Speaker
Description
We study the co-evolution between host galaxies and their central supermassive black hole (SMBH) with an unprecedented large sample of SDSS type-1 quasars which are also detected by the far-infrared (FIR) SPIRE instrument on Herschel. This subset of optical quasars gives us a unique opportunity to study systems for which both star-formation activity and active galactic nucleus (AGN) activity are at the most extreme. Thanks to the well-established far-infrared to radio correlation, we make use of the high angular resolution of the radio observations from telescopes such LOFAR, Meerkat and VLA to cross-match the Herschel sources with the SDSS quasar catalogue. Our sample spans over a wide range of redshifts ($0<z<5$) and is spread over 9 extragalactic fields (Boötes, Elais-N1, GAMA-09, GAMA-12, GAMA-15, HATLAS-NGP, Lockman Hole, Stripe-82 and XMM-LSS). We analyse the scaling relation between stellar mass and star-formation rate (SFR). This is done by assembling an extensive multi-wavelength catalogue (from X-ray to radio wavelengths) and individually modelling the spectral energy distributions (SED) to derive physical properties on the accreting SMBH and its host galaxy. We show that 22% of the quasars are hosted by ‘starburst’ (SB) galaxies while normal star-forming galaxies account for the rest of our sample. We find that the fraction of SB galaxies increases towards higher redshifts. By studying the specific SFR we also observe a downsizing effect, namely massive galaxies accreted most of their mass earlier on while less massive galaxies are more actively assembling at lower redshifts. The specific black hole accretion rate (sBHAR), however, does not exhibit such a trend and shows no similarity to the downsizing phenomenon. The AGN bolometric luminosity derived from SED fitting agrees well with bolometric luminosities obtained by measuring broad-line emissions (Wu & Shen (2022)). We observe a positive correlation between BHAR and the SFRs of the host galaxies, which becomes less steep at higher redshifts.
