Accretion and star formation in quasars
<p>Studying the interplay of accretion and star formation is crucial to our understanding of galaxy evolution. The new generation of radio surveys are able to play a key role in this area, since both processes produce radio emission. As we probe low radio-luminosities, the two main populations...
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| Format: | Thesis |
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2015
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| _version_ | 1797082962227888128 |
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| author | White, S |
| author2 | Jarvis, M |
| author_facet | Jarvis, M White, S |
| author_sort | White, S |
| collection | OXFORD |
| description | <p>Studying the interplay of accretion and star formation is crucial to our understanding of galaxy evolution. The new generation of radio surveys are able to play a key role in this area, since both processes produce radio emission. As we probe low radio-luminosities, the two main populations are star-forming galaxies and radio-quiet quasars (RQQs). How they contribute to the total radio emission is under debate, with previous authors arguing that star formation dominates. In this thesis I investigate the relative levels of radio emission due to accretion and star formation in RQQs.</p> <p>Firstly, I select a sample of 74 quasars from the VISTA Deep Extragalactic Observations (VIDEO) survey, whose depth allows me to study very low accretion rates and/or lower-mass black holes. By comparing radio emission from the quasars with that from a control sample of galaxies, and calculating two independent estimates of star-formation rate, I show that this emission is predominantly related to the accretion process. A second sample of 72 RQQs is obtained from the <em>Spitzer-Herschel</em> Active Galaxy Survey, spanning a factor of &Tilde;100 in optical luminosity over a narrow redshift range at <em>z</em>&Tilde;1. This enables evolutionary effects to be decoupled when comparisons are made with the VIDEO sample. I reduce radio data from the Karl G. Jansky Very Large Array (JVLA) for these objects, and find further support that accretion makes a significant contribution to the radio emission in RQQs. In addition, the levels of accretion and star formation appear to be weakly correlated with each other, and with optical luminosity.</p> <p>These findings offer an insight into how the mechanisms behind galaxy evolution may interact differently in RQQs compared to their radio-loud counterparts. They also have important implications for modelling radio populations below 1mJy, which is necessary for the development of the Square Kilometre Array.</p> |
| first_indexed | 2024-03-07T01:35:21Z |
| format | Thesis |
| id | oxford-uuid:94fa7a0c-83be-4283-9bf5-558b9354044d |
| institution | University of Oxford |
| last_indexed | 2024-03-07T01:35:21Z |
| publishDate | 2015 |
| record_format | dspace |
| spelling | oxford-uuid:94fa7a0c-83be-4283-9bf5-558b9354044d2022-03-26T23:43:10ZAccretion and star formation in quasarsThesishttp://purl.org/coar/resource_type/c_db06uuid:94fa7a0c-83be-4283-9bf5-558b9354044dAccretionQuasarsStar FormationActive Galactic NucleiGalaxy EvolutionRadio AstronomyORA Deposit2015White, SJarvis, M<p>Studying the interplay of accretion and star formation is crucial to our understanding of galaxy evolution. The new generation of radio surveys are able to play a key role in this area, since both processes produce radio emission. As we probe low radio-luminosities, the two main populations are star-forming galaxies and radio-quiet quasars (RQQs). How they contribute to the total radio emission is under debate, with previous authors arguing that star formation dominates. In this thesis I investigate the relative levels of radio emission due to accretion and star formation in RQQs.</p> <p>Firstly, I select a sample of 74 quasars from the VISTA Deep Extragalactic Observations (VIDEO) survey, whose depth allows me to study very low accretion rates and/or lower-mass black holes. By comparing radio emission from the quasars with that from a control sample of galaxies, and calculating two independent estimates of star-formation rate, I show that this emission is predominantly related to the accretion process. A second sample of 72 RQQs is obtained from the <em>Spitzer-Herschel</em> Active Galaxy Survey, spanning a factor of &Tilde;100 in optical luminosity over a narrow redshift range at <em>z</em>&Tilde;1. This enables evolutionary effects to be decoupled when comparisons are made with the VIDEO sample. I reduce radio data from the Karl G. Jansky Very Large Array (JVLA) for these objects, and find further support that accretion makes a significant contribution to the radio emission in RQQs. In addition, the levels of accretion and star formation appear to be weakly correlated with each other, and with optical luminosity.</p> <p>These findings offer an insight into how the mechanisms behind galaxy evolution may interact differently in RQQs compared to their radio-loud counterparts. They also have important implications for modelling radio populations below 1mJy, which is necessary for the development of the Square Kilometre Array.</p> |
| spellingShingle | Accretion Quasars Star Formation Active Galactic Nuclei Galaxy Evolution Radio Astronomy White, S Accretion and star formation in quasars |
| title | Accretion and star formation in quasars |
| title_full | Accretion and star formation in quasars |
| title_fullStr | Accretion and star formation in quasars |
| title_full_unstemmed | Accretion and star formation in quasars |
| title_short | Accretion and star formation in quasars |
| title_sort | accretion and star formation in quasars |
| topic | Accretion Quasars Star Formation Active Galactic Nuclei Galaxy Evolution Radio Astronomy |
| work_keys_str_mv | AT whites accretionandstarformationinquasars |