Probing the circumgalactic baryons through cross-correlations
  We study the cross-correlation of distribution of galaxies, the
Sunyaev-Zel'dovich (SZ) and X-ray power spectra of galaxies from current and
upcoming surveys and show these to be excellent probes of the nature, i.e.
extent, evolution and energetics, of the circumgalactic medium (CGM). The
SZ-galaxy cross-power spectrum, especially at large multipoles, depends on the
steepness of the pressure profile of the CGM. This property of the SZ signal
can, thus, be used to constrain the pressure profile of the CGM. The X-ray
cross power spectrum also has a similar shape. However, it is much more
sensitive to the underlying density profile. We forecast the detectability of
the cross-correlated galaxy distribution, SZ and X-ray signals by combining
South Pole Telescope-Dark Energy Survey (SPT-DES) and eROSITA-DES/eROSITA-LSST
(extended ROentgen Survey with an Imaging Telescope Array-Large Synoptic Survey
Telescope) surveys, respectively. We find that, for the SPT-DES survey, the
signal-to-noise ratio (SNR) peaks at high mass and redshift with SNR $\sim 9$
around $M_h\sim 10^{13} h^{-1} M_{\odot}$ and $z\sim 1.5\hbox{--} 2$ for flat
density and temperature profiles. The SNR peaks at $\sim 6 (12 )$ for the
eROSITA-DES (eROSITA-LSST) surveys. We also perform a Fisher matrix analysis to
find the constraint on the gas fraction in the CGM in the presence or absence
of an unknown redshift evolution of the gas fraction. Finally, we demonstrate
that the cross-correlated SZ-galaxy and X-ray-galaxy power spectrum can be used
as powerful probes of the CGM energetics and potentially discriminate between
different feedback models recently proposed in the literature; for example, one
can distinguish a `no active galactic nuclei feedback' scenario from a CGM
energized by `fixed-velocity hot winds' at greater than $3\sigma$.
