Andrew Wetzel edited quiescent_fraction.tex  about 9 years ago

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Figure~\ref{fig:quiescent_fraction} shows the quiescent fraction for all satellite dwarf galaxies of the MW and/or M31 versus $\mstar$ \citep[see also][]{Phillips2014, SlaterBell2014}.  We show fractions for all such satellites (blue circles) as well as separately for those in the MW (violet squares) and M31 (green triangles) halos.  The error Error  bars show the  68\% uncertainty for the binomial counts in each bin via a beta distribution \citep{Cameron2011}. Of the 56 satellites, only 4 (7\%) are star-forming/gas-rich: LMC and SMC around the MW, LGS 3 and IC 10 around M31.  Moreover, at $\mstar<8\times10^7\msun$, only 1 (LGS 3) of the 51 satellites is star-forming, and at $\mstar<9\times10^5\msun$ \emph{all} 40 satellites are quiescent.  These near-unity quiescent fractions for satellites in the LG contrast strongly with the effectively \emph{zero} quiescent fraction for isolated (non-satellite)  dwarf galaxiesthat are isolated, that is, $>1500\kpc$ from a more massive host  \citep{Geha2012, Phillips2014}, and thus are/were not satellites. as outlined in the Introduction.  (The only known exception is KKR 25, a quiescent dwarf spheroidal with $\mstar=1.4\times10^6\msun$ that is $1853\kpc$ from M31.)