An X-ray cooling-core cluster surrounding a low-power compact steep spectrum radio source 1321+045

摘要

We discovered an X-ray cluster in a Chandra observation of the compact steep spectrum (CSS) radio source 1321+045 (z = 0.263). CSS sources are thought to be young radio objects at the beginning of their evolution and can potentially test the cluster heating process. 1321+045 is a relatively low-luminosity source and its morphology consists of two radio lobes on the opposite sides of a radio core with no evidence for jets or hotspots. The optical emission line ratios are consistent with an interstellar medium dominated by active galactic nucleus photoionization with a small contribution from star formation, and no contributions from shocks. Based on these ratios, we classify 1321+045 as a low excitation galaxy (LEG) and suggest that its radioactivity is in a coasting phase. The X-ray emission associated with the radio source is detected with 36.1 ± 8.3 counts, but the origin of this emission is highly uncertain. The current X-ray image of the cluster does not show any signatures of a radio source impact on the cluster medium. Chandra detects the cluster emission at >3σ level out to ～60″ (240 kpc). We obtain the best-fit beta model parameters of the surface brightness profile of β = 0.58 ± 0.2 and a core radius of 9.4 arcsec. The average temperature of the cluster is equal to keV, with a temperature and cooling profile indicative of a cooling core. We measure the cluster luminosity L _((0.5-2 keV)) = 3 × 10~(44) erg s~(-1) and mass 1.5 × 10~(14) M_⊙.