building Blocks of the Milky Way
Dr. Diederik Kruijssen (ARI)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to HITS, LSW, MPIA,
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Abstract
Dr. Kruijssen will introduce his new SFB subproject P1.

2016-11-23
15:15
The new PARSEC evolutionary tracks and isochrones with alpha enhancement: Calibration with 47Tuc and improvement on the RGB bump prediction
Xiaoting Fu (SISSA)
SFB Seminar - The Milky Way System
ARI basement seminar room, video broadcast to HITS, LSW, MPIA,
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Abstract
Precise studies on the Galactic bulge and multiple populations of globular cluster require stellar model with alpha enhancement and various helium contents. It is also important for extra- Galactic study to have alpha enhanced population synthesis. For this purpose we expand PARSEC model from solar-scaled composition to alpha enhanced mixtures. The new model is calibrated with globular cluster 47Tuc (NGC104). We then apply the calibration and alpha enhanced mixture based on the two 47Tuc populations ( [alpha/Fe] ∼0.4 and 0.2) to other metallicities. The new model closes the gap between the observation and model prediction on the RGB bump. Besides the alpha enhanced metal mixture in 47Tuc, we also calculate evolutionary tracks based on metal mixtures from ATLAS9 APOGEE atmosphere model.

2016-11-09
16:00
Open Cluster Groups and Complexes
Dr. Claudia Conrad (Mannheim)
SFB Seminar - The Milky Way System
ARI basement seminar room,
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Abstract
It is generally agreed upon that stars form in open clusters and stellar associations, but little is known about structures in the Galactic open cluster population. Are open clusters and stellar associations born isolated or do they prefer to form in groups? Answering this question provides new insight into star and cluster formation, along with a better understanding of Galactic structures. In the past decade studies of open cluster groupings were either based solely on spatial criteria or also included tangential velocities for the identification. In contrast to previous approaches, we assumed that real open cluster groupings occupy a well defined area in the sky and show similar velocity vectors. Therefore, we used 6D phase-space information for the detection of open cluster groupings. In addition, we checked the age spread for the potential candidates, to distinguish between genuine groupings and chance alignments. We explored the Catalogue of Open Cluster Data (COCD; Kharchenko et al. 2005a,b) and determined 6D phase-space information for 432 out of the 650 listed open clusters and compact associations. The group identification was performed using an adapted version of the Friends-of-Friends algorithm, as used in cosmology, with linking lengths of 100 pc and 10-20 km/s. For the verification of the identified structures, we applied Monte-Carlo simulations with randomised samples. For the linking lengths 100 pc and 10 km/s we detected 19 groupings, including 14 pairs, fours groups with 3-5 members, and one complex with 15 members. The Monte-Carlo simulations revealed that in particular the complex is most likely genuine, whereas the pairs are more likely chance alignments. A closer look at the age spread of the complex and the comparison between the spatial distributions of the young and old cluster population suggested that OC groupings likely originated from a common molecular cloud.

2016-11-09
15:15
Thermonuclear supernovae as sources of iron group elements in the Milky Way
Prof. Dr. Friedrich Röpke (HITS/ITA)
SFB Seminar - The Milky Way System
ARI basement seminar room,
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Abstract
Prof. Röpke will introduce his new SFB subproject A10.

2016-10-26
16:00
Tidally Induced Offset Disks in Magellanic Spiral Galaxies
Dr. Elena D'Onghia (University of Wisconsin-Madison)
SFB Seminar - The Milky Way System
ARI basement seminar room,
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Abstract
Magellanic spiral galaxies are a class of one-armed systems that often exhibit an offset stellar bar and are rarely found around massive spiral galaxies. Using a set of N-body and hydrodynamic simulations, we consider a dwarf-dwarf galaxy interaction as the driving mechanism for the formation of this peculiar class of systems. We investigate and I will present here the relation between the dynamical, stellar, and gaseous disk center and the bar during and after the interaction. We explain the nature of the offset bar found in many Magellanic-type galaxies, including the Large Magellanic Cloud (LMC) and NGC 3906. In particular, these results, once applied to the LMC, suggest that the dynamical center should reside in the bar center instead of the HI center as previously assumed, pointing to a variation in the current estimate of the north component of the LMC proper motion.

2016-10-26
15:15
Preparing for Public Surveys for the MOSAIC multi-object spectrograph on the E-ELT
Dr. Bertrand Lemasle (ARI)
SFB Seminar - The Milky Way System
ARI basement seminar room,
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Abstract
MOSAIC is the future multi-object spectrograph (MOS) for the E-ELT. After giving a brief overview of the instrument and its operating mode, I will highlight some SFB-relevant aspects of the current phase A study (March 2016 - March 2018), during which the conceptual design of the instrument will be refined. The phase A study includes the preparation of public surveys that could follow the implementation of the instrument at the telescope (~2025-26). Even if MOSAIC is a long-term project, it is now that we have to prepare the design of the MOS and accompanying surveys on the largest telescope of the next decades.

2016-09-28
15:15
Enrichment of r-process elements in the Local Group galaxies in chemo-dynamical evolution model
Yutaka Hirai (University of Tokyo)
SFB Seminar - The Milky Way System
ARI, Main seminar room **1st floor**
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Abstract
The abundance of r-process elements of stars in the Milky Way (MW) provides clues to clarify the early evolutionary history of galaxies. Astronomical high dispersion observations show that metal-poor stars in the MW halo have large star-to-star scatters in the distribution of r-process elements. Neutron star mergers (NSMs) are one of the most promising sites of r-process. Previous chemical evolution studies, however, suggested that the merger timescale of NSMs is too long to reproduce the observed scatters. In this study, we performed a series of N-body/hydrodynamic simulations of the MW progenitor galaxies. We show that the scatters can be explained by NSMs due to the slow chemical enrichment of such galaxies. This result suggests that stars in the MW halo formed with a star formation rate of less than 10^-3 Msun/yr. We also find that the dynamical time of halos affects the early evolutionary history of galaxies. Our results demonstrate that the future observations of r-process elements in metal-poor stars will be able to constrain the early chemo-dynamical evolution of the Local Group galaxies. (Special SFB guest seminar. Host: D. Kruijssen)

2016-02-03
15:15
Searching for substructures around the Milky Way dwarf satellites with a telephoto lens
David Martinez-Delgado (ARI/ZAH)
SFB Seminar - The Milky Way System
ARI (first floor seminar room),
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Abstract
I will present the proof of concept and first results on the search for stellar substructures around a sample of Milky Way dwarf satellites, as part of the objectives of the SFB881 subproject A2. In particular, I will show deep optical images of the Magellanic Clouds using a low cost telephoto lens to explore stellar substructures in their outskirts, and a comparison of these results with detailed simulations of the LMC-SMC interaction. Finally, I will briefly discuss the future plans for installing the instrumental equipment of the SFB881 A2 project devoted to undertake a search for distant, diffuse Milky Way satellites in a huge sky area.

2016-01-13
16:00
Massive stars and the chemical enrichment of the universe
Dr. Joachim Bestenlehner (MPIA)
SFB Seminar - The Milky Way System
ARI (basement seminar room); video conference to LSW on request,
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Abstract
The first part of my talk will be about massive stars as progenitors of type II, Ib/c and pair-instability supernovae . Until the first SN Ia occurred these supernova types were the main sources to chemically enrich the early universe. The second part will be about my on going and future research within Gaia-ESO.

2016-01-13
15:15
Chemical composition of Milky Way open clusters in APOGEE and SEGUE
Clio Bertelli Motta (ARI/ZAH)
SFB Seminar - The Milky Way System
ARI (basement seminar room); video conference to LSW on request,
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Abstract
Open clusters are very interesting objects not only because they are known to be the birthplace of stars, but also because studying their chemical composition can teach us a lot about stellar and galaxy evolution. We crossmatched the Kharchenko et al. (2013) catalogue of open clusters with the APOGEE and SEGUE spectroscopical surveys. After an accurate membership analysis of the stars found within the radius of each cluster, based on proper motions, radial velocity, colour-magnitude diagrams and metallicities, we investigated the chemical abundances of several elements of the selected member stars resulting from the APOGEE pipeline ASPCAP. In few cases, for clusters very well sampled with giants, it was possible to observe the effects of the first dredge-up after the sub-giant branch on the atmosphere of the stars. Besides, for some of the clusters we could compare the results of ASPCAP with those of the SEGUE pipeline SSPP and, in the case of SEGUE spectra, we were also able to determine the metallicities and the alpha abundances as well as the radial velocities with the code SP_Ace (Boeche & Grebel 2015). In this talk I will give an overview on the method and the results that we obtained so far.

2015-11-25
16:00
Recent Results from Abundance and Radial Velocity Surveys of Milky Way Field Stars
Prof. Eva K. Grebel (ARI/ZAH)
SFB Seminar - The Milky Way System
ARI (basement seminar room); video conference to LSW on request,
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Abstract
The stellar radial velocities and abundances measured by recent and ongoing massive spectroscopic surveys are providing an unprecedentedly detailed picture of the evolution of our Galaxy. In combination with photometric and astrometric information, they reveal the enrichment histories of the Milky Way's field populations and make the determination of age-metallicity-velocity dispersion relations for the different Galactic components possible. The rapidly growing data bases help us to uncover abundance gradients and mixing, to reveal dynamical resonances or parent clusters in which the field stars formed originally, or to trace yet other field stars back to accreted dwarf galaxy progenitors. The emerging picture of Galactic evolution is complex, full of surprises, and still evolving. In the future, new multi-object facilities such as 4MOST, MOONS, and WEAVE will allow us to further refine our understanding of Milky Way evolution. In my talk, I will highlight some of the important breakthroughs obtained in recent years. [Note: This is a review talk given at the Multi-Object Spectroscopy conference in Cefalu in September 2015.]

2015-11-25
15:15
Globular clusters and the assembly of the stellar halo
Dr. Julio Chaname (Pontificia Universidad Catolica de Chile)
SFB Seminar - The Milky Way System
ARI (basement seminar room); video conference to LSW on request,
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Abstract
In the context of the hierarchical framework of cosmological structure formation, the stellar halos of galaxies like the Milky Way assembled via the accumulation and shredding of smaller entities formed at earlier times. Until recently, the focus of the search and characterization of such building blocks has been on dwarf galaxies, but evidence has been accumulating that hint at a significant contribution from massive globular clusters (GCs) as well. I will briefly review current constraints on such contribution, which come from a variety of indicators, and will present results from our work on the chemodynamical tagging of moving groups in the solar neighborhood that have been historically associated to existing GCs such as omega Centauri and others.

2015-10-28
16:00
The Optical-Infrared Extinction Curve and its Variation in the Milky Way
Dr. Edward Schlafly (MPIA)
SFB Seminar - The Milky Way System
ARI, basement seminar room; video broadcast to other institutes on request - please notify organizer
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Abstract
The dust extinction curve is an important diagnostic of the physics of the interstellar medium, as well as a critical element to many observational programs. Detailed studies of the extinction curve and its variation have so far been limited to samples of hundreds of specially chosen stars. We make new measurements of the dust extinction curve and its variation towards of tens of thousands of stars using the APOGEE spectroscopic survey in combination with photometry in ten bands, from Pan-STARRS1, 2MASS, and WISE. We find that the extinction curve in the optical through infrared is well characterized by a one-parameter family of curves described by R(V), with little need for further parameters. The local curvature of the extinction curve increases with decreasing R(V) throughout the optical and infrared: the extinction curve in the infrared, while less variable than in the optical, is not “universal,” in contrast to several widely-used extinction curve parameterizations. Meanwhile we find that the optical extinction curve is somewhat more uniform than suggested in past works, with σ(R(V)) = 0.2, and with less than two percent of sight lines having R(V) > 4. However, significant spatially coherent variations in R(V) do exist. The primary variations are on scales much larger than individual molecular clouds, indicating that grain growth in dense molecular cloud environments is not the primary driver of R(V) variations in dust at large. Indeed, we find no correlation between R(V) and dust column density up to E(B−V) ≈ 2.

2015-10-28
15:15
What processes set the structure of the Galactic disk
Prof. Hans-Walter Rix (MPIA)
SFB Seminar - The Milky Way System
ARI, basement seminar room; video broadcast to other institutes on request - please notify organizer
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Abstract
This is adapted from a keynote I gave at a recent ESO workshop on spectrosopic surveys. After a few broad comments on the role of theses surveys, I will talk about recent work with APOGEE that allowed to look at the abundance-dependent radial structure and the age structure of the Galactic disk empirically, spanning 4 to 15 kpc, with surprising and exciting results.

2015-10-14
16:00
Vertical heating of the Galactic disc: Contribution of infalling satellites
Reza Moetazedian (ARI/ZAH)
SFB Seminar - The Milky Way System
ARI (basement seminar room); video conference to LSW on request,
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Abstract
There exist few mechanisms which are believed to be responsible for the heating of the Milky Way disc, i.e. increasing the velocity dispersion of disc stars. Within the framework of this analysis, using high resolution N-body simulations, we would like to quantify the contribution of infalling satellite galaxies to the vertical heating of the galactic disc. In order to have a realistic picture, the properties of satellites are extracted from cosmological simulations of Milky Way like systems. We also take advantage of initial conditions for the case of isolated Milky Way which is in much better equilibrium state than previous studies.

2015-10-14
15:15
Modeling Galactic-Scale ISM-Dynamics and Star Formation
Prof. Ralf Klessen (ITA/ZAH)
SFB Seminar - The Milky Way System
ARI (basement seminar room); video conference to LSW on request,

2015-07-15
16:00
Carbon enhanced metal-poor stars: new insights from the TOPoS project
Piercarlo Bonifacio (GEPI, Observatoire de Paris)
SFB Seminar - The Milky Way System
ARI, ARI basement seminar room; broadcast to LSW Seminarraum Nordinstitut and MPIA Seminarraum
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Abstract
It has been known for the last twenty years, among metal-poor stars the fraction of carbon-enhanced metal poor stars (CEMP, [C/Fe]> +1) increases with decreasing metallicity. I will present new results from the TOPoS project, including three newly discovered CEMP stars with metallicity below -4.5, raising to a total of nine the known metal-poor stars in this metallicity regime. Eight out of nine of these stars are CEMP. Five of these nine stars are unevolved (TO or SGB) and only one has a measured Li abundance, about 0.4 dex below the Spite plateau. A low lithium abundance seems to be a general characteristic of these stars. Another striking characteristic of the extremely metal-poor stars is the very low scatter in the [X/Ca] ratios for all elements heavier than Si, in spite of the fact that they span 3 orders of magnitude in Fe (or Ca) abundance. Our proposed scenario for the formation of the first generations of stars, is the formation of several massive stars in a mini-halo, at least one of which should explode as a faint supernova, to produce the excess carbon. I will finally discuss future perspectives for the search of and analysis of EMP stars.

2015-07-15
15:15
Probing the effects of secular evolution in numerical simulations of the Milky Way
Robert Grand (HITS/ARI)
SFB Seminar - The Milky Way System
ARI, ARI basement seminar room; broadcast to LSW Seminarraum Nordinstitut and MPIA Seminarraum
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Abstract
In recent years, radial migration has been highlighted to be an important evolutionary process that has helped shape the current state of the Milky Way. For example, it can explain the scatter in the age-metallicity relation and metal distribution function in the solar neighbourhood, and has been indicated to affect structural parameters as well. To investigate this phenomenon, we perform a series of simulations with the state of the art Arepo hydrodynamics code, and make use of a cosmological zoom technique that allows us to simulate the evolution of a Milky Way sized haloes from z=127 to present day at high resolution. We focus on evolution after z=1, and find that radial migration does not change the radial metallicity gradient in galaxies with spiral structure only, but can flatten it if a bar is present. In all cases the metal distribution function broadens at all radii. We find also that radial migration does not seem responsible for disc thickening, and instead may actually help keep the disc thin. This is however a complicated process with many dependencies, including the formation history of the disc component (inside-out formation) and satellite interactions.

2015-07-01
16:00
The Pan-STARRS1 Astrometric Survey
Eugene Magnier (IfA, University of Hawaii)
SFB Seminar - The Milky Way System
MPIA Seminarraum; video broadcast to ARI basement seminar room,
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Abstract
The Pan-STARRS1 Science Consortium is preparing for the public release of data from the 5 year PS1 Sky Surveys. The 3pi Survey component includes ~75 billion measurements of ~3 billion stars and galaxies. The large data set allows us to explore a wide range of systematic effects, helping to tie down the astrometric and photometric calibration. I will discuss the upcoming release with an emphasis on astrometry.

2015-07-01
15:15
High-precision stellar spectroscopy and fundamental parameters of stars
Maria Bergemann (MPIA)
SFB Seminar - The Milky Way System
ARI basement seminar room; video broadcast to MPIA Seminarraum,
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Abstract
Spectroscopic observations of stars have shaped our understanding of the Galactic evolution and stellar structure. This is because spectra of stars are the only way to determine their chemical composition, which is the fundamental resource to study cosmic nucleosynthesis in different environments and on different time-scales. Research in this field has never been more exciting and important to astronomy: the ongoing and future large-scale stellar spectroscopic surveys are making gigantic steps along the way towards high-precision stellar, Galactic, and extra-galactic archaeology. However, the data we extract from stellar spectra are not strictly-speaking ‘observational’. These data - fundamental parameters and chemical abundances - heavily rely upon physical models, which describe atmospheres of stars and provide model predictions for the analysis of raw observations. I will describe our efforts to provide the most realistic models of radiation transport in stellar atmospheres, based upon 3D non-local thermodynamic equilibrium physics. I will outline the fundamental principles, show how these improvements transform quantitative spectroscopy, and discuss the implications for stellar and Galactic chemical evolution.

2015-06-17
16:00
Physical conditions in Orion's Veil
Dr. Nick Abel (University of Cincinnati)
SFB Seminar - The Milky Way System
ARI, ARI
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Abstract
Orion's Veil is a foreground cloud of gas and dust, between us and the Trapezium cluster, which is the primary source of extinction towards the Nebula. Observations in the radio and optical regime have allowed us to create maps of the extinction and line-of-sight magnetic field across the Veil. These maps, combined with optical and UV absorption line studies towards the Trapezium stars, provide a wealth of observational data which makes the Veil an ideal laboratory with which to study the physical processes in the ISM. This talk will review the observations of the Veil, and how these unique set of observations combined with theoretical calculations have improved our understanding of the geometry, chemistry, and energetics of the environment. Specifically, this merger of observation and theory has allowed us to determine that the Veil’s energetics is dominated by magnetic fields, have helped us to explain the lack of molecules in the region, and has allowed us to determine the thickness of the Veil and its distance away from the Trapezium.

2015-06-17
15:15
Mapping dust in the Galaxy in three dimensions with Gaia
Priv.-Doz. Dr. Coryn Bailer-Jones (MPIA)
SFB Seminar - The Milky Way System
ARI, ARI
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Abstract
We are developing a nonparametric model to reconstruct the three-dimensional (3D) distribution of dust in the Milky Way. Our approach uses observed line-of-sight extinctions towards stars at different positions in the Galaxy. These give the integrated dust density along each line-of-sight. Making weak assumptions about the correlation of the dust, we infer the most probable 3D distribution of dust which explains the observed extinctions, also at points which have not been observed. Given distances and extinctions estimated from the Gaia photometry and astrometry for tens of millions of stars, we plan to build a detailed map of dust in our Galaxy.

2015-05-20
16:00
Globular cluster models star by star
Dr. Anna Sippel (Swinburne University)
SFB Seminar - The Milky Way System
ARI (basement seminar room), NO video link,
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Abstract
Using N-body models of globular clusters can provide an excellent addition to observations and allows to analyze the clusters according to each single star's influence. Anna uses this approach to study remnant black hole dynamics or the influence of bright stars on cluster size and colour and shows some of the insights she and her collaborators have gained from 'observing' those models.

2015-05-20
15:15
SP_Ace: a new code to estimate stellar parameters and elemental abundances
Dr. Corrado Boeche (ZAH/ARI)
SFB Seminar - The Milky Way System
ARI (basement seminar room), NO video link,
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Abstract
Corrado will outline the method that SP_Ace employs to derive stellar parameters and chemical abundances and show its performances on synthetic and real spectra.

2015-05-06
16:00
4MOST - 4-meter Multi-Object Spectroscopic Telescope
Prof. Andreas Quirrenbach (ZAH/LSW)
SFB Seminar - The Milky Way System
ARI (basement seminar room), Video conference to MPIA and LSW
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Abstract
4MOST is a wide-field, high-multiplex spectroscopic survey facility under development for the VISTA telescope of the European Southern Observatory. Its main science drivers are in the fields of galactic archeology, high-energy physics, galaxy evolution and cosmology. Andreas will give a short introduction to the technical concept and scientific goals of 4MOST.

2015-05-06
15:15
A8: The Globular Cluster Contribution to the Build-up of the Galactic Halo
Prof. Eva K. Grebel (ZAH/ARI)
SFB Seminar - The Milky Way System
ARI (basement seminar room), Video conference to MPIA and LSW
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Abstract
Globular clusters in the Galactic halo are believed to have formed in part in situ or to come from accreted dwarf galaxies. In both cases, they can contribute stars to the halo field star population, particularly when experiencing dissolution processes due to internal or external effects. There is growing evidence that all massive globular clusters show light element abundance variations (possibly due to a second generation of star formation). A subset of stars lost from globular clusters can be identified in the halo due to their unusual element abundance ratios and allows us to constrain the fraction of halo field stars once born in massive globulars.

2015-02-04
16:00
The anatomy of the star-formation complex NGC346/N66 in the SMC
Sacha Hony (ZAH/ITA)
SFB Seminar - The Milky Way System
ARI, ARI
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Abstract
Sacha is a postdoc in the SFB and will be reporting on results related to his sub-project B1.

2015-02-04
15:15
Star formation at the centre of the Milky Way
Simon Glover (ZAH/ITA)
SFB Seminar - The Milky Way System
ARI, ARI
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Abstract
Simon will talk about the scientific goals of the SFB subproject B8 led by him, and will review the progress made on tackling these goals during the period when this was funded as a pilot SFB project.

2015-01-28
16:00
The census and kinematic structure of the Solar neighbourhood.
Bertrand Goldman (MPIA)
SFB Seminar - The Milky Way System
ARI, Seminar room basement
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Abstract
Bertrand will give an overview of the planned research in this new SFB subproject B7.

2015-01-28
15:15
Uncovering the Galactic stellar halo build-up through chemo-dynamics of globular clusters
Glenn van de Ven (MPIA)
SFB Seminar - The Milky Way System
ARI, Seminar room basement
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Abstract
Glenn will present an overview of the new SFB subproject A8, which focuses on Galactic halo globular clusters. Up to two thirds of these have likely been accreted as part of dwarf galaxies that got tidally disrupted. The inner parts of the compact GCs survived as fossil records of this build-up of the Galactic stellar halo.

2015-01-07
15:15
'SFB 881 in the second funding period'
Eva Grebel (ARI)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2015-01-07
15:15
'Dynamical modelling beyond vertical Jeans'
Alex Buedenbender (MPIA)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-11-26
15:15
"A HST multi band survey of the young massive star cluster Westerlund 2"
Peter Ziedler (ARI)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-11-26
15:15
"The  abilities  of  the new yebisu-OpenCL library of the phi-GRAPE+GPU code. The current performance analysis & status of the SUPERBOX+FFT/GPU code."
Oleksandr Veles (ARI)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-11-05
15:15
"An new method for the construction of N-body galaxy models in collisionless equilibrium"
Dennis Yurin (HITS)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-11-05
15:15
"Horizontal Branch Stars in Pan-Starrs"
John Vickers (ARI)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-10-29
15:15
"Reading the chemical evolutionary signatures of the Fornax dSph"
Ben Hendriks (LSW)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-10-29
15:15
"Dynamical modelling for extragalactic (and Galactic) tidal streams"
Nicola Amorisco (University of Copenhagen)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-02-05
14:15
"Bipolar jet launching from accretion disc- (MHD simulations and Physical evolution)"
Somayeh Sheikhnezami (MPIA)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-02-05
14:15
"Kinematically distinct stellar populations in the globular cluster M15"
Paolo Bianchini (MPIA)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-01-22
14:15
"Education and Public outreach activities for the SFB 881"
Cecilia Scorza (HdA)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-01-22
14:15
"3D Galactic dust extinction mapping"
Richard Hanson (MPIA)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-01-08
14:15
'3D Galactic dust extinction mapping'
Richard Hanson (MPIA)
SFB Seminar - The Milky Way System
ARI, basement seminar room

2014-01-08
14:15
'Launching Jets and Winds from alpha-omega-dynamo Disks'
Deniss Stepanovs (MPIA)
SFB Seminar - The Milky Way System
ARI, basement seminar room

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