The CO Legacy Database for GASS

The CO Legacy Database for GASS (COLD GASS) is a large program that measured the molecular gas contents of 366 massive galaxies through CO(1-0) observations using the IRAM 30-m telescope. COLD GASS is an international collaboration led by Guinevere Kauffmann (MPA), Amelie Saintonge (MPE, UCL), and Carsten Kramer (IRAM).

Since cold gas is the fuel for star formation, we need a better picture of how galaxies are supplied in gas, how they process this gas into stars, and how some of the gas is then returned to the outside
environment. Only then can we hope to really understand how galaxies evolve. Key aspects of the survey are: (1) a purely mass-selected, SDSS-based sample, fully representative of the local galaxy population with log(M*/Msun)>10.0 - the sample therefore includes everything from star-forming spirals to passive ellipticals, (2) a homogeneous observing strategy that allowed us to put stringent upper-limits on the molecular gas contents of passive galaxies, (3) a very rich complementary multi-wavelength dataset that allows for the derivation of robust scaling relations between the cold gas contents of galaxies (both atomic and molecular) and their stellar, star formation, chemical, and structural properties.

 
CO 1-0 spectra and SDSS images of 6 galaxies observed as part of the COLD GASS survey.

 

The survey so far has been used to trace the abundance of molecular gas in galaxies as a function of their mass, colour and morphology. Science highlights from the survey include studies of the variations of the molecular mass fraction and of star formation efficiency across the local galaxy population (Saintonge et al. 2011a,b, 2012). The CO observations allowed to identify a sample of galaxies with no more than trace amounts of molecular gas and with no significant traces of star formation. However, these galaxies do contain large amounts of atomic gas. One key question therefore is: Why can these galaxies be rich in atomic gas and yet not be able to form stars ? To address this and other questions, the sample is now routinely used to test and constrain the prediction of galaxy evolution models (e.g. Lagos et al. 2011, Krumholz & Dekel 2012, Kauffmann et al. 2012, Popping et al. 2012), and to anchor studies of the redshift evolution of molecular gas in galaxies (e.g. Tacconi et al. 2013, Saintonge et al. 2013).

Relation between the amount of gas in a galaxy and its color. While the atomic gas fraction is a continuous function of color, there is a sharp break in the molecular gas abundance in the reddest galaxies

 

The official COLD GASS repository is at MPA and IRAM. The COLD GASS catalog provides integrated CO(1-0) line fluxes (or upper limits), with and without aperture corrections, as well as line widths and the inferred total molecular gas masses. Our public catalog also includes a range of measurements from SDSS/GALEX imaging and our Arecibo and optical spectroscopy observing campaigns. These includes among others stellar masses, star formation rates, atomic gas masses, morphological measurements, and metallicities.

Please do not hesitate to contact Guinevere Kauffmann, Amelie Saintonge, and Carsten Kramer to tell them about your use of the data for scientific analysis. The following acknowledgement would be appreciated: "This work made use of COLD GASS, 'The CO Legacy Database for GASS' (Saintonge et al. 2011a,b, 2012)." Acknowledgement of the COLD GASS project is also appreciated if data are used in public presentations.

 

Last updated: November 20, 2013