Pre-main-sequence isochrones - II. Revising star and planet formation time-scales
Pre-main-sequence isochrones - II. Revising star and planet formation time-scales
复制标题
DOI：
10.1093/mnras/stt1075
复制
发表时间：
2013-09-01
影响因子：
4.8
通讯作者：
Littlefair, S. P.
中科院分区：
文献类型：
--
作者：
Bell, Cameron P. M.;Naylor, Tim;Littlefair, S. P.
我们已经推导出了13个年轻（<3000万年）恒星形成区的年龄，发现它们比文献中通常采用的年龄大2倍。这一结果具有广泛的意义，包括拱星盘的寿命更长（近似或等于1012百万年），平均I类寿命比目前认为的更长（近似或等于1百万年）。对于每个恒星形成区，我们从色星等图中得到了两个年龄。首先，我们拟合零年龄主层序和末龄主层序之间的演化模型，以获得一组具有统计学意义的不确定性的主层序年龄、距离和红度。我们的第二个年龄为每个恒星形成区的拟合前主序星新的半经验模型等时线。对于第一次（一组年龄小于5000万年的星团），我们发现这两个年龄之间有广泛的一致性，因为它们来自两个不同的质量体系，依赖于恒星物理学的不同方面，这使我们对新的年龄尺度有信心。这种一致性主要是由于我们采用了经验色-T-eff关系和主序前温度低于4000 K的恒星的热辐射修正。在我们的样本中，恒星形成区的修订年龄为：（鹰星云; M 16），IC 5146（茧星云），NGC 6530（泻湖星云; M 8）和NGC 2244（玫瑰星云）;与猎户座Sigma、Cep OB 3b和IC 348的600万年相似;与猎户座lambda的1000万年相似或相等（Collinder 69）; NGC 2169类似或等于1100万年; NGC 2362类似或等于1200万年; NGC 7160类似或等于1300万年; chi Per（NGC 884）类似或等于1400万年; NGC 1960（M 36）的年平均值约等于2000万年。
We have derived ages for 13 young (< 30 Myr) star-forming regions and find that they are up to a factor of 2 older than the ages typically adopted in the literature. This result has wide-ranging implications, including that circumstellar discs survive longer (similar or equal to 1012 Myr) and that the average Class I lifetime is greater (similar or equal to 1 Myr) than currently believed. For each star-forming region, we derived two ages from colour-magnitude diagrams. First, we fitted models of the evolution between the zero-age main sequence and terminal-age main sequence to derive a homogeneous set of main-sequence ages, distances and reddenings with statistically meaningful uncertainties. Our second age for each star-forming region was derived by fitting pre-main-sequence stars to new semi-empirical model isochrones. For the first time (for a set of clusters younger than 50 Myr), we find broad agreement between these two ages, and since these are derived from two distinct mass regimes that rely on different aspects of stellar physics, it gives us confidence in the new age scale. This agreement is largely due to our adoption of empirical colour-T-eff relations and bolometric corrections for pre-main-sequence stars cooler than 4000 K. The revised ages for the star-forming regions in our sample are: similar to 2 Myr for NGC 6611 (Eagle Nebula; M 16), IC 5146 (Cocoon Nebula), NGC 6530 (Lagoon Nebula; M 8) and NGC 2244 (Rosette Nebula); similar to 6 Myr for Sigma Ori, Cep OB3b and IC 348; similar or equal to 10 Myr for lambda Ori (Collinder 69); similar or equal to 11 Myr for NGC 2169; similar or equal to 12 Myr for NGC 2362; similar or equal to 13 Myr for NGC 7160; similar or equal to 14 Myr for chi Per (NGC 884); and similar or equal to 20 Myr for NGC 1960 (M 36).