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We estimate the fraction of AGNs hosted in starburst galaxies (f_bursty) as a function of the AGN luminosity predicted under the assumption that starburst events and AGN activity are triggered by galaxy interactions during their merging histories. The latter are described through Monte Carlo realizations, and are connected to star formation and BH accretion using a semi-analytic model of galaxy formation in a cosmological framework. The predicted fraction f_bursty increases steeply with AGN luminosity from <0.2 at L_X < 10^44 erg/s to >0.9 at L_X > 10^45 erg/s over a wide redshift interval from z=0 to z=6. We compare the model predictions with new measurements of f_bursty from a sample of X-ray selected AGNs in the XMM-COSMOS field at 0.3< z< 2, and from a sample of QSOs (L_X > 10^45 erg/s) in the redshift range 2< z< 6.5. We find preliminary indications that under conservative assumptions half of the QSO hosts are starburst galaxies. This result provide motivation for future systematic studies of the stellar properties of high luminosity AGN hosts in order to constrain AGN triggering mechanisms.
The triggering mechanisms for Active Galactic Nuclei (AGN) are still debated. Some of the most popular ones include galaxy interactions (IT) and disk instabilities (DI). Using an advanced semi analytic model (SAM) of galaxy formation, coupled to accu
There exist strong evidence supporting the co-evolution of central supermassive black holes and their host galaxies. It is however still unclear what the exact role of nuclear activity, in the form of accretion onto these supermassive black holes, in
We analyze a sample of 30,000 nearby obscured AGNs with optical spectra from SDSS and mid-IR photometry from WISE. Our aim is to investigate the AGN host galaxy properties with mid-IR luminosities as AGN activity indicator, and to compare with previo
We use a stacking technique to measure the average HI content of a volume-limited sample of 1871 AGN host galaxies from a parent sample of galaxies selected from the SDSS and GALEX imaging surveys with stellar masses greater than 10^10 M_sun and reds
We present the results from a study of the morphologies of moderate luminosity X-ray selected AGN host galaxies in comparison to a carefully mass-matched control sample at 0.5 < z < 3 in the CANDELS GOODS-S field. We apply a multi-wavelength morpholo