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arXiv 1006.1189astro-ph.CO
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星暴星系Henize~2-10的弥散和致密X射线成分

The Diffuse and Compact X-ray Components of the Starburst Galaxy Henize~2-10

Henry A. Kobulnicky, Crystal L. Martin

摘要:

钱德拉X射线成像光谱的恒星爆发星系Henize 2-10揭示了一个强大的核点源和至少两个较暗的紧凑源嵌入在一个更明亮的漫热组件。对核X射线源的光谱拟合表明,对于合理的幂律或黑体模型,未吸收的X射线光度L_x >10^40 erg/s,这与吸积到一个质量大于50太阳质量的黑洞上的情况相一致,该黑洞位于前景吸收柱N_H>10^23 /cm ^2。其中两个点源的L_x=2-5 x 10^38 erg/s,与发光的X射线双星相当。这些致密源在0.3- 6.0 keV波段占He~2-10的总X射线通量的一小部分(<16%),在1.1- 6.0 keV硬波段占31%。两个温度的太阳能成分等离子体(kT~0.2 keV和kT~0.7 keV)适合扩散X射线成分,以及单温等离子体与增强的α/Fe比。由于观测到的X射线表面亮度的径向梯度与H α发射的径向梯度密切相关,因此X射线等离子体的成分可能反映了环境冷/暖ISM与更热、低发射测量等离子体的混合,从而解释了~太阳ISM成分。孔径合成21厘米图显示了一个半径为60”的扩展中性介质,因此ISM的温暖和热相(延伸到约30”)被包裹在冷中性介质的8x10^20 /cm^2轮廓内。这种延伸的中性晕可能会抑制恒星暴驱动的外流,除非它主要沿着视线。如果Henize 2-10处于发展星系风的早期阶段,那么恒星形成的高面密度也可以与缺乏显著的外流特征相协调。

英文摘要:

Chandra X-ray imaging spectroscopy of the starburst galaxy Henize 2-10 reveals a strong nuclear point source and at least two fainter compact sources embedded within a more luminous diffuse thermal component. Spectral fits to the nuclear X-ray source imply an unabsorbed X-ray luminosity L_x >10^40 erg/s for reasonable power law or blackbody models, consistent with accretion onto a >50 solar mass black hole behind a foreground absorbing column of N_H>10^23 /cm^2. Two of these point sources have L_x=2-5 x 10^38 erg/s, comparable to luminous X-ray binaries. These compact sources constitute a small fraction (<16%) of the total X-ray flux from He~2-10 in the 0.3--6.0 keV band and just 31% of the X-rays in the hard 1.1--6.0 keV band which is dominated by diffuse emission. Two-temperature solar-composition plasmas (kT~0.2 keV and kT~0.7 keV) fit the diffuse X-ray component as well as single-temperature plasmas with enhanced alpha/Fe ratios. Since the observed radial gradient of the X-ray surface brightness closely follows that of the Halpha emission, the composition of the X-ray plasma likely reflects mixing of the ambient cool/warm ISM with an even hotter, low emission measure plasma, thereby explaining the ~solar ISM composition. Aperture synthesis 21-cm maps show an extended neutral medium to radii of 60" so that the warm and hot phases of the ISM, which extend to ~30", are enveloped within the 8x10^20 /cm^2 contour of the cool neutral medium. This extended neutral halo may serve to inhibit a starburst-driven outflow unless it is predominantly along the line of sight. The high areal density of star formation can also be reconciled with the lack of prominent outflow signatures if Henize 2-10 is in the very early stages of developing a galactic wind.

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