Tidal features of classical Milky Way satellites in a Λ cold dark matter universe

Abstract

We use the APOSTLE cosmological hydrodynamic simulations to examine the effects of tidal stripping on cold dark matter (CDM) subhaloes that host three of the most luminous Milky Way (MW) dwarf satellite galaxies: Fornax, Sculptor, and Leo I. We identify simulated satellites that match the observed spatial and kinematic distributions of stars in these galaxies, and track their evolution after infall. We find ∼ 30% of subhaloes hosting satellites with present-day stellar mass 10 6 -10 8 M ⊙ experience > 20% stellar mass loss after infall. Fornax analogues have earlier infall times compared to Sculptor and Leo I analogues. Star formation in Fornax analogues continues for ∼ 3-6 Gyr after infall, whereas Sculptor and Leo I analogues stop forming stars < 2-3 Gyr after infall. Fornax analogues typically show more significant stellar mass loss and exhibit stellar tidal tails, whereas Sculptor and Leo I analogues, which are more deeply embedded in their host DM haloes at infall, do not show substantial mass loss due to tides. When additionally comparing the orbital motion of the host subaloes to the measured proper motion of Fornax we find the matching more difficult; host subhaloes tend to have pericentres smaller than that measured ones for Fornax itself. From the kinematic and orbital data, we estimate that Fornax has lost 10 − 20% of its infall stellar mass. Our best estimate for the surface brightness of a stellar tidal stream associated with Fornax is Σ ∼ 32.6 mag arcsec −2 , which may be detectable with deep imaging surveys such as DES and LSST.

The survival of globular clusters in a cuspy Fornax

“…However, our estimates are in good agreement with the abundancematching result of Read et al (2019), who found a total mass of ∼2 × 10 10 M . The discrepancy could be due to the Fornax halo having experienced a large amount of tidal stripping, as suggested by Fattahi et al (2016), Wang et al (2017), andGenina et al (2020). These studies used hydrodynamical simulations to select Fornax counterparts by matching the observed stellar velocity dispersion and stellar half-mass radius in the first two of these papers and the stellar mass in the last one.…”

“…2. Secondly, the Fornax dSph is thought to have experienced considerable mass-loss due to tidal stripping by our galaxy (Wang et al 2017;Borukhovetskaya et al 2021). For satellite dwarfs, we refer to the M 200 of their main progenitors, before they became a satellite of a more massive host, as their host halo mass.…”

“…2, which is for z = 0 isolated Fornax-mass galaxies, and mass estimates for the actual Fornax dSph galaxy is complicated because (i) the infall time of Fornax is largely unconstrained (Fillingham et al 2019) and (ii) the degree of tidal stripping in Fornax is highly uncertain (e.g. Wang et al 2017). For example, Borukhovetskaya et al (2021) have shown that current orbital solutions for Fornax allow from very little to as much as 50 per cent DM mass-loss from within the stellar halfmass radius.…”

Both starvation and outflows drive galaxy quenching

“…In the absence of stellar mass loss (e.g. through tidal stripping, Chang et al 2013;Tollet et al 2017;Wang et al 2017), this implies that galaxies form a minor amount of additional stellar mass during the quenching phase. However, high-z star-forming galaxies have large gas fractions (e.g.…”

Dark matter in dwarf spheroidal galaxies and indirect detection: a review

“…However the hydro simulations are most valuable in determining the structure of the stellar distributions, and how these distributions differ from that of the dark matter. Also, they can determine whether there is faint tidal debris associated with a dSph beyond the current photometric thresholds [53,54,55]. Satellites in cosmological simulations with baryons are found to be more spherical than field halos [48], which may be explained by tidal stripping [56].…”