2000ApJ...545L..99O

We report on the first attempts at searching for CO in red low surface brightness galaxies, and the first detection of molecular gas in a low surface brightness [µ_B(0)_obs>23 mag.arcsec^–2] galaxy. Using the IRAM 30 m telescope, CO (1-0) and CO (2-1) lines were searched for in four galaxies–P06-1, P05-5, C05-3, and C04-2. In three of the galaxies no CO was detected, to T_MB∼1.8 mK (at the 3 σ level). In the fourth galaxy, P06-1, both lines were detected. Comparing our findings with previous studies shows P06-1 to have a molecular-to-atomic mass ratio considerably lower than is predicted using theoretical models based on high surface brightness galaxy studies. This indicates the N(H₂)/{integral}T(CO)dv conversion factor for low surface brightness galaxies may currently be consistently underestimated by a factor of 3-20.