THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. V. AGES AND MASSES OF THE YEAR 1 STELLAR CLUSTERS
THE PANCHROMATIC HUBBLE ANDROMEDA TREASURY. V. AGES AND MASSES OF THE YEAR 1 STELLAR CLUSTERS
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全色哈勃仙女座宝藏。
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
B. Williams
中科院分区：
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作者：
M. Fouesneau;L. Johnson;D. Weisz;D. Weisz;J. Dalcanton;E. Bell;L. Bianchi;N. Caldwell;D. Gouliermis;D. Gouliermis;P. Guhathakurta;J. Kalirai;S. Larsen;H. Rix;A. Seth;E. Skillman;B. Williams
我们给出了M31中601个星团的年龄和质量，这是通过分析作为全色哈勃仙女座金库(PHAT)的一部分的从近紫外线到近红外波长的六个滤光片综合光测量得出的。我们使用概率技术来计算年龄和质量，该技术考虑了恒星初始质量函数随机抽样的影响。对合成数据的测试表明，这种方法结合了PHAT观测的高灵敏度及其宽波长基线，为从∼102 到 2×106 M☉的星系团提供了稳健的年龄和质量恢复。我们发现，在过去的100MYR期间，星团的年龄分布是一致的，这表明M31内的星团分裂的影响很小。较老的(>；100 MYR)星团的年龄分布趋向于老年，这与指数−1的指数下降是一致的，这可能是由于星团的褪色和破坏的组合。结果表明，在10~3×10~5−-3×10~5 M☉范围内，整个样品的质量分布可用一次幂函数很好地描述，其光谱指数为1.90±0.1.然而，如果我们将样本除以半乳中心半径，我们发现年龄分布保持不变。然而，质量谱指数变化很大，在−2.2和−1.8之间显示出最佳拟合值，在恒星形成强度最高的区域有较浅的斜率。我们探讨了我们的研究对势系统学的稳健性，并得出结论：星团质量函数可能随着环境的不同而不同。
We present ages and masses for 601 star clusters in M31 from the analysis of the six filter integrated light measurements from near-ultraviolet to near-infrared wavelengths, made as part of the Panchromatic Hubble Andromeda Treasury (PHAT). We derive the ages and masses using a probabilistic technique, which accounts for the effects of stochastic sampling of the stellar initial mass function. Tests on synthetic data show that this method, in conjunction with the exquisite sensitivity of the PHAT observations and their broad wavelength baseline, provides robust age and mass recovery for clusters ranging from ∼102 to 2 × 106 M☉. We find that the cluster age distribution is consistent with being uniform over the past 100 Myr, which suggests a weak effect of cluster disruption within M31. The age distribution of older (>100 Myr) clusters falls toward old ages, consistent with a power-law decline of index −1, likely from a combination of fading and disruption of the clusters. We find that the mass distribution of the whole sample can be well described by a single power law with a spectral index of −1.9 ± 0.1 over the range of 103–3 × 105 M☉. However, if we subdivide the sample by galactocentric radius, we find that the age distributions remain unchanged. However, the mass spectral index varies significantly, showing best-fit values between −2.2 and −1.8, with the shallower slope in the highest star formation intensity regions. We explore the robustness of our study to potential systematics and conclude that the cluster mass function may vary with respect to environment.