New Optical Reddening Maps of the Large and Small Magellanic Clouds

Abstract

We present new reddening maps of the Small and Large Magellanic Cloud based on the data of the third phase of the Optical Gravitational Lensing Experiment (OGLE III). We have used two different methods to derive optical reddening maps. We adopt a theoretical mean unreddened colour for the red clump in the SMC and LMC, respectively. We subdivide the photometric data for both Clouds into subfields and calculate the difference between the observed red clump position and the theoretical value for each field, which provides us with the reddening value in (V − I). Furthermore reddening values are obtained for 13490 LMC RR Lyrae ab and 1529 SMC RR Lyrae ab stars covering the whole OGLE III region of the MCs. The observed colours (V − I) of the RR Lyrae stars are compared with the colour from the absolute magnitudes. The absolute magnitude of each RR Lyrae star is computed using its period and metallicity derived from Fourier decomposition of its lightcurve.In general we find a low and uniform reddening distribution in both Magellanic Clouds. The red clump method indicates a mean reddening of the LMC of E(V − I) = 0.09 ± 0.07 mag, while for the SMC E(V − I) = 0.04 ± 0.06 mag is obtained. With RR Lyrae stars a median value of E(V − I) = 0.11 ± 0.06 mag for the LMC and E(V − I) = 0.07 ± 0.06 mag for the SMC is found. The LMC shows very low reddening in the bar region, whereas the reddening in the star-forming leading edge and 30 Doradus is considerably higher. In the SMC three pronounced regions with higher reddening are visible. Two are located along the bar, while the highest reddening is found in the starforming wing of the SMC. In general the regions with higher reddening are in good spatial agreement with infrared reddening maps as well as with reddening estimations of other studies. The positiondependent reddening values from the red clump method are available via the German Astrophysical Virtual Observatory interface at

The VMC Survey

“…By applying the extinction law from Cardelli et al (1989) extinction values of A(Y) = 0.14 mag, A(J) = 0.10 mag and A(K s ) = 0.04 mag were derived. These values may be too high since in the less populated regions of the LMC differences in E(V −I) between Haschke et al (2011) and Zaritsky et al (2004) amount to 0.07-0.10 mag on average. In addition, while these values are applicable to LMC stars they are certainly too high towards foreground MW stars and too low towards extra-galactic sources.…”

“…Reddening values in terms of E(V − I) were extracted from the extinction map from Haschke et al (2011) for all but 10 (located outside the map) of the 117 QSOs. Using the Cardelli et al (1989) extinction law, the average QSO extinction is A(Y) = 0.045 mag, A(J) = 0.032 and A(K s ) = 0.013 mag.…”

“…In tile LMC 8_8, which is outside the region studied by Haschke et al (2011), reddening values were extracted from the Zaritsky et al (2004) extinction map. Here, instead of dereddening each individual star, an average value referring to cool stars only, A(V) = 0.35 mag, was obtained in a region centred on the tile and with a radius of 12 .…”

“…Here, instead of dereddening each individual star, an average value referring to cool stars only, A(V) = 0.35 mag, was obtained in a region centred on the tile and with a radius of 12 . Cool stars were chosen because they have similar characteristics to red clump giant and RR Lyrae stars used by Haschke et al (2011). The size of the region, whilst being smaller than the extent of a tile, is representative of the average extinction since this tile is located in the outer disc of the LMC where the reddening is uniform.…”

The VMC Survey – XIII. Type II Cepheids in the Large Magellanic Cloud★

“…In particular, we derived P L relations in J and Ks as well as P W and P LC relations for the following combinations: (J, V − J); (Ks,V − Ks); (Ks,J − Ks). We first corrected magnitudes and colours for reddening using the recent extinction maps by Haschke, Grebel & Duffau (2011). Individual E(V −I) reddening values for the 120 T2CEPs with useful VMC data are reported in column 10 of Table 4.…”