A CLEAR AGE–VELOCITY DISPERSION CORRELATION IN ANDROMEDA’S STELLAR DISK
A CLEAR AGE–VELOCITY DISPERSION CORRELATION IN ANDROMEDA’S STELLAR DISK
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仙女座恒星盘中清晰的年龄与速度色散相关性
DOI：
10.1088/0004-637x/803/1/24
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
B. Williams
中科院分区：
文献类型：
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作者：
C. Dorman;P. Guhathakurta;A. Seth;D. Weisz;E. Bell;J. Dalcanton;K. Gilbert;K. Hamren;A. Lewis;E. Skillman;E. Toloba;B. Williams
星系盘的恒星运动学是限制星系盘形成和演化过程的关键。在本文中，我们首次测量了M31内部20 kpc（∼3.5盘尺度长度）内的恒星年龄-速度色散相关性，并表明它与银河系（MW）中的恒星年龄-速度色散相关性有显着不同。我们使用光学哈勃太空望远镜/高级相机对来自全色哈勃仙女座宝藏巡天的 5800 颗恒星进行光度测量，并使用 Keck/DEIMOS 径向速度测量来自仙女座恒星晕巡天的光谱和光度景观的相同恒星。我们表明，平均视距色散是 R = 10 kpc 之外的年龄的稳定增长函数，从主序星的 30 km s − 1 ?> 增加到红巨星分支星的 90 km s−1 。这种单调增加意味着连续或重复的过程促进了圆盘的演化。色散与年龄关系的斜率和归一化均明显大于 MW 中的关系，这使得 M31 圆盘有可能比 MW 圆盘具有更剧烈的历史，更符合 Λ 冷暗物质预测。除了主要的圆盘成分之外，我们还从第二个运动学成分中发现了恒星不均匀分布的证据。最大和最热的高色散斑块之一存在于所有年龄组中，并且可能是长条末端的签名。
The stellar kinematics of galactic disks are key to constraining disk formation and evolution processes. In this paper, for the first time, we measure the stellar age–velocity dispersion correlation in the inner 20 kpc (∼3.5 disk scale lengths) of M31 and show that it is dramatically different from that in the Milky Way (MW). We use optical Hubble Space Telescope/Advanced Camera for Surveys photometry of 5800 individual stars from the Panchromatic Hubble Andromeda Treasury survey and Keck/DEIMOS radial velocity measurements of the same stars from the Spectroscopic and Photometric Landscape of Andromeda’s Stellar Halo survey. We show that the average line-of-sight dispersion is a steadily increasing function of age exterior to R = 10 kpc, increasing from 30 km s − 1 ?> for the main-sequence stars to 90 km s−1 for the red giant branch stars. This monotonic increase implies that a continuous or recurring process contributed to the evolution of the disk. Both the slope and normalization of the dispersion versus age relation are significantly larger than in the MW, allowing for the possibility that the disk of M31 has had a more violent history than the disk of the MW, more in line with Λ cold dark matter predictions. We also find evidence for an inhomogeneous distribution of stars from a second kinematical component in addition to the dominant disk component. One of the largest and hottest high-dispersion patches is present in all age bins and may be the signature of the end of the long bar.