Jack Singal
University of Richmond

20th Lomonosov Conference
August 23, 2021

Mechanics and Evolution ofSupermassive Black Holes withAGN Population Studies

Outline
1. The Case for multiwavelength AGN population studies
I. The case for AGN
II. The case for multiwavelength population studies
2. Statistical challenges because of truncated data
3. Luminosity Evolutions and implications for SMBHs
1. Optical
2. Radio
3. Infrared
4. Luminosity Correlations and implications for SMBHs
1. Optical-radio
2. Optical-infrared

Supermassive Black HolesThe phenomenon of Active Galaxies

Radio emission goes inall directions but
higher energy lightgoes more forward
Accretion Disk ofmatter swirls aroundcentral supermassiveblack hole(a billion times themass of the Sun)

“Host”
galaxyCharge particles interact with themagnetic field and each other tosend out light
RadioGalaxy

Jets of high energy
charged particles
stream out both sides“Quasar”(some radio,X-rays)
Blazar

Active Galaxies (AGN)
What’s going on at the center?
This is (very) incompletely understoodIn the Blandford-Znajek mechanism (1977,MNRAS, 179, 433) the rotational energy of thespinning supermassive black hole is extracted toaccelerate matter into jets
Faster BH rotation  brighter jets
The amount of matter that gets near the black hole isdetermined by the black hole mass and the amount ofmaterial available
More massive BH  more matter  brighter jets
More massive BH  more matter  brighter accretion disk
If we could discover how active galaxies change over the history of the Universe, wecould learn about the evolution over time of supermassive black hole systems

AGN in Multiwavelength
Faster BH rotation  brighter jets
More massive BH  more matter  bigger jets  brighter jets
More massive BH  more matter  brighter accretion disk
Accretion disk is hot gas
 glows primarily in optical, UV, X-rays
Jets are high energy charged particles
interacting with magnetic field and eachother glow primarily in radio, X-rays, andhigher energy X- and gamma-rays ifaligned with observer
Possible torus of dust
 Glows in infrared, obscuresaccretion disk at certain angles

AGN in Multiwavelength
Faster BH rotation  brighter jets
More massive BH  more matter  bigger jets  brighter jets
More massive BH  more matter  brighter accretion disk
Accretion disk is hot gas
 glows primarily in optical, UV, X-rays
Jets are high energy charged particles
interacting with magnetic field and eachother glow primarily in radio, X-rays, andhigher energy X- and gamma-rays ifaligned with observer
Possible torus of dust
 Glows in infrared, obscuresaccretion disk at certain angles

To learn about the nature andevolution of supermassive blackhole systems:
One possibility: Study a few resolved,
nearby objects in great detail… or…

We could do population
studies of tens of thousands ofunresolved objects to find out
how the radio, infrared, optical,
X-ray, and gamma-ray emission
have changed over the historyof the universe, and how they
are correlated with each other.

AGN Population Studies

To learn about the nature and evolution of supermassive blackhole systems:
We will do population studies of tens of thousands of unresolved
AGN to find out how the radio, infrared, optical, X-ray, and gammaray emission have changed over the history of the universe, andhow they are correlated with each other.
“Population Distributions and Correlations”
 Utilize the publically available data from large scale surveys
Optical: Sloan Digital Sky Survey (SDSS)Radio: FIRSTInfrared: Wide-Field Infrared Explorer (WISE), Spitzer
Space Telescope
X-Ray: Chandra X-Ray observatory, XMM- Newton
Gamma-ray: Fermi Gamma-ray Space TelescopeOutline
1. The Case for multiwavelength AGN population studies
I. The case for AGN
II. The case for multiwavelength population studies
2. Statistical challenges because of truncated data
3. Luminosity Evolutions and implications for SMBHs
1. Optical
2. Radio
3. Infrared
4. Luminosity Correlations and implications for SMBHs
1. Optical-radio
2. Optical-infrared

Consider – radio vs. optical output:
Radio output

Are these“luminosities”
correlated?

Radio output

Not (intrinsically)correlated!

An observed correlation canbe induced by observational
selection effects or similar
redshift evolutions of theluminosities
Observed correlations do not accuratelyreflect intrinsic correlations!
(in flux-limited data)

Optical output

“Flux” and “Luminosity”
Luminosity –how bright anobject actually is𝐿𝐿𝜈𝜈 𝐾𝐾 𝑧𝑧
𝐹𝐹𝜈𝜈 =
4𝜋𝜋 𝐷𝐷𝐿𝐿2 𝑧𝑧

Flux – how bright anobject appears to us –what we measure

Luminosity
Distance

Example: SDSS optical x FIRST radio
Optical Luminosity
5445 quasars seen inoptical and radio

Missing theseRadio Luminosity

Distance
Back in time
We are ‘missing’ mostof the data because ofthe flux limits!

and these

Distance
Back in time

Methods
Determining the correlations between the luminosities, andthe changes in the luminosities over time, is a nuanced
statistical challenge
Can’t go into it here but:

Techniques explored in :- Singal et al., 2019, ApJ, 877, 63- Singal, George, & Gerber, 2016, ApJ, 831, 60- Petrosian & Singal, 2015, Proc IAU S313
- Singal, 2015, MNRAS, 115, 122- Singal et al., 2011, ApJ, 743, 104- Singal et al., 2012, ApJ, 753, 45- Singal et al., 2013, ApJ, 764, 43- Singal, Petrosian, & Ko, 2014, ApJ, 786, 109

Let’s look at some results:

Outline
1. The Case for multiwavelength AGN population studies
I. The case for AGN
II. The case for multiwavelength population studies
2. Statistical challenges because of truncated data3. Luminosity Evolutions and implications for SMBHs
1. Optical
2. Radio
3. Infrared
4. Luminosity Correlations and implications for SMBHs
1. Optical-radio
2. Optical-infrared

Evolving Luminosity Functions
If a class of object changes in average luminosity over time, that iscalled “Luminosity Evolution”
Let’s parameterize the luminosity evolution in waveband a - as afunction of redshift (z) - like this:La (z ) = La z =0 ⋅ g a ( z )withg a ( z ) = (1 + z ) akor

g a (z ) =(1 + z )ka1+ z 1 +  zcr kaga(z) is the best-fit correlation function between band a luminosity and redshift

If ka is positive, the objects get brighter (on average) inwaveband a with increasing redshift (back in time).

Optical & Radio: Luminosity Evolutions
𝐿𝐿𝐿𝐿′𝑎𝑎 → 𝑎𝑎
𝑔𝑔𝑎𝑎 𝑧𝑧g a (z ) =(1 + z )ka1+ z 
1 + z cr ka

For combined Have to do aradio andsimultaneous τ comb =
optical dataset minimization of22
τ opt+ τ radLa (z ) = La z =0 ⋅ g a ( z )τcomb = 1 and 2 σ contours

kopt=3.4±0.2, krad=5.5±0.2
Quasars have undergone significant evolution with redshift in both radio and optical,
with greater evolution in radio. Quasars were more “radio loud” in the past!

Implications of these quasar radio
and optical results• Quasars were brighter in the past
• Quasars were more radio loud in the past (ratio of radio to opticalemission was higher) Going back in the past, jets get bigger relative to disks
Reminder: Radio emission comes primarily from jet and optical comesprimarily from accretion disk. For a given size of accretion disk, fasterspinning black holes will make bigger jets.

• Supermassive Black Holes used to be spinning fasterNext: SDSS (optical) x WISE (mid-infrared)
Optical Luminosity

Infrared Luminosity

Singal, George, & Gerber, 2016, ApJ, 831, 60

SDSS x WISE: Luminosity Evolutions
𝐿𝐿𝐿𝐿′𝑎𝑎 → 𝑎𝑎
𝑔𝑔𝑎𝑎 𝑧𝑧g a (z ) =(1 + z )ka1+ z 
1 + z cr ka

For combined Have to do asimultaneous τ comb =radio andoptical dataset minimization of22
τ opt+ τ inf

La ( z ) = La z =0 ⋅ g a ( z )τcomb = 1 and 2σ contours

kopt=3.35±0.1, kinf=2.75±0.05
Quasars have undergone less evolution withredshift in 22 μm infrared than optical or radio

Singal, George, & Gerber, 2016,ApJ, 831, 60

Implications of these quasar midinfrared and opical results• Quasars were brighter in the past, and there were more of them
• Quasars were less “mid-infrared loud” loud in the past
• Quasars seem to have a minimum mid-infrared luminosity• The tori grow over time as more dust is available in theUniverse (makes sense)• Infrared emission dominated by something other than the jet.

Probably even the lowest spin black holes (with the weakestjets) still have a torus to re-process accretion disk emission.
Further discussion / info: J. Singal, George, & Gerber, 2016, ApJ, 831, 60

Honorable Mention: Gamma-Rays
FSRQ Blazars
Singal, Petrosian, & Ko, 2014, ApJ, 786, 109kLγ=6.5±0.3
FSRQ blazars have undergone significant gamma-ray luminosity evolution withredshift
Reminder: Gamma-ray emission comes from the jet. For a given size ofaccretion disk, faster spinning black holes will make bigger jets.

• Supports conclusion that black holes used to be spinning
fasterOutline
1. The Case for multiwavelength AGN population studies
I. The case for AGN
II. The case for multiwavelength population studies
2. Statistical challenges because of truncated data
3. Luminosity Evolutions and implications for SMBHs
1. Optical
2. Radio
3. Infrared
4. Luminosity Correlations and implications for SMBHs
1. Optical-radio
2. Optical-infrared

(Intrinsic) Luminosity Correlations
Two issues:• How closely are the two luminosities (say radioand optical) intrinsically correlated?
• What is the form of the correlation?
𝐿𝐿𝐿𝑟𝑟𝑟𝑟𝑟𝑟 ∝𝐿𝐿′𝑜𝑜𝑜𝑜𝑜𝑜

𝛼𝛼if 𝛼𝛼 = 1 then liner correlation, etc..

Form of Correlation:
Real Radio-Optical &Mid-Infrared-Optical𝐿𝐿𝐿𝑎𝑎 ∝ 𝐿𝐿′ 𝑜𝑜𝑜𝑜𝑜𝑜

𝛼𝛼Luminosity Correlations Conclusions• We can access at least a good approximation of the degreeof and form of intrinsic correlation between two luminosities
by assessing the correlations and partial correlations in bins
• In quasars the optical and mid-infrared luminosities are very
highly intrinsically correlated (both in degree of correlationand power-law form), while optical and radio luminosities
are less intrinsically correlated• This makes sense if accretion disk luminosity (related toSMBH size) is primarily responsible for the optical and midinfrared emission while the radio emission depends on both
SMBH size and spin(Some) Overall Conclusions• Large-scale AGN population studies are enabled by large extragalactic surveys and statisticaltechniques to access the true intrinsic distributions from flux-limited and truncated data
• We have employed one particular non-parametric technique to access the distributions• We can estimate the intrinsic Luminosity-Luminosity correlations
A fairly consistent picture is emerging where:• AGNs were brighter in all wavebands in the past relative to now• AGN activity was more common in the past
• Considering optical (weaker) and radio (stronger) luminosity evolution we see that jetemission in the past was proportionally brighter when compared to accretion disk emission• The weak correlation between radio and optical luminosities supports the Blandford-Znajek
model of the black hole spin launching the jets
• Black holes were spinning more rapidly in the past relative to now• The strong correlation between mid-infrared and optical luminosities supports the pictureof infrared emission from a heated torus• The weaker mid-Infrared luminosity evolution relative to the other bands indicates thattorus emission is proportionally more important at later times than earlier, so tori have grown