Dissecting the Gaia HR diagram within 200 pc
Dissecting the Gaia HR diagram within 200 pc
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DOI：
10.1093/mnras/stab1964
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发表时间：
2021-07
影响因子：
4.8
通讯作者：
Piero Dal Tio-Piero-Dal Tio-2129526832;A. Mazzi;L. Girardi;M. Barbieri;S. Zaggia;A. Bressan;Yang Chen;G. Costa;P. Marigo
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作者：
Piero Dal Tio-Piero-Dal Tio-2129526832;A. Mazzi;L. Girardi;M. Barbieri;S. Zaggia;A. Bressan;Yang Chen;G. Costa;P. Marigo
我们分析了高质量的Hertzsprung-Russell图(HRD)，该图来自Gaia太阳近邻数据发布2。我们开始在200台PC内为|b|>；250构建一个几乎完整的样本，以限制GAIA目录中已知错误和人工制品的影响。然后特别努力改进双星种群的模型，这在HRD中产生了两个显著的特征：沿着较低的主序列的质量接近相同的双星序列，以及孤立的热次矮星群。我们描述了一个新的工具，BinaPSE，它可以用来跟踪相互作用的双星的演化，这种方法可以改善与单星的几秒演化轨迹的一致性。BinaPSE被实现到Trilegl代码中，用于生成单星和双星群的‘部分模型’，并考虑到已解析和未解析双星的存在。然后，我们通过马尔可夫链蒙特卡罗方法来拟合Gaia HRD，该方法搜索恒星形成历史和最大化可能性的初始二进制分数(按质量)。主要结果是：(1)从较低的MS得到的二进制分数接近于0.4，而当HRD的上部被拟合时，则倾向于两倍大的值：(Ii)目前的模型预测热次矮星的观测数目在2倍以内；无论双星的配方如何，恒星形成率在年龄略高于2Gyr时在10^-4}{\rm{M}_{\odot}}\mathm{yr}^{-1}$时达到峰值，然后在很高年龄时下降到$\sim\0.8×10^-4}{\rm{M}{\odot}}\mathm{yr}^{-1}$。
We analyse the high-quality Hertzsprung–Russell diagram (HRD) derived from Gaia data release 2 for the Solar Neighbourhood. We start building an almost complete sample within 200 pc and for |b| > 25○, so as to limit the impact of known errors and artefacts in the Gaia catalogue. Particular effort is then put into improving the modelling of population of binaries, which produce two marked features in the HRD: the sequence of near-equal mass binaries along the lower main sequence, and the isolated group of hot subdwarfs. We describe a new tool, BinaPSE, to follow the evolution of interacting binaries in a way that improves the consistency with PARSEC evolutionary tracks for single stars. BinaPSE is implemented into the TRILEGAL code for the generation of ‘partial models’ for both single and binary stellar populations, taking into account the presence of resolved and unresolved binaries. We then fit the Gaia HRD via Markov chain Monte Carlo methods that search for the star formation history and an initial binary fraction (by mass) that maximize the likelihood. The main results are (i) the binary fraction derived from the lower MS is close to 0.4, while twice larger values are favoured when the upper part of the HRD is fitted; (ii) present models predict the observed numbers of hot subdwarfs to within a factor of 2; and (iii) irrespective of the prescription for the binaries, the star formation rate peaks at values $\sim \!1.5\times 10^{-4}{\rm{M}_{\odot }}\mathrm{yr}^{-1}$ at ages slightly above 2 Gyr, and then decreases to $\sim \!0.8\times 10^{-4}{\rm{M}_{\odot }}\mathrm{yr}^{-1}$ at very old ages.