Two-phase ICM in the central region of the rich cluster of galaxies Abell 1795: A joint Chandra, XMM-Newton, and Suzaku view

Abstract

Based on a detailed analysis of the high-quality Chandra, XMM-Newton, and Suzaku data of the X-ray bright cluster of galaxies Abell 1795, we report clear evidence for a two-phase intracluster medium (ICM) structure, which consists of a cool (with a temperature T c ≈ 2.0 − 2.2 keV) and a hot (T h ≈ 5.0 − 5.7 keV) component that coexist and dominate the X-ray emission at least in the central 80 kpc. A third weak emission component (T 3 ≈ 0.8 keV) is also detected within the innermost 144 kpc and is ascribed to a portion of inter-stellar medium (ISM) of the cD galaxy. Deprojected spectral analysis reveals flat radial temperature distributions for both the hot phase and cool phase components. These results are consistent with the ASCA measurements reported in Xu et al. (1998), and resemble the previous findings for the Centaurus cluster (e.g., Takahashi et al. 2009). By analyzing the emission measure ratio and gas metal abundance maps created from the Chandra data, we find that the cool phase component is more metal-enriched than the hot phase one in 50 − 100 kpc region, which agrees with that found in M87 (Simionescu et al. 2008). The coexistence of the cool phase and hot phase ICM cannot be realized by bubble uplifting from active galactic nuclei (AGN) alone. Instead, the two-phase ICM properties are better reconciled with a cD corona model (Makishima et al. 2001). In this model, the -2 -cool phase may be ascribed to the plasmas confined in magnetic loops, which are surrounded by the intruding hot phase ICM and have been polluted by metals synthesized in the cD galaxy. AGN feedback energy released in the innermost 10 kpc can serve as the heating source to prevent the loop-interior gas from cooling down to temperatures much lower than the observed value. The total gravitating mass profile exhibits a hierarchical structure, regardless of the ICM temperature modeling.

Observations of a pre-merger shock in colliding clusters of galaxies

“…The abundances and redshifts of the two components are fixed to unity and zero, respectively, while their normalizations are set free to vary. The CXB component is represented as an absorbed power law, with a fixed photon index of 1.4 and flux of 6.4 × 10 −8 ergs cm −2 s −1 sr −1 [34].…”