Coffee talks
Friday 21/03/2025 @ 11:30, Sala riunioni quarto piano e on line (meet.google.com/sue-bwvk-axf)
Davide Brustio (Università di Bologna, BO, Italy), "The interplay between relativistic plasma and thermal gas in a galaxy group"
In this Thesis, I investigate NGC 7618, a galaxy group in the local Universe (z = 0.017). While previously studied in X-rays, no comprehensive radio analysis exists. My goal is to examine its radio properties and compare them with X-ray data using LOFAR 144 MHz, GMRT323 MHz and 608 MHz, and JVLA 1.5 GHz observations, combined with Chandra data. I report the discovery of extended radio emission (50–90 kpc) centered on the group. My radio images show that this emission is more extended at lower frequencies. A key morphological feature is a sharp radio surface brightness edge, co-located with a sloshing cold front in X-rays. To understand the origin of the newly discovered emission, I conduct a multi-frequency spectral analysis, producing spectral index and aging maps, as well as color-color diagrams. Additionally, I analyze thermal and non-thermal components by comparing radio and X-ray surface brightness profiles across different sectors and on a point-to-point basis. The picture emerging from my analysis suggests a complex scenario, with projection effects likely playing a major role. It suggests that the active galactic nucleus (AGN) in the central galaxy has injected radio plasma into the medium, which has subsequently undergone a tumultuous evolution due to gas sloshing. In particular, I interpret the emission as originating from different electron populations: a younger, more confined population still reminiscent of its AGN origin, and an older, more extended population likely tracing AGN material being redistributed by sloshing.