http://arxiv.org/abs/1807.07093
Classical abundance matching has been shown to produce mass estimates, $M^{\rm abund}{200}$, that agree well with independent dynamical estimates, $M^{\rm dyn}{200}$, for isolated dwarfs. However, for satellite galaxies, it is expected to fail. This is because tidal stripping lowers $M_$ and $M^{\rm dyn}{200}$, causing satellites to scatter above the $M-M_{200}$ relation for isolated dwarfs, while ram-pressure stripping quenches star formation on infall, causing satellites to scatter below the relation.
In this paper, we introduce a novel abundance matching technique that produces a more accurate estimate of $M_{200}$ for satellite galaxies. To achieve this, we abundance match with the mean star formation rate, averaged over the time when a galaxy was forming stars, $\langle {\rm SFR}\rangle$, instead of $M_*$. Using data from the Sloan Digital Sky Survey and the Bolshoi simulation, we obtain a statistical $\langle {\rm SFR}\rangle-{\rm M}_{200}$ relation in $\Lambda{\rm CDM}$. We then compare $M^{\rm abund}_{200}$ derived from this relation with $M^{\rm dyn}_{200}$ for 21 nearby dSph and dIrr galaxies, finding a good agreement between the two.
As a first application, we use our new $\langle {\rm SFR}\rangle-{\rm M}_{200}$ relation to empirically measure the cumulative mass function of a volume-complete sample of bright Milky Way satellites within 280 kpc of the Galactic centre. We compare this with a suite of cosmological ‘zoom’ simulations of Milky Way-mass halos that account for subhalo depletion by the Milky Way disc. Including a conservative lower bound on the number of ‘ultra-faint’ dwarfs in this same volume, we find no missing satellites problem above $M_{200} \sim 10^9$M$_\odot$ in the Milky Way. We discuss how this empirical method can be applied to a larger sample of spiral galaxies in the Local Volume.
J. Read and D. Erkal
Fri, 20 Jul 18
18/63
Comments: 13 pages, 7 figures. Submitted to MNRAS. Comments welcome!
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