Empirical Calibration of the Reddening Maps in the Magellanic Clouds

Abstract

We present reddening maps of the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC), based on color measurements of the red clump. Reddening values of our maps were obtained by calculating the difference of the observed and intrinsic color of the red clump in both galaxies. To obtain the intrinsic color of the red clump, we used reddenings obtained from late-type eclipsing binary systems, measurements for blue supergiants and reddenings derived from Strömgren photometry of B-type stars. We obtained intrinsic color of the red clump (V − I) 0 = 0.838 ± 0.034 mag in the LMC, and (V − I) 0 = 0.814 ± 0.034 mag in the SMC. We prepared our map with 3 arcmin resolution,

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“…These authors found similar results as Haschke et al (2011) and Subramanian & Subramaniam (2012). Very recently Górski et al (2020) produced revised reddening maps which show similar spatial variations of the reddening as Haschke et al (2011), but their values are systematically higher.…”

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“…Another technique for estimating the extinction is based on the OGLE reddening maps [31] using Red Clump stars as tracers and RR Lyrae stars in the LMC, leading to intermediate adopted values [17,21,32]…”

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“…The widely used reddening maps of Haschke et al (2011) adopted a theoretical value of 0.92 mag and 0.89 mag for (V−I) 0 in the center of the LMC and SMC, respectively. Górski et al (2020) measured (V−I) 0 =0.838 mag for the LMC and (V−I) 0 =0.814 mag for the SMC, which are a mean of four distinct methods. Nataf et al (2020) employed a hybrid theoretical and empirical approach and derived (V−I) 0 ={0.89, 0.92, 0.88} mag for the LMC, using three different methods, and (V−I) 0 ={0.84, 0.84} mag for the SMC.…”

“…We also provide ±34.1% percentile values from the median as a measure of confidence intervals and of differential reddening. Previous studies of reddening in the Magellanic Clouds typically used a combination of a Gaussian and a polynomial to fit the RC distribution (e.g., Haschke et al 2011;Choi et al 2018;Górski et al 2020). However, this has a tendency to miss the RGB contamination entirely and focus the polynomial on the smooth stellar background instead.…”

“…The majority of stellar population studies require accounting for interstellar extinction in order to acquire precise distances; thus, it is very important to have accurate reddening maps of the Magellanic System. Previous efforts to construct reddening maps employed various tracers such as Red Clump (RC) stars (Udalski et al 1999a(Udalski et al , 1999bSubramaniam 2005;Subramanian & Subramaniam 2009Haschke et al 2011;Tatton et al 2013;Choi et al 2018;Górski et al 2020), classical Cepheids (Inno et al 2016;Joshi & Panchal 2019), or RR Lyrae-type variables (Pejcha & Stanek 2009;Haschke et al 2011;Deb 2017). Interstellar reddening has also been inferred from equivalent widths of spectral lines (Munari & Zwitter 1997), stellar atmosphere fitting (Zaritsky et al 2002(Zaritsky et al , 2004, and through the analysis of spectral energy distributions of background galaxies (Bell et al 2019).…”