Is the stellar mass-stellar metallicity relation universal in the Milky Way satellites and beyond?

Kavli Affiliate: Qingjuan Yu

| First 5 Authors: Moran Xia, Qingjuan Yu, , ,

| Summary:

Observations reveal a universal stellar mass-stellar metallicity relation
(MZR) existing in Local Group dwarfs of different types, $Z_*propto
M_*^{alpha}$ with $alpha=0.30pm0.02$. In this work, we investigate the
"universality" of the MZRs for both satellites and central galaxies in a large
number of different host dark matter halos covering a large mass range of
$10^9$-$10^{15}h^{-1}M_odot$, by using a semianalytical galaxy formation and
evolution model. We obtain the following results. (1) The exponents ($alpha$)
for the MZRs of the satellites in halos with the same mass as the Milky Way
halo but different individual assembly histories are mostly $sim$0.2-0.4,
i.e., having a scatter of $sim 0.2$; and the scatter of $alpha$ increases
with decreasing halo masses. (2) The MZR relations are changed little by the
variation of halo masses and the classification between central galaxies and
satellites, if many halos with the same mass are stacked together. (3) A double
power law exists in the MZR relations for both central galaxies and stacked
satellites, with $alphasim$0.2-0.4 at $10^3M_odot< M_*<10^{8} M_odot$ and a
relatively higher $alphasim0.5$ at $10^8M_odot<M_*<10^{11}M_odot$. (4) The
high-mass satellites ($M_*>10^8M_odot$) existing mostly in high-mass halos can
lead to an apparent increase of $alpha$ (from $sim0.2$ to $sim0.4$) with
increasing host halo masses shown in the single power law fitting results of
stacked satellites. The universality of the MZR suggests the common physical
processes in stellar formation and chemical evolution of galaxies can be
unified over a large range of galaxy masses and halo masses.

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