The AGORA High-resolution Galaxy Simulations Comparison Project. V: Satellite Galaxy Populations In A Cosmological Zoom-in Simulation of A Milky Way-mass Halo

Kavli Affiliate: Tom Abel

| First 5 Authors: Minyong Jung, Santi Roca-Fàbrega, Ji-hoon Kim, Anna Genina, Loic Hausammann

| Summary:

We analyze and compare the satellite halo populations at $zsim2$ in the
high-resolution cosmological zoom-in simulations of a $10^{12},{rm
M}_{odot}$ target halo ($z=0$ mass) carried out on eight widely-used
astrophysical simulation codes ({sc Art-I}, {sc Enzo}, {sc Ramses}, {sc
Changa}, {sc Gadget-3}, {sc Gear}, {sc Arepo-t}, and {sc Gizmo}) for the
{it AGORA} High-resolution Galaxy Simulations Comparison Project. We use
slightly different redshift epochs near $z=2$ for each code (hereafter
“$zsim2$’) at which the eight simulations are in the same stage in the target
halo’s merger history. After identifying the matched pairs of halos between the
{it CosmoRun} simulations and the DMO simulations, we discover that each {it
CosmoRun} halo tends to be less massive than its DMO counterpart. When we
consider only the halos containing stellar particles at $zsim2$, the number of
satellite {it galaxies} is significantly fewer than that of dark matter halos
in all participating {it AGORA} simulations, and is comparable to the number
of present-day satellites near the Milky Way or M31. The so-called “missing
satellite problem’ is fully resolved across all participating codes simply by
implementing the common baryonic physics adopted in {it AGORA} and the stellar
feedback prescription commonly used in each code, with sufficient numerical
resolution ($lesssim100$ proper pc at $z=2$). We also compare other properties
such as the stellar mass$-$halo mass relation and the mass$-$metallicity
relation. Our work highlights the value of comparison studies such as {it
AGORA}, where outstanding problems in galaxy formation theory are studied
simultaneously on multiple numerical platforms.

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