Deep search for CO emission in the Low Surface Brightness galaxy Malin 1

A sensitive search for CO emission from the Low Surface Brightness Galaxy Malin 1 has yielded negative results. The nucleus and several positions corresponding to regions of star formation in the disk were observed in the CO(1– 0) and CO(2–1) lines with no detection. Use of a " standard " N (H 2)/I CO(1−0) conversion factor yields M H2 /M HI < 0.03. However, rather than argue that there is very little molecular gas in Malin 1, where some star formation is currently taking place, we attribute the non-detection chiefly to the low temperature of the gas. Detection of CO may be rendered still more difficult by a subsolar metallicity.