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arXiv 1502.07460astro-ph.SR
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M矮星金属丰度的光学-近红外光度标定及其应用

Optical - Near Infrared Photometric Calibration of M-dwarf Metallicity and Its Application

Neda Hejazi, Michael M. De Robertis, Peter C. Dawson

摘要:

基于一个精心构造的矮星样本,提出了一种新的光学-近红外光度定标方法来估算晚型K矮星和早-中型M矮星的金属丰度。校准样品有两个部分;第一部分包括18个M矮星,其金属丰度由高分辨率光谱确定,第二部分包含49个矮星,其金属丰度通过中等分辨率光谱获得。通过对斯隆数字巡天和2微米全天巡天的约130万颗M矮星的大样本进行校准,确定了该样本的金属丰度分布,并与以前的研究结果进行了比较。利用光度计测量了大样本M矮星的银河高度。我们的研究结果表明,离银道面较远的恒星,平均而言,具有较低的金属丰度,这可以归因于年龄-金属丰度关系。相对于简单闭盒模型,贫金属矮星的金属丰度分布稀少,这表明存在类似于先前已知的G矮星和K矮星问题的“M矮星问题”。几个更复杂的银河系化学演化模型已提出解决G和K矮星问题进行了测试,并表明,这些模型可以,在一定程度上,减轻M矮星问题。

英文摘要:

Based on a carefully constructed sample of dwarf stars, a new optical-near infrared photometric calibration to estimate the metallicity of late-type K and early-to-mid-type M dwarfs is presented. The calibration sample has two parts; the first part includes 18 M dwarfs with metallicities determined by high-resolution spectroscopy and the second part contains 49 dwarfs with metallicities obtained through moderate-resolution spectra. By applying this calibration to a large sample of around 1.3 million M dwarfs from the Sloan Digital Sky Survey and the Two-Micron All Sky Survey, the metallicity distribution of this sample is determined and compared with those of previous studies. Using photometric parallaxes, the Galactic heights of M dwarfs in the large sample are also estimated. Our results show that stars farther from the Galactic plane, on average, have lower metallicity, which can be attributed to the age-metallicity relation. A scarcity of metal-poor dwarf stars in the metallicity distribution relative to the Simple Closed Box Model indicates the existence of the "M dwarf problem," similar to the previously known G and K dwarf problems. Several more complicated Galactic chemical evolution models which have been proposed to resolve the G and K dwarf problems are tested and it is shown that these models could, to some extent, mitigate the M dwarf problem as well.

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