ALMA archive mining: A3COSMOS

 A3COSMOS is a joint project between our research group and that led by E. Schinnerer at the Max-Planck-Institut für Astronomie (MPIA). Its goal is the full exploration of the ALMA observations toward millions of galaxies in the COSMOS two square degree field. ALMA is the most powerful and sensitive (sub-)millimeter interferometer array, but its small field of view (~30") makes dedicated large-area surveys very expensive, in fact too expensive for the large samples of galaxies needed to properly understand galaxy evolution throughout cosmic history. Fortunately, through many individual Principal Investigators (PI) observations, ALMA has by now deeply mapped a significant area of some popular extra-galactic survey fields, such as the COSMOS field.

The goal of our A3COSMOS project has been to exploit the ALMA science archive to assemble albeit spotty, but deep (sub)millimeter survey of the COSMOS field. Our carefully and uniformly reduced database is provided to the COSMOS collaboration and the larger astronomy community. It can be used to study the formation of galaxies by measuring their star formation and interstellar medium properties, or performing 'blind' CO and [CII] line searches.

To assemble this database, we developed an automatic tool to query, retrieve and image the ALMA archive. The MPIA group developed a pipeline to perform the source extraction within these images and cross-match those with the wealth of panchromatic observations available in the COSMOS field. Our database, which we update annually, currently covers an area of about 520 square arcmin including 2500 galaxies detected with ALMA. This unique sample allows us to pursue a number of exciting studies.

Recently, we extended A3COSMOS to include ALMA observations from the GOODS-South field, which is another extra-galactic survey field with plenty of panchromatic data. GOODS-South spans 10 by 16 arcmin, and along the multitude of individual ALMA pointings, it includes several ALMA blind surveys, adding up to about 150 square arcmin of area including 800 galaxies.