DISCOVERY OF A 3RD GIANT LOW SURFACE BRIGHTNESS DISK GALAXY

We report the discovery of a third very large, gas-rich low surface brightness (LSB) disk galaxy, which we designate 1226+0105. Its equatorial coordinates are alpha = 12h26m39.2s and delta = 1-degrees 05'38'' (1950), and it is at a redshift of 23,660 km s-1 It exhibits a number of similarities to the previous described examples of this class, Malin 1 (Bothun et al. 1987; Impey & Bothun 1989) and F568-6 (Bothun et al. 1990), in that it has a large total H I mass of approximately 2 x 10(10) M., a long disk scale length of approximately 14 kpc, a high total luminosity of M(B) = -21.6, and it harbors an active nucleus. It also shows some striking differences from the previous two. In particular, the newest member of the class shows evidence of pronounced color variations in the disk that are not present in Malin 1 or F568-6. The discovery of this galaxy shows that surveys for LSB galaxies can succeed in finding these giant LSB disks, and the common properties of the three galaxies indicate that they may form a unique class among spirals.