Radio and X-ray Observations of the Restarted Radio Galaxy in the Galaxy Cluster CL 0838+1948

oleh: Simona Giacintucci, Tracy Clarke, Namir E. Kassim, Wendy Peters, Emil Polisensky

Format: Article
Diterbitkan: MDPI AG 2021-11-01

Deskripsi

We present VLA Low-band Ionosphere and Transient Experiment (VLITE) 338 MHz observations of the galaxy cluster CL 0838+1948. We combine the VLITE data with Giant Metrewave Radio Telescope 610 MHz observations and survey data. The central galaxy hosts a 250 kpc source whose emission is dominated by two large lobes at low frequencies. At higher frequencies, a pair of smaller lobes (∼30 kpc) is detected within the galaxy optical envelope. The observed morphology is consistent with a restarted radio galaxy. The outer lobes have a spectral index <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>α</mi><mi>out</mi></msub><mo>=</mo><mn>1.6</mn></mrow></semantics></math></inline-formula>, indicating that they are old, whereas the inner lobes have <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>α</mi><mi>inn</mi></msub><mo>=</mo><mn>0.6</mn></mrow></semantics></math></inline-formula>, typical for an active source. Spectral modeling confirms that the outer emission is a dying source whose nuclear activity switched off not more than 110 Myr ago. Using archival <i>Chandra</i> X-ray data, we compare the radio and hot gas emission. We find that the active radio source is contained within the innermost and X-ray brightest region, possibly a galactic corona. Alternatively, it could be the remnant of a larger cool core whose outer layers have been heated by the former epoch of activity that has generated the outer lobes.