arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2004.10296astro-ph.HEastro-ph.CO
收藏

星系团的宇宙X射线亮度和软Gamma-ray背景的降低

Decrease in the Brightness of the Cosmic X-ray and Soft Gamma-ray Background toward Clusters of Galaxies

S. A. Grebenev, R. A. Sunyaev

摘要:

我们发现星系团中炽热星系际气体的电子的康普顿散射会导致宇宙背景X射线和软γ射线辐射的特殊畸变--在E<60-100 keV时亮度增加,在更高能量时亮度下降。失真允许测量最重要的聚类参数。的光谱形状的扭曲和它的依赖于气体温度,光学深度,和表面密度分布规律进行了研究,使用Monte Carlo计算和确认的分析估计。在集群框架中的最大背景减少由于反冲效应发生在~500-600 keV。类氢和类氦铁和镍离子的光电离导致背景光谱的额外扭曲-阈值为~9 keV的强吸收线(对于冷团簇,也导致~2 keV的吸收跳跃)。这些离子对团簇气体的固有热辐射的吸收也导致了这样的谱线。在附近的(z<1)星系团中,~2 keV的吸收线被周围较冷的(~10^6 K)等离子体(~3 Mpc)区域的吸收显著增强;此外,~1.3 keV的吸收线从它分裂出来;遥远星系团的红移使背景光谱(~2、~9和~500 keV)中的吸收线向较低的能量移动。因此,与微波背景散射效应相反,这种效应取决于星系团红移z,但方式非常特殊。当观察z>1的星系团时,这种效应允许人们确定X射线背景是如何演化的,以及它是如何随着z“聚集”的。为了检测这种影响,测量的准确度应该达到~ 0.1%。我们认为最有前途的集群观察效果和讨论的技术,从而阻碍检测背景失真的热气体辐射的影响应该是最小的。

英文摘要:

We show that Compton scattering by electrons of the hot intergalactic gas in galaxy clusters should lead to peculiar distortions of the cosmic background X-ray and soft gamma-ray radiation - an increase in its brightness at E<60-100 keV and a drop at higher energies. The distortions allow the most important cluster parameters to be measured. The spectral shape of the distortions and its dependence on the gas temperature, optical depth, and surface density distribution law have been studied using Monte Carlo computations and confirmed by analytical estimations. In the cluster frame the maximum of the background decrease due to the recoil effect occurs at ~500-600 keV. The photoionization of H- and He-like iron and nickel ions leads to additional distortions in the background spectrum - a strong absorption line with the threshold at ~9 keV (and also to an absorption jump at ~2 keV for cold clusters). The absorption of intrinsic thermal radiation from the cluster gas by these ions also leads to such lines. In nearby (z<1) clusters the line at ~2 keV is noticeably enhanced by absorption in the colder (~10^6 K) plasma of their peripheral (~3 Mpc) regions; moreover, the absorption line at ~1.3 keV splits off from it. The redshift of distant clusters shifts the absorption lines in the background spectrum (at ~2, ~9, and ~500 keV) to lower energies. Thus, in contrast to the microwave background scattering effect, this effect depends on the cluster redshift z, but in a very peculiar way. When observing clusters at z>1, the effect allows one to determine how the X-ray background evolved and how it was "gathered" with z. To detect the effect, the accuracy of measurements should reach ~0.1%. We consider the most promising clusters for observing the effect and discuss the techniques whereby the influence of the thermal gas radiation hindering the detection of background distortions should be minimal.

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。

↑