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 M alin 1 has yielded negative results. The nucleus and several positions corr esponding 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)/ICO(1- 0) conversion factor yields MH2/M-HI < 0.03 However, rather than argue that there is very little molecular gas in Malin 1, where some star formation i s currently taking place, we attribute the non-detection chiefly to the low temperature of the gas. Detection of CO may be rendered still more difficu lt by a subsolar metallicity.