Andrew Wetzel edited quenching_time.tex  about 9 years ago

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The latter results in longer quenching timescales, though it primarily shifts the upper 16\% of the distribution.  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 less than $1.5\gyr$ 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 that quenching must be occur  extremely rapid rapidly  after infall. We next compare these statistically based quenching timescales to infall/quenching 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}. 

Altogether, Figure~\ref{fig:quench_times} indicates a complex dependence of the environmental quenching timescale on satellite $\mstar$.  Specifically, the typical timescale for satellites in the MW/M31 halos increases with $\mstar$, from $\lesssim1\gyr$ at $\mstar<10^7\msun$ to $\sim5\gyr$ at $\mstar\approx10^{8.5}\msun$.  \citet{Wheeler2014} indicate that this mass dependence continues, though with a rapid increase ($\sim2\times$) to $\approx9.5\gyr$, and no change from $\mstar\approx10^{8.5}$ to $10^{9.5}\msun$.  This rapid increase implies some tension with our results, specifically, the two satellites of M31, NGC 205 and M32 ($\mstar\approx10^{8.5}\msun$), unless either (1) both experienced unusually early infall $>9.5\gyr$ replace_contentgt;9.5\gyr$  ago, or (2) M31 quenches its satellites particularly rapidly, even compared with the massive hosts in \citet{Wheeler2014}. %(\citeauthor{Wheeler2014}'s results are consistent with the star-forming LMC/SMC of the MW.)  Finally, \citet{Wetzel2013} indicate that the quenching timescale rapidly \emph{decreases} at $\mstar>5\times10^9\msun$ and continues to decline with increasing $\mstar$.  Overall, the typical environmental quenching timescales are shortest for the lowest-mass satellites and is longest for satellites with $\mstar\sim10^9\msun$ (roughly Magellanic-Cloud mass).