Detections of CO in Late-Type, Low Surface Brightness Spiral Galaxies

International audienceUsing the IRAM 30 m telescope, we have obtained 12CO J=1-0 and 2-1 spectral line observations toward the nuclear regions of 15 edge-on, low surface brightness (LSB) spiral galaxies. Our sample comprises extreme late-type LSB spirals with disk-dominated morphologies and rotational velocities Vrot~5 sigma) for the remainder of the sample we provide upper limits on the nuclear CO content. Adopting a standard Galactic ICO-to-H2 conversion factor implies molecular gas masses of (3.3-9.8)×106 Msolar in the nuclear regions (inner 1.1-1.8 kpc) of the detected galaxies. Combining our new data with samples of late-type spirals from the literature, we find that CO-detected LSB spirals adhere to the same MH2-far-infrared correlation as more luminous and higher surface brightness galaxies. The amount of CO in the central regions of late-type spirals appears to depend more strongly on mass than on central optical surface brightness, and CO detectability declines significantly for moderate to low surface brightness spirals with Vrot