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\section{Introduction}
Galaxies in
dense denser environments are more likely to have suppressed (quiescent) star-formation rates
(SFR), more elliptical/spheroidal morphologies, (SFR) and
less little-to-no cold
atomic/molecular gas
in/around them than galaxies of similar stellar mass, $\mstar$, in less dense environments.
While such The observed environmental effects
long have been studied for galaxies in massive galaxy groups and clusters \citep[for example,][for review]{Oemler1974, Dressler1980, DresslerGunn1983, Balogh1997, BlantonMoustakas2009}, within the
observed effects Local Group (LG) on the
satellite dwarf galaxies
in the Local Group (LG), in particular, the satellites within the host halos of the Milky Way (MW) and
M31, are even stronger M31 \citep[for example,][]{Mateo1998, McConnachie2012, Phillips2014, SlaterBell2014,
Spekkens2014}. Spekkens2014} are particularly strong, even compared to the effects on (more massive) satellite galaxies within massive groups/clusters.
Specifically, the galaxies around the Milky Way (MW) and Andromeda (M31) show a strikingly sharp transition in their properties within $\approx 300 \kpc$, corresponding to the virial radii, $\rvir$, of the halos of the MW and M31 for $\mvir \approx 10 ^ {12} \msun$ \citep[for example,][]{Deason2012, vanderMarel2012, BoylanKolchin2013}.
Within this distance, galaxies transition from (1) having irregular to elliptical/spheroidal morphologies, (2) having most of their baryonic mass in cold atomic/molecular gas to having little-to-no
detectible measured cold gas, and (3) being actively star-forming to quiescent \citep[][and references
therein]{McConnachie2012}. therein]{Einasto1974, McConnachie2012}.
This environmental transition of the population is almost complete, with just a few exceptions.
Four gas-rich, star-forming, irregular galaxies persist within the halos of the MW (the LMC and SMC) and M31 (LGS 3 and IC 10).
However, the LMC and SMC are likely on their first infall \citep{Besla2007, Kallivayalil2013}, and given their distances to M31, LGS 3 and IC 10 may be as well.
...
The fact that almost all of the satellite galaxies within the MW/M31 halos show such strong environmental effects is particularly striking given that, other than KKR 25, all known galaxies at $\mstar < 10 ^ 9 \msun$ that are isolated (not within $1500 \kpc$ of a more massive galaxy, and thus not strongly influenced by environmental effects) are actively star-forming \citep{Geha2012}.
Thus, the MW and M31 halos exert the strongest environmental influence on their galaxy populations of any observed systems, making the LG one of the most compelling laboratories to study environmental effects on galaxy evolution.
Several environmental processes within a host halo regulate the gas content, star formation, morphology, and eventual tidal disruption of satellite
galaxies.
Gravitationally, the strong galaxies, including gravitational tidal forces
of the host halo will strip mass from the satellite (subhalo) from the outside-in \citep{Dekel2003, Diemand2007, WetzelWhite2010}.
In addition, the dense collection of satellites within a host halo can drive impulsive gravitational \citep[e.g.,][]{Dekel2003}, galaxy-galaxy interactions
with each other \citep{FaroukiShapiro1981, Moore1998}, \citep[e.g.,][]{FaroukiShapiro1981} and
satellites can merge with one another \citep{Angulo2009, Wetzel2009a, Wetzel2009b, Deason2014a}.
Moreover, mergers \citep[e.g.,][]{Deason2014a}, tidal shocking and resonant interactions with the
host's galactic disk can lead to particularly efficient morphological evolution, coring, stripping, and disruption \citep{Mayer2001, DOnghia2010, Zolotov2012}.
Hydrodynamically, if the host
halo contains thermalized hot gas, this can strip and heat the \citep[e.g.,][]{Mayer2001, DOnghia2010}, ram-pressure stripping of extended gas
from around the
orbiting satellite
subhalo \citep{Balogh2000, McCarthy2008}, leading to reduced gas cooling/accretion into \citep[e.g.,][]{Larson1980, McCarthy2008} of the
satellite's disk \citep{Larson1980}.
More drastically, given a sufficiently high density cold inter-stellar medium \citep[e.g.,][]{GunnGott1972, Tonnesen2009}, many of
hot gas and high orbital velocity, ram-pressure which can
strip cold gas directly from the satellite's disk \citep{GunnGott1972, Abadi1999, Mayer2006, Chung2009, Tonnesen2009}.
Furthermore, be assisted by feedback from stars and/or AGN within the satellites
can drive galactic winds that can enable these environmental process to operate even more efficiently \citep[for example,][]{BaheMcCarthy2015}. \citep[e.g.,][]{BaheMcCarthy2015}.
In this letter, we examine the environmental quenching timescales of the current satellite galaxies in the LG, considering the possible impact of group preprocessing.
