A blind HI survey in the Ursa Major region

Abstract

We have conducted the first blind HI survey covering 480 deg2 and a heliocentric velocity range from 300 to 1900 km s-1 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 catalogue of HI sources. The HI data were obtained with the four-beam receiver mounted on the 76.2-m Lovell telescope [full width at half-maximum (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 107-1010.5 M=. 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. © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.