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arXiv 1003.0667astro-ph.CO
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河外射电源的演化

The evolution of extragalactic radio sources

Q. Luo, E. M. Sadler

摘要:

本文提出了一个低光度射电星系演化的模型。在该模型中,被低功率射流膨胀的叶片被假定为在接近压力平衡的情况下对外部介质膨胀。考虑了外压恒定和外压减小两种情况。单个源的演化由功率大小轨迹描述。当它的波瓣膨胀,射电光度增加到探测水平以上时,源出现;然后源沿着轨道移动,并最终消失,因为它的光度下降到探测极限以下。功率大小的轨道计算,包括由于同步辐射,绝热膨胀和逆康普顿散射的组合能量损失。它示出,在一般情况下,恒定压力模型预测的发光,小尺寸的源,而低估的功率尺寸图中的大尺寸源的过量。对于大多数源,预测的光谱是陡峭的,这与观测结果不一致。相比之下,压力限制模型更适合观测。在这个模型中,低光度源在初始阶段经历大量的膨胀损失,因此,它预测较少的发光,小尺寸的源。除了最古老的源外,大多数源的光谱都是平坦的,这似乎与观测结果一致。与高光度的射电星系相比,功率大小的轨道的特点是在大部分的源的生命中光度缓慢增加,然后在同步加速器或逆康普顿散射损失时迅速下降。

英文摘要:

A model for the evolution of low-luminosity radio galaxies is presented. In the model, the lobes inflated by low-power jets are assumed to expand in near pressure-balance against the external medium. Both cases of constant external pressure and decreasing external pressure are considered. Evolution of an individual source is described by the power-size track. The source appears as its lobe is inflated and radio luminosity increases to above the detection level; the source then moves along the track and eventually disappears as its luminosity drops below the detection limit. The power-size tracks are calculated including the combined energy losses due to synchrotron radiation, adiabatic expansion, and inverse Compton scattering. It is shown that in general, the constant-pressure model predicts an excess number of luminous, small-size sources while underpredicting large-size sources in the power-size diagram. The predicted spectra are steep for most sources, which is inconsistent with observations. By comparison, the pressure-limiting model fits observations better. In this model, low-luminosity sources undergo substantial expansion losses in the initial phase and as a result, it predicts fewer luminous, small-size sources. The resultant spectra are flat for most sources except for the oldest ones, which seems consistent with observations. The power-size tracks, in contrast to that of high-luminosity radio galaxies, are characterized by a slow increase in luminosity for most of the source's life, followed by a rapid decline when the synchrotron or inverse Compton scattering losses set in.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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