Abstract
We report the discovery of a very H i-massive disk galaxy, HIZOA J0836{43, at a velocity of vhel = 10689 km s 1 , corresponding to a distance of 148 Mpc (assuming H0 = 75 km s 1 Mpc 1 ). It was found during the course of a systematic H i survey of the southern Zone of Avoidance (jbj 5 ) with the multibeam system at the 64 m Parkes radio telescope. Follow-up observations with the Australia Telescope Compact Array (ATCA) reveal an extended H i disk. We derive an H i mass of 7:5 10 10 M . Using the H i radius, we estimate a total dynamical mass of 1:4 10 12 M , similar to the most massive known disk galaxies such as Malin 1. HIZOA J0836{43 lies deep in the Zone of Avoidance (‘; b = 262: 48; 1: 64) where the optical extinction is very high, AB = 9: m 8. However, in the near-infrared wavebands, where the extinction is considerably lower, HIZOA J0836{43 is clearly detected by both DENIS and 2MASS. Deep AAT near-infrared (Ks and H-band) images show that HIZOA J0836{43 is an inclined disk galaxy with a prominent bulge (scale length 2.5 00 or 1.7 kpc), and an extended disk (scale length 7 00 or 4.7 kpc) which can be traced along the major axis out to a radius of 20 00 or 13.4 kpc (at 20 mag arcsec 2 in Ks). The H i disk is much more extended, having a radius of 66 kpc at 1 M pc 2 . Detections in the radio continuum at 1.4 GHz and at 60 m (IRAS) are consistent with HIZOA J0836{43 forming stars at a rate of 35 M yr 1 . We compare the properties of HIZOA J0836{43 with those of the most H i-massive galaxies currently known, UGC 4288, UGC 1752 and Malin 1, all of which are classied as giant low surface brightness galaxies.
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