The stellar populations of quiescent ultra-diffuse galaxies from optical to mid-infrared spectral energy distribution fitting

We use spectral energy distribution (SED) fitting to place constraints on the stellar population properties of 29 quiescent ultra-diffuse galaxies (UDGs) across different environments. fully Bayesian routine PROSPECTOR coupled with archival data in optical, near, and mid-infrared from Spitzer WISE under assumption an exponentially declining star formation history. recover mass, age, metallicity, dust content, time scales photometric redshifts (photo-zs) UDGs studied. Using data, we probe existence UDGs. Although its presence cannot be confirmed, find that inclusion small amounts models brings populations closer those reported spectroscopy. Additionally, fit all galaxies. a high accuracy recovering photo-zs compared spectroscopy, allowing us provide new photo-z estimates for three field unknown distances. evidence dependence environment, being systematically younger than their cluster counterparts. Lastly, lie below mass--metallicity relation normal dwarf Particularly, globular (GC)-poor are consistently more metal-rich GC-rich ones, suggesting GC-poor may puffed-up dwarfs, while most better explained by failed galaxy scenario. As byproduct, show two our sample, NGC 1052-DF2 1052-DF4, share equivalent properties, ages consistent 8 Gyr. This finding supports scenarios where were formed together.