Tidal features of classical Milky Way satellites in a $\Lambda$CDM universe

TL;DR

This study uses cosmological simulations to analyze tidal effects on Milky Way satellite galaxies, revealing their mass loss, star formation history, and potential for detectable stellar streams.

Contribution

It provides the first detailed simulation-based analysis of tidal stripping effects on MW dwarf satellites, linking orbital history to observable features.

Findings

Approximately 30% of satellites with stellar mass 10^6-10^8 M_sun experience >20% stellar mass loss.

Fornax analogues show earlier infall and longer star formation post-infall compared to Sculptor and Leo I.

Predicted surface brightness of Fornax's stellar tidal stream is around 32.6 mag/arcsec^2.

Abstract

We use the APOSTLE cosmological hydrodynamic simulations to examine the effects of tidal stripping on cold dark matter (CDM) sub haloes 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 $\sim$ 30$\%$ of subhaloes hosting satellites with present-day stellar mass $10^6$-$10^8$ $M_{\odot}$ 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 $\sim3$-$6$ 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 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 $\Sigma \sim$ 32.6 mag $ {\rm arcsec^{-2}}$, which may be detectable with deep imaging surveys such as DES and LSST.