The ATLAS3D project - XVIII. CARMA CO imaging survey of early-type galaxies

TL;DR

This study presents a comprehensive survey of molecular gas in early-type galaxies, revealing diverse morphologies and a correlation between galaxy mass and gas distribution, with implications for galaxy evolution.

Contribution

It provides the largest, most detailed CO imaging survey of early-type galaxies, linking molecular gas morphology to galaxy properties and merger history.

Findings

Molecular gas and dust distributions are well aligned in early-type galaxies.

Galaxies show diverse CO morphologies, including discs, rings, and disrupted structures.

Most massive galaxies tend to host molecular gas in disc form.

Abstract

We present the Combined Array for Research in Millimeter Astronomy (CARMA) ATLAS3D molecular gas imaging survey, a systematic study of the distribution and kinematics of molecular gas in CO-rich early-type galaxies. Our full sample of 40 galaxies (30 newly mapped and 10 taken from the literature) is complete to a 12CO(1-0) integrated flux of 18.5 Jy km/s, and it represents the largest, best-studied sample of its type to date. A comparison of the CO distribution of each galaxy to the g-r color image (representing dust) shows that the molecular gas and dust distributions are in good agreement and trace the same underlying interstellar medium. The galaxies exhibit a variety of CO morphologies, including discs (50%), rings (15%), bars+rings (10%), spiral arms (5%), and mildly (12.5%) and strongly (7.5%) disrupted morphologies. There appear to be weak trends between galaxy mass and CO morphology, whereby the most massive galaxies in the sample tend to have molecular gas in a disc morphology. We derive a lower limit to the total accreted molecular gas mass across the sample of 2.48x10^10 Msuns, or approximately 8.3x10^8 Msuns per minor merger within the sample, consistent with minor merger stellar mass ratios.