We report the discovery of a very H i -massive disk galaxy , HIZOA J0836–43 , at a velocity of v _ { hel } = 10689 km s ^ { -1 } , corresponding to a distance of 148 Mpc ( assuming H _ { 0 } = 75 km s ^ { -1 } Mpc ^ { -1 } ) .
It was found during the course of a systematic H i survey of the southern Zone of Avoidance ( |b| \leq 5 \degr ) 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 \times 10 ^ { 10 } M _ { \odot } .
Using the H i radius , we estimate a total dynamical mass of 1.4 \times 10 ^ { 12 } M _ { \odot } , similar to the most massive known disk galaxies such as Malin 1 .
HIZOA J0836–43 lies deep in the Zone of Avoidance ( \ell,b = 262 \aas@@fstack { \circ } 48 , -1 \aas@@fstack { \circ } 64 ) where the optical extinction is very high , A _ { B } = 9 \aas@@fstack { 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 ( K _ { s } and H -band ) images show that HIZOA J0836–43 is an inclined disk galaxy with a prominent bulge ( scale length 2.5″ or 1.7 kpc ) , and an extended disk ( scale length 7″ or 4.7 kpc ) which can be traced along the major axis out to a radius of 20″ or 13.4 kpc ( at 20 mag arcsec ^ { -2 } in K _ { s } ) .
The H i disk is much more extended , having a radius of 66 kpc at 1 M _ { \odot } pc ^ { -2 } .
Detections in the radio continuum at 1.4 GHz and at 60 µm ( IRAS ) are consistent with HIZOA J0836–43 forming stars at a rate of \sim 35 M _ { \odot } 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 classified as giant low surface brightness galaxies .