2MASS Two-Color Interstellar Reddening Lines: the Band-Width Effect

TL;DR

This paper investigates how the band-width effect influences interstellar reddening lines in the 2MASS J-H vs. H-K_s diagram, revealing deviations from linearity at high reddening levels through synthetic models and observational data.

Contribution

It introduces a quadratic approximation for reddening lines accounting for the band-width effect, enhancing understanding of interstellar reddening at large extinctions.

Findings

Reddening lines deviate from straight lines at E(H-K_s) > 1.0

The lines can be modeled by a quadratic equation with specific coefficients

Observational data confirms the curvature predicted by models

Abstract

The band-width effect on interstellar reddening lines in the J-H vs. H-K_s diagram of the 2MASS survey is investigated using synthetic color indices and color excesses based on the Kurucz model atmospheres. At large interstellar reddenings (E(H-K_s) larger than 1.0) reddening lines deviate considerably from a straight line. The lines can be approximated by an equation: E(J-H) = r E(H-K_s) + s E(H-K_s)^2, where the slope coefficient, r, and the curvature coefficient, s, depend slightly on the intrinsic energy distribution of the source. The curvature of the reddening lines is confirmed by the J-H vs. H-K_s diagrams plotted by Straizys and Laugalys (2008) from 2MASS observations.