Reddening and metallicity maps of the Milky Way bulge from VVV and 2MASS II. The complete high resolution extinction map and implications for Bulge studies

TL;DR

This paper presents a high-resolution extinction map of the Milky Way bulge using VVV survey data, revealing small-scale reddening variations crucial for accurate stellar population analysis.

Contribution

It provides a detailed, high-resolution reddening map of the Galactic bulge, improving upon previous maps in resolution and coverage, and highlights the importance of accounting for differential reddening.

Findings

Reddening varies significantly on 2'-6' scales.

The new map aligns well with existing maps but offers higher resolution.

Differential reddening must be considered in bulge studies.

Abstract

We use the Vista Variables in the Via Lactea (VVV) ESO public survey data to measure extinction values in the complete area of the Galactic bulge covered by the survey at high resolution. We derive reddening values using the method described in Paper I. This is based on measuring the mean (J-Ks) color of red clump giants in small subfields of 2' to 6' in the following bulge area: -10.3<b<+5.1 and -10<l<+10.4. To determine the reddening values E(J-Ks) for each region, we measure the RC color and compare it to the (J-Ks) color of RC stars measured in Baade's window, for which we adopt E(B-V)=0.55. This allows us to construct a reddening map sensitive to small scale variations minimizing the problems arising from differential extinction. The significant reddening variations are clearly observed on spatial scales as small as 2'. We find a good agreement between our extinction measurements and Schlegel maps in the outer bulge, but, as already stated in the literature the Schlegel maps are not reliable for regions within |b| < 6. In the inner regions we compare our results with maps derived from DENIS and Spitzer surveys. While we find good agreement with other studies in the corresponding overlapping regions, our extinction map has better quality due to both higher resolution and a more complete spatial coverage in the Bulge. We investigate the importance of differential reddening and demonstrate the need for high resolution extinction maps for detailed studies of Bulge stellar populations and structure. The extinction variations on scales of up to 2'-6', must be taken into account when analysing the stellar populations of the Bulge.