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arXiv 1003.5425astro-ph.GA
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当今恒星形成星系外流的普遍性和性质的吸收线探测

Absorption-line probes of the prevalence and properties of outflows in present-day star-forming galaxies

Yan-Mei Chen, Christy A. Tremonti, Timothy M. Heckman, Guinevere Kauffmann, Benjamin J. Weiner, Jarle Brinchmann, Jing Wang

摘要:

我们分析恒星形成的星系从SDSS DR 7显示如何星际介质(ISM)Na I 5890,5896(Na D)吸收线依赖于星系的物理性质,并寻找证据的星系风。我们将具有相似几何/物理参数的星系的光谱结合起来,以创建信噪比约为300的复合光谱。用恒星星族合成模型模拟了恒星的连续谱,用两个Na I吸收分量拟合了连续谱。我们发现:(1)等效宽度EW > 0.8A的ISM Na D吸收线只在具有大消光(Av)、高恒星形成率(SFR)、高单位面积恒星形成率($Σ_{\rm SFR}$)或高恒星质量(M*)的盘星系中普遍存在。(2)ISM Na D吸收线可分为两个分量:在星系系统速度下的静止盘状分量和外流分量:(3)盘状分量在边缘系统中较强,而外流分量覆盖较宽的角度,但在盘旋转轴的60 °以内较强;(4)盘状组分的EW和覆盖因子与尘埃衰减密切相关,说明尘埃屏蔽对Na I的存活起重要作用。(5)流出分量的EW主要取决于$Σ_{\rm SFR}$,其次取决于Av;(6)流出速度在~120 ~ 160 km/s之间变化,但在我们样本探测的适度动态范围内(log $Σ_{\rm SFR}$为1.2 dex,log M* 为1 dex),几乎没有显示出与星系物理性质相关的迹象。

英文摘要:

We analyze star forming galaxies drawn from SDSS DR7 to show how the interstellar medium (ISM) Na I 5890, 5896 (Na D) absorption lines depend on galaxy physical properties, and to look for evidence of galactic winds. We combine the spectra of galaxies with similar geometry/physical parameters to create composite spectra with signal-to-noise ~300. The stellar continuum is modeled using stellar population synthesis models, and the continuum-normalized spectrum is fit with two Na I absorption components. We find that: (1) ISM Na D absorption lines with equivalent widths EW > 0.8A are only prevalent in disk galaxies with specific properties -- large extinction (Av), high star formation rates (SFR), high star formation rate per unit area ($Σ_{\rm SFR}$), or high stellar mass (M*). (2) the ISM Na D absorption lines can be separated into two components: a quiescent disk-like component at the galaxy systemic velocity and an outflow component; (3) the disk-like component is much stronger in the edge-on systems, and the outflow component covers a wide angle but is stronger within 60deg of the disk rotation axis; (4) the EW and covering factor of the disk component correlate strongly with dust attenuation, highlighting the importance that dust shielding may play the survival of Na I. (5) The EW of the outflow component depends primarily on $Σ_{\rm SFR}$ and secondarily on Av; (6) the outflow velocity varies from ~120 to 160km/s but shows little hint of a correlation with galaxy physical properties over the modest dynamic range that our sample probes (1.2 dex in log$Σ_{\rm SFR}$ and 1 dex in log M*).

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