Brightest cluster galaxies in the extended GMRT radio halo cluster sample

Abstract

Aims. First-ranked galaxies in clusters, usually referred to as brightest cluster galaxies (BCGs), show exceptional properties over the whole electromagnetic spectrum. They are the most massive elliptical galaxies and show the highest probability to be radio loud. Moreover, their special location at the centres of galaxy clusters raises the question of the role of the environment in shaping their radio properties. In the attempt to separate the effect of the galaxy mass and of the environment on their statistical radio properties, we investigate the possible dependence of the occurrence of radio loudness and of the fractional radio luminosity function on the dynamical state of the hosting cluster. Methods. We studied the radio properties of the BCGs in the Extended GMRT Radio Halo Survey (EGRHS), which consists of 65 clusters in the redshift range 0.2-0.4, with X-ray luminosity L X ≥ 5 × 10 44 erg s −1 , and quantitative information on their dynamical state from high-quality Chandra imaging. We obtained a statistical sample of 59 BCGs, which we divided into two classes, depending on whether the dynamical state of the host cluster was merging (M) or relaxed (R). Results. Of the 59 BCGs, 28 are radio loud and 31 are radio quiet. The radio-loud sources are favourably located in relaxed clusters (71%), while the reverse is true for the radio-quiet BCGs, which are mostly located in merging systems (81%). The fractional radio luminosity function for the BCGs in merging and relaxed clusters is different, and it is considerably higher for BCGs in relaxed clusters, where the total fraction of radio loudness reaches almost 90%, to be compared to the ∼30% in merging clusters. For relaxed clusters, we found a positive correlation between the radio power of the BCGs and the strength of the cool core, consistent with previous studies on local samples. Conclusions. Our study suggests that the radio loudness of the BCGs strongly depends on the cluster dynamics; their fraction is considerably higher in relaxed clusters. We compare our results with similar investigations and briefly discuss them in the framework of AGN feedback.

Inquiring into the nature of the Abell 2667 brightest cluster galaxy: physical properties from MUSE

“…If we spatially resolve the diagnostic diagrams, the line intensity ratios show that the very core of the BCG is consistent with an AGN, in agreement with Kale et al (2015) and Yang et al (2018), while the outer regions exhibit signs of both AGN and SF activity. We hypothesise that these two physical mechanisms could be linked to the different components of the gas we reported in Sec.…”

“…Therefore, the cluster hosts a cool core with an estimated cooling time of t cool = 0.5 Gyr, as derived from Chandra data by Cavagnolo et al (2009). Using the NRAO VLA Sky Survey radio data at 1.4 GHz, Kale et al (2015) listed the Abell 2667 central galaxy as a radio-loud source with a radio power of P= 3.16 × 10 24 W Hz −1 , thus corroborating the AGN classification of the galaxy by Russell et al (2013). The analysis of Chandra data has confirmed the presence of an AGN in a recent work by Yang et al (2018).…”

Gas Density Perturbations in the Cool Cores of CLASH Galaxy Clusters

“…If gas sloshing is responsible for creating a radio mini-halo, our results support this assumption. In fact, a diffuse radio emission has been detected in seven clusters out of our sample: MACSJ 0329.6-0211 (Giacintucci et al 2014), MACSJ 1115.8+0129 (Pandey-Pommier et al 2016), RXJ 1347.5-1145(Gitti et al 2007), RXJ 1532.9+3021 (Kale et al 2013), MACS J1720.2+3536 (Giacintucci et al 2017), MACS J1931.8-2634 (Giacintucci et al 2014), and RXJ 2129.6+0005 (Kale et al 2015). We note that MACS J1931.8-2634 is classified into an unclassified source (Giacintucci et al 2014;van Weeren et al 2019), and MACSJ 1115.8+0129 and MACS J1720.2+3536 are recognized as a candidate for radio mini-halo (Pandey-Pommier et al 2016;Giacintucci et al 2017;van Weeren et al 2019).…”

Simulated Interactions between Radio Galaxies and Cluster Shocks. II. Jet Axes Orthogonal to Shock Normals

“…Radio galaxies (RGs) are found from the cores to the extremities of galaxy clusters (e.g., Kale et al 2015;Padovani 2016;Garon et al 2019). Cluster RGs frequently appear significantly distorted from simple, bilateral, axial symmetry (e.g., Terni de Gregory et al 2017;Garon et al 2019), revealing non-axisymmetric environmental impacts.…”