OGLE-ing the Magellanic System: Optical Reddening Maps of the Large and Small Magellanic Cloud from Red Clump Stars

TL;DR

This paper provides the most detailed optical reddening maps of the Magellanic Clouds using Red Clump stars from OGLE-IV data, revealing spatial variations and metallicity effects with high resolution.

Contribution

It introduces refined methods for calculating RC star colors and presents extensive, high-resolution reddening maps for the Magellanic Clouds based on deep photometric data.

Findings

Reddening maps cover 180 deg2 in LMC and 75 deg2 in SMC.

Mean reddening values are E(V-I)=0.100 mag in LMC and 0.047 mag in SMC.

Metallicity gradients cause slight decreases in intrinsic RC color with distance.

Abstract

We present the most extensive and detailed reddening maps of the Magellanic Clouds (MCs) derived from the color properties of Red Clump (RC) stars. The analysis is based on the deep photometric maps from the fourth phase of the Optical Gravitational Lensing Experiment (OGLE-IV), covering approximately 670 deg2 of the sky in the Magellanic System region. The resulting maps provide reddening information for 180 deg2 in the Large Magellanic Cloud (LMC) and 75 deg2 in the Small Magellanic Cloud (SMC), with a resolution of 1.7x1.7 arcmin in the central parts of the MCs, decreasing to approximately 27x27 arcmin in the outskirts. The mean reddening is E(V-I) = 0.100 +- 0.043 mag in the LMC and E(V-I) = 0.047 +- 0.025 mag in the SMC. We refine methods of calculating the RC color to obtain the highest possible accuracy of reddening maps based on RC stars. Using spectroscopy of red giants, we find the metallicity gradient in both MCs, which causes a slight decrease of the intrinsic RC color with distance from the galaxy center of ~0.002 mag/deg in the LMC and between 0.003 and 0.009 mag/deg in the SMC. The central values of the intrinsic RC color are 0.886 and 0.877 mag in the LMC and SMC, respectively. The reddening map of the MCs is available on-line both in the downloadable form and as an interactive interface.