A method to determine distances to molecular clouds using near-IR photometry

TL;DR

This paper presents a near-infrared photometry method to determine distances to molecular clouds by spectral classification of stars and dereddening their colours to estimate cloud distances accurately.

Contribution

The paper introduces a novel technique combining spectral classification and dereddening of near-IR colours to measure molecular cloud distances.

Findings

Distances to four molecular clouds were estimated with good agreement to previous measurements.

The method effectively classifies stars and determines cloud distances using near-IR photometry.

The estimated distances have uncertainties of approximately 20-30 parsecs.

Abstract

Aims: We aim to develop a method to determine distances to molecular clouds using JHK near-infrared photometry. Methods: The method is based on a technique that aids spectral classification of stars lying towards the fields containing the clouds into main sequence and giants. In this technique, the observed (J-H) and (H-K_s) colours are dereddened simultaneously using trial values of A V and a normal interstellar extinction law. The best fit of the dereddened colours to the intrinsic colours giving a minimum value of Chi^2 then yields the corresponding spectral type and A_V for the star. The main sequence stars, thus classified, are then utilized in an A V versus distance plot to bracket the cloud distances. Results: We applied the method to four clouds, L1517, Chamaeleon I, Lupus 3 and NGC 7023 and estimated their distances as 167+-30, 151+-28, 157+-29 and 408+-76 pc respectively, which are in good agreement with the previous distance estimations available in the literature