Milky Way demographics with the VVV survey^⋆

II. Color transformations and near-infrared photometry for 136 million stars in the southern Galactic disk

¹ Departamento de Física, Universidad de La Serena, 980 Benavente, La Serena, Chile
e-mail: msoto@dfuls.cl
² Instituto de Ciencias Astronómicas, del la Tierra y del Espacio (ICATE-CONICET), Av. España Sur 1512, J5402 DSP San Juan, Argentina
³ Observatório Astronómico de Córdoba, Universidad Nacional de Córdoba, Laprida 854, x5000 BGR, Córdoba, Argentina
⁴ Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Vicuña Mackena 4860, Casilla 306, Santiago 22, Chile
⁵ Vatican Observatory, Vatican City State 00120, Italy
⁶ European Southern Observatory, 3107 Vitacura, Santiago, Chile
⁷ Department of Astrophysical Sciences, Princeton University, Princeton NJ 08544-1001, USA
⁸ The Milky Way Millennium Nucleus, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile
⁹ Departamento de Ciencia Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago, Chile
¹⁰ Centre for Astrophysics Research, Science and Technology Research Institute, University of Hertfordshire, Hatfield AL10 9AB, UK
¹¹ Department of Astronomy and Physics, Saint Mary’s University, Halifax, Nova Scotia, B3K 5L3, Canada
¹² Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹³ Astronomy Unit, School of Physics and Astronomy, Queen Mary University of London, Mile End Road, London, E1 4NS, UK
¹⁴ Departamento de Física y Astronomía, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, Chile
¹⁵ Instituto de Astronomía Teórica y Experimental, CONICET, Laprida 922, 5000 Córdoba, Argentina
¹⁶ Departmento de Astronomía, Universidad de Concepción, Casilla 160-C, Concepción, Chile
¹⁷ Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos 0610, Antofagasta, Chile
¹⁸ Atacama Large Millimeter Array, Alonso de Córdova 3107, Vitacura, Santiago, Chile

Received: 18 July 2012
Accepted: 25 January 2013

Abstract

The new multi-epoch near-infrared VISTA Variables in the Vía Láctea (VVV) survey is sampling 562   deg² of the Galactic bulge and adjacent regions of the disk. Accurate astrometry established for the region surveyed allows the VVV data to be merged with overlapping surveys (e.g., GLIMPSE, WISE, 2MASS, etc.), thereby enabling the construction of longer baseline spectral energy distributions for astronomical targets. However, in order to maximize use of the VVV data, a set of transformation equations are required to place the VVV JHK_s photometry onto the 2MASS system. The impetus for this work is to develop those transformations via a comparison of 2MASS targets in 152 VVV fields sampling the Galactic disk. The transformation coefficients derived exhibit a reliance on variables such as extinction. The transformed data were subsequently employed to establish a mean reddening law of E_J−H/E_H−Ks = 2.13 ± 0.04, which is the most precise determination to date and merely emphasizes the pertinence of the VVV data for determining such important parameters.