2MASS Two-Color Interstellar Reddening Lines in the Inner Galaxy

TL;DR

This study measures interstellar reddening lines in the inner Galaxy using 2MASS data, finding consistent ratios for less reddened stars and deviations for heavily reddened objects, indicating effects like curvature and different stellar types.

Contribution

It provides new measurements of reddening line slopes in the inner Galaxy and discusses deviations caused by stellar and dust properties.

Findings

Reddening ratio E(J-H)/E(H-Ks) is between 1.9 and 2.0 for stars with less than 12 mag extinction.

Deviations occur for stars with higher extinction, likely due to reddening line curvature.

Heavily reddened stars include evolved giants and pre-main-sequence objects.

Abstract

The slopes of interstellar reddening lines in the 2MASS J-H versus H-Ks diagrams for 26 areas in the inner Galaxy (from Vulpecula to Centaurus) are determined. For this aim we use the red-clump giants located inside and behind spiral arms, or behind dense dust clouds of the Local arm. In most of the investigated directions the ratio E(J-H)/E(H-K_s) is found to be between 1.9 and 2.0, taking the stars with the visual extinction less than 12 mag. The stars with larger extinction deviate down from the reddening lines corresponding to less reddened stars. Probably, this is related to the curvature of reddening lines due to the band-width effect. However, some of the deviating stars may be heavily reddened oxygen- and carbon-rich AGB stars (giants of the latest M subclasses or N-type carbon stars), and pre-main-sequence objects (YSOs).