Studies of galaxies in voids. I. HI observations of Blue Compact Galaxies

TL;DR

This study investigates the properties of blue compact galaxies in voids, revealing that those in lower density environments tend to have higher HI content relative to their blue luminosity, with the relationship varying by environment density.

Contribution

First detailed HI observations of BCGs in voids, comparing their properties across different environmental densities to understand environmental effects on galaxy gas content.

Findings

Void BCGs have higher HI-to-luminosity ratios than those in denser regions.

The slope of the HI-to-luminosity relation steepens as environment density decreases.

HI content correlates with environment density, affecting galaxy evolution.

Abstract

We present here results of studies of the properties of galaxies located in very low density environments. We observed 26 blue compact galaxies (BCGs) from the Second Byurakan (SBS) and Case surveys located in voids with the radial velocities V < 11000 km/s, two BCGs in the void behind the Virgo cluster and 11 BCGs in denser environments. HI fluxes and profile widths, as well as estimates of total HI masses, are presented for the 27 detected galaxies (of which 6 are in three galaxy pairs and are not resolved by the radiotelescope beam). Preliminary comparisons of void BCGs with similar objects from intermediate density regions - in the general field and the Local Supercluster (sub-samples of BCGs in the SBS zone) and in the dense environment of the Virgo Cluster (a BCD sample) - are performed using the hydrogen-to-blue-luminosity ratio M(HI)/L_B. We find that for the same blue luminosity, for M_B > -18.0, BCGs in lower density environment have on average more HI. The slope (beta) of the M(HI)/L_B proportional to L^(beta) for BCGs shows a trend of steepening with decreasing bright galaxy density, being very close to zero for the densest environment considered here and reaching (beta) = -0.4 for voids.