A Prediction of Brown Dwarfs in Ultracold Molecular Gas

摘要: A recent model for the stellar initial mass function (IMF), in which masses are randomly sampled down to thermal Jeans from hierarchically structured prestellar clouds, predicts that regions of ultracold CO gas, such as those recently found nearby galaxies by Allen and collaborators, should make an abundance brown dwarfs with relatively few normal stars. This result comes low value mass, scales MJ ∝ T2/P1/2 temperature T pressure P, considering hierarchical cloud always gives Salpeter IMF slope above this lower limit. The clouds inner disk M31 have ~ 3 K pressures probably 10 times higher than solar neighborhood. a at peak equal 0.01 M☉, well below dwarf limit 0.08 M☉. Using functional approximation given [1 - e-(M/MJ)2]M -1.35d log M > MJ, fits local expected 0.3 = M☉ has 50% 90% objects brightest apparent extinction-corrected K-band magnitude ~30 mag their pre-main-sequence phase. For typical star formation efficiencies ≤10%, any associated stars up ~2.5 not heat gas noticeably, but if continues arbitrarily high masses, then efficiency must be ≤10-4 avoid heating massive