Exploring star formation in galaxy populations using the far-infrared - radio correlation

White, Richard F (2015) Exploring star formation in galaxy populations using the far-infrared - radio correlation. Doctoral thesis (PhD), University of Sussex.

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Abstract

In this thesis I take a close look at the far-infrared radio - correlation, a puzzlingly persistent
and tight relationship identified between the far-infrared and radio luminosities of
star forming galaxies. Two disparate processes are attributed to this phenomenon. In the
first, starlight from massive stars is reprocessed by dust to be re-emitted in the infrared
and secondly, radio emission in the form of synchrotron radiation originating in shocks
driven by these same high mass stars as they end their lives as supernovae. Cosmic ray
electrons are accelerated by these shocks, their paths subsequently spiralling in their host
galaxies magnetic fields, produce a continuum of synchrotron radiation. I investigate this
far-infrared radio correlation for a large sample of IRAS galaxies and compare my results
to previous studies. I look at the effect of peak galaxy dust temperature on the correlation,
dividing my sample into ‘warm’ and ‘cool’ bins and find a lower flux ratio in the warm
sample. The correlation at low radio frequencies is tested, probing the constancy of the
dominant synchrotron radiation where absorption or other effects are expected to lead to
a divergence from the linear continuum spectrum. Finally I look at a smaller sample of
galaxies in the ELAIS-N1 field using HerMES and GMRT data to investigate the correlation
to higher redshifts. The interest and rational for investigating this correlation is its
evident link to star formation. Any deviation for example will imply an evolution in one
or both of these processes which are closely linked to star formation. With the advent
of new dedicated low frequency array radio telescopes such as LOFAR it is increasingly
necessary to trust the correlation at these longer wavelengths if observational data is to
be used as a reliable predictive tool in the study of star formation.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy > QB0495 Descriptive astronomy > QB0799 Stars
Depositing User: Library Cataloguing
Date Deposited: 20 Mar 2015 11:00
Last Modified: 28 Sep 2015 13:36
URI: http://srodev.sussex.ac.uk/id/eprint/53463

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