arXiv 1107.36752011-07-19astro-ph.COastro-ph.HE

椭圆星系中AGN反馈的X射线特性

X-ray properties expected from AGN feedback in elliptical galaxies

S. Pellegrini, L. Ciotti, J. P. Ostriker

备注：: 40 pages, submitted to ApJ
DOI：: 10.1088/0004-637X/744/1/21

摘要：

椭圆星系的ISM演化经历的反馈吸积到一个中心的黑洞最近进行了研究与高分辨率的一维流体动力学模拟，包括辐射加热和压力的影响，RIAF的辐射效率，机械输入AGN风，和吸积驱动的星爆。在这里，我们专注于观测性质的模型在X射线波段（核光度;热ISM光度和温度;温度和亮度的轮廓在平静和爆发期间）。核爆发持续约10^7年，占空比为几个X（10^-3-10^-2）;目前的辐射热核发射非常亚爱丁顿。ISM热光度\lx与核光度同相振荡;这有助于在统计上再现观测到的大的\lx变化。在静止时，温度分布有一个负梯度;由于过去的爆发，亮度分布没有流入模式的典型陡峭形状。爆发在这些剖面中产生扰动。最重要的是，在星系中心，受到冲击的热气体膨胀成一个热气泡;气泡的形状是圆锥形的，并显示出无线电发射。在~ 2亿年的时间尺度上，ISM恢复了平滑的外观; ISM中扰动的占空比为5- 10%。从目前的分析，额外的输入物理是很重要的ISM-黑洞共同进化，充分考虑到真正的星系的属性，作为一个封闭的外部介质和喷流。喷流将进一步减少可用于吸积的质量（然后减少爱丁顿比$l$），并可能有助于与外部压力一起产生平坦或正的温度梯度分布（在高密度环境中观察到）。或者，如果从高到低辐射效率的转换发生在比常规假设的更大的$l$处，则可以减小$l$。

英文摘要：

The ISM evolution of elliptical galaxies experiencing feedback from accretion onto a central black hole was studied recently with high-resolution 1D hydrodynamical simulations including radiative heating and pressure effects, a RIAF-like radiative efficiency, mechanical input from AGN winds, and accretion-driven starbursts. Here we focus on the observational properties of the models in the X-ray band (nuclear luminosity; hot ISM luminosity and temperature; temperature and brightness profiles during quiescence and during outbursts). The nuclear bursts last for ~10^7 yr, with a duty-cycle of a few X (10^-3-10^-2); the present epoch bolometric nuclear emission is very sub-Eddington. The ISM thermal luminosity \lx oscillates in phase with the nuclear one; this helps reproduce statistically the observed large \lx variation. In quiescence the temperature profile has a negative gradient; thanks to past outbursts, the brightness profile lacks the steep shape typical of inflowing models. Outbursts produce disturbances in these profiles. Most significantly, a hot bubble from shocked hot gas is inflated at the galaxy center; the bubble would be conical in shape, and show radio emission. The ISM resumes a smooth appearance on a time-scale of ~200 Myr; the duty-cycle of perturbances in the ISM is of the order of 5-10%. From the present analysis, additional input physics is important in the ISM-black hole coevolution, to fully account for the properties of real galaxies, as a confining external medium and a jet. The jet will reduce further the mass available for accretion (and then the Eddington ratio $l$), and may help, together with an external pressure, to produce flat or positive temperature gradient profiles (observed in high density environments). Alternatively, $l$ can be reduced if the switch from high to low radiative efficiency takes place at a larger $l$ than routinely assumed.

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