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arXiv 1807.04592astro-ph.GA
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由LAMOST单年龄恒星群体揭示的银河系盘的恒星质量分布和恒星形成历史

Stellar mass distribution and star formation history of the Galactic disk revealed by mono-age stellar populations from LAMOST

Maosheng Xiang, Jianrong Shi, Xiaowei Liu, Haibo Yuan, Bingqiu Chen, Yang Huang, Chun Wang, Zhijia Tian, Zhiying Huo, Huawei Zhang, Meng Zhang

摘要:

我们提出了一个详细的测定和分析的3D恒星质量分布的银河系盘的单年龄人口使用的样本0.93万主序星关闭和次巨星从LAMOST银河系巡天。结果表明:(1)小于10 μ gyr的恒星星族都表现出强烈的星盘耀斑,并伴随着一个矮胖的垂直密度分布,其密度分布可以用$sech^n$函数来描述,该函数的指数依赖于半径和年龄:(2)在径向和垂直方向都表现出不对称性和波动性振荡,其强度随恒星星族的不同而不同;(3)由于本旋臂的贡献,在太阳半径400 - 800,pc范围内的中面恒星质量密度(3 - 6 $^\circ$)的值为$0.0594\pm0.0008$,$M_\odot$/pc $^3$,为0.0164,$M_\odot$/pc $^3$高于之前在太阳附近的估计。(4)表面质量密度的径向分布产生了一个盘尺度长度,从年轻的$\sim$ 4,kpc到年老的$\sim$ 2,kpc。总星族的盘尺度长度为$2.48\pm0.05$\,kpc,恒星总质量为$3.6(\pm0.1)\times10^{10}$\,$M_\odot$(假设$R_{\odot}=8.0$\,kpc),如果$R_{\odot}=8.3$\,kpc,则该值变为$4.1(\pm0.1)\times10^{10}$\,$M_\odot$;(5)星盘有一个恒星形成率峰值({\rm SFR})从内部的6 - 8\\f2 Gyr变化到外部的4 - 6\f2 Gyr,表明组装历史是由内而外的。0--1\f25 Gyr-1人口产生最近的磁盘总数{\rm SFR}为$1.96\pm0.12$\,$M_\odot$/年。

英文摘要:

We present a detailed determination and analysis of 3D stellar mass distribution of the Galactic disk for mono-age populations using a sample of 0.93 million main-sequence turn-off and subgiant stars from the LAMOST Galactic Surveys. Our results show (1) all stellar populations younger than 10\,Gyr exhibit strong disk flaring, which is accompanied with a dumpy vertical density profile that is best described by a $sech^n$ function with index depending on both radius and age; (2) Asymmetries and wave-like oscillations are presented in both the radial and vertical direction, with strength varying with stellar populations; (3) As a contribution by the Local spiral arm, the mid-plane stellar mass density at solar radius but 400--800\,pc (3--6$^\circ$) away from the Sun in the azimuthal direction has a value of $0.0594\pm0.0008$\,$M_\odot$/pc$^3$, which is 0.0164\,$M_\odot$/pc$^3$ higher than previous estimates at the solar neighborhood. The result causes doubts on the current estimate of local dark matter density; (4) The radial distribution of surface mass density yields a disk scale length evolving from $\sim$4\,kpc for the young to $\sim$2\,kpc for the old populations. The overall population exhibits a disk scale length of $2.48\pm0.05$\,kpc, and a total stellar mass of $3.6(\pm0.1)\times10^{10}$\,$M_\odot$ assuming $R_{\odot}=8.0$\,kpc, and the value becomes $4.1(\pm0.1)\times10^{10}$\,$M_\odot$ if $R_{\odot}=8.3$\,kpc; (5) The disk has a peak star formation rate ({\rm SFR}) changing from 6--8\,Gyr at the inner to 4--6\,Gyr ago at the outer part, indicating an inside-out assemblage history. The 0--1\,Gyr population yields a recent disk total {\rm SFR} of $1.96\pm0.12$\,$M_\odot$/yr.

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