NOIRCAT - The Northern HIPASS Optical/IR Catalogue

TL;DR

NOIRCAT is a comprehensive catalog linking HI radio sources from HIPASS with optical and near-infrared counterparts, revealing correlations between gas and stellar content and highlighting the need for further follow-up to confirm dark galaxy candidates.

Contribution

This work provides the first large-scale optical/IR catalog for HIPASS sources, including velocity matches and analysis of galaxy properties, expanding understanding of HI-selected galaxy populations.

Findings

66% of NHICAT sources have optical counterparts with matching velocities.

HI-selected isolated galaxies show a wider range of NIR colours.

Over 200 matched galaxies lack velocity data, requiring follow-up.

Abstract

We present the Northern HIPASS Optical/InfraRed CATalogue (NOIRCAT), an optical/near-infrared counterpart to the Northern HIPASS catalogue (NHICAT). Of the 1002 sources in NHICAT, 655 (66%) have optical counterparts with matching optical velocities. A further 85 (8%) sources have optical counterparts with matching velocities from previous radio emission-line surveys. We find a correlation between the gas and stellar content of the NOIRCAT sources. Our HI-selected sample of isolated galaxies also present a wider range in near-infrared (NIR) colours than previous optically-selected studies of regular, isolated galaxies. All HI detections in optically unobscured fields could be matched with either a NED optical counterpart, or a galaxy visible in POSSII or DSS images. However, as over 200 of these matched galaxies have no velocity information, further follow-up observations are needed to confirm the matches, and hence confirm or deny the existence of dark galaxies in this dataset.