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arXiv 1606.04536astro-ph.GA
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O哈勃空间望远镜对星系的VI发射成像:围绕强烈星爆的暖气晕SDSS J115630 .63+500822.1

O VI Emission Imaging of a Galaxy with the Hubble Space Telescope: a Warm Gas Halo Surrounding the Intense Starburst SDSS J115630.63+500822.1

Matthew Hayes, Jens Melinder, Göran Östlin, Claudia Scarlata, Matthew D. Lehnert, Gustav Mannerström-Jansson

摘要:

我们报告的结果,从一个新的HST研究的OVI 1032,1038的双重辐射周围强烈的恒星形成的星系。该方案的目的是描述星暴星系的能量平衡和难以绘制的2-5 x $10^5$ K日冕温度范围内的气体冷却。我们提出了第一个解决的气体排放的OVI线的图像。我们的目标,SDSS J1156+5008,是非常紧凑的连续,但显示OVI发射半径为23千秒差距。表面亮度分布可用7.5kpc尺度的指数拟合。这是光致电离气体大小的十倍,我们估计总OVI光度的1/6来自共振散射连续辐射。光谱-非常类似于档案光谱的堆叠样品-证实了OVI发射,并确定了蓝移吸收的柱密度和流出速度。测量值的组合使得能够在很少假设的情况下进行几种新的计算。OVI区域仅填充体积的~ $10^{-3}$。通过比较冷却时间与云的声音穿越时间,冷却距离与大小,和OVI和星云气体的压力,我们得出结论,OVI轴承气体不能被提升到刻度高度在这个温度下,必须通过这个日冕温度制度在原地冷却。日冕阶段包含约1%的电离质量,其动能目前约为超新星反馈预算的1%。然而,在恒星形成阶段,大量的气体必须通过这个阶段冷却下来。流出物超过逃逸速度,气体可能变得不受束缚,但它会在逃逸之前重新结合,并变得对莱曼(和OI)光谱可见。绘制这种气体的地图是进一步限制星系形成情景和指导未来卫星发展的关键一步。

英文摘要:

We report results from a new HST study of the OVI 1032,1038Å doublet in emission around intensely star-forming galaxies. The programme aims to characterize the energy balance in starburst galaxies and gas cooling in the difficult-to-map coronal temperature regime of 2-5 x $10^5$K. We present the first resolved image of gas emission in the OVI line. Our target, SDSS J1156+5008, is very compact in the continuum but displays OVI emission to radii of 23 kpc. The surface brightness profile is well fit by an exponential with a scale of 7.5kpc. This is ten times the size of the photoionized gas, and we estimate that 1/6 the total OVI luminosity comes from resonantly scattered continuum radiation. Spectroscopy - which closely resembles a stacked sample of archival spectra - confirms the OVI emission, and determines the column density and outflow velocity from blueshifted absorption. The combination of measurements enables several new calculations with few assumptions. The OVI regions fill only ~$10^{-3}$ of the volume. By comparing the cooling time with the cloud sound-crossing time, the cooling distance with the size, and the pressure in the OVI and nebular gas, we conclude that the OVI-bearing gas cannot have been lifted to the scale height at this temperature, and must be cooling in situ through this coronal temperature regime. The coronal phase contains ~1% of the ionized mass, and its kinetic energy is currently ~1% of the budget set by supernova feedback. However a much larger amount of the gas must have cooled through this phase during the star formation episode. The outflow exceeds the escape velocity and the gas may become unbound, but it will recombine before it escapes and become visible to Lyman (and OI) spectroscopy. The mapping of this gas represents a crucial step in further constraining galaxy formation scenarios and guiding the development of future satellites.

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