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An optical imaging study of 0.4 < z < 0.8 quasar host galaxies: II. Analysis and interpretation
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Astronomy and Space Physics, The Uppsala Astronomical Observatory.
2005 In: Astronomy and Astrophysics, ISSN 0004-6361, Vol. 443, 61-78 p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2005. Vol. 443, 61-78 p.
URN: urn:nbn:se:uu:diva-90499OAI: oai:DiVA.org:uu-90499DiVA: diva2:162871
Available from: 2003-05-07 Created: 2003-05-07Bibliographically approved
In thesis
1. Quasar host galaxies at intermediate and high redshifts
Open this publication in new window or tab >>Quasar host galaxies at intermediate and high redshifts
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Quasars form one of the most energetic phenomena in the universe, and can be traced out to very large redshifts. By studying the galaxies which host the active nuclei, important insights can be gained into the processes that trigger and maintain the quasar powerhouse. The evolution rate of the quasar population is furthermore similar to that of ordinary galaxies, which implies a connection between black hole accretion and star formation in the host galaxies. While the properties of quasar host galaxies at low redshift have become better constrained in recent years, less is known about hosts at earlier cosmic epochs. In addition, though radio-quiet quasars are by far more common than their radio-loud counterparts their host galaxies have not been studied to the same extent, in particular not at higher redshifts.

An imaging campaign of a large sample of quasars at intermediate redshift (0.4 < z < 0.8) was carried out at optical wavelengths using the Nordic Optical Telescope, and is studied in this thesis together with two smaller samples. The joint material forms more than half of the total number of observed sources in this redshift interval and increases the number of resolved radio-quiet hosts at z>0.4 considerably. The morphology and mean magnitudes are found to be similar for radio-loud and radio-quiet host galaxies. Both types of host are shown to have optical colours as blue as those of present-day late-type spirals and starburst galaxies, which is likely the result of ongoing star formation.

With increasing redshift, observations of host galaxies become more difficult. High spatial resolution can be achieved with adaptive optics, but the variation of the point spread function in the near-infrared wavelength band which is most suited for detection is large and rapid. A statistical approach to the problem of characterizing the point spread function has been developed, making use of simulated objects which are matched to the different atmospheric conditions. Bright, compact host galaxies showing signs of merging and interaction were detected in this way for three quasars at z~2.2, which were observed with the ESO 3.6 m telescope. The method is not restricted to host galaxy analysis but can be utilized in other applications as well, provided that the underlying extended source can be described by an analytical model.

Place, publisher, year, edition, pages
Uppsala: Uppsala Astronomiska Observatorium, 2003. 64 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 842
Astronomy, Active galaxies, Quasars, Host galaxies, Imaging, Photometry, Magnitudes, Colours, Morphology, Statistical methods, High-redshift, Infrared, Astronomi
National Category
Astronomy, Astrophysics and Cosmology
Research subject
Theoretical Astrophysics
urn:nbn:se:uu:diva-3451 (URN)91-554-5642-1 (ISBN)
Public defence
2003-05-30, Häggsalen, Ångströmlaboratoriet, Uppsala, 10:15
Available from: 2003-05-07 Created: 2003-05-07Bibliographically approved

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