Publications of the MPIfR
Optical & Infrared
Interferometry Group
Naoi, T., Tamura, M.,
Nakajima, Y., Nagata, T., Suto, H., Murakawa, K.,
Kandori, R., Sasaki, S., Baba, D., Kato, D., Kurita, M.,
Nagashima, C., Nagayama, T., Nakaya, H., Nishiyama,
S., Oasa, Y., Sato, S., Sugitani, K.
Near-Infrared Extinction Law in the ρ Ophiuchi
and Chamaeleon Dark Clouds
The Astrophysical Journal, Volume 640, Issue 1, pp.
373-382.
Abstract
We determine and compare the color excess ratios EJ-H/EH-KS for the ρ
Ophiuchi and Chamaeleon dark clouds with the J-, H-, and Ks-band
simultaneous camera, SIRIUS, on the IRSF 1.4 m telescope at SAAO.
Determining accurate ratios is indispensable for discussions of the
extinction law. However, previous surveys suffered from uncertainties
in transforming one photometric system to another when comparing data
on different systems. To overcome the problem, we observe both clouds
in exactly the same photometric system on the same telescope, greatly
simplifying the comparison of the extinction laws between two clouds.
From our surveys covering about 1.56 deg2 (ρ Oph) and 2.77 deg2
(Chamaeleon), which are complete for J~19.0, H~18.3, and KS~17.0 mag at
a 10 σ limiting magnitude, we did not find a significant difference in
the extinction law EJ-H/EH-KS for the two clouds, in contrast to
previous work. From calculations of a model star with the effects of
filter and atmosphere transmissions, the differences of the color
excess ratios EJ-H/EH-K for two clouds described in the past literature
can be attributed to the different photometric systems so far employed.
We also note a change of the color excess ratio that occurs with
increasing optical depth.
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