The Galaxy Progenitors of Stellar Streams around Milky Way-mass Galaxies in the FIRE Cosmological Simulations

Abstract

Stellar streams record the accretion history of their host galaxy. We present a set of simulated streams from disrupted dwarf galaxies in 13 cosmological simulations of Milky Way (MW)-mass galaxies from the FIRE-2 suite at z = 0, including 7 isolated Milky Way-mass systems and 6 hosts resembling the MW-M31 pair (full dataset at: https://flathub.flatironinstitute.org/sapfire). In total, we identify 106 simulated stellar streams, with no significant differences in the number of streams and masses of their progenitors between the isolated and paired environments. We resolve simulated streams with stellar masses ranging from ∼ 5 × 10 5 up to ∼ 10 9 M , similar to the mass range between the Orphan and Sagittarius streams in the MW. We confirm that present-day simulated satellite galaxies are good proxies for stellar stream progenitors, with similar properties including their stellar mass function, velocity dispersion, [Fe/H] and [α/H] evolution tracks, and orbital distribution with respect to the galactic disk plane. Each progenitor's lifetime is marked by several important timescales: its infall, star-formation quenching, and stream-formation times. We show that the ordering of these timescales is different between progenitors with stellar masses higher and lower than ∼ 2 × 10 6 M . Finally, we show that the main factor controlling the rate of phase-mixing, and therefore fading, of tidal streams from satellite galaxies in MW-mass hosts is non-adiabatic evolution of the host potential. Other factors commonly used to predict phase-mixing timescales, such as progenitor mass and orbital circularity, show virtually no correlation with the number of dynamical times required for a stream to become phase-mixed.

Reading the CARDs: the Imprint of Accretion History in the Chemical Abundances of the Milky Way's Stellar Halo

“…While the satellite galaxies in these simulations have been shown to have many properties in common with the observed satellites around the MW and M31, they are generally found to be too metal-poor compared to the observed dwarf galaxies (Escala et al 2018, Wheeler et al 2019, Panithanpaisal et al 2021. This is likely at least in part because of the assumed delay-time distributions for SNe Ia.…”

“…In this section, we introduce the catalog of halo star particles and dwarf galaxies that we use for this experiment. We limit our study to the catalog of star particles belonging to dwarf galaxies, stellar streams, and phase-mixed debris constructed in Panithanpaisal et al (2021) (hereafter P21) 3 . By using this subset of particles, we can explore the efficacy of the CARDs framework for a purely accreted stellar halo in a more realistic setting than L15 while retaining control of the precise composition of the accreted stellar halo, and make comparisons between halo progenitor and present-day dwarf galaxy populations.…”

The effects of LMC-mass environments on their dwarf satellite galaxies in the FIRE simulations

“…Recently, Panithanpaisal et al (2021) investigated the formation of stellar streams around MW-mass galaxies in the FIRE-2 simulations. They find that present-day satellites are good proxies for the progenitors of stellar streams.…”

Orbital phase-driven biases in galactic mass constraints from stellar streams

“…The resolution of this suite of simulations allows both luminous and dark subhalos to be resolved well even near each MW-like galaxy, and follows the formation of tidal streams from dwarf galaxies down to slightly below the mass of the MW's "classical" dSphs: around 10 8 𝑀 in total mass or 10 6 𝑀 in stellar mass (at 𝑧 = 0). Panithanpaisal et al (2021) search these simulated galaxies for accreted structures that are spatially coherent and stream-like at present day. They identify 100 such streams across 13 simulations (see their Table 1) and confirm that the progenitor galaxies of these coherent streams are consistent with the mass-size-velocity dispersion relationship of observed present-day Milky Way satellites.…”