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 bars show 68\% uncertainty fora beta distribution \citep{Cameron2011} based on  the binomial  counts in each bin. bin via a beta distribution \citep{Cameron2011}.  Of the 56 satellites, only 4 (7\%) are star-forming/gas-rich:the  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 satellite dwarfs satellites  in the LG contrast strongly with the effectively \emph{zero} quiescent fraction for dwarf galaxies that are isolated, that is, $>1500\kpc$ from a more massive host \citep{Geha2012, Phillips2014}, and thus are not/were never are/were not  satellites. The (The  only known exception is KKR 25, a quiescent dwarf spheroidal with $\mstar=1.4\times10^6\msun$ that is $1853\kpc$ from M31. M31.)