Caught in the Act of Quenching? -- A Population of Post-Starburst Ultra-Diffuse Galaxies

Abstract

We report the discovery of post-starburst ultra-diffuse galaxies (UDGs), identified through spectroscopic analysis with KCWI at the Keck II Telescope. Our analysis is based on a sample of 44 candidate UDGs selected from the Systematically Measuring Ultra-Diffuse Galaxies (SMUDGes) program. Our measured spectroscopic redshifts reveal $\sim 85\%$ of the entire KCWI sample exhibit large physical sizes ($R_e\gtrsim 1\mathrm{kpc}$) and low surface brightnesses ($24\lesssim {\mu }_{0,g}\lesssim 25$ mag arcsec${}^{-2}$) which categorize them as UDGs. We find $20\%$ of the confirmed UDG population contain post-starburst (or K+A) features, characterized by minimal to no emission in H$\beta$ indicative of quenched star formation and a predominant presence of spectral A-type stars. In surveying the local environments of the post-starburst UDGs, we find that nearly half are isolated systems, which is unusual given that isolated UDGs are most commonly found to be star-forming. Two of these systems reside $2-3R_{\mathrm{vir}}$ away from potential nearby massive hosts ($M_{\star }>10^{10}{\mathrm{M}}_{\odot }$), indicating the absence of environmental influence. These post-starburst UDGs may represent systems experiencing star formation feedback such that a recent burst may lead to (at least temporary) quenching. Overall, our results highlight the potentially diverse quenching pathways of UDGs in the local Universe.

10 pages, 5 figures, 1 table, Published in OJAp

Cited by in corpus (1)

• Ultra Diffuse Galaxies in clusters : the peculiar gas loss of VCC 1964