Extinction in the Large Magellanic Cloud

We present an extinction map of the Large Magellanic Cloud (LMC), using 204,502 stars from the Two Micron All-Sky Survey point-source catalog. We first use the NICE method to determine the reddening distribution, E ( H - K ) and E ( J - H ), which we compare to the H I distribution to find a near-infrared reddening law of E ( J - H )/ E ( H - K ) = 1.20 ± 0.04. A visual extinction map (~6° × 6°) of the LMC is created using the NICER method; at 4' resolution, a mean value of A V = 0.3 mag is found. We derive the LMC CO-to-H 2 conversion factor, X LMC , independent of assumptions about the virialization of giant molecular clouds, by comparing the NICER extinction map with NANTEN 12 CO observations. In regions where A V > 1 mag and 12 CO emission is ≥2 K km s -1 , we measure X LMC = 9.3 ± 0.4 × 10 20 cm -2 (K km s -1 ) -1 . In the same regions, the LMC contains a total molecular mass of (4.5 ± 0.2) × 10 7 M ☉ .