2009ApJ...701..122H

Identification of Abell 3120 as a galaxy cluster has recently been questioned with alternative suggestions including a fossil remnant of a group merger, non-thermal emission from a radio galaxy, and projected emission from a filamentary string of galaxies. We report on our analysis of the Chandra observation and evaluate these hypotheses based on our results. Abell 3120 shows X-ray emission extending 158 kpc, well beyond the central galaxy. The spatial distribution of X-rays in the core more closely follows the radio emission showing a jet-like structure extending to the north that is misaligned with the stellar light distribution of the central galaxy. At larger radii, the X-ray emission is aligned with the SE-NW running axis of the galaxy distribution in the cluster core. Modeling the X-ray spectrum excludes purely non-thermal emission. The emission-weighted temperature is 1.93-2.19 keV and the 0.3-10 keV luminosity is 1.23x10⁴³ erg/s. Abell 3120 appears to be a poor cluster with Virgo and MKW 4 as peers. The best-fitting model consists of a thermal component and a second component that may be either thermal or non-thermal, with luminosity ∼25% of the total X-ray luminosity. While a more detailed spatial-spectral search failed to detect a central active galactic nucleus, there is some evidence for an extended hard X-ray component. Cooler gas, 1.28-1.80 keV, was detected in the central 20 kpc. The second thermal component marginally requires a higher redshift, >0.12, which may be due to a second cluster in the rich surrounding environment consisting of nearly a thousand cataloged galaxies.