2025/11/20 by Haonan Zheng, Fangzhou Jiang, Zheng, Haonan +5 · 1 citation
Engineering · Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Space Technology and Applications
paper · pdf · doi:10.48550/arxiv.2511.16726
openalex publication_date 2025/11/20 · openalex created_date 2025/11/25 · openalex updated_date 2026/07/28
We present our investigation of HI-rich 'Dark' galaxiEs in Simulations (HIDES), specifically using the Hestia and Auriga simulations in this work. We select galaxies that are faint (Mg > -10) and contain sufficient HI (MHI > 105 M_\odot), and identify 89 such objects, only one of which is completely starless. Their demographics generally converge across simulations of different resolution, with M200 ∼ 109.5 M_\odot, Mgas ∼ 107.4 M_\odot, MHI ∼ 106.5 M_\odot, M_* ∼ 105.6 M_\odot, low gas metallicity, little or no current star formation, and a mean stellar age of ∼ 11 Gyr, and with some of them can survive in dense environments as close as ∼ 300 kpc from a Milky-Way mass neighbor. We find a large scatter in their HI density profiles and MHI - M_* relation, which cannot be fully explained by current halo mass or concentration, but can be attributed to ram pressure stripping in dense environments, past mergers, and stellar feedback. In particular, close encounters with massive halos and dense environments can reshape the HI content, which may explain the asymmetric HI map of an intriguing observed analogue, Cloud-9. An empirical fit, n = 0.25 (dMW/1 Mpc)-1.4 Mpc-3, based on their number density extended to 3.7 Mpc in constrained local volume simulations, is also provided to aid observational forecasts. We conclude that both mass assembly history and environmental history play a crucial role in the formation and subsequent diversity of these galaxies.