Mapping the stellar age of the Milky Way bulge with the VVV

III. High-resolution reddening map^{⋆,⋆⋆,⋆⋆⋆}

¹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
e-mail: frsurot@uc.cl
² Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna Tenerife, Spain
³ European Southern Observatory, Karl Schwarzschild-Straße 2, 85748 Garching bei München, Germany
⁴ Excellence Cluster ORIGINS, Boltzmann-Straße 2, 85748 Garching bei München, Germany
⁵ UK Astronomy Technology Centre, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
⁶ Instituto de Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Santiago, Chile
⁷ Millennium Institute of Astrophysics, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile
⁸ Departamento de Ciencias Físicas, Universidad Andrés Bello, República 220, Santiago, Chile
⁹ Vatican Observatory, V00120 Vatican City State, Italy

Received: 5 May 2020
Accepted: 21 September 2020

Abstract

Context. A detailed study of the Galactic bulge stellar population necessarily requires an accurate representation of the interstellar extinction, particularly toward the Galactic plane and center, where severe and differential reddening is expected to vary on sub-arcmin scales. Although recent infrared surveys have addressed this problem by providing extinction maps across the whole Galactic bulge area, dereddened color-magnitude diagrams near the plane and center appear systematically undercorrected, prompting the need for higher resolution. These undercorrections affect any stellar study sensitive to color (e.g., star formation history analyses via color-magnitude diagram fitting), either making them inaccurate or limiting them to small and relatively stable extinction windows where this value is low and better constrained.

Aims. This study is aimed at providing a high-resolution (2 arcmin to ∼10 arcsec) color excess map for the VVV bulge area in J − K_s color.

Methods. We used the MW-BULGE-PSFPHOT catalogs, sampling ∼300 deg² across the Galactic bulge (|l| < 10° and −10° < b <  5°) to isolate a sample of red clump and red giant branch stars, for which we calculated the average J − K_s color in a fine spatial grid in (l, b) space.

Results. We obtained an E(J − K_s) map spanning the VVV bulge area of roughly 300 deg², with the equivalent of a resolution between ∼1 arcmin for bulge outskirts (l <  6°) to below 20 arcsec within the central |l| < 1°, and below 10 arcsec for the innermost area (|l| < 1° and |b| < 3°).