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arXiv 1207.3797astro-ph.GA
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Apache Point天文台星系演化实验:首次探测高速Milky Way棒星

The Apache Point Observatory Galactic Evolution Experiment: First Detection of High Velocity Milky Way Bar Stars

David L. Nidever, Gail Zasowski, Steven R. Majewski, Jonathan Bird, Annie C. Robin, Inma Martinez-Valpuesta, Rachael L. Beaton, Ralph Schoenrich, Mathias Schult… 展开作者

David L. Nidever, Gail Zasowski, Steven R. Majewski, Jonathan Bird, Annie C. Robin, Inma Martinez-Valpuesta, Rachael L. Beaton, Ralph Schoenrich, Mathias Schultheis, John C. Wilson, Michael F. Skrutskie, Robert W. O'Connell, Matthew Shetrone, Ricardo P. Schiavon, Jennifer A. Johnson, Benjamin Weiner, Ortwin Gerhard, Donald P. Schneider, Carlos Allende Prieto, Kris Sellgren, Dmitry Bizyaev, Howard Brewington, Jon Brinkmann, Daniel J. Eisenstein, Peter M. Frinchaboy, Ana Elia Garcia Perez, Jon Holtzman, Fred R. Hearty, Elena Malanushenko, Viktor Malanushenko, Demitri Muna, Daniel Oravetz, Kaike Pan, Audrey Simmons, Stephanie Snedden, Benjamin A. Weaver

摘要:

作为斯隆数字巡天III的一部分,阿帕奇点天文台星系演化实验(APOGEE)的委托观测已经产生了银河系凸起中~4700 K/M巨星的径向速度(RV)。这些高分辨率(R \sim 22,500)、高信噪比(每个分辨率元素>100)、近红外(1.51-1.70微米; NIR)光谱为18个银河系球区的恒星样本提供了精确的RV(RV ~0.2 km/s),这些球区跨度为-1<l<20 deg,|b| <20 deg,dec>-32 deg。这是有史以来在银河系这一区域聚集的最大的巨星近红外高分辨率光谱样本。在这些区域中,发现一个冷的(sigma_v~30 km/s)、高速的峰值(V_GSR \sim +200 km/s)包含了相当一部分(~10%)的恒星。这些高RV在以前的MW调查中没有被检测到,并且不期望用于简单的圆形旋转盘。初步的距离估计排除了人马座潮汐流或MW盘中新流的起源。与各种银河系模型的比较表明,这些高RV最好用银河系棒势轨道上的恒星来解释,尽管一些观测特征仍然无法解释。

英文摘要:

Commissioning observations with the Apache Point Observatory Galactic Evolution Experiment (APOGEE), part of the Sloan Digital Sky Survey III, have produced radial velocities (RVs) for ~4700 K/M-giant stars in the Milky Way bulge. These high-resolution (R \sim 22,500), high-S/N (>100 per resolution element), near-infrared (1.51-1.70 um; NIR) spectra provide accurate RVs (epsilon_v~0.2 km/s) for the sample of stars in 18 Galactic bulge fields spanning -1<l<20 deg, |b|<20 deg, and dec>-32 deg. This represents the largest NIR high-resolution spectroscopic sample of giant stars ever assembled in this region of the Galaxy. A cold (sigma_v~30 km/s), high-velocity peak (V_GSR \sim +200 km/s) is found to comprise a significant fraction (~10%) of stars in many of these fields. These high RVs have not been detected in previous MW surveys and are not expected for a simple, circularly rotating disk. Preliminary distance estimates rule out an origin from the background Sagittarius tidal stream or a new stream in the MW disk. Comparison to various Galactic models suggests that these high RVs are best explained by stars in orbits of the Galactic bar potential, although some observational features remain unexplained.

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