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ABSTRACT 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 α in the nearby cluster A1367. 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 ∼3.1 × 1041 erg s−1, and a hot gas mass of ∼1010 M⊙. From the Multi-Unit Spectroscopic Explorer (MUSE) data, the OC shows an interesting velocity gradient nearly along the east-west direction with a low level of velocity dispersion of ∼80 km s−1, which may suggest a low level of the ICM turbulence. The emission line diagnostics suggest little star formation in the main H α cloud and a low-ionization (nuclear) emission-line regions like spectrum, but the excitation mechanisms remain unclear. This example shows that stripped ISM, even long after the initial removal from the galaxy, can still induce ICM inhomogeneities. We suggest that the magnetic field can stabilize the OC by suppressing hydrodynamic instabilities and thermal conduction. This example also suggests that at least some ICM clumps are multiphase in nature and implies that the ICM clumps can also be traced in H α. Thus, future deep and wide-field H α surveys can be used to probe the ICM clumping and turbulence. 

ABSTRACT We present results from a deep (174 ks) Chandra observation of the FR-II radio galaxy 3C 220.1, the central brightest cluster galaxy (BCG) of a kT ∼ 4 keV cluster at z = 0.61. The temperature of the hot cluster medium drops from ∼5.9 to ∼3.9 keV at ∼35 kpc radius, while the temperature at smaller radii may be substantially lower. The central active galactic nucleus (AGN) outshines the whole cluster in X-rays, with a bolometric luminosity of 2.0 × 1046 erg s−1 (∼10 per cent of the Eddington rate). The system shows a pair of potential X-ray cavities ∼35 kpc east and west of the nucleus. The cavity power is estimated within the range of 1.0 × 1044 and 1.7 × 1045 erg s−1, from different methods. The X-ray enhancements in the radio lobes could be due to inverse Compton emission, with a total 2–10 keV luminosity of ∼8.0 × 1042 erg s−1. We compare 3C 220.1 with other cluster BCGs, including Cygnus A, as there are few BCGs in rich clusters hosting an FR-II galaxy. We also summarize the jet power of FR-II galaxies from different methods. The comparison suggests that the cavity power of FR-II galaxies likely underestimates the jet power. The properties of 3C 220.1 suggest that it is at the transition stage from quasar-mode feedback to radio-mode feedback.