The evolution of stellar metallicity gradients of the Milky Way disk from LSS-GAC main sequence turn-off stars: a two-phase disk formation history?
The evolution of stellar metallicity gradients of the Milky Way disk from LSS-GAC main sequence turn-off stars: a two-phase disk formation history?
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LSS-GAC 主序关闭星的银河系盘恒星金属丰度梯度的演化：两相盘形成历史？
DOI：
10.1088/1674-4527/15/8/009
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发表时间：
2015-05
影响因子：
1.8
通讯作者：
Rebassa-Mansergas Alberto
中科院分区：
文献类型：
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作者：
Xiang Mao-Sheng;Liu Xiao-Wei;Yuan Hai-Bo;Huang Yang;Wang Chun;Ren Juan-Juan;Chen Bing-Qiu;Sun Ning-Chen;Zhang Hua-Wei;Huo Zhi-Ying;Rebassa-Mansergas Alberto
精确测量银河系盘径向和垂直方向上的恒星金属丰度梯度及其时间变化，对银河系盘的形成和演化提供了重要的约束。利用LAMOST银河系反心光谱巡天（LSS-GAC）中选取的297042颗主序星，测定了恒星金属丰度的径向和垂直梯度Δ[Fe/H]/ΔR和Δ[Fe/H]/Δ| Z|银河系盘的反中心方向。通过等时线拟合确定了这些变星的年龄，并测量了它们的金属丰度梯度随时间的变化。我们已经进行了详细的分析LSS-GAC目标的选择，观察和数据处理的选择效果和潜在的偏差的幅度有限的样品上的金属丰度梯度的测定。我们的研究结果表明，梯度，在径向和垂直方向上，表现出显着的空间和时间变化。年龄最大的恒星（1011 Gyr）产生的径向梯度在距盘中平面的所有高度上基本上为零，而年轻恒星产生的径向梯度总是负值。从年龄最大的恒星（1011 Gyr）推导出的垂直梯度是负的，并且只显示出非常微弱的银心距变化，而年轻恒星的垂直梯度则显示出强烈的银心距变化。在星盘形成的最早时期基本上是平坦的，随着年龄的减小，径向梯度变陡，在7-8 Gyr时达到最大值（最陡），然后再次变平。垂直梯度也发现了类似的时间趋势。我们推断，银河系盘的组装可能经历了至少两个不同的阶段。早期阶段可能与气体的缓慢的、压力支持的坍缩有关，此时气体主要在垂直方向上沉降到盘上。在后期阶段，有显着的径向流动的气体在磁盘上，并在太阳附近的气体流入的速度达到最大值约7-8 Gyr的回望时间。两个相位之间的过渡发生在8和11 Gyr之间的回顾时间附近。这两个阶段可能分别负责银河系厚盘和薄盘的形成。此外，作为一个结果，我们建议恒星年龄是一个自然的，物理标准，以区分恒星的薄和厚的磁盘。从早于11 Gyr的时代到8 - 11 Gyr之间，径向和垂直金属丰度梯度的大小都发生了突然的显著变化，这表明恒星径向迁移不太可能在厚盘的形成中发挥重要作用。
Accurate measurements of stellar metallicity gradients in the radial and vertical directions of the disk and their temporal variations provide important constraints on the formation and evolution of the Milky Way disk. We use 297 042 main sequence turn-off stars selected from the LAMOST Spectroscopic Survey of the Galactic Anti-center (LSS-GAC) to determine the radial and vertical gradients of stellar metallicity, Δ[Fe/H]/ΔR and Δ[Fe/H]/Δ|Z| of the Milky Way disk in the direction of the anticenter. We determine ages of those turn-off stars by isochrone fitting and measure the temporal variations of metallicity gradients. We have carried out a detailed analysis of the selection effects resulting from the selection, observation and data reduction of LSS-GAC targets and the potential biases of a magnitude limited sample on the determinations of metallicity gradients. Our results show that the gradients, both in the radial and vertical directions, exhibit significant spatial and temporal variations. The radial gradients yielded by stars with the oldest ages (≳ 11 Gyr) are essentially zero at all heights from the disk midplane, while those given by younger stars are always negative. The vertical gradients deduced from stars with the oldest ages (≳ 11 Gyr) are negative and only show very weak variations with Galactocentric distance in the disk plane, R, while those yielded by younger stars show strong variations with R. After being essentially flat at the earliest epochs of disk formation, the radial gradients steepen as age decreases, reaching a maximum (steepest) at age 7–8 Gyr, and then they flatten again. Similar temporal trends are also found for the vertical gradients. We infer that the assembly of the Milky Way disk may have experienced at least two distinct phases. The earlier phase is probably related to a slow, pressure-supported collapse of gas, when the gas settles down to the disk mainly in the vertical direction. In the later phase, there are significant radial flows of gas in the disk, and the rate of gas inflow near the solar neighborhood reaches a maximum around a lookback time of 7–8 Gyr. The transition between the two phases occurs around a lookback time between 8 and 11 Gyr. The two phases may be responsible for the formation of the Milky Way's thick and thin disks, respectively. Also, as a consequence, we recommend that stellar age is a natural, physical criterion to distinguish stars from the thin and thick disks. From an epoch earlier than 11Gyr to one between 8 and 11Gyr, there is an abrupt, significant change in magnitude of both the radial and vertical metallicity gradients, suggesting that stellar radial migration is unlikely to play an important role in the formation of the thick disk.
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DOI：
10.1051/0004-6361:20034539
发表时间：
2004-05
期刊：
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影响因子：
--
作者：
R. Costa;W. J. Maciel;Monica M.M. Uchida
通讯作者：
R. Costa;W. J. Maciel;Monica M.M. Uchida
基于SDSS DR8红色水平分支星的厚盘金属度梯度
影响因子：
5.3
作者：
Chen, Y. Q.;Zhao, G.;Carrell, K.;Zhao, J. K.
通讯作者：
Zhao, J. K.
DOI：
10.1086/519976
发表时间：
2007-03
期刊：
The Astronomical Journal
影响因子：
--
作者：
Ž. Ivezić;J. A. Smith;G. Miknaitis;Huan Lin;D. Tucker;R. Lupton;J. Gunn;G. Knapp;M. Strauss-M.-Str
通讯作者：
Ž. Ivezić;J. A. Smith;G. Miknaitis;Huan Lin;D. Tucker;R. Lupton;J. Gunn;G. Knapp;M. Strauss-M.-Str
DOI：
10.1088/0004-637x/761/2/160
发表时间：
2011-12
期刊：
The Astrophysical Journal
影响因子：
--
作者：
K. Schlesinger;Jennifer A. Johnson;C. Rockosi;Y. S. Lee;H. Morrison;R. Schoenrich;C. Allende Prieto-C.-Allende-Pri
通讯作者：
K. Schlesinger;Jennifer A. Johnson;C. Rockosi;Y. S. Lee;H. Morrison;R. Schoenrich;C. Allende Prieto-C.-Allende-Pri
DOI：
--
发表时间：
2005
期刊：
--
影响因子：
--
作者：
通讯作者：
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