The First CO Map of a Low Surface Brightness Galaxy

Abstract

Using the Owens Valley Radio Observatory (OVRO) Millimeter-Wavelength Array, we have obtained the first CO map of a low surface brightness (LSB) galaxy. The studied galaxy, UGC 01922, was chosen for these observations because of both its previous CO detection with the IRAM 30 m telescope and its classification as a Malin 1 ``cousin'' an LSB galaxy with MHI>=1010 Msolar. The OVRO map detected approximately 65% of the CO (1-0) flux found earlier with the single-dish measurements, giving a detected gas mass equivalent to MH2=1.1×109 Msolar. The integrated gas peak lies at the center of the galaxy and coincides with both the optical and 1.4 GHz continuum emission peaks. The molecular gas extends well beyond the OVRO beam size (~4" or 3 kpc), covering ~25% of the optical bulge. In all, perhaps the most remarkable aspect of this map is its unexceptional appearance. Given that it took over 10 years to successfully detect molecular gas in any LSB system, it is surprising that the appearance and distribution of UGC 01922's CO is similar to what would be expected for a high surface brightness galaxy in the same morphological class.