Résumé / Abstract Journal-club_Galaxies

Journal-club Galaxies

« Rapidly growing black holes and host galaxies in the distant Universe from the Herschel Radio Galaxy Evolution Project »

Guillaume Drouart

The HeRGE (Herschel Radio Galaxy Evolution) project consists of a sample of 70 powerful radio galaxies spanning the redshift range from 1 to 5.2. They benefit from continuous coverage from 3 to 870um with Spitzer, Herschel and sub-mm ground-based instruments (SCUBA, LABOCA) providing us for the first time with a well sampled IR spectral energy distribution (SED). As a calorimeter, IR is an excellent proxy to estimate the contribution of both AGN and starburst (SB) components through the reprocessed light from the UV/optical wavelengths. This appoints to the radio galaxies as ideal candidates to provide insights into the so-called ``AGN-SB connection"". Performing SED fitting on the entire sample (Drouart et al., accepted), we are able to disentangle their relative contribution and estimate their infrared luminosities. Assuming simple physical relations, we estimate both the star formation and accretion rates. We find evidences that super massive black holes in radio galaxies have out-grown or are outgrowing their host galaxies. In order to ``catch up"" and eventually fall onto the local Mbh-Mgal relation, the host galaxies require further intense star-forming episodes and/or merging events across cosmic time. We will also present results on the careful SED decomposition of ~12 selected radio galaxies (ARPEGE) into two stellar populations (evolved and a starburst) with the PEGASE.3 model and an AGN torus model. Best fits confirm that galaxies are still growing and that their mass bulk already formed at redshifts larger than 4.
jeudi 3 avril 2014 - 11:30
Salle 281, Institut d'Astrophysique
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