Coupled spheroid and black hole formation, and the multifrequency detectability of active galactic nuclei and submillimetre sources
Coupled spheroid and black hole formation, and the multifrequency detectability of active galactic nuclei and submillimetre sources
复制标题
耦合球体和黑洞的形成，以及活动星系核和亚毫米源的多频率可探测性
DOI：
--
复制
发表时间：
2001
期刊：
影响因子：
--
通讯作者：
D. Hughes
中科院分区：
文献类型：
--
作者：
E. Archibald;J. Dunlop;R. Jimenez;A. Friaça;R. McLure;D. Hughes
我们使用一个简单的球体形成模型来探索大质量原星系中恒星和尘埃的产生与其中心黑洞的生长之间的关系。这个模型预测，亚毫米级的光度峰值仅在0.2Gyr之后。然而，如果没有一个非常大质量的种子黑洞，爱丁顿限制的增长意味着一个质量为109 M <$m的黑洞，因此非常明亮的活动星系核（AGN）活动，直到晕中第一颗大质量恒星形成后>0.5 Gyr才能产生。因此，该模型预测的时间滞后之间的峰值的亚毫米光度和AGN光度在一个大规模的原椭圆的几倍108年。对于红移z = 5的星系团来说，这意味着活动星系核的强烈活动被推迟到z = 3.5，到那时，宿主星系中的星星形成已经完成了90%，亚毫米级的光度已经下降到峰值的25%。这就很自然地解释了为什么在亚毫米波段成功探测到的亮射电星系大多局限于z > 2.5。相反，该模型还预测，虽然所有高红移发光的亚毫米选择源都应该包含一个活跃（且正在生长）的黑洞，但此类物体中活动星系核的典型亮度比最强大的活动星系核的亮度小1000倍。这与现有的X射线观测几乎完全无法探测到亚毫米选定星系的情况是一致的。最后，该模型得到一个黑洞-椭球体质量比，它在第一个Gyr中迅速演化，但在低红移处渐近线为0.001-0.003，与结果一致。这个比率的出现并不是因为活动星系核终止了星星的形成，而是因为大质量黑洞的燃料供应与宿主中可用于星星形成的气体的总质量有关。
We use a simple model of spheroid formation to explore the relationship between the creation of stars and dust in a massive protogalaxy and the growth of its central black hole. This model predicts that submillimetre luminosity peaks after only ≃0.2 Gyr. However, without a very massive seed black hole, Eddington-limited growth means that a black hole mass of 109 M⊙, and hence very luminous active galactic nuclei (AGN) activity, cannot be produced until >0.5 Gyr after the formation of the first massive stars in the halo. The model thus predicts a time-lag between the peak of submillimetre luminosity and AGN luminosity in a massive protoelliptical of a few times 108 yr. For a formation redshift z≃ 5, this means that powerful AGN activity is delayed until z≃ 3.5, by which time star formation in the host is ≃90 per cent complete, and submillimetre luminosity has declined to ≃25 per cent of its peak value. This provides a natural explanation for why successful submillimetre detections of luminous radio galaxies are largely confined to z > 2.5. Conversely the model also predicts that while all high-redshift luminous submillimetre-selected sources should contain an active (and growing) black hole, the typical luminosity of the AGN in such objects is ≃1000 times smaller than that of the most powerful AGN. This is consistent with the almost complete failure to detect submillimetre selected galaxies with existing X-ray surveys. Finally, the model yields a black hole–spheroid mass ratio, which evolves rapidly in the first Gyr, but asymptotes to ≃0.001–0.003 in agreement with results at low redshift. This ratio arises not because the AGN terminates star formation, but because fuelling of the massive black hole is linked to the total mass of gas available for star formation in the host.