Photometric redshifts and cosmology

Details Photometric redshifts and cosmology Photometric redshifts and cosmology

Dec 1985

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1985phdt........17s&link_type=abstract

Ph.D. Thesis Princeton Univ., NJ.

Mathematics

Logic

5

Cosmology, Galactic Radiation, Photometry, Red Shift, Charge Coupled Devices, Deceleration, Galactic Evolution, Spectrographs, Stellar Luminosity

Scientific paper

How to obtain redshifts of galaxies from photometry through medium width filters is demonstrated. By exploiting the efficiency and red response of a Charge Coupled Device one is able to obtain redshifts for hundreds of faint galaxies in a few hours, which is a considerable speed improvement over spectrographic methods. The sizes of the errors in the redshifts are predictable and are smaller then 0.08 in z. The redshift data is applied to the question of galactic evolution. Comparing the luminosity distribution of galaxies in the sample with that of nearby galaxies it is concluded that galaxies have grown fainter by 0.5 + or - 0.2 mag in the visual band since the epoch of z = 0.55. The ratio of red galaxies to blue galaxies has decreased by 10 + or - 20%. We review the current theoretical understanding of galactic evolution and find our data consistent with it. If evolution does not change the number of galaxies in an undecipherable way, the number per volume fixes the amount of volume at different redshifts. Knowledge of the volume allows the determination of the cosmological deceleration parameter qzero. The difficulties in using photometric redshifts to understand the effects of evolution and determine qzero are outlined.

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