FIGGS2: An HI survey of extremely faint irregular galaxies

TL;DR

The FIGGS2 survey extends the study of extremely faint irregular galaxies, revealing that their HI disks are often offset from optical disks and that HI diameter correlates with HI mass, providing new insights into faint galaxy properties.

Contribution

This paper presents the first results from FIGGS2, extending HI observations to fainter irregular galaxies and analyzing their HI disk properties and correlations.

Findings

HI disks are often offset from optical disks.

HI diameter correlates with HI mass with a slope of ~2.08.

HI disks are generally larger than optical disks, with a ratio of ~1.54.

Abstract

We present the observations and first results from the FIGGS2 survey. FIGGS2 is an extension of the earlier Faint Irregular Galaxies GMRT survey (FIGGS) towards faint luminosity end. The sample consists of 20 galaxies of which 15 were detected in HI 21cm line using the Giant Meter-wave Radio Telescope (GMRT). The median blue band magnitude of our sample is ~ -11.6, which is more than one magnitude fainter than earlier FIGGS survey. From our GMRT observations we find that, for many of our sample galaxies, the HI disks are offset from their optical disks. The HI diameters of the FIGGS2 galaxies show a tight correlation with their HI mass. The slope of the correlation is 2.08 +/- 0.20 similar to what is found for FIGGS galaxies. We also find that for almost all galaxies, the HI disks are larger than the optical disks which is a common trend for dwarf or spiral galaxies. The mean value of the ratio of HI to optical diameter is ~ 1.54.