Astrophys. J., 776, 7 (2013/October-2)
The mid-infrared extinction law in the Large Magellanic Cloud.
GAO J., JIANG B.W., LI A. and XUE M.Y.
Abstract (from CDS):
Based on photometric data from the Spitzer/SAGE survey, using red giants as extinction tracers, the mid-infrared (MIR) extinction laws in the Large Magellanic Cloud (LMC) are derived for the first time in the form of Aλ/AKs. This quantity refers to the extinction in the four Infrared Array Camera (IRAC) bands (i.e., [3.6], [4.5], [5.8], and [8.0] µm) relative to the Two Micron All Sky Survey KS band at 2.16 µm. We obtain the near-infrared extinction coefficient to be E(J - H)/E(H - KS) ~ 1.29±0.04 and E(J - KS)/E(H - KS) ~ 1.94±0.04. The wavelength dependence of the MIR extinction Aλ/AKs in the LMC varies from one sightline to another. The overall mean MIR extinction is A[3.6]/AKs ≈ 0.72 ± 0.03, A[4.5]/AKs ≈ 0.94 ± 0.03, A[5.8]/AKs ≈ 0.58 ± 0.04, and A[8.0]/AKs ≈ 0.62 ± 0.05. Except for the extinction in the IRAC [4.5] µm band, which may be contaminated by the 4.6 µm CO gas absorption of red giants used to trace LMC extinction, the extinction in the other three IRAC bands show a flat curve, close to the Milky Way RV = 5.5 model extinction curve, where RV is the optical total-to-selective extinction ratio. The possible systematic bias caused by the correlated uncertainties of KS- λ and J - KS is explored in terms of Monte Carlo simulations. We find that this bias could lead to an overestimation of Aλ/AKs in the MIR.
dust, extinction - galaxies: ISM - infrared: ISM - Magellanic Clouds
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