X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies

In this thesis, I have investigated the evolution of the high-redshift (z > 3) AGN population by collecting data from some of the major Chandra and XMM-Newton surveys. The final sample (141 sources) is one of the largest selected at z> 3 in the X- rays and it is characterised by a very high re...

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Bibliographic Details
Main Author: Vito, Fabio <1986>
Other Authors: Vignali, Cristian
Format: Doctoral Thesis
Language:en
Published: Alma Mater Studiorum - Università di Bologna 2014
Subjects:
Online Access:http://amsdottorato.unibo.it/6729/
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spelling ndltd-unibo.it-oai-amsdottorato.cib.unibo.it-67292015-02-10T04:49:41Z X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies Vito, Fabio <1986> FIS/05 Astronomia e astrofisica In this thesis, I have investigated the evolution of the high-redshift (z > 3) AGN population by collecting data from some of the major Chandra and XMM-Newton surveys. The final sample (141 sources) is one of the largest selected at z> 3 in the X- rays and it is characterised by a very high redshift completeness (98%). I derived the spectral slopes and obscurations through a spectral anaysis and I assessed the high-z evolution by deriving the luminosity function and the number counts of the sample. The best representation of the AGN evolution is a pure density evolution (PDE) model: the AGN space density is found to decrease by a factor of 10 from z=3 to z=5. I also found that about 50% of AGN are obscured by large column densities (logNH > 23). By comparing these data with those in the Local Universe, I found a positive evolution of the obscured AGN fraction with redshift, especially for luminous (logLx > 44) AGN. I also studied the gas content of z < 1 AGN-hosting galaxies and compared it with that of inactive galaxies. For the first time, I applied to AGN a method to derive the gas mass previously used for inactive galaxies only. AGN are found to live preferentially in gas-rich galaxies. This result on the one hand can help us in understanding the AGN triggering mechanisms, on the other hand explains why AGN are preferentially hosted by star-forming galaxies. Alma Mater Studiorum - Università di Bologna Vignali, Cristian 2014-12-12 Doctoral Thesis PeerReviewed application/pdf en http://amsdottorato.unibo.it/6729/ info:eu-repo/semantics/openAccess
collection NDLTD
language en
format Doctoral Thesis
sources NDLTD
topic FIS/05 Astronomia e astrofisica
spellingShingle FIS/05 Astronomia e astrofisica
Vito, Fabio <1986>
X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies
description In this thesis, I have investigated the evolution of the high-redshift (z > 3) AGN population by collecting data from some of the major Chandra and XMM-Newton surveys. The final sample (141 sources) is one of the largest selected at z> 3 in the X- rays and it is characterised by a very high redshift completeness (98%). I derived the spectral slopes and obscurations through a spectral anaysis and I assessed the high-z evolution by deriving the luminosity function and the number counts of the sample. The best representation of the AGN evolution is a pure density evolution (PDE) model: the AGN space density is found to decrease by a factor of 10 from z=3 to z=5. I also found that about 50% of AGN are obscured by large column densities (logNH > 23). By comparing these data with those in the Local Universe, I found a positive evolution of the obscured AGN fraction with redshift, especially for luminous (logLx > 44) AGN. I also studied the gas content of z < 1 AGN-hosting galaxies and compared it with that of inactive galaxies. For the first time, I applied to AGN a method to derive the gas mass previously used for inactive galaxies only. AGN are found to live preferentially in gas-rich galaxies. This result on the one hand can help us in understanding the AGN triggering mechanisms, on the other hand explains why AGN are preferentially hosted by star-forming galaxies.
author2 Vignali, Cristian
author_facet Vignali, Cristian
Vito, Fabio <1986>
author Vito, Fabio <1986>
author_sort Vito, Fabio <1986>
title X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies
title_short X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies
title_full X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies
title_fullStr X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies
title_full_unstemmed X-ray properties and evolution of high-redshift AGN, and the gas content of host galaxies
title_sort x-ray properties and evolution of high-redshift agn, and the gas content of host galaxies
publisher Alma Mater Studiorum - Università di Bologna
publishDate 2014
url http://amsdottorato.unibo.it/6729/
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