Outflows and Dust in Quasars

Supermassive black holes (SMBHs) at the centres of galaxies are known to actively accrete, forming so-called `active galactic nuclei' (AGN) or `quasars'. These AGN are believed to feed back energy into their host galaxies, regulating star formation and the growth of the SMBH itself. This thesis investigates the outflow properties in quasars at 1<z<3, corresponding to the peak epoch of galaxy formation and SMBH growth. First, I make use of recent improvements to atomic energy-level data and photoionisation models to constrain the properties of the Fe III emitting material in quasars. I show that this material must be dense and micro-turbulent to explain the observed strength of emission, and thus arise from the inner parts of the broad line region. The strength of this emission is shown to correlate with the outflow properties. Second, I develop an SED model capable of reproducing the median observed photometric colours in the SDSS quasar population. This model is then used to investigate the properties of the emission from the hottest, sublimation-temperature dust components in the near infrared spectra of quasars. This dust is believed to be located at the inner edge of the toroidal obscuring structure. The strength of hot dust emission is found to correlate with the quasar outflow properties, providing evidence of a link between the broad line region and the dusty structures surrounding the inner regions of the AGN. Finally, I quantify the outflow properties in a sample of heavily dust-reddened quasars. When matched in redshift and luminosity, there is no significant difference between the outflow kinematics of reddened and unobscured quasars. Assuming a paradigm in which dust-reddened quasars arise from major galaxy mergers, quasar-driven outflows must therefore persist after the obscuring dust is cleared from the line of sight.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2020

Author dc:creator

• Temple, Matthew

Advisors dc:contributor.advisor

• Banerji, Manda
• Hewett, Paul

• quasars:general

Licence

• https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/11d98502-d027-4cc3-bfb8-ba84217688d4/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

Author Identifier

0000-0001-8433-550X
0000-0002-6528-1937

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/321251