The hidden chemistry at the heart of the Milky Way
Astronomers have unveiled a complex network of filaments of cosmic gas in in the central region of our Milky Way with unprecedented detail and precision. Obtained with the Atacama Large Millimeter/submillimeter Array (ALMA), this dataset allows to probe the lives of stars close to the supermassive black hole at its centre. The study is linked to a coordinated, multiscale simulation framework, in which the research group of Ralf Klessen from the Centre for Astronomy of Heidelberg University (ZAH) is also significantly involved.
The new observations provide a unique view of the raw material from which stars form within the so-called Central Molecular Zone (CMZ) of our Galaxy. It is the first time the cold gas across this whole region has been explored in such detail.
“It’s a place of extremes, invisible to our eyes, but now revealed in extraordinary detail,” says Ashley Barnes, an astronomer at the European Southern Observatory (ESO) in Germany who is part of the team that obtained the new data.
The region mapped in the new data set spans more than 650 light-years. It harbors dense clouds of gas and dust, surrounding the supermassive black hole at the centre of our Galaxy. “It is the only galactic nucleus close enough to Earth for us to study in such fine detail,” says Barnes. The dataset reveals the CMZ like never before, from gas structures dozens of light-years across all the way down to small gas clouds around individual stars.
ACES - the ALMA CMZ Exploration Survey - specifically explores cold molecular gas. The survey unpacks the intricate chemistry of the CMZ, detecting dozens of different molecules, from simple ones such as silicon monoxide to more complex organic ones like methanol, acetone or ethanol.
Cold molecular gas flows along filaments feeding into clumps of matter out of which stars can grow. In the outskirts of the Milky Way we know how this process happens, but within the central region the events are much more extreme. “The CMZ hosts some of the most massive stars known in our Galaxy, many of which live fast and die young, ending their lives in powerful supernova explosions, and even hypernovae,“ says ACES leader Steve Longmore, a professor of astrophysics at Liverpool John Moores University, UK. With ACES, astronomers hope to better understand how these phenomena influence the birth of stars and whether our theories of star formation hold in extreme environments.
The survey is paired with a coordinated multi-scale simulation framework, which is where Ralf Klessen (ZAH), Robin Tress (Observatoire de Sauverny) and Mattia Sormani (Como Lake Centre for AstroPhysics), who both have worked as researchers at ZAH in the past, play particularly important roles. Their science objective is to determine the mechanisms driving mass flows as a function of size scale and location.
The contributions from Heidelberg to this project stem from the modeling of the Central Molecular Zone. This modeling is primarily carried out by Robin Tress and Mattia Sormani and was initiated during their time at ZAH. “For this modeling, the physical implementation of microphysical and astrochemical processes is essential,“ says Ralf Klessen, Heidelberg star formation expert and head of the ZAH research group, where these processes had been integrated into the simulation software AREPO, and where the radiation-magnetohydrodynamic calculations were performed.
To collect this new dataset, astronomers used ALMA, which is operated by ESO and partners in Chile’s Atacama Desert. This is the first time such a large area has been scanned with this facility in the Galactic centre, which seen in the sky is as long as three full Moons side-by-side.
“We anticipated a high level of detail when designing the survey, but we were genuinely surprised by the complexity and richness revealed in the final mosaic," says Katharina Immer, an ALMA astronomer at ESO who is also part of the project. The data from ACES are presented in five papers accepted for publication in Monthly Notices of the Royal Astronomical Society, with a sixth in the final review stages.
ORIGINAL PUBLICATION
ACES overview paper
ADDITIONAL INFORMATION
ESO press release
European Southern Observatory
Photos of ALMA
Research Group of Ralf Klessen
SCIENTIFIC CONTACT
Prof. Dr. Ralf Klessen
Centre for Astronomy of Heidelberg University (ZAH)
Institute for Theoretical Astrophysics (ITA)
klessen(at)uni-heidelberg.de
CONTACT FOR MEDIA INQUIRIES
Dr. Guido Thimm
Centre for Astronomy of Heidelberg University (ZAH)
thimm@uni-heidelberg.de
