A new near-IR window of low extinction in the Galactic plane^★

¹ Departamento de Física, Facultad de Ciencias Exactas, Universidad Andres Bello, Av. Fernández Concha 700, Las Condes, Santiago, Chile
² Instituto Milenio de Astrofísica, Santiago, Chile
³ Vatican Observatory, 00120 Vatican City State, Italy
⁴ Departamento de Física, Universidade Federal de Santa Catarina, Trindade 88040-900 Florianópolis, SC, Brazil
e-mail: saito@astro.ufsc.br
⁵ UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
⁶ Unidad de Astronomía, Facultad Ciencias Básicas, Universidad de Antofagasta, Avenida Universidad de Antofagasta, 02800 Antofagasta, Chile
⁷ European Southern Observatory, Karl-Schwarszchild-Strasse 2, 85748 Garching bei München, Germany
⁸ Excellence Cluster Universe, Boltzmannstrasse 2, 85748 Garching bei München, Germany
⁹ Departamento de Física y Astronomía, Universidad de La Serena, Chile
¹⁰ Institute of Astronomy, University of Cambridge, Cambridge, UK
¹¹ Department of Astronomy, University of Hertfordshire, Hertfordshire, UK
¹² Mount Saint Vincent University, Halifax, Nova Scotia, Canada
¹³ Saint Mary’s University, Halifax, Nova Scotia, Canada

Received: 13 October 2017
Accepted: 15 April 2018

Abstract

Aims. The windows of low extinction in the Milky Way (MW) plane are rare but important because they enable us to place structural constraints on the opposite side of the Galaxy, which has hither to been done rarely.

Methods. We use the near-infrared (near-IR) images of the VISTA Variables in the Vía Láctea (VVV) Survey to build extinction maps and to identify low extinction windows towards the Southern Galactic plane. Here we report the discovery of VVV WIN 1713−3939, a very interesting window with relatively uniform and low extinction conveniently placed very close to the Galactic plane.

Results. The new window of roughly 30 arcmin diameter is located at Galactic coordinates (l, b) = (347.4, −0.4) deg. We analyse the VVV near-IR colour-magnitude diagrams in this window. The mean total near-IR extinction and reddening values measured for this window are A_Ks = 0.46 and E(J − K_s) = 0.95. The red clump giants within the window show a bimodal magnitude distribution in the K_s band, with peaks at K_s = 14.1 and 14.8 mag, corresponding to mean distances of D = 11.0 ± 2.4 and 14.8 ± 3.6 kpc, respectively. We discuss the origin of these red clump overdensities within the context of the MW disk structure.