deletions | additions       diff --git a/introduction.tex b/introduction.tex  index 131d3f3..3c3d822 100644  --- a/introduction.tex  +++ b/introduction.tex 
...
\section{Introduction}  Words. Galaxies in dense environments are more likely to have suppressed (quiescent) star-formation rates (SFR), more elliptical/spheroidal morphologies, and less cold gas in/around them than galaxies of similar stellar mass, $\mstar$, in less dense environments.  While such environmental effects long have been studied for galaxies in massive galaxy groups and clusters \citep[for example,][for review]{Oemler1974, Dressler1980, DresslerGunn1983, Balogh1997, BlantonMoustakas2009}, the observed effects on the 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 \citep[for example,][]{Mateo1998, McConnachie2012, Phillips2014, SlaterBell2014, Spekkens2014}.  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 cold gas, and (3) being actively star-forming to quiescent \citep[][and references therein]{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.  Furthermore, 3 - 4 gas-poor, quiescent, spheroidal galaxies exist just beyond the halos of the MW (Cetus and Tucana) and M31 (KKR 25 and possibly Andromeda XVIII), though the radial velocities of Cetus and Tucana imply that they likely orbited within the MW halo \citep{Teyssier2012}.  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 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 interactions with each other \citep{FaroukiShapiro1981, Moore1998}, and satellites can merge with one another \citep{Angulo2009, Wetzel2009a, Wetzel2009b, Deason2014a}.  Moreover, 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 extended gas from the orbiting satellite subhalo \citep{Balogh2000, McCarthy2008}, leading to reduced gas cooling/accretion into the satellite's disk \citep{Larson1980}.  More drastically, given a sufficiently high density of hot gas and high orbital velocity, ram-pressure can strip cold gas directly from the satellite's disk \citep{GunnGott1972, Abadi1999, Mayer2006, Chung2009, Tonnesen2009}.  Furthermore, 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}.