Periodic Reporting for period 5 - PhysSF (Physics of Star Formation and Its Regulation)
Reporting period: 2022-10-01 to 2023-09-30
In the past decade we learned when and where stellar mass was built up in galaxies through cosmic time, now we must
understand the physical causes in order to answer `How do galaxies form and evolve?’. This ERC project was designed
to advance our understanding of the physics of the star formation process and its regulation in typical
star-forming galaxies. It consists of two complementary parts: (A) an unparalleled characterization of
the star formation process in nearby galaxies through exploitation of the revolutionary capabilities of the latest ground-
and space-based observatories. This study will constrain the key physical parameters for the star-formation process on only
50-100pc scales - the scale of large HII regions and their predecessors, giant
molecular clouds (PHANGS -- Physics at High Angular resolution in Nearby GalaxieS). At this crucial scale, the surveys will
uncover the physical conditions that control and regulate the star formation process. Part (B) will place
the results of part (A) in a cosmological context, by characterizing key galaxy quantities in fully representative galaxy samples across
cosmic time utilising data products from the A3COSMOS effort as part of this
ERC project. In addition to critically needed constraints on the conditions that govern the star formation process, this
ERC project provides observational benchmark for state-of-the-art galaxy simulations and models.
understand the physical causes in order to answer `How do galaxies form and evolve?’. This ERC project was designed
to advance our understanding of the physics of the star formation process and its regulation in typical
star-forming galaxies. It consists of two complementary parts: (A) an unparalleled characterization of
the star formation process in nearby galaxies through exploitation of the revolutionary capabilities of the latest ground-
and space-based observatories. This study will constrain the key physical parameters for the star-formation process on only
50-100pc scales - the scale of large HII regions and their predecessors, giant
molecular clouds (PHANGS -- Physics at High Angular resolution in Nearby GalaxieS). At this crucial scale, the surveys will
uncover the physical conditions that control and regulate the star formation process. Part (B) will place
the results of part (A) in a cosmological context, by characterizing key galaxy quantities in fully representative galaxy samples across
cosmic time utilising data products from the A3COSMOS effort as part of this
ERC project. In addition to critically needed constraints on the conditions that govern the star formation process, this
ERC project provides observational benchmark for state-of-the-art galaxy simulations and models.
PHANGS — Physics at High Angular resolution in Nearby GalaxieS:
Four large observing programs on ALMA, HST, JWST, and VLT/MUSE have mapped the star-forming disks of a representative sample of nearby,
massive galaxies on the main sequence of star-forming galaxies in tracers of the interstellar medium (dust, molecular & ionized gas)
as well as the stellar populations. The resulting unique multi-wavelength database forms the basis for studying the physics underlying the
star formation process on cloud-scales. Data preparation/calibration and analysis were done in collaboration with members of the PHANGS team.
Processed science-ready data products from the observing programs were publicly released in the form of images and catalogs via the observatory
archives and CADC. Newly developed methods included an automatic reduction and imaging pipeline for ALMA data, a new robust kinematic analysis
tool, and 2D metallicity mapping via machine learning methods among others. Key results from this project appear in an invited review article,
while results are presented in over 100 peer-reviewed publications by the PHANGS team (~10% led by ERC group members).
On cloud-scales, variations in molecular gas properties and its ability to form massive stars are linked to the local environment demonstrating
unambiguously that the kpc-scale physical conditions set the cloud-scale properties. Determination of the molecular cloud life-cycle shows a
short ramp up time leading to cloud collapse and the formation of massive stars that is followed be an equally short cloud dispersal time lasting
only a few Myr. This implies that radiation and winds from massive stars start the clearing of the gas reservoir surrounding newly formed stars
before the first core-collapse supernovae explode. Gas-rich galaxy centers stand out as extreme star formation environments in disk galaxies.
A3COSMOS — Automatic mining for the ALMA Archive in the COSMOS field:
A procedure for (semi-)automatic mining of the ALMA archive in the COSMOS field (A3COSMOS) has been developed and implemented
in collaboration with members of the German ALMA Regional Centre (ARC) node. The resulting (blind and prior-based) catalogs have
been thoroughly tested via sophisticated simulations providing robust estimates of the (sub-)mm source parameters plus
associated uncertainties, the completeness and purity. The first version of the catalog contained about 1,000 sources from more
than 1,500 images. Combined with publicly available multi-band photometric catalogs, a catalog of >650 (sub-)mm detected galaxies
including their key properties (redshift, stellar, star formation rate) has been created. Both catalogs were publicly released and used by
members of the astronomical community. In the meantime, a third catalog adding more data has been compiled by team members in
Bonn and used for science exploitation demonstrating the robustness of the pipeline.
The catalogs have enabled comprehensive studies of the cosmic evolution of the (cold) gas content and gas depletion time of galaxies.
Scientific exploitation of these catalogs as part of this ERC project resulted in the first comprehensive analysis of the cosmic evolution
of the cold gas content and cold gas depletion time showing general agreement with results using different methodologies and revealing
a bias in the sample selection which might impact the inferred relations for the galaxy populations that are currently not probed.
This publication further includes a thorough assessment of different methods to obtain the cold gas mass from (sub-)mm continuum
measurements including the potential impact of metallicity variations over cosmic time.
Tools allowing for the structural analysis of the stellar mass distribution of massive, star-forming galaxies in the early universe have been
developed and applied to a pilot sample. Showing that the stellar mass distribution is quite compact and that the overall properties of these
massive galaxies are consistent with being the progenitors of today's massive elliptical galaxies. Exploring different CO emission lines in local
and high redshift galaxies reveal a dependence of the CO excitation on the interstellar radiation field. This together with extensive modeling
of the expected CO excitation is presented in a publication.
Four large observing programs on ALMA, HST, JWST, and VLT/MUSE have mapped the star-forming disks of a representative sample of nearby,
massive galaxies on the main sequence of star-forming galaxies in tracers of the interstellar medium (dust, molecular & ionized gas)
as well as the stellar populations. The resulting unique multi-wavelength database forms the basis for studying the physics underlying the
star formation process on cloud-scales. Data preparation/calibration and analysis were done in collaboration with members of the PHANGS team.
Processed science-ready data products from the observing programs were publicly released in the form of images and catalogs via the observatory
archives and CADC. Newly developed methods included an automatic reduction and imaging pipeline for ALMA data, a new robust kinematic analysis
tool, and 2D metallicity mapping via machine learning methods among others. Key results from this project appear in an invited review article,
while results are presented in over 100 peer-reviewed publications by the PHANGS team (~10% led by ERC group members).
On cloud-scales, variations in molecular gas properties and its ability to form massive stars are linked to the local environment demonstrating
unambiguously that the kpc-scale physical conditions set the cloud-scale properties. Determination of the molecular cloud life-cycle shows a
short ramp up time leading to cloud collapse and the formation of massive stars that is followed be an equally short cloud dispersal time lasting
only a few Myr. This implies that radiation and winds from massive stars start the clearing of the gas reservoir surrounding newly formed stars
before the first core-collapse supernovae explode. Gas-rich galaxy centers stand out as extreme star formation environments in disk galaxies.
A3COSMOS — Automatic mining for the ALMA Archive in the COSMOS field:
A procedure for (semi-)automatic mining of the ALMA archive in the COSMOS field (A3COSMOS) has been developed and implemented
in collaboration with members of the German ALMA Regional Centre (ARC) node. The resulting (blind and prior-based) catalogs have
been thoroughly tested via sophisticated simulations providing robust estimates of the (sub-)mm source parameters plus
associated uncertainties, the completeness and purity. The first version of the catalog contained about 1,000 sources from more
than 1,500 images. Combined with publicly available multi-band photometric catalogs, a catalog of >650 (sub-)mm detected galaxies
including their key properties (redshift, stellar, star formation rate) has been created. Both catalogs were publicly released and used by
members of the astronomical community. In the meantime, a third catalog adding more data has been compiled by team members in
Bonn and used for science exploitation demonstrating the robustness of the pipeline.
The catalogs have enabled comprehensive studies of the cosmic evolution of the (cold) gas content and gas depletion time of galaxies.
Scientific exploitation of these catalogs as part of this ERC project resulted in the first comprehensive analysis of the cosmic evolution
of the cold gas content and cold gas depletion time showing general agreement with results using different methodologies and revealing
a bias in the sample selection which might impact the inferred relations for the galaxy populations that are currently not probed.
This publication further includes a thorough assessment of different methods to obtain the cold gas mass from (sub-)mm continuum
measurements including the potential impact of metallicity variations over cosmic time.
Tools allowing for the structural analysis of the stellar mass distribution of massive, star-forming galaxies in the early universe have been
developed and applied to a pilot sample. Showing that the stellar mass distribution is quite compact and that the overall properties of these
massive galaxies are consistent with being the progenitors of today's massive elliptical galaxies. Exploring different CO emission lines in local
and high redshift galaxies reveal a dependence of the CO excitation on the interstellar radiation field. This together with extensive modeling
of the expected CO excitation is presented in a publication.
The first comprehensive database for cloud-scale studies of the star formation process in a representative sample of nearby,
massive main sequence galaxies provides a unique resource for the community and the ERC project has demonstrated the richness
of scientific questions that can be addressed. The emerging relations between galaxy components (ISM, stars) at cloud-scales show
a significant dependence on galactic environment pointing towards new exciting directions to explore for furthering our understanding
of the physics of the star formation process.
The systematic exploitation of the ALMA imaging in the COSMOS field is providing new insights into how the gas fraction and gas depletion
time of galaxy populations evolve over cosmic time. The obtained photometric catalogs in conjunction with a homogeneous sub-mm detected
galaxies catalog form a dataset of long-term value for the community. The combination of diverse observing programs have provided an insight
into the effects of selection biases when studying the gas content. Further the database holds the key to identify currently missed populations which
could potentially significantly contribute to the cosmic star formation density in the early universe.
massive main sequence galaxies provides a unique resource for the community and the ERC project has demonstrated the richness
of scientific questions that can be addressed. The emerging relations between galaxy components (ISM, stars) at cloud-scales show
a significant dependence on galactic environment pointing towards new exciting directions to explore for furthering our understanding
of the physics of the star formation process.
The systematic exploitation of the ALMA imaging in the COSMOS field is providing new insights into how the gas fraction and gas depletion
time of galaxy populations evolve over cosmic time. The obtained photometric catalogs in conjunction with a homogeneous sub-mm detected
galaxies catalog form a dataset of long-term value for the community. The combination of diverse observing programs have provided an insight
into the effects of selection biases when studying the gas content. Further the database holds the key to identify currently missed populations which
could potentially significantly contribute to the cosmic star formation density in the early universe.