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Lynds 1622: a nearby star-forming cloud projected on Orion B?



On leave from University of Szeged, Dóm tér 9, Szeged, H-6720 Hungary.


We present results of optical spectroscopic and photometric observation of the pre-main-sequence stars associated with the cometary shaped dark cloud Lynds 1622, and 12CO and 13CO observations of the cloud. We determined the effective temperatures and luminosities of 14 pre-main-sequence stars associated with the cloud from their positions in the Hertzsprung–Russell diagram, as well as constructed their spectral energy distributions using optical, 2MASS and Spitzer IRAC and MIPS data. We derived physical parameters of L 1622 from the molecular observations. Our results are not compatible with the assumption that L 1622 lies on the near side of the Orion–Eridanus loop, but suggest that L 1622 is as distant as Orion B. At a distance of 400 pc the mass of the cloud, derived from our 12CO data, is 1100 M, its star formation efficiency is ∼1.8 per cent, and the average age of its low-mass pre-main-sequence star population is about 1 Myr.