Some Like It Hot: Linking Diffuse X-ray Luminosity, Baryonic Mass, and
  Star Formation Rate in Compact Groups of Galaxies
  We present an analysis of the diffuse X-ray emission in 19 compact groups of
galaxies (CGs) observed with Chandra. The hottest, most X-ray luminous CGs
agree well with the galaxy cluster X-ray scaling relations in $L_X-T$ and
$L_X-\sigma$, even in CGs where the hot gas is associated with only the
brightest galaxy. Using Spitzer photometry, we compute stellar masses and
classify HCGs 19, 22, 40, and 42 and RSCGs 32, 44, and 86 as fossil groups
using a new definition for fossil systems that includes a broader range of
masses. We find that CGs with total stellar and HI masses $\gtrsim10^{11.3}$
M$_\odot$ are often X-ray luminous, while lower-mass CGs only sometimes exhibit
faint, localized X-ray emission. Additionally, we compare the diffuse X-ray
luminosity against both the total UV and 24 $\mu$m star formation rates of each
CG and optical colors of the most massive galaxy in each of the CGs. The most
X-ray luminous CGs have the lowest star formation rates, likely because there
is no cold gas available for star formation, either because the majority of the
baryons in these CGs are in stars or the X-ray halo, or due to gas stripping
from the galaxies in CGs with hot halos. Finally, the optical colors that trace
recent star formation histories of the most massive group galaxies do not
correlate with the X-ray luminosities of the CGs, indicating that perhaps the
current state of the X-ray halos is independent of the recent history of
stellar mass assembly in the most massive galaxies.
