HI Selected Galaxies in the Sloan Digital Sky Survey I: Optical Data

TL;DR

This paper provides improved optical photometry for 195 HI-selected galaxies from SDSS and Parkes surveys, highlighting differences in properties compared to optically-selected samples and addressing photometric uncertainties.

Contribution

It introduces a new photometric pipeline optimized for large and low surface brightness galaxies, correcting SDSS photometry issues for HI-selected galaxies.

Findings

HI-selected galaxies are bluer and more luminous than optically-selected ones.

The new photometric method reduces sky subtraction errors in SDSS data.

The sample differs in color, luminosity, and mass from typical SDSS galaxy samples.

Abstract

We present the optical data for 195 HI-selected galaxies that fall within both the Sloan Digital Sky Survey (SDSS) and the Parkes Equatorial Survey (ES). The photometric quantities have been independently recomputed for our sample using a new photometric pipeline optimized for large galaxies, thus correcting for SDSS's limited reliability for automatic photometry of angularly large or low surface brightness (LSB) galaxies. We outline the magnitude of the uncertainty in the SDSS catalog-level photometry and derive a quantitative method for correcting the over-sky subtraction in the SDSS photometric pipeline. The main thrust of this paper is to present the ES/SDSS sample and discuss the methods behind the improved photometry, which will be used in future scientific analysis. We present the overall optical properties of the sample and briefly compare to a volume-limited, optically-selected sample. Compared to the optically-selected SDSS sample (in the similar volume), HI-selected galaxies are bluer and more luminous (fewer dwarf ellipticals and more star formation). However, compared to typical SDSS galaxy studies, which have their own selection effects, our sample is bluer, fainter and less massive.