NICEST, a near-infrared color excess method tailored for small-scale structures

TL;DR

NICEST is a new method designed to correct for small-scale inhomogeneities in molecular cloud extinction measurements, improving accuracy by reducing biases caused by substructures and foreground stars.

Contribution

The paper introduces NICEST, a novel correction technique for extinction studies that effectively accounts for small-scale cloud inhomogeneities, validated through simulations and real data application.

Findings

NICEST reduces biases in extinction maps caused by substructures.

Application to the Pipe cloud shows higher extinction peaks than previous methods.

Bias effects increase with distance and poorer resolution.

Abstract

Observational data and theoretical calculations show that significant small-scale substructures are present in dark molecular clouds. These inhomogeneities can provide precious hints on the physical conditions inside the clouds, but can also severely bias extinction measurements. We present NICEST, a novel method to account and correct for inhomogeneities in molecular cloud extinction studies. The method, tested against numerical simulations, removes almost completely the biases introduced by sub-pixel structures and by the contamination of foreground stars. We applied NICEST to 2MASS data of the Pipe molecular complex. The map thereby obtained shows significantly higher (up to 0.41 mag in A_K) extinction peaks than the standard NICER (Lombardi et al. 2001) map. This first application confirms that substructures in nearby molecular clouds, if not accounted for, can significantly bias extinction measurements in regions with A_K > 1 mag; the effect, moreover, is expected to increase in more distant molecular cloud, because of the poorer physical resolution achievable.