The Properties of Galaxies in Low Density Regions from the ALFALFA Survey

TL;DR

This paper analyzes the properties of galaxies detected in low-density regions using the ALFALFA survey, comparing their morphological indicators with non-detections to better understand the characteristics of HI-rich galaxies in sparse environments.

Contribution

It provides a detailed comparison of morphological features of HI-detected and non-detected galaxies in low-density regions, establishing a basis for future statistical analysis of galaxy environments.

Findings

HI detections tend to have different morphological indicators than non-detections.

The study characterizes the types of galaxies detected in low-density environments.

Provides a reference sample for future HI content studies in various environments.

Abstract

Galaxies detected in the 21-cm line of neutral hydrogen (HI) from the on-going Arecibo Legacy Fast ALFA (ALFALFA) blind extragalactic HI survey have been cross-correlated with Sloan Digital Sky Survey Data Release 7 (Abazajian et al. 2009) in order to define a reference sample of HI content in regions of low galactic density. This observational sample will be used in the future to derive new standards of normal atomic gas content that allow a statistical investigation of the HI properties of galaxies in differing environments of the local universe. As a previous step, we compare here morphological indicators, like color or light concentration index, of ALFALFA detections and non-detections in low density regions. Our examination is extended also to a small data set of isolated galaxies. This kind of analysis is necessary in order to characterize as accurately as possible the type of galaxies that ALFALFA is detecting.