An H$\alpha$/X-ray orphan cloud as a signpost of the intracluster medium
  clumping
  Recent studies have highlighted the potential significance of intracluster
medium (ICM) clumping and its important implications for cluster cosmology and
baryon physics. Many of the ICM clumps can originate from infalling galaxies,
as stripped interstellar medium (ISM) mixing into the hot ICM. However, a
direct connection between ICM clumping and stripped ISM has not been
unambiguously established before. Here we present the discovery of the first
and still the only known isolated cloud (or orphan cloud, OC) detected in both
X-rays and H$\alpha$ in the nearby cluster Abell 1367. With an effective radius
of 30 kpc, this cloud has an average X-ray temperature of 1.6 keV, a bolometric
X-ray luminosity of $\sim 3.1\times 10^{41}$ erg s$^{-1}$ and a hot gas mass of
$\sim 10^{10}\ {\rm M}_\odot$. From the MUSE data, the OC shows an interesting
velocity gradient nearly along the east-west direction with a low level of
velocity dispersion of $\sim 80$ km/s, which may suggest a low level of the ICM
turbulence. The emission line diagnostics suggest little star formation in the
main H$\alpha$ cloud and a LI(N)ER-like spectrum, but the excitation mechanism
remain unclear. This example shows that the stripped ISM, even long time after
the initial removal from the galaxy, can still induce the ICM inhomogeneities.
We suggest that magnetic field can stabilize the OC by suppressing hydrodynamic
instabilities and thermal conduction. This example also suggests that at least
some ICM clumps are multi-phase in nature and implies that the ICM clumps can
also be traced in H$\alpha$. Thus, future deep and wide-field H$\alpha$ survey
can be used to probe the ICM clumping and turbulence.
