Andrew Wetzel edited quiescent_fraction.tex  about 9 years ago

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\subsection{ObservedSatellite  Quiescent Fractions} Fractions for Satellites}  Based on our above definitions of ``satellite'' and ''quiescent'' dwarf galaxies, we group all satellites in the LG into 1-dex bins of $\mstar$ and compute the fraction that are quiescent in each bin.  We do not attempt any correction for observational completeness as a function of $\mstar$, because we measure the \emph{relative fraction} that are quiescent in each bin. 

Of the 56 known 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 are star-forming, and at $\mstar<9\times10^5\msun$ \emph{all} 40 satellites are quiescent.  These near-unity quiescent fractions for satellite dwarf galaxies contrast strongly with the effectively \emph{zero} quiescent fraction for dwarf galaxies that are isolated ($>1500\kpc$ from a more massive host) and thusare unambiguously  not satellites \citep{Geha2012, Phillips2014}. The only known exception is KKR 25, a dwarf spheroidal with $\mstar=1.4\times10^6\msun$ that is $1853\kpc$ from M31.