An HI Survey of Six Local Group Analogs. II. HI properties of group galaxies

TL;DR

This study surveys six Local Group analogs to analyze their HI properties, revealing a flatter HI mass function and velocity distribution consistent with the Local Group, providing insights into galaxy formation in loose groups.

Contribution

It presents the first detailed HI survey of Local Group analogs, deriving their HI mass and velocity functions and comparing them to the Local Group and theoretical models.

Findings

HI mass function is flatter than the field HIMF

Velocity distribution matches the Local Group and HIPASS galaxies

Results support galaxy formation models with shallower halo distributions

Abstract

We have conducted an HI 21 cm emission-line survey of six loose groups of galaxies chosen to be analogs to the Local Group. The survey was conducted using the Parkes Multibeam instrument and the Australia Telescope Compact Array (ATCA) over a ~1 Mpc^2 area and covering the full depth of each group, with a M(HI) sensitivity of ~7x10^5 M(sun). Our survey detected 110 sources, 61 of which are associated with the six groups. All of these sources were confirmed with ATCA observations or were previously cataloged by HIPASS. The sources all have optical counterparts and properties consistent with dwarf irregular or late-type spiral galaxies. We present here the HI properties of the groups and their galaxies. We derive an HI mass function for the groups that is consistent with being flatter than the equivalent field HIMF. We also derive a circular velocity distribution function, tracing the luminous dark matter halos in the groups, that is consistent with those of the Local Group and HIPASS galaxies, both of which are shallower than that of clusters or predictions from CDM models of galaxy formation.