A catalog of photometric redshift and the distribution of broad galaxy morphologies

TL;DR

This paper presents a large catalog of photometric redshifts for about 3 million SDSS galaxies, annotated with broad morphological classifications, using optimized pattern recognition algorithms.

Contribution

It introduces a new, extensive galaxy catalog with photometric redshifts and morphology annotations, surpassing previous SDSS catalogs in scope and detail.

Findings

Number of spiral galaxies peaks at redshift ~0.085

Spiral-to-elliptical galaxy ratio decreases with redshift

Catalog is publicly available for further research

Abstract

We created a catalog of photometric redshift of ~3,000,000 SDSS galaxies annotated by their broad morphology. The photometric redshift was optimized by testing and comparing several pattern recognition algorithms and variable selection strategies, trained and tested on a subset of the galaxies in the catalog that had spectra. The galaxies in the catalog have i magnitude brighter than 18 and Petrosian radius greater than 5.5''. The majority of these objects are not included in previous SDSS photometric redshift catalogs such as the photoz table of SDSS DR12. Analysis of the catalog shows that the number of galaxies in the catalog that are visually spiral increases until redshift of ~0.085, where it peaks and starts to decrease. It also shows that the number of spiral galaxies compared to elliptical galaxies drops as the redshift increases. The catalog is publicly available at https://figshare.com/articles/Morphology_and_photometric_redshift_catalog/4833593