2006MNRAS.369.1741D

We report the discovery of a very Hi-massive disc galaxy, HIZOAJ0836-43, at a velocity of v_hel= 10689km/s, corresponding to a distance of 148Mpc (assuming H₀= 75km/s/Mpc). It was found during the course of a systematic HI survey of the southern Zone of Avoidance (ZOA) (|b| ≤ 5°) with the multibeam system at the 64-m Parkes radio telescope. Follow-up observations with the Australia Telescope Compact Array reveal an extended HI disc. We derive an HI mass of 7.5x10¹⁰M_☉. Using the HI radius, we estimate a total dynamical mass of 1.4x10¹²M_☉, similar to the most massive known disc galaxies such as Malin1. HIZOAJ0836-43 lies deep in the ZOA where the optical extinction is very high, A_B_= 9.8mag. However, in the near-infrared (NIR) wavebands, where the extinction is considerably lower, HIZOAJ0836-43 is clearly detected by both the Deep Near Infrared Survey of the Southern Sky (DENIS) and Two-Micron All-Sky Survey (2MASS). Deep Anglo-Australian Telescope NIR (K_sand H band) images show that HIZOAJ0836-43 is an inclined disc galaxy with a prominent bulge (scalelength 2.5arcsec or 1.7kpc), and an extended disc (scalelength 7arcsec or 4.7kpc) which can be traced along the major axis out to a radius of 20arcsec or 13.4kpc (at 20mag/arcsec2 in K_s). The HI disc is much more extended, having a radius of 66kpc at 1M_☉/pc2. Detections in the radio continuum at 1.4GHz and at 60µm (IRAS) are consistent with HIZOAJ0836-43 forming stars at a rate of ∼35M_☉/yr. We compare the properties of HIZOAJ0836-43 with those of the most Hi-massive galaxies currently known, UGC4288, UGC1752 and Malin1, all of which are classified as giant low surface brightness galaxies.