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arXiv 0902.0577astro-ph.CO
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巨型射电源III的多频研究。选定震源的波瓣的动力年龄与光谱年龄

A multifrequency study of giant radio sources III. Dynamical age vs. spectral age of the lobes of selected sources

J. Machalski, M. Jamrozy, D. J. Saikia

摘要:

用Machalski等人的DYNAGE算法估算了选定的巨射电源对瓣的动力学年龄,并与Jamrozy等人在论文II中估计和研究的光谱年龄进行了比较。正如预期的那样,DYNAGE拟合给出了彼此独立建模的相对叶的略微不同的动力学年龄和其他模型参数,例如年龄比在~1.1到~1.4之间。相同的源,要求类似的值的喷流功率和无线电核心密度,我们寻找一个自洽的解决方案,为相反的叶,这导致不同的密度分布沿他们发现的拟合。我们还表明,偏离均分条件假设在模型中,合理的X射线观测的叶片附近的一些射电星系,和相关的变化的磁场强度可能提供一个均衡的叶片的年龄。动力学年龄和光谱年龄的比较表明,所研究的巨型射电星系的动力学年龄与光谱年龄的比值在~1和~5之间,即与较小的射电星系相似(例如Parma et al. 1999)。补充了文献中已经讨论过的这种效应的可能原因,如模型假设参数的不确定性,可能偏离能量均分假设的影响等。给出的论据表明,DYNAGE算法可以更好地考虑在较低频率下的辐射效应比光谱老化分析。DYNAGE算法是特别有效的在高红移源,其固有频谱曲率向低频移动。

英文摘要:

The dynamical ages of the opposite lobes of selected giant radio sources are estimated using the DYNAGE algorithm of Machalski et al., and compared with their spectral ages estimated and studied by Jamrozy et al. in Paper II. As expected, the DYNAGE fits give slightly different dynamical ages and other model's parameters for the opposite lobes modelled independently each other, e.g. the age ratios are found between ~1.1 to ~1.4. Demanding similar values of the jet power and the radio core density for the same source, we look for a self-consistent solution for the opposite lobes, which results in different density profiles along them found by the fit. We also show that a departure from the equipartition conditions assumed in the model, justified by X-ray observations of the lobes of some nearby radio galaxies, and a relevant variation of the magnetic-field strengths may provide an equalisation of the lobes' ages. A comparison of the dynamical and spectral ages shows that a ratio of the dynamical age to the spectral age of the lobes of investigated giant radio galaxies is between ~1 and ~5, i.e. is similar to that found for smaller radio galaxies (e.g. Parma et al. 1999). Supplementing possible causes for this effect already discussed in the literature, like uncertainty of assumed parameters of the model, an influence of a possible departure from the energy equipartition assumption, etc. Arguments are given to suggest that DYNAGE can better take account of radiative effects at lower frequencies than the spectral-ageing analysis.The DYNAGE algorithm is especially effective for sources at high redshifts, for which an intrinsic spectral curvature is shifted to low frequencies.

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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