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arXiv 0808.3207astro-ph
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变色龙属

Chamaeleon

Kevin L. Luhman

备注：
to appear in the Handbook of Star Forming Regions, ASP Monograph Series
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摘要：

变色龙星座中的乌云距离太阳160-180 pc，总质量约为5000 M_sun。三个主要的云，茶I，II和III，有几个平方度的角大小和最大的反射率A_V=5-10。这些星云中的大部分恒星形成发生在Cha I，其余的则发生在Cha II。目前对茶一号的普查包含237颗已知成员，其中33颗的光谱类型表明是棕矮星（>M6）。大约有50个Cha II成员已经被确认，包括一些褐矮星。当用Chabrier和Baraffe的演化模型解释时，Cha I的H-R图显示其年龄中位数约为200万年，与IC 348同时代，略早于金牛座（约100万年）。Cha I的IMF在质量为0.1-0.15 M_sun时达到最大值，因此与IC 348和猎户座星云团的IMF非常相似。在0.01 ~ 0.3 Msun的范围内，Cha I的盘状部分大约为50%，在更大的质量下增加到65%。相比之下，IC 348在低质量时有类似的盘分数，但在M>1 M_sun时盘分数要低得多，这表明太阳型恒星在Cha I中有更长的盘寿命。

英文摘要：

The dark clouds in the constellation of Chamaeleon have distances of 160-180 pc from the Sun and a total mass of ~5000 M_sun. The three main clouds, Cha I, II, and III, have angular sizes of a few square degrees and maximum extinctions of A_V=5-10. Most of the star formation in these clouds is occurring in Cha I, with the remainder in Cha II. The current census of Cha I contains 237 known members, 33 of which have spectral types indicative of brown dwarfs (>M6). Approximately 50 members of Cha II have been identified, including a few brown dwarfs. When interpreted with the evolutionary models of Chabrier and Baraffe, the H-R diagram for Cha I exhibits a median age of ~2 Myr, making it coeval with IC 348 and slightly older than Taurus (~1 Myr). The IMF of Cha I reaches a maximum at a mass of 0.1-0.15 M_sun, and thus closely resembles the IMFs in IC 348 and the Orion Nebula Cluster. The disk fraction in Cha I is roughly constant at ~50% from 0.01 to 0.3 M_sun and increases to ~65% at higher masses. In comparison, IC 348 has a similar disk fraction at low masses but a much lower disk fraction at M>1 M_sun, indicating that solar-type stars have longer disk lifetimes in Cha I.

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