论文标题
使用Apogee探索银河系凸起的恒星年龄分布
Exploring the stellar age distribution of the Milky Way Bulge using APOGEE
论文作者
论文摘要
我们提出了使用年龄的$ \ sim $ 6,000高亮度($ \ log(g)<2.0 $),金属富含金属($ \ rm [fe/h] \ ge -0.5 $)凸起的凸起的凸起凸起的凸起凸起星星,由Apache Pointation Pointation Pointation Pointeration Pointeration Pointeration Pointeration Pointeration Pointeration Pointeration Pointeration观测值观察到。使用{\ it Cannon}标签转移方法得出年龄,该方法在附近的发光巨头样本中训练,并具有精确的视差,我们使用贝叶斯同色匹配技术获得了年龄。我们发现,金属富含的凸起主要由旧星星组成($> $ 8 GYR)。我们发现有证据表明,凸起的平面区域($ | z {\ rm gc} | \ le 0.25 $ kpc)以金属性($ z $)的速度更快地($ dz/dt \ sim $ 0.0034 $ 0.0034 $ { $ {\ rm gyr^{ - 1}} $ at $ | z _ {\ rm gc} |> 1.00 $ kpc)。我们以$ \ rm +0.2 <[fe/h] < +0.4 $的金属质量确定了年轻恒星(年龄$ \ sim $ 2-5 GYR)的不可忽略的部分。这些恒星优先在飞机上找到($ | z {\ rm gc} | \ le 0.25 $ kpc),在$ r _ {\ rm cy} \大约2-3 $ kpc之间,具有与旋转更一致的运动学比在同一基团的旧星星的Kinematics更一致。我们不能衡量条形内外发现的恒星之间的显着年龄差异。这些发现表明,凸起经历了一个初始的星爆,它比离飞机更远的飞机更紧密。然后,在2 kpc $ \ lyssim r _ {\ rm cy} \ lysesim $ 3 kpc的薄磁盘中,恒星形成在薄磁盘上以超极金属性继续进行,直到$ \ sim $ 2 $ 2 gyr of。
We present stellar age distributions of the Milky Way (MW) bulge region using ages for $\sim$6,000 high-luminosity ($\log(g) < 2.0$), metal-rich ($\rm [Fe/H] \ge -0.5$) bulge stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Ages are derived using {\it The Cannon} label-transfer method, trained on a sample of nearby luminous giants with precise parallaxes for which we obtain ages using a Bayesian isochrone-matching technique. We find that the metal-rich bulge is predominantly composed of old stars ($>$8 Gyr). We find evidence that the planar region of the bulge ($|Z_{\rm GC}| \le 0.25$ kpc) enriched in metallicity, $Z$, at a faster rate ($dZ/dt \sim$ 0.0034 ${\rm Gyr^{-1}}$) than regions farther from the plane ($dZ/dt \sim$ 0.0013 ${\rm Gyr^{-1}}$ at $|Z_{\rm GC}| > 1.00$ kpc). We identify a non-negligible fraction of younger stars (age $\sim$ 2--5 Gyr) at metallicities of $\rm +0.2 < [Fe/H] < +0.4$. These stars are preferentially found in the plane ($|Z_{\rm GC}| \le 0.25$ kpc) and between $R_{\rm cy} \approx 2-3$ kpc, with kinematics that are more consistent with rotation than are the kinematics of older stars at the same metallicities. We do not measure a significant age difference between stars found in and outside of the bar. These findings show that the bulge experienced an initial starburst that was more intense close to the plane than far from the plane. Then, star formation continued at super-solar metallicities in a thin disk at 2 kpc $\lesssim R_{\rm cy} \lesssim$ 3 kpc until $\sim$2 Gyr ago.