Quantifying radial migration in the Milky Way: inefficient over short time-scales but essential to the very outer disc beyond ∼15 kpc
Quantifying radial migration in the Milky Way: inefficient over short time-scales but essential to the very outer disc beyond ∼15 kpc
复制标题
量化银河系中的径向迁移：在短时间内效率较低，但对于超过 15 kpc 的最外层盘至关重要
DOI：
10.1093/mnras/stac479
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发表时间：
2022
影响因子：
4.8
通讯作者：
Nitschelm, Christian
中科院分区：
文献类型：
--
作者：
Lian, Jianhui;Zasowski, Gail;Hasselquist, Sten;Holtzman, Jon A.;Boardman, Nicholas;Cunha, Katia;Fernández-Trincado, José G.;Frinchaboy, Peter M.;Garcia-Hernandez, D. A.;Nitschelm, Christian
恒星径向迁移对星系结构的重塑和星族性质的径向分布起着重要的作用。在这项工作中，我们重新审视了径向迁移的观测证据，并使用APOGEE数据的银河系恒星的年龄[Fe/H]分布来量化其强度。我们发现银盘在r> 6 kpc时年龄-[Fe/H]关系破裂，在较大半径处破裂更明显。为了量化径向迁移的强度，我们假设在每个半径处出生的恒星具有唯一的年龄和金属丰度，然后将单年龄年轻种群的金属丰度分布函数（Ep）分解为不同的高斯分量，这些分量来自不同的出生半径atrbirth< 13 kpc。我们发现，在2 Gyr和3 Gyr年龄时，大约一半的恒星是在其目前半径1 kpc范围内形成的，很少有恒星（<5%）是在距离其目前半径超过4 kpc的地方形成的。这些结果表明，有限的短距离径向迁移和低效率的长距离迁移在银河系的最后3 Gyr。在超过15千秒差距的最外层盘中，观察到的年龄-[Fe/H]分布与从较小半径的纯径向迁移的预测一致，表明最外层盘的迁移起源。我们还估计了2和3 Gyr年龄的内在金属丰度梯度分别为-0.061和-0.063 dex kpc-1。
Stellar radial migration plays an important role in reshaping a galaxy’s structure and the radial distribution of stellar population properties. In this work, we revisit reported observational evidence for radial migration and quantify its strength using the age–[Fe/H] distribution of stars across the Milky Way with APOGEE data. We find a broken age–[Fe/H] relation in the Galactic disc atr> 6 kpc, with a more pronounced break at larger radii. To quantify the strength of radial migration, we assume stars born at each radius have a unique age and metallicity, and then decompose the metallicity distribution function (MDF) of mono-age young populations into different Gaussian components that originated from various birth radii atrbirth< 13 kpc. We find that, at ages of 2 and 3 Gyr, roughly half the stars were formed within 1 kpc of their present radius, and very few stars (<5 per cent) were formed more than 4 kpc away from their present radius. These results suggest limited short-distance radial migration and inefficient long-distance migration in the Milky Way during the last 3 Gyr. In the very outer disc beyond 15 kpc, the observed age–[Fe/H] distribution is consistent with the prediction of pure radial migration from smaller radii, suggesting a migration origin of the very outer disc. We also estimate intrinsic metallicity gradients at ages of 2 and 3 Gyr of −0.061 and −0.063 dex kpc−1, respectively.