Exploring the AGN clustering
using a semi-analytic model ofgalaxy formation
Galaxy evolution workshop
June 5th, 2019
Taira Oogi
Kavli IPMU
Collaborators: Hikari Shirakata (Tadano Ltd.), Masahiro Nagashima (Bunkyo University),Toshihiro Kawaguchi (Onomichi City University),
Takashi Okamoto (Hokkaido University), Tomoaki Ishiyama (Chiba University)

Outline• Co-evolution of supermassive black holes andgalaxies• AGN host halo masses• Previous work
• Model• AGN triggering mechanisms• Results• Redshift evolution of AGN host halo masses• Two-point correlation functions of AGNs• AGN halo occupation distributions (HODs)

MBH-Mbulge relation/00(&)
22&(0(MBH (Msun)

10#$10%• Implication for the co-evolutionof SMBHs and galaxies.

10&10'3)710(10%1&10#$ 10## 10#)Mbulge (Msun)• Statistical properties of active
galactic nuclei (AGNs) are
important for understanding theco-evolution.

AGN host dark matter (DM) halos

Redshift evolution of DM halo mass inferred from AGN
clustering for AGN populations (Alexander & Hickox 2012)

AGN clustering and host halo
mass can be constraints on theSMBH growth and AGN
triggering mechanisms.

AGN host dark matter (DM) halos

Redshift evolution of DM halo mass inferred from AGN
clustering for AGN populations (Alexander & Hickox 2012)

For optically luminous quasars,
the host halo mass inferred fromclustering is ! − #×%&%! '(% )⨀.DM halo mass of X-ray AGNs

Redshift evolution of DM halo mass for moderate luminosity(X-ray) AGNs (compilation by Georgakakis et al. 2019)DM halo mass of X-ray AGNs

Redshift evolution of DM halo mass for moderate luminosity(X-ray) AGNs (compilation by Georgakakis et al. 2019)For moderately luminous X-rayselected AGNs, clustering studies
have obtained higher typical halo
masses, !"!#.%&!'.% (&! )⨀.DM halo mass of X-ray AGNs

Redshift evolution of DM halo mass for moderate luminosity(X-ray) AGNs (compilation by Georgakakis et al. 2019)
X-ray AGNs

For moderately luminous X-rayselected AGNs, clustering studies
have obtained higher typical halo
masses, !"!#.%&!'.% (&! )⨀.
Luminous quasars

Previous work

DM halo mass distribution of quasars• The DM halo mass of luminous quasars can be
explained by models in which quasar activity is$% ~10)*ℎ,)$⨀triggered by galaxy major mergers (at least ! ≲ #).

Hot-halomode• The X-ray AGN host halo can be explained by“hot-halo mode AGN” (Fanidakis et al. 2013).

hot-halo

Fanidakis et al. 201311.0 12.0 13.0 14.0
log[$2345/(ℎ,)$⨀)]
Oogi et al. 2016

Aim of this study
We explore whether the hot-halo mode AGN activity isnecessary to explain the host halo mass ofmoderately-luminous AGNs or not.
We investigate this issue with our semi-analytic modelof galaxy and AGN formation (Shirakata et al. 2019)

Semi-analytic model ν2GC

1. Galaxy formation model••

Dark matter halo merger trees from cosmological simulations (Ishiyama et al. 2015)
Baryon physics：gas cooling, star formation, and feedback through supernovaeand AGNs (Shirakata et al. 2019)

Hot gasDisk stars

Bulge stars

Cold gas

Supermassiveblack hole

Semi-analytic model ν2GC

Galaxy mergers

Disk instability

2. AGN triggering model

Assumption: a major/minor merger of galaxies anddisk instability trigger cold gas accretion on to a SMBH
and AGN activity.
The mass accretion rate:"̇ #$ =∆"'(()-)'.) − )exp)'(()'(()'(( = 012345 )678,12345 + );<==

3. Gas accretion timescales onto black holes

Assumption: the timescale of BH growth, i.e. gas accretion, iscontrolled by the timescale of angular momentum loss at < 100 pc,EF)loss ∝ "B.D#$ ∆"'(( ,where "#$ is the SMBH mass and ∆"'(( is the accreted gas mass.

QSO 3C273(ESA/Hubble& NASA)

AGN luminosity functions

Shirakata et al. 2019

The model reproduces the observed AGN luminosity function at z<6.

Results

Lx-Mhalo relation

At high redshifts (z=2), the halo mass a
weak dependence on AGN luminosity.

At low redshifts (z=0.5), there are many faintAGNs in high mass halos (!"#$% ≳ '(') "*' !⨀ ,dashed circle).
These AGNs have long gas accretion timescales.

Lx-Mhalo relation: model dependence
Model with tloss (fiducial)

Model without tloss

Relatively faint AGNs in massive halos with !"#$% ≳ '(') "*' !⨀ are an important featureof the fiducial model with tloss .

Redshift evolution of AGN host halo mass:model

The effective halo mass is defined as the mass which satisfied ! "#$$ = !&'( , where!("* ) is the halo bias of mass "* (Tinker et al. 2010).

• The AGN host halo mass of low
luminosity AGNs is higher thanthat of luminous AGNs at low-z.
• At high-z, there is no significant
luminosity dependence.

Redshift evolution of host halo masslog (Lx / erg s-1) = [41.5, 42.5]log (Lx / erg s-1) = [42.5, 43.5]

log (Lx / erg s-1) = [43.5, 44.5]• Overall, our model is consistent with the current measurements.
• typical host halo mass, !"!#.%&!'.% (&! )⨀.
• There is a large scatter of the observationally estimated halo masses.
• Difficult to explain the massive host halo mass for luminous AGNs.

2PCF of X-ray AGN: comparison with Obs.
Cappelluti et al. 2010100

10z=01

100

10z~1
10.1

1rp [h••z~3

Koutoulidis et al. 2013
Model: log10 LX = [43.5,44.5]
Model: log10 LX = [42.5,43.5]
Model: log10 LX = [41.5,42.5]

1000wp(rp) [h-1 Mpc]

1000

wp(rp) [h-1 Mpc]

z~1-110Mpc]

Allevato et al. 2014

1000wp(rp) [h-1 Mpc]

z=010010z~310.11

rp [h-110Mpc]

0.11rp [h-110Mpc]

Our model results are in agreement with observed AGN clustering.
At low redshifts (z=0, 1), the clustering amplitude of less luminous
AGNs is higher than luminous AGNs.

HOD for different triggering mechanisms
Central AGNs

z=1z=3

Satellite AGNs

Major merger
Minor merger
Disk instability

X-ray AGNs with 42.5 < log (Lx / erg s-1) < 43.5

z=1

z=3

• Minor mergers are the main triggering mechanism of AGN.
• Satellite AGNs contribute the HOD.

Summary• We can predict the AGN host halo mass andclustering by using our latest semi-analytic model.

• Our model is consistent with the current observations.
• Typical host halo mass, !"!#.%&!'.% (&! )⨀.

• Hot-halo mode AGNs is not necessary to explain thehost halo mass of X-ray AGNs.

• Minor mergers are the main triggering mechanism ofAGNs.
• Halo occupation distributions of AGNs can be anadditional constraint.