Herschel observed Stripe 82 quasars and their host galaxies: connections between the AGN activity and the host galaxy star formation

Kavli Affiliate: Xuebing Wu

| First 5 Authors: Xiaoyi Dong, Xuebing Wu, , ,

| Summary:

In this work, we present a study of 207 quasars selected from the Sloan
Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars
within this sample are high luminosity quasars with a mean bolometric
luminosity of $10^{46.4}$ erg s$^{-1}$. The redshift range of this sample is
within $z<4$, with a mean value of $1.5pm0.78$. Because we only selected
quasars that have been detected in all three Herschel-SPIRE bands, the quasar
sample is complete yet highly biased. Based on the multi-wavelength photometric
observation data, we conducted a spectral energy distribution (SED) fitting
through UV to FIR. Parameters such as active galactic nucleus (AGN) luminosity,
FIR luminosity, stellar mass, as well as many other AGN and galaxy properties
are deduced from the SED fitting results. The mean star formation rate (SFR) of
the sample is 419 $M_{odot}$ yr$^{-1}$ and the mean gas mass is $sim
10^{11.3}$ $M_{odot}$. All these results point to an IR luminous quasar
system. Comparing with star formation main sequence (MS) galaxies, at least 80
out of 207 quasars are hosted by starburst galaxies. It supports the statement
that luminous AGNs are more likely to be associated with major mergers. The SFR
increases with the redshift up to $z=2$. It is correlated with the AGN
bolometric luminosity, where $L_{rm FIR} propto L_{rm Bol}^{0.46pm0.03}$.
The AGN bolometric luminosity is also correlated with the host galaxy mass and
gas mass. Yet the correlation between $L_{rm FIR}$ and $L_{rm Bol}$ has
higher significant level, implies that the link between AGN accretion and the
SFR is more primal. The $M_{rm BH}/M_{ast}$ ratio of our sample is 0.02,
higher than the value 0.005 in the local Universe. It might indicate an
evolutionary trend of the $M_{rm BH} – M_{ast}$ scaling relation.

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