Kavli Affiliate: Risa H. Wechsler
| First 5 Authors: Deveshi Buch, Ethan O. Nadler, Risa H. Wechsler, Yao-Yuan Mao,
| Summary:
We present Milky Way-est, a suite of 20 cosmological cold-dark-matter-only
zoom-in simulations of Milky Way (MW)-like host halos. Milky Way-est hosts are
selected such that they: ($i$) are consistent with the MW’s measured halo mass
and concentration, ($ii$) accrete a Large Magellanic Cloud (LMC)-like ($approx
10^{11}~M_{odot}$) subhalo within the last $1.3~mathrm{Gyr}$ on a realistic
orbit, placing them near $50~mathrm{kpc}$ from the host center at $zapprox
0$, and ($iii$) undergo a $>$1:5 sub-to-host halo mass ratio merger with a
Gaia-Sausage-Enceladus (GSE)-like system at early times ($0.67<z<3$). Hosts
satisfying these LMC and GSE constraints constitute $< 1%$ of all halos in the
MW’s mass range, and their total masses grow rapidly at late times due to LMC
analog accretion. Compared to hosts of a similar final halo mass that are not
selected to include LMC and GSE analogs, Milky Way-est hosts contain $22%$
more subhalos with present-day virial masses above $10^8~M_{odot}$ throughout
the virial radius, on average. This enhancement reaches $approx 80%$ in the
inner $100~mathrm{kpc}$ and is largely, if not entirely, due to LMC-associated
subhalos. These systems also induce spatial anisotropy in Milky Way-est subhalo
populations, with $approx 60%$ of the total subhalo population within
$100~mathrm{kpc}$ found in the current direction of the LMC. Meanwhile, we
find that GSE-associated subhalos do not significantly contribute to
present-day Milky Way-est subhalo populations. These results provide context
for our Galaxy’s dark matter structure and subhalo population and will help
interpret a range of measurements that are currently only possible in the MW.
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