Two novel methods of measuring cosmic distances in the Universe

Lindholmer, Mikkel Ortving

Abstract

We present two novel methods of distance measurement using photometric techniques. We compare the methods to each other and independently created methods to measure photometric redshifts.
The first method we present in this thesis is based on SFR of galaxies which are typically either star forming, quenched, or in transition between the two. This causes the SFR measurements to group up into two distinct and well defined groups in SFR-M? space. We measure how these groups evolve with redshift and see a distinct non degenerate evolutionary path which makes it possible to use it for distance measurements. Since this method requires measurements of several different galaxies we apply this method to several galaxy clusters to test it and see how well it works.
The second method uses BL Lac objects to measure distance. While using these objects is not by itself a novel concept, we do extract the host galaxy magnitudes needed to measure the distance in a way that has not before been done on this large an amount of data. We also present several thousand new BL Lac candidates in the SDSS BOSS catalogue which has not previously undergone a systematic and dedicated search for BL Lacs. By doing this we also find many more radio quiet BL Lac like objects which have previously not been detected in a high enough number to properly analyse through the use of statistics.
Finally we compare the two methods to each other as well with an independent photometric redshift method as well as measure the Hubble constant to be able to compare the methods to the distance ladder as a whole. Here the SFR method does not match up well to the independent methods giving worse results, but the BL Lac method give results with similar precision to the independent methods.

Citation

Lindholmer, M. O. Two novel methods of measuring cosmic distances in the Universe. (Thesis). University of Hull. https://hull-repository.worktribe.com/output/4223654

• Thesis Type: Thesis
• Deposit Date: Nov 24, 2021
• Publicly Available Date: Feb 24, 2023
• Keywords: Physics
• Public URL: https://hull-repository.worktribe.com/output/4223654
• Additional Information: Department of Physics and Mathematics, The University of Hull
• Award Date: Nov 1, 2020