eprintid: 1446357
rev_number: 9
eprint_status: archive
userid: 636
dir: disk0/01/44/63/57
datestamp: 2016-03-08 13:18:49
lastmod: 2016-03-08 13:18:49
status_changed: 2016-03-08 13:18:49
type: thesis
metadata_visibility: show
item_issues_count: 0
creators_name: Ashton, C.E.
title: A study of warm absorbers in active galactic nuclei.
ispublished: unpub
divisions: F63
note: Thesis digitised by Proquest
abstract: This thesis explores the 'warm absorber' phenomenon observed in Active Galactic Nuclei (AGN). Warm absorbers are clouds of ionised gas within AGN, that cause absorption at soft X-ray wavelengths. They are observed in half of all Type 1 AGN, hence they play an important part in the framework of our under standing of Active Galactic Nuclei. Observations with the satellite XMM-Newton have given us the highest signal-to-noise data yet. XMM-Newton observations of the quasars PG 1114+445 and PG 1309+355 are studied. Both quasars exhibit evidence for absorption by warm material in the line-of-sight. We define a 'phase' of absorption to have a single ionisation param eter and column density. From fits to the data, the absorption in PG 1114+445 is found to be in two phases, a 'hot' phase with a log ionisation parameter f of 2.57 and a column of 1022 cm-2, and a 'cooler' one with log f of 0.83 and a column of 1021 cm-2. The absorption in PG 1309+355 consists of a single phase, with log f of 1.87 and a column of 1021 cm-2. The absorbing gas lies at distances of 1019 - 1022 cm from the continuum radiation sources in these AGN, suggesting origins in a wind emanating from a molecular torus, according to the 'Standard Model' of AGN. The kinetic luminosities of the outflowing absorbers represent insignificant fractions (< 10 3) of the energy budgets of the AGN. Using data for the Seyfert 1 H 0557 385, the warm absorption is characterised by two phases, a phase with log £ of 0.48 and a column of 1021 cm-2, and a phase with log f of 1.63 and a column of 1022 cm-2. Neutral absorption is also present in the source, and possible origins for this are discussed. For a large sample, observations of warm absorbers are collated and compared with models.
date: 2005
id_number: PQ ETD:593875
oa_status: green
full_text_type: other
thesis_class: res_masters_open
language: eng
primo: open
primo_central: open_green
verified: verified_manual
full_text_status: public
pages: 94
institution: University of London
thesis_type: Masters
citation:        Ashton, C.E.;      (2005)    A study of warm absorbers in active galactic nuclei.                   Masters thesis , University of London.     Green open access   
 
document_url: https://discovery.ucl.ac.uk/id/eprint/1446357/1/U593875.pdf