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The dust temperatures of the pre-stellar cores in the ? Oph main cloud and in other star-forming regions: consequences for the core mass function
We estimate the dust temperatures of the clumps in the ? Oph maincloud taking into account the 3D geometry of the region, and externalheating from the interstellar radiation field and from HD 147879, anearby luminous B2V star, which is believed to dominate the radiationfield in the region. We find that the regions where pre-stellar coresare observed (i.e. at optical visual extinctions >7 mag) are colderthan ~10 -11 K. These dust temperatures are smaller than those whichprevious studies of the same region have assumed. We use the new dusttemperatures to estimate the masses of the pre-stellar cores in the? Oph main cloud from millimetre observations, and we find coremasses that are larger than previous estimates by a factor of ~2 -3.This affects the core mass function (CMF) of the region; we find thatthe mass at which the core mass spectrum steepens from a slope ? ~1.5 to a slope ? ~ 2.5 has moved from ~0.5 to ~1Msolar.In contrast with the CMF in other star-forming regions (e.g. Orion),there is no indication for a turnover down to the completeness limit(~0.2Msolar), but the CMF may flatten at around~0.4Msolar.We generalize our results to the pre-stellar cores in Taurus and inOrion. In Taurus, the ambient radiation field heating the pre-stellarcores is believed to be weaker than that in ? Oph. Hence, the dusttemperatures of the cores in Taurus are expected to be below ~10 -11 K.In Orion, the radiation field is believed to be 103 timesstronger than the standard interstellar radiation field. Based on thisassumption, we estimate that the dust temperatures of the pre-stellarcores in Orion are around ~20 -30 K.
| SANTIAGO 91, a right ascension catalogue of 3387 stars (equinox J2000).
The positions in right ascension of 3387 stars belonging to the Santiago67 Catalogue, observed with the Repsold Meridian Circle at Cerro Calan,National Astronomical Observatory, during the period 1989 to 1994, aregiven. The average mean square error of a position, for the wholeCatalogue, is +/-0.009 s. The mean epoch of the catalogue is 1991.84.
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