The undiscovered ultra-diffuse galaxies of the Local Group

Monday 23 Jan 2023, 13:50 → 14:10 Europe/Rome

0/0-3 - Sala Rosino (Dipartimento di Fisica e Astronomia - Edificio ex-Rizzato)

Speakers: Nicola Bellucco (Università degli Studi di Padova)

Ultra-diffuse galaxies (UDGs) are attractive candidates to probe cosmological models and test theories of galaxy formation at low masses; however, they are difficult to detect because of their low surface brightness. In the Local Group (LG) a handful of UDGs have been found to date, most of which are satellites of the Milky Way and M31, and only two are isolated galaxies. It is unclear whether so few UDGs are expected. We address this by studying the population of UDGs formed in hydrodynamic constrained simulations of the LG from the HESTIA suite. For a LG with mass MLG(<2.5Mpc)=8×10¹² M⊙, we predict that there are 12±3 UDGs (68 per cent confidence) with stellar masses 10⁶≤M∗/M⊙<10⁹, and effective radii Re≥1.5kpc, in the field of the LG, of which 2⁺²_-1 (68 per cent confidence) are detectable in the footprint of the Sloan Digital Sky Survey (SDSS). Accounting for survey incompleteness, we find that up to 82, 90, and 100 per cent of all UDGs in the LG field would be observable in a future all-sky survey with a depth similar to the SDSS, the Dark Energy Survey, or the Legacy Survey of Space and Time, respectively. Our results suggest that there is a population of UDGs in the LG awaiting discovery.

2212.05066.pdf

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