The mass density in black holes inferred from the X-ray background
The mass density in black holes inferred from the X-ray background
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从 X 射线背景推断出的黑洞质量密度
DOI：
10.1046/j.1365-8711.1999.02404.x
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发表时间：
1999
影响因子：
4.8
通讯作者：
K. Iwasawa
中科院分区：
文献类型：
--
作者：
A. Fabian;K. Iwasawa
X射线背景（XRB）可能来源于活动星系核（AGN）的积分X射线辐射。平坦光谱的模拟暗示了大多数活动星系核有相当大的吸收。康普顿下散射意味着吸收是康普顿厚度的源不太可能是背景强度的主要贡献者，因此在约30 keV处观察到的光谱强度几乎不受光电吸收的影响。假设活动星系核的内禀光子指数为2，我们用30 keV的XRB强度来推断背景的吸收校正能量密度。假设吸积效率为0.1，活动星系核的平均红移为2，那么索尔坦的论证使我们能够将其转换为黑洞的平均局域密度。结果是在Haehnelt等人估计的2倍之内。从Magorrian等人的光学确定的黑洞质量，我们得出结论，没有强烈的需要，任何辐射效率低下的吸积模式建设的质量黑洞。此外，我们表明，XRB的吸收模型意味着宇宙中约85%的吸积功率被吸收。这种能量可能出现在红外波段，在那里它可以是最近推断的背景的百分之几十。吸积所释放的总能量大约是恒星的五分之一。
The X-ray background (XRB) probably originates from the integrated X-ray emission of active galactic nuclei (AGN). Modelling of its flat spectrum implies considerable absorption in most AGN. Compton down-scattering means that sources in which the absorption is Compton-thick are unlikely to be major contributors to the background intensity, so the observed spectral intensity at about 30 keV is little affected by photoelectric absorption. Assuming that the intrinsic photon index of AGN is 2, we then use the 30-keV intensity of the XRB to infer the absorption-corrected energy density of the background. Soltan's argument then enables us to convert this to a mean local density in black holes, assuming an accretion efficiency of 0.1 and a mean AGN redshift of 2. The result is within a factor of 2 of that estimated by Haehnelt et al. from the optically determined black hole masses of Magorrian et al. We conclude that there is no strong need for any radiatively inefficient mode of accretion for building the masses of black holes. Furthermore, we show that the absorption model for the XRB implies that about 85 per cent of accretion power in the Universe is absorbed. This power probably emerges in the infrared bands where it can be several tens per cent of the recently inferred backgrounds there. The total power emitted by accretion is then about one fifth that of stars.