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Developing a photometric estimate of quasar redshifts: An independent measurement of the distances to the most powerful objects in the Universe

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posted on 2021-12-08, 08:16 authored by Jeremy MossJeremy Moss

While spectroscopy is the standard method of measuring the redshift of luminous objects, it is a time-intensive technique, requiring, in some cases, hours of telescope time for a single source. Additionally, spectroscopy favours brighter objects, and therefore introduces an intrinsic bias towards luminous or closer sources. A simple method of estimating the redshift through photometry would prove invaluable to forthcoming surveys on the next generation of large radio telescopes, as well as alleviating the inherent bias towards the most optically bright sources. While there is a well-established correlation between the near-infrared K-band magnitude and redshift for galaxies, we find that the K-z relation breaks down for samples dominated by quasi-stellar objects (QSOs).  Current methods of estimating photometric redshift rely either on template spectra, which requires a high number of infrared photometry points, or computationally intensive machine learning methods.  Using photometric data from the Sloan Digital Sky Survey (SDSS) we investigate the relationship between combinations of magnitudes of a group of quasars, and their redshift. We find a high correlation between the colour relation (I-W2)/(W3-U) and redshift for a group of broad-line emission sources from the SDSS, and we conclude that this could be a robust estimator of the redshift.

History

Copyright Date

2019-01-01

Date of Award

2019-01-01

Publisher

Te Herenga Waka—Victoria University of Wellington

Rights License

Author Retains Copyright

Degree Discipline

Physics

Degree Grantor

Te Herenga Waka—Victoria University of Wellington

Degree Level

Masters

Degree Name

Master of Science

ANZSRC Type Of Activity code

970102 Expanding Knowledge in the Physical Sciences

Victoria University of Wellington Item Type

Awarded Research Masters Thesis

Language

en_NZ

Victoria University of Wellington School

School of Chemical and Physical Sciences

Advisors

Curran, Stephen