Photometric redshifts and luminosoty functions from the SPITZER SWIRE survey
Author(s)
Babbedge, Thomas Sebastian Reed
Abstract
This Thesis presents a study of galaxies and quasars from the viewpoint of their optical and infrared properties. Rather than focusing in on individual objects, the general characteristics of extragalactic sources are explored by classifying them as one of a small set of generic 'types'. This template-fitting approach opens up a wealth of possible applications, from deriving redshifts to tracing the distribution and evolution of different galaxy populations in both space and time. More precisely, this Thesis develops a photometric redshift technique that derives redshifts and dust extinction for both galaxies and quasars. This is first applied to optical data and then extended to incorporate infrared data as well. Following on from the recent successful launch and ongoing operation of the SPITZER infrared space observatory, this Thesis utilises data from the SWIRE extragalactic survey which combines SPITZER and ground-based observations in six extragalactic fields. As well as reducing ground-based optical photometry to produce band-merged source catalogues this Thesis uses the optical-infrared catalogues to derive redshifts and then applies an infrared template-fitting technique to the mid- to far-infrared emission of these sources in order to derive luminosities. The large-scale nature of the SWIRE survey then allows luminosity functions to be constructed in a number of SPITZER wavebands, which are an important probe of galaxy evolution and star formation. Evolution of both the galaxy and quasar luminosity functions is seen with redshift, such that there are more high-luminosity sources to higher redshifts. There is then a drop in space densities at redshifts of 1.5 to 2 for galaxies, and 3 to 4 for quasars, indicating the likely onset of main activity.
Version
Open Access
Date Awarded
2004
Copyright Statement
Attribution-Non Commercial-No Derivatives 4.0 International Licence (CC BY-NC-ND)
License URL
Advisor
Rowan-Robinson., Michael
Sponsor
Particle Physics and Astronomy Research Council
Grant Number
PPA/S/S/2001/03217
Publisher Department
Department of Physics
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)