Do post-starburst galaxies host compact molecular gas reservoirs?. Issue 1 (18th October 2022)

• Record Type: Journal Article
• Authors: Sun, Fengwu; Egami, Eiichi
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 517:Issue 1(2022)
• Page Start: L126
• Page End: L131
• Publication Date: 2022-10-18
• Subjects: galaxies: evolution -- galaxies: ISM -- galaxies: star formation; Astronomy -- Research -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnrasl/slac128
• Languages: English
• ISSNs: 1745-3933

Abstract

ABSTRACT: We analysed the high-resolution (up to ∼0.2 arcsec) ALMA CO (2–1) and 1.3 mm dust continuum data of eight gas-rich post-starburst galaxies (PSBs) in the local Universe, six of which had been studied by a recent work. In contrast to this study reporting the detections of extraordinarily compact (i.e. unresolved) reservoirs of molecular gas in the six PSBs, our visibility-plane analysis resolves the CO (2–1) emission in all eight PSBs with effective radii ( R e, CO ) of $0.8_{-0.4}^{+0.9}$ kpc, typically consisting of gaseous components at both circumnuclear and extended disc scales. With this new analysis, we find that the CO sizes of gas-rich PSBs are compact with respect to their stellar sizes (median ratio $=0.43_{-0.21}^{+0.27}$ ), but comparable to the sizes of the gas discs seen in local luminous infrared galaxies (LIRGs) and early-type galaxies. We also find that the CO-to-stellar size ratio of gas-rich PSBs is potentially correlated with the gas depletion time-scale, placing them as transitional objects between LIRGs and early-type galaxies from an evolutionary perspective. Finally, the star formation efficiency of the observed PSBs appear consistent with those of star-forming galaxies on the Kennicutt–Schmidt relation, showing no sign of suppressed star formation from turbulent heating.