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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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 |
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Doctoral Thesis |
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FIS/05 Astronomia e astrofisica |
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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/ |
work_keys_str_mv |
AT vitofabio1986 xraypropertiesandevolutionofhighredshiftagnandthegascontentofhostgalaxies |
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1716730535270678528 |