2004ApJ...615L.109O

To date, the only low surface brightness (LSB) galaxies that have been detected in CO are the massive LSB (MLSB) galaxies. In 2003, O'Neil, Schinnerer, & Hofner hypothesized that it is the prominent bulge component in MLSB galaxies, not present in less massive LSB galaxies, that gives rise to the detectable quantities of CO gas. To test this hypothesis, we have used the IRAM 30 m telescope to obtain three new, deep CO J(1-0) and J(2-1) observations of MLSB galaxies. Two of the three galaxies observed were detected in CO–one in the J(1-0) line and the other in both the J(1-0) and J(2-1) lines–bringing the total number of MLSB galaxies with CO detections to five, out of a total of nine MLSB galaxies observed at CO to date. The third object had no detection to 2 mK at CO J(1-0). Comparing all MLSB galaxy CO results with surveys of high surface brightness galaxies, we find that the MLSB galaxies' M_H2and M_H2/M_HIvalues fall within the ranges typically found for high surface brightness objects, albeit at the low end of the distribution, with the two MLSB galaxies detected at CO in this survey having the highest M_H2/M_HIvalues yet measured for any LSB system, by factors of 2-3.