用加拿大-法国成像巡天对Milky Way的化学作图：星系的非参数金属性距离分解
Chemical Mapping of the Milky Way With The Canada-France Imaging Survey: A Non-parametric Metallicity-Distance Decomposition of the Galaxy
摘要：
我们目前的化学分布的银河系，根据2,900 $\, {\rm deg^2}$的$u$波段测光采取的加拿大-法国成像调查的一部分。完成后，这项调查将覆盖北方天空的10，000 $\, {\rm deg^2}$。通过将CFHT $u$ -波段测光与SDSS和泛星$g,r,$和$i$相结合，我们证明我们能够可靠地测量单个恒星的金属丰度到$\sim 0.2$ dex，从而获得良好的测光距离估计。因此，这次调查允许测量的金属丰度和距离的占主导地位的主序人口约30千秒差距，并提供了更多的恒星在大面外距离比以前的调查。我们开发了一个非参数的距离金属丰度分解算法，并将其应用到天空中的$30°< |b| < 70°$和北银河帽。我们发现，金属丰度距离分布是很好的代表三个人口的金属丰度分布不随垂直高度以上的磁盘显着。在主序星中，恒星晕的垂直密度分布接近于指数分布，刻度高度约为3千秒差距。这可能表明内晕部分是由盘状恒星在古代的小合并中喷出而形成的。
英文摘要：
We present the chemical distribution of the Milky Way, based on 2,900$\, {\rm deg^2}$ of $u$-band photometry taken as part of the Canada-France Imaging Survey. When complete, this survey will cover 10,000$\, {\rm deg^2}$ of the Northern sky. By combing the CFHT $u$-band photometry together with SDSS and Pan-STARRS $g,r,$ and $i$, we demonstrate that we are able to measure reliably the metallicities of individual stars to $\sim 0.2$ dex, and hence additionally obtain good photometric distance estimates. This survey thus permits the measurement of metallicities and distances of the dominant main-sequence population out to approximately 30 kpc, and provides much higher number of stars at large extraplanar distances than have been available from previous surveys. We develop a non-parametric distance-metallicity decomposition algorithm and apply it to the sky at $30°< |b| < 70°$ and to the North Galactic Cap. We find that the metallicity-distance distribution is well-represented by three populations whose metallicity distributions do not vary significantly with vertical height above the disk. As traced in main-sequence stars, the stellar halo component shows a vertical density profile that is close to exponential, with a scale height of around 3 kpc. This may indicate that the inner halo was formed partly from disk stars ejected in an ancient minor merger.
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