Allsky NICER and NICEST extinction maps based on the 2MASS near-infrared survey^⋆

¹ Department of Physics, PO Box 64, 00014 University of Helsinki, Finland
e-mail: mika.juvela@helsinki.fi
² Institut UTINAM, CNRS UMR 6213, OSU THETA, Université de Franche-Comté, 41 bis avenue de l’Observatoire, 25000 Besançon, France

Received: 5 October 2014
Accepted: 22 October 2015

Abstract

Context. Extinction remains one of the most reliable methods of measuring column density of nearby Galactic interstellar clouds. The current and ongoing near-infrared surveys enable the mapping of extinction over large sky areas.

Aims. We produce allsky extinction maps using the 2MASS near-infrared survey.

Methods. We use the NICER and NICEST methods to convert the near-infrared colour excesses to extinction estimates. The results are presented in Healpix format at the resolutions of 3.0, 4.5, and 12.0 arcmin.

Results. The main results of this study are the calculated J-band extinction maps. The comparison with earlier large-scale extinction mappings shows good correspondence but also demonstrates the presence of resolution-dependent bias. A large fraction of the bias can be corrected by using the NICEST method.

Conclusions. For individual regions, best extinction estimates are obtained by careful analysis of the local stellar population and the use of the highest resolution afforded by the stellar density. However, the uniform allsky maps should still be useful for many global studies and as the first step into the investigation of individual clouds.