Kavli Affiliate: Luis C. Ho
| First 5 Authors: Yang A. Li, Luis C. Ho, Jinyi Shangguan, Zhao-Yu Li, Yingjie Peng
| Summary:
Quiescent galaxies (QGs) typically have little cold gas to form stars. The
discovery of gas-rich QGs challenges our conventional understanding of the
evolutionary paths of galaxies. We take advantage of a new catalog of nearby,
massive galaxies with robust, uniformly derived physical properties to better
understand the origin of gas-rich QGs. We perform a comparative analysis of the
cold interstellar medium and star formation properties of carefully matched
samples of galaxies with varying degrees of star formation activity and gas
richness. QGs with different gas content have virtually identical morphological
types, light concentration, mass-size relation, stellar age, dark matter halo
mass, and black hole activity. The only distinguishing characteristic is the
environment. Gas-rich satellite QGs reside in a lower-density environment than
their gas-poor counterparts, as a consequence of which they manage to retain
their gas and experience a higher probability of cold gas accretion or gas-rich
mergers. The environmental densities of central QGs are similar regardless of
their gas content. We suggest that the cold gas resides mainly in the outskirts
of the gas-rich QGs, where bars, if present, cannot transport it inward
efficiently to fuel central star formation. The prominent bulges in gas-rich
QGs stabilize the cold gas from fragmentation and leads to low star formation
efficiency.
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