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Abstract: We present an analysis of wide-field infrared extinction maps of a region inPerseus just north of the Taurus-Auriga dark cloud complex. From this analysiswe have identified a massive, nearby, but previously unrecognized, giantmolecular cloud GMC. From comparison of foreground star counts with Galacticmodels we derive a distance of 450 +- 23 parsecs to the cloud. At thisdistance the cloud extends over roughly 80 pc and has a mass of approximately10^5 solar masses, rivaling the Orion A Molecular Cloud as the largest andmost massive GMC in the solar neighborhood. Although surprisingly similar inmass and size to the more famous Orion Molecular Cloud OMC the newlyrecognized cloud displays significantly less star formation activity with morethan an order of magnitude fewer young stellar objects than found in the OMC,suggesting that both the level of star formation and perhaps the star formationrate in this cloud are an order of magnitude or more lower than in the OMC.Analysis of extinction maps of both clouds shows that the new cloud containsonly 10% the amount of high extinction A K > 1.0 mag material as is found inthe OMC. This, in turn, suggests that the level of star formation activity andperhaps the star formation rate in these two clouds may be directlyproportional to the total amount of high extinction material and presumablyhigh density gas within them and that there might be a density threshold forstar formation on the order of a few times 10^4 hydrogen molecules per cc.

Autor: Charles J. Lada, Marco Lombardi, Joao F. Alves



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