  A recent model for the stellar initial mass function (IMF), in which the
stellar masses are randomly sampled down to the thermal Jeans mass from
hierarchically structured pre-stellar clouds, predicts that regions of
ultra-cold CO gas, such as those recently found in nearby galaxies by Allen and
collaborators, should make an abundance of Brown Dwarfs with relatively few
normal stars. This result comes from the low value of the thermal Jeans mass,
considering that the hierarchical cloud model always gives the Salpeter IMF
slope above this lower mass limit. The ultracold CO clouds in the inner disk of
M31 have T~3K and pressures that are probably 10 times higher than in the solar
neighborhood. This gives a mass at the peak of the IMF equal to 0.01 Msun, well
below the Brown Dwarf limit of 0.08 Msun. Using a functional approximation to
the IMF, the ultracold clouds would have 50% of the star-like mass and 90% of
the objects below the Brown Dwarf limit. The brightest of the Brown Dwarfs in
M31 should have an apparent, extinction-corrected K-band magnitude of ~21 mag
in their pre-main sequence phase.
