Andrew Wetzel edited quenching_time.tex  about 9 years ago

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Both panels show shorter median quenching timescales for less massive satellites: $\sim5\gyr$ at $\mstar=10^{8-9}\msun$, $2-3\gyr$ at $\mstar=10^{7-8}\msun$, and $ < 1.5\gyr$ at $\mstar<10^7\msun$, depending on the inclusion of group preprocessing.  Moreover, the median timescale for two of the lowest $\mstar$ bins is $0\gyr$ because 100\% of those satellites are quiescent, which implies extremely rapid quenching after infall.  This mass trend is consistent the results of \citep{Weisz2015}, based on star-formation histories, that more massive dwarf galaxies in the LG quenched more recently.  We next compare these statistically based quenching timescales to infall timescales directly measured for satellites of the MW.  The 3-D orbital velocity measured for the LMC/SMC strongly suggests that they are on their first infall and passed inside $\rvir$ of the MW $\approx2\gyr$ ago \citep{Kallivayalil2013}.  Given that both remain star-forming, this places a lower limit to their quenching timescale (gray triangle), consistent with our statistical timescales.  Similarly, measurements of the 3-D orbital velocity and star-formation history for Leo I ($\mstar=5.5\times10^6\msun$) indicate that it fell into the MW halo $\approx2.3\gyr$ ago and quenched $\approx1\gyr$ ago (near its $\approx90\kpc$ pericentric passage), implying a quenching timescale of $\approx1.3\gyr$ \citep[][gray pentagon]{Sohn2013}, again consistent with our results.  Additionally, our mass trend is broadly consistent the star-formation-history results of \citep{Weisz2015} that the more massive dwarf galaxies in the LG quenched more recently.  We also compare these timescales with previous studies of more massive satellites of other hosts.  The red squares in Figure~\ref{fig:quench_times} show the timescales from \citet{Wheeler2014}, who used nearly identical methodology, combining the the galaxy catalog from \citet{Geha2012} with satellite infall times (including group preprocessing) from the Millennium II simulation \citep{BoylanKolchin2009}.