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AGN Demographics

This article provides an overview of demographical studies of active galactic nuclei (AGNs) and their role in galaxy evolution. It explores the fueling mechanisms, morphology, and host galaxy properties of AGNs, and examines studies conducted in the local universe and at different redshifts. The article concludes by discussing the connection between AGNs and galaxy quenching, as well as the role of mergers in AGN activity.

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AGN Demographics

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  1. AGN Demographics Christine Black 3/1/12 http://www.redorbit.com/news/space/1018193/satellites_unveil_new_type_of_active_galaxy/

  2. Major Points • 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

  3. 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

  4. 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+)

  5. Galaxy Evolution • Move through ‘clouds’ • Blue cloud • Green Valley (Transition Zone) • Red Cloud/Sequence Georgakakis 08

  6. 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

  7. 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

  8. 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 1-2 GY ago

  9. 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 bulge-disk ratios and SMBH

  10. Local • Best 05 • Radio luminosity is independent of BH mass • More massive BHs host a larger fraction of radio-loud AGN • Ho 08 • 2/3 E-Sb galaxies have activity in nuclei • Most are AGNs fueled by accretion • Detect AGNs in bulge-less galaxies

  11. 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

  12. Other Theories • More in Blue/Green by factor of 2 • 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 Aird ‘12

  13. 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

  14. 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

  15. 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

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