A blind HI survey in the Ursa Major region

TL;DR

This paper presents the first blind HI survey of the Ursa Major region, cataloging 166 HI sources, including 10 new detections, and analyzing their optical counterparts and properties.

Contribution

It provides a comprehensive HI source catalog for Ursa Major, including new detections and detailed analysis of optical counterparts and a unique HI source without optical emission.

Findings

Identified 166 HI sources with masses from 10^7 to 10^{10.5} M_sun.

Discovered 10 new HI sources not previously cataloged.

Found that 99% of HI sources have optical counterparts.

Abstract

We have conducted the first blind HI survey covering 480 deg^2 and a heliocentric velocity range from 300-1900 km/s to investigate the HI content of the nearby spiral-rich Ursa Major region and to look for previously uncatalogued gas-rich objects. Here we present the catalog of HI sources. The HI data were obtained with the 4-beam receiver mounted on the 76.2-m Lovell telescope (FWHM 12 arcmin) at the Jodrell Bank Observatory (UK) as part of the HI Jodrell All Sky Survey (HIJASS). We use the automated source finder DUCHAMP and identify 166 HI sources in the data cubes with HI masses in the range of 10^7 - 10^{10.5} M_sun. Our Ursa Major HI catalogue includes 10 first time detections in the 21-cm emission line. We identify optical counterparts for 165 HI sources (99 per cent). For 54 HI sources (33 per cent) we find numerous optical counterparts in the HIJASS beam, indicating a high density of galaxies and likely tidal interactions. Four of these HI systems are discussed in detail. We find only one HI source (1 per cent) without a visible optical counterpart out of the 166 HI detections. Green Bank Telescope (FWHM 9 arcmin) follow-up observations confirmed this HI source and its HI properties. The nature of this detection is discussed and compared to similar sources in other HI surveys.