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Interstellar Extinction Law in the J , H , and K s Bands toward the Galactic Center

2006; IOP Publishing; Volume: 638; Issue: 2 Linguagem: Inglês

10.1086/499038

1538-4357

Shogo Nishiyama, Tetsuya Nagata, Nobuhiko Kusakabe, Noriyuki Matsunaga, Takahiro Naoi, Daisuke Kato, Chie Nagashima, Koji Sugitani, Motohide Tamura, Toshihiko Tanabé, Shuji Sato,

Galaxies: Formation, Evolution, Phenomena

We have determined the ratios of total to selective extinction in the near-infrared bands (J, H, Ks) toward the Galactic center from the observations of the region |l| < 2.0deg and 0.5deg < |b| < 1.0deg with the IRSF telescope and the SIRIUS camera. Using the positions of red clump stars in color-magnitude diagrams as a tracer of the extinction and reddening, we determine the average of the ratios of total to selective extinction to be A(Ks)/E(H-Ks) = 1.44+-0.01, A(Ks)/E(J-Ks) = 0.494+-0.006, and A(H)/E(J-H) = 1.42+-0.02, which are significantly smaller than those obtained in previous studies. From these ratios, we estimate that A(J) : A(H) : A(Ks) = 1 : 0.573+-0.009 : 0.331+-0.004 and E(J-H)/E(H-Ks) = 1.72+-0.04, and we find that the power law A(lambda) \propto lambda^{-1.99+-0.02} is a good approximation over these wavelengths. Moreover, we find a small variation in A(Ks)/E(H-Ks) across our survey. This suggests that the infrared extinction law changes from one line of sight to another, and the so-called ``universality'' does not necessarily hold in the infrared wavelengths.