Abstract/Details

The relationship of active galactic nuclei & quasars with their local galaxy environment


2009 2009

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Abstract (summary)

We explore how the local environment is related to properties of active galactic nuclei (AGNs) of various luminosities. Recent simulations and observations are converging on the view that the extreme luminosity of quasars, the brightest of AGNs, is fueled in major mergers of gas-rich galaxies. In such a picture, quasars, the highest luminosity AGNs, are expected to be located in regions with a higher density of galaxies on small scales where mergers are more likely to take place. However, in this picture, the activity observed in low-luminosity AGNs is due to secular processes that are less dependent on the local galaxy density. To test this hypothesis, we compare the local photometric galaxy density on kiloparsec scales around spectroscopic type I and type II quasars to the local density around lower-luminosity spectroscopic type I and type II AGNs. To minimize projection effects and evolution in the photometric galaxy sample we use to characterize AGN environments, we place our random control sample at the same redshift as our AGNs and impose a narrow redshift window around both the AGNs and control targets. Our results support these merger models for bright AGN origins. We find that the brightest sources have overdensities that increase on the smallest scales compared to dimmer sources. In addition, we investigate the nature of the quasar and AGN environments themselves and find that the increased overdensity of early-type galaxies in the environments of bright type I sources suggests that they are located in richer cluster environments than dim sources. We measure increased environment overdensity with increased quasar black hole mass, consistent with the well-known M DMH – MBH relationship, and find evidence for quenching in the environments of high accretion efficiency type I quasars.

Indexing (details)


Subject
Astronomy
Classification
0606: Astronomy
Identifier / keyword
Pure sciences; Active galactic nuclei; Cosmology: observations; Large-scale structure of Universe; Quasars
Title
The relationship of active galactic nuclei & quasars with their local galaxy environment
Author
Strand, Natalie Erin
Number of pages
191
Publication year
2009
Degree date
2009
School code
0090
Source
DAI-B 71/01, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9781109580297
Advisor
Stack, John; Brunner, Robert
University/institution
University of Illinois at Urbana-Champaign
University location
United States -- Illinois
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3395505
ProQuest document ID
304897812
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304897812
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