A New Derivation of the Extinction-to-CO Column Density Ratio in the Chamaeleon I Dark Cloud
A New Derivation of the Extinction-to-CO Column Density Ratio in the Chamaeleon I Dark Cloud
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Chamaeleon I 暗云中消光与 CO 柱密度比的新推导
DOI：
10.1093/pasj/51.6.919
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发表时间：
1999
影响因子：
2.3
通讯作者：
Y. Fukui
中科院分区：
文献类型：
--
作者：
T. Hayakawa;A. Mizuno;T. Onishi;Y. Yonekura;A. Hara;R. Yamaguchi;Y. Fukui
我们分析了通过 NANTEN 获得的 13CO (J = 1-0) 和 C 18 0 (J = 1-0) 发射的新数据集以及源自 Chamaeleon I 暗云中 DENIS J 波段观测的视觉消光 Ay。分子同位素 7V(13CO) 和 iV(C180) 的柱密度已通过 LTE 求和得出。 7V(13CO) 和 7V(C180) 在 Ay < 10 mag 范围内与 Ay 线性相关。我们建立了关系 iV(13CO)(cm-2) = (1.2 ± 0.1) x 10 15Av(mag) + (0.7 ± 0.3) x 10 15 和 7V(C180)(cmT2) - (3.5 ± 0.3) x 10 14Av(mag) - (5.7 ± 1.3) x 10 14。然而，对于簇状的金牛座 T 星，Ay-N(13CO) 和 Ay-N(ClsO) 关系都比上述关系陡峭约 2 倍。这可能主要是由于低估了 Ay 值，并且 J 波段恒星计数可能值得更仔细地检查，以发现可能低估的相关年轻恒星。与其他云的关系相比，Ay-N(13CO)关系的斜率相对较浅，非星团形成区域的Ay-N(ClsO)关系的斜率稍陡。这些事实表明，云与云之间的变化在 Ay-N(CO) 关系中非常重要。
We have analyzed new datasets of 13CO (J = 1-0) and C 18 0 (J = 1-0) emission obtained with NANTEN and visual extinction, Ay, derived from DENIS J-band observations in the Chamaeleon I dark cloud. The column densities of both molecular isotopes, 7V(13CO) and iV(C180), have been derived as suming LTE. Both 7V(13CO) and 7V(C180) are linearly correlated with Ay in the range Ay < 10 mag. We established the relationships iV(13CO)(cm-2) = (1.2 ± 0.1) x 10 15Av(mag) + (0.7 ± 0.3) x 10 15 and 7V(C180)(cmT2) - (3.5 ± 0.3) x 10 14Av(mag) - (5.7 ± 1.3) x 10 14. In a region of clustered T Tauri stars, however, both the Ay-N(13CO) and Ay-N(ClsO) relationships are by a factor of ~ 2 steeper than the above. This may be mainly due to underestimate s of the Ay values, and the J-band star count might deserve a more careful examination for possible underestimates of associated young stars. Compared with the relationships for the other clouds, the slope of the Ay-N(13CO) relationship is relatively shallower and that of the Ay-N(ClsO) relationship in a non-cluster forming region is slightly steeper. These facts suggest that cloud-to-cloud variation is significant in the Ay-N(CO) relationships.