Distances to nearby molecular clouds and star forming regions.III. Localizing extinction jumps with a Hipparcos calibration of 2mass photometry

Jens Knude

paper

Distances to nearby molecular clouds and star forming regions.III. Localizing extinction jumps with a Hipparcos calibration of 2mass photometry

arXiv:1006.3676

Abstract

We want to estimate the distance to molecular clouds in the solar vicinity in a statistically precise way. Clouds are recognized as extinction discontinuities. The extinction is estimated from the $(H - K) v s . (J - H)$ diagram and distances from a $(J - K)_{0} v s . M_{J}$ relation based on Hipparcos. The stellar sample of relevance for the cloud distance is confined by the FWHM of the $A_{V} / D_{⋆} (p c)$ or of its derivative. The cloud distance is estimated from fitting a function to the $(A_{V}, 1/ π_{J H K})$ pairs in this sample with a function like $a r c t an h^{p} (D_{⋆} / D_{c l o u d})$ where the power $p$ and $D_{c l o u d}$ both are estimated. The fit follows the $(A_{V}, 1/ π_{J H K})_{c l o u d}$ data rather well. Formal standard deviations less than a few times 10 pc seem obtainable implying that cloud distances are estimated on the $≲$ 10 $%$ level. Such a precision allows estimates of the depths of cloud complexes in some cases. As examples of our results we present distances for $\sim$ 25 molecular clouds in Table ~\ref{t2}. $K ey w or d s$ : interstellar medium: molecular cloud distances

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VLBA determination of the distance to nearby star-forming regions II. Hubble 4 and HDE 283572 in Taurus

Distances to nearby molecular clouds and star forming regions.III. Localizing extinction jumps with a Hipparcos calibration of 2mass photometry

Abstract

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