AGN Demographics
Christine Black
3/1/12
http://www.redorbit.com/news/space/1018193/satellites_unveil_new_type_of_active_galaxy/
Major Points
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What is a demographical study?
Very brief overview of AGNs
Galaxy evolution roadmap
Studies of AGN in the local universe
Studies from 0 < z < 1
Studies around z = 1
What is a Demographical
Study?
• Compare fraction of AGN to normal
galaxies in collection
• How are AGN fueled
• Galaxy morphology
• Must be able to see host galaxy, that
way can study stellar pop., structure,
mass, etc
AGN vs ‘normal’ galaxy
• Actively accreting SMBH at center of
host
• Seen in several wavelengths
– Radio, optical, Hard/Soft Xray
• Luminosities of L > 1042 ergs/s
– This helps in seeing them at higher z (1+)
Galaxy Evolution
• Move through
‘clouds’
– Blue cloud
– Green Valley
(Transition Zone)
– Red
Cloud/Sequence
Georgakakis 08
Local Studies
• Kauffmann 03
– Looked at ~ 123,000 galaxies from SDSS
• 22,623 host AGN
• From 0.02 < z < 0.3
• Use OIII emission line
– Strong for AGN
– Weak for metal-rich, star forming galaxies
Local
• Type 2 AGN found in
more massive hosts
– 3x1010-1011 M
• AGN fraction of
massive galaxies is
dependent on z
• Hosts are similar in
size and mass to
‘early type’ galaxies
Local
• Stars in Type 2 AGN
are the same as those
found in QSO with the
same redshift and OIII
luminosity
• Strong correlation btwn
age and OIII luminosity
– Low-luminosity have
older stars
– High-luminosity are like
late-type galaxies
• Large number type 2
AGN had burst of SF 12 GY ago
Local
Koss 11
BAT Ulta Hard Xray
0.01 < z < 0.07
• Bluer hosts than normal
galaxies of same mass
• Massive Galaxies (log(M)
> 10.5) are preferentially
spirals
• Ultra hard luminosity
increases with stellar
mess
• BAT AGN found massive
hosts with large bulgedisk ratios and SMBH
Local
• Best 05
– Radio luminosity is independent of BH mass
– More massive BHs host a larger fraction of radioloud AGN
• Ho 08
– 2/3 E-Sb galaxies have activity in nuclei
• Most are AGNs fueled by accretion
– Detect AGNs in bulge-less galaxies
0<z<1
• Haggard ‘10
– Chandra and SDSS
– 100k+ galaxies to .7z
– L >1042 ergs/s
• Fraction evolves with z
and correlates with mag
– (1+z)3 and (1+z)4
• Larger fraction
of bluer hosts
• possibly
dependent on z
Other Theories
• More in Blue/Green by
factor of 2
Aird ‘12
• Probability of a host with
AGN defined by a universal
Eddington Ratio is
independent of stellar mass
• AGN not related to
quenching or color change
z~1
• Nandra 07
– 0.6 < z < 1.4
– See low-level AGN in
dense environments
– Majority of AGN in red
sequence
• Supports quenching
– AGN activity is linked to
host evolution in the late
stages
z~1
• Gerogakakis 08
– Chandra All Wavelength
– 0.4 < z < 0.9
• Find AGN in the valley
– Some are obscured:
gas/dust must reform
• Based on morphology not major mergers
• Accretion last longer
than SF
– Find post-starburst at z ~
0.8
Conclusions
• Red vs Green vs Blue?
– Depends on z
• Star formation is not only fuel for AGN
• Morphology
– Soft-Hard Xray may not need bulges
– Ultra hard Xray found in Spirals
• Mergers
– Yes and No