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arXiv 1209.2453astro-ph.COastro-ph.GA
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不规则星系NGC LITTLE THINGS 1569的恒星和气体动力学

The Stellar and Gas Kinematics of the LITTLE THINGS Dwarf Irregular Galaxy NGC 1569

Megan Johnson, Deidre A. Hunter, Se-Heon Oh, Hong-Xin Zhang, Bruce Elmegreen, Elias Brinks, Erik Tollerud, Kimberly Herrmann

备注：
49 pages, 25 figures, accepted in AJ
发表信息：
2012 The Astronomical Journal 144 152
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摘要：

为了理解dIm星系的形成和演化，人们需要了解它们的三维结构。我们目前的恒星速度色散的测量在NGC1569，附近的后星爆dIm星系。恒星的垂直速度色散$σ_{\rm z}$，再加上从\ion{H}{1}观测得到的最大旋转速度$V_{\rm max}$，给出了一个测量星系运动学温度的方法，因此，表明了它的结构。我们的结论是，在NGC 1569的恒星是在一个厚盘与$V_{\rm max} / σ_{\rm z}$ = 2.4 $\pm$ 0.7。除了结构，我们分析了电离气体的运动学从\ion{O}{3}观测沿形态主轴。这些数据显示了来自内部星暴区域的外流和超大质量星团（SSC）A附近潜在的膨胀壳层的证据。与恒星运动学相比，恒星的速度色散在SSC A区域增加，支持了膨胀壳的假设。恒星的运动学紧密地跟随着气体的运动。对高分辨率\ion{H}{1}数据的分析清楚地揭示了一个\ion{H}{1}云的存在，它似乎正在影响NGC 1569的东部边缘。此外，可以看到一个超密集的\ion{H}{1}云延伸到撞击\ion{H}{1}云的西部。这片密集的星云很可能是一座密集的\ion{H}{1}桥的残骸，这座桥延伸穿过现在的中央星爆区。撞击的\ion{H}{1}云是星暴的催化剂，因此在很短的时间尺度内将致密气体转化为恒星，$\sim$ 1 Gyr。我们进行了仔细的研究光谱能量分布，使用红外线，光学和紫外线测光产生一个国家的最先进的质量模型的恒星盘。这个质量模型表明，恒星在内部1 kpc的引力势中占主导地位。

英文摘要：

In order to understand the formation and evolution of dIm galaxies, one needs to understand their three-dimensional structure. We present measurements of the stellar velocity dispersion in NGC 1569, a nearby post-starburst dIm galaxy. The stellar vertical velocity dispersion, $σ_{\rm z}$, coupled with the maximum rotational velocity derived from \ion{H}{1} observations, $V_{\rm max}$, gives a measure of how kinematically hot the galaxy is, and, therefore, indicates its structure. We conclude that the stars in NGC 1569 are in a thick disk with a $V_{\rm max} / σ_{\rm z}$ = 2.4 $\pm$ 0.7. In addition to the structure, we analyze the ionized gas kinematics from \ion{O}{3} observations along the morphological major axis. These data show evidence for outflow from the inner starburst region and a potential expanding shell near supermassive star cluster (SSC) A. When compared to the stellar kinematics, the velocity dispersion of the stars increase in the region of SSC A supporting the hypothesis of an expanding shell. The stellar kinematics closely follow the motion of the gas. Analysis of high resolution \ion{H}{1} data clearly reveals the presence of an \ion{H}{1} cloud that appears to be impacting the eastern edge of NGC 1569. Also, an ultra-dense \ion{H}{1} cloud can be seen extending to the west of the impacting \ion{H}{1} cloud. This dense cloud is likely the remains of a dense \ion{H}{1} bridge that extended through what is now the central starburst area. The impacting \ion{H}{1} cloud was the catalyst for the starburst, thus turning the dense gas into stars over a short timescale, $\sim$ 1 Gyr. We performed a careful study of the spectral energy distribution using infrared, optical, and ultraviolet photometry producing a state-of-the-art mass model for the stellar disk. This mass modeling shows that stars dominate the gravitational potential in the inner 1 kpc.

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