CMB distortion from circumgalactic gas
  We study the Sunyaev-Zel'dovich (SZ) distortion of the cosmic microwave
background radiation (CMBR) from extensive circumgalactic gas (CGM) in massive
galactic halos. Recent observations have shown that galactic halos contain a
large amount of X-ray emitting gas at the virial temperature, as well as a
significant amount of warm OVI absorbing gas. We consider the SZ distortion
from the hot gas in those galactic halos in which the gas cooling time is
longer than the halo destruction time scale. We show that the SZ distortion
signal from the hot gas in these galactic halos at redshifts $z\approx
1\hbox{--}8$ can be significant at small angular scales ($\ell\sim 10^4$), and
dominate over the signal from galaxy clusters. The estimated SZ signal for most
massive galaxies (halo mass $\ge 10^{12.5}$ M$_\odot$) is consistent with the
marginal detection by {\it Planck} at these mass scales. We also consider the
SZ effect from warm circumgalactic gas. The integrated Compton distortion from
the warm OVI absorbing gas is estimated to be $y\sim 10^{-8}$, which could
potentially be detected by experiments planned for the near future. Finally, we
study the detectability of the SZ signal from circumgalactic gas in two types
of surveys, a simple extension of the SPT survey and a more futuristic cosmic
variance-limited survey. We find that these surveys can easily detect the kSZ
signal from CGM. With the help of a Fisher Matrix analysis, we find that it
will be possible for these surveys to constrain the gas fraction in CGM, after
marginalizing over cosmological parameters, to $\le 33$\%, in case of no
redshift evolution of the gas fraction.
