由吸收线光谱研究早型星系中恒星的初始质量函数。I.数据和经验趋势
The Stellar Initial Mass Function in Early-Type Galaxies From Absorption Line Spectroscopy. I. Data and Empirical Trends
摘要：
老恒星星族积分光中引力敏感吸收线的强度是在银河系外对恒星初始质量函数（IMF）的少数直接探测之一。由于全耗尽CCD的出现，几乎没有或没有边缘，最近已成为可能，以获得这些功能的精确测量。在这里，我们目前的光谱覆盖的波长范围为0.35 - 0.55微米和0.72 - 1.03微米的M31和34个早型星系的SAURON样品，获得与凯克低分辨率成像光谱仪的凸起。信噪比大于200埃/1微米，这足以测量单个星系的重力敏感特征，并确定它们如何依赖于星系的其他属性。结合新的数据与以前获得的光谱的球状星团在M31和最大质量的椭圆星系的室女星系团，我们发现，矮敏感的Na I双和FeH Wing-Ford带系统增加速度色散，而巨敏感的Ca II三重态减少色散。这些趋势与不同的IMF相一致，因此具有更深势阱的星系具有更多的矮星富集质量函数。在一篇配套论文（Conroy & van Dokkum 2012）中，我们使用了一个全面的恒星星族合成模型来证明IMF效应可以与年龄和丰度变化分开，并量化了早期星系之间的IMF变化。
英文摘要：
The strength of gravity-sensitive absorption lines in the integrated light of old stellar populations is one of the few direct probes of the stellar initial mass function (IMF) outside of the Milky Way. Owing to the advent of fully depleted CCDs with little or no fringing it has recently become possible to obtain accurate measurements of these features. Here we present spectra covering the wavelength ranges 0.35 - 0.55 micron and 0.72 - 1.03 micron for the bulge of M31 and 34 early-type galaxies from the SAURON sample, obtained with the Low Resolution Imaging Spectrometer on Keck. The signal-to-noise ratio is >200 per Angstrom out to 1 micron, which is sufficient to measure gravity-sensitive features for individual galaxies and to determine how they depend on other properties of the galaxies. Combining the new data with previously obtained spectra for globular clusters in M31 and the most massive elliptical galaxies in the Virgo cluster we find that the dwarf-sensitive Na I doublet and the FeH Wing-Ford band increase systematically with velocity dispersion, while the giant-sensitive Ca II triplet decreases with dispersion. These trends are consistent with a varying IMF, such that galaxies with deeper potential wells have more dwarf-enriched mass functions. In a companion paper (Conroy & van Dokkum 2012) we use a comprehensive stellar population synthesis model to demonstrate that IMF effects can be separated from age and abundance variations and quantify the IMF variation among early-type galaxies.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
