Revised distances to several Bok globules

TL;DR

This paper provides revised distance estimates to several Bok globules using extinction and stellar distance data, revealing some are closer than previously thought, which impacts understanding of their physical properties.

Contribution

The study introduces a new method combining extinction measurements and stellar distances to accurately determine Bok globule distances, updating previous estimates.

Findings

CB24, CB25, CB26 are at 407±27 pc, farther than previous estimates.

CB245, CB246 are at 272±20 pc, indicating previous underestimates.

CB3 is at about 1400 pc, closer than previously believed.

Abstract

Distances to Bok globules and small dark nebulae are important for a variety of reasons. We provide new distance estimates to several small clouds, some of them known to harbor YSO and molecular outflows, and thus being of particular interest. We use a procedure based on extinctions determined from the (H-K) vs. (J-H) diagram, and stellar distances based on a Hipparcos calibration of the main sequence locus: $M_J[(J-K)_0]$. The cloud confinement on the sky is determined from contours of the average (H-K) color formed in reseaus. Along the sight line stars affected by the clouds extinction may be extracted from the variation of the number density of atomic hydrogen $n_H\sim A_{V,\star}/D_\star$ to provide the cloud distance and its uncertainty. According to our estimates, the group of three globules CB24, CB25 and CB26 is located at 407+/-27 pc, farther than the previous estimates. CB245 and CB246 are found at 272+/-20 pc, suggesting that the current distance to these clouds is underestimated. Toward CB244 we detect a layer at 149+/-16 pc and the cloud at 352+/-18, in good agreement with previous studies. CB52 and CB54, though to be at 1500 pc, are found at 421+/-28 pc and slightly beyond 1000 pc, respectively. It seems that the most distant Bok globule known, CB3, is located at about 1400 pc, also significantly closer than currently accepted.