X-ray Constraints on the Hot Gas Content of Early-type Galaxies in Virgo
  We present a systematic study of the diffuse hot gas around early-type
galaxies (ETGs) residing in the Virgo cluster, based on archival {\it Chandra}
observations. Our representative sample consists of 79 galaxies with
low-to-intermediate stellar masses ($M_* \approx 10^{9-11}\rm~M_\odot$), a mass
range that has not been extensively explored with X-ray observations thus far.
We detect diffuse X-ray emission in only eight galaxies and find that in five
cases a substantial fraction of the detected emission can be unambiguously
attributed to truly diffuse hot gas, based on their spatial distribution and
spectral properties. For the individually non-detected galaxies, we constrain
their average X-ray emission by performing a stacking analysis, finding a
specific X-ray luminosity of $L_{\rm X}/M_* \sim
10^{28}{\rm~erg~s^{-1}~M_{\odot}^{-1}}$, which is consistent with unresolved
stellar populations. The apparent paucity of truly diffuse hot gas in these
low- and intermediate-mass ETGs may be the result of efficient ram pressure
stripping by the hot intra-cluster medium. However, we also find no significant
diffuse hot gas in a comparison sample of 57 field ETGs of similar stellar
masses, for which archival {\it Chandra} observations with similar sensitivity
are available. This points to the alternative possibility that galactic winds
evacuate the hot gas from the inner region of low- and intermediate-mass ETGs,
regardless of the galactic environment. Nevertheless, we do find strong
morphological evidence for on-going ram pressure stripping in two galaxies (NGC
4417 and NGC 4459). A better understanding of the roles of ram pressure
stripping and galactic winds in regulating the hot gas content of ETGs, invites
sensitive X-ray observations for a large galaxy sample.
