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arXiv 1209.4903astro-ph.CO
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吸收和发射中的银河系外流:1 <z <2的银河系近紫外光谱

Galactic Outflows in Absorption and Emission: Near-UV Spectroscopy of Galaxies at 1<z<2

Dawn K. Erb, Anna M. Quider, Alaina L. Henry, Crystal L. Martin

摘要:

我们研究了96个恒星形成星系的样本中的大规模外流,在1 <z <2,使用近紫外光谱的Fe II和Mg II的吸收和发射。在z~1.5处,FeII星际吸收线相对于系统速度的平均蓝移为-85 +/-10 km/s,标准差为87 km/s;这比在z~2处类似选择的星系中测量的远紫外星际吸收线的平均蓝移减少了2倍。MgII 2796,2803线的配置文件显示更多的变化比FeII的配置文件,这是总是看到在吸收; MgII的范围从强发射到纯吸收,发射更常见的星系与蓝色的紫外线斜率和较低的恒星质量。外流速度,跟踪的质心和最大程度的吸收线,增加与2 - 3sigma的显着性,与以前的结果一致,随着恒星质量的增加。我们研究精细结构的发射从Fe II *,找到几条线的证据支持的模型,在该模型中,这种发射是由连续的光子吸收的Fe II的共振跃迁中流出的气体的再发射。与此相反,光电离模型表明,MgII发射产生的HII区域中产生的光子的共振散射,占不同的配置文件的MgII和FeII线。FeII吸收和FeII * 发射线的强度的比较表明,大质量的星系有更多的扩展流出和/或更大的灭绝,而二维复合光谱表明,从流出的发射是强在一个半径为10千秒差距的高质量星系比低质量星系。

英文摘要:

We study large-scale outflows in a sample of 96 star-forming galaxies at 1<z<2, using near-UV spectroscopy of FeII and MgII absorption and emission. The average blueshift of the FeII interstellar absorption lines with respect to the systemic velocity is -85+/-10 km/s at z~1.5, with standard deviation 87 km/s; this is a decrease of a factor of two from the average blueshift measured for far-UV interstellar absorption lines in similarly selected galaxies at z~2. The profiles of the MgII 2796, 2803 lines show much more variety than the FeII profiles, which are always seen in absorption; MgII ranges from strong emission to pure absorption, with emission more common in galaxies with blue UV slopes and at lower stellar masses. Outflow velocities, as traced by the centroids and maximum extent of the absorption lines, increase with increasing stellar mass with 2-3sigma significance, in agreement with previous results. We study fine structure emission from FeII*, finding several lines of evidence in support of the model in which this emission is generated by the re-emission of continuum photons absorbed in the FeII resonance transitions in outflowing gas. In contrast, photoionization models indicate that MgII emission arises from the resonant scattering of photons produced in HII regions, accounting for the differing profiles of the MgII and FeII lines. A comparison of the strengths of the FeII absorption and FeII* emission lines indicates that massive galaxies have more extended outflows and/or greater extinction, while two-dimensional composite spectra indicate that emission from the outflow is stronger at a radius of ~10 kpc in high mass galaxies than in low mass galaxies.

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