Andrew Wetzel edited quiescent_fraction.tex  about 9 years ago

Commit id: af2c9e1c3f3b56cabd90025ade4fbd8811f08ecc

deletions | additions      

       

\subsection{Observed Quiescent Fractions for Satellites}  Figure~\ref{fig:quiescent_fraction} shows, for all satellite galaxies at $\mstar\lesssim10^9\msun$ within $300\kpc$ of the MW or M31, the fraction that are quiescent in 1-dex bins of $\mstar$ \citep[see also][]{Phillips2014, SlaterBell2014}.  We do not attempt any correction correct  for any  observational completeness as a function of versus  $\mstar$, because we measure the \emph{relative fraction} in each bin, which is likelyan  unbiasedmetric  at these satellites' distances. distances $\lesssim300\kpc$.  %absent significant differential completeness as a function of recent star formation, which is unlikely because star-forming galaxies are generally brighter, but the quiescent fraction is near unity across almost all $\mstar$.  We show fractions for all satellites (blue circles) and separately for those in the MW (violet squares) and M31 (green triangles) halos.  Error bars show 68\% uncertainty for the binomial countsin each bin  using a beta distribution \citep{Cameron2011}. Of the 56 satellites, only 4 (7\%) are star-forming/gas-rich: LMC and SMC of the MW, LGS 3 and IC 10 of 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 of the MW/M31 contrast strongly with the effectively \emph{zero} quiescent fraction observed  for isolated (non-satellite) galaxies at $\mstar<10^9\msun$ \citep{Geha2012, Phillips2014}, as outlined in the Introduction.  (The \citep[][see Introduction]{Geha2012, Phillips2014}.  The  only known exception is KKR 25, a quiescent spheroidal with $\mstar=1.4\times10^6\msun$ that is $1853\kpc$ from M31.) M31.