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From Cloud to Star Formation

Periodic Reporting for period 3 - CSF (From Cloud to Star Formation)

Reporting period: 2018-09-01 to 2020-02-29

The goal of the project is to study the global processes related to star formation on all spatial scales. This starts on large scales where the diffuse atomic gas forms molecular clouds which then collapse and form stars on small scales. During these processes, atomic gas converts to the molecular phase, clouds become dense and fragment and accretion disks and their associated outflows form. The physical scales covered range from several 10ths of parsec clouds to accretion disks sizes on the order of 100AU.

The project is observationally driven and based on two PI-led large observing programs at two of the most advanced radio and mm interferometers, the Very Large Array (VLA), and the Northern Extended Millimeter Array (NOEMA, formerly known as Plateau der Bute Interferometer, PdBI). The THOR program at the VLA investigates the cloud formation and conversion of atomic to molecular gas, as well as feedback processes back to the interstellar medium (ISM). To reach these goals, THOR observes the Milky Way in atomic HI, molecular OH, and cm continuum and radio recombination lines tracing the ionized components of the ISM. At smaller spatial scales, the CORE conduceted with NOEMA studies the fragmentation of the gas clumps to form clusters, the formation of accretion disks and outflows, and the gas infall rates as proxy for the accretion rates. Assisted by Atacama Large Millimeter Array (ALMA) observations, we are investigating a sample of high-mass star-forming regions at the highest spatial resolution of (<=0.2’’) to dissect the physical processes during the assembly of the highest mass stars.
All data for the project are taken, and most of the calibration and imaging of the data has been conducted in the last couple of years. During that period sub-sets of the data were already scientifically exploited, analyzed and interpreted. Currently, we are following diverse approaches to address the scientific questions. On the one hand, several individually very interesting targets of the two surveys are investigated as case-studies, whereas on the other hand we also already started addressing several topics from a statistical and sample point of view to give answers in a more general sense. These diverse approaches have resulted already in a number of publications outlined in the publications section.

Most of the ERC money is used for postdocs and Phd students to scientifically work on the data. Three postdocs and one PhD have been hired in that framework (one additional PhD student was already working beforehand on the project. His salary is not funded by this project). In addition to this, we acquired computing resources to efficiently reduce the data and analyze the results.
The innovative approach of this ERC program in connecting the relevant scales is based on two large observing programs at the worlds leading cm and mm interferometers, the VLA and NOEMA. The connection from large scales of molecule and cloud formation, down to small scales of individual star formation, and then feeding back energy into the interstellar medium allows the project to study the properties of the interstellar medium, atomic/molecular clouds and the ISM in a unique and interconnected way.