Constraining magnetic fields in the circumgalactic medium
Constraining magnetic fields in the circumgalactic medium
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DOI：
10.1093/mnras/staa1750
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发表时间：
2020-06
影响因子：
4.8
通讯作者：
Ting-Wen Lan 藍鼎文;J. Prochaska
中科院分区：
文献类型：
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作者：
Ting-Wen Lan 藍鼎文;J. Prochaska
我们通过将 ~1000 个高红移射电源的法拉第旋转测量 (RM) 与 DESI 传统成像巡天估计的前景星系数密度相关联，研究 z < 1 星系的环绕星系介质 (CGM) 中的磁场特性。这种方法使我们能够提取由多个星系周围的介入气体贡献的 RM 信号。我们的结果表明，RM 的分布与前景星系的数量之间没有可检测到的相关性，这与之前的几个结果相反。利用非检测信号，我们估计 50 kpc 内 $\sim \!20 \rm \ rad\, m^{-2}$ 的 CGM 和 100 kpc 间隔 $\sim \!10 \rm \ rad \, m^{-2}$ 的 RM 的 3σ 上限。通过采用吸收线测量获得的电离气体柱密度分布，我们进一步估计了 CGM 中平行于 $\lt \rm 2 \ \mu G$ 视线的相干磁场的强度。我们表明，RM 和磁场强度的估计上限足以限制最近星系磁流体动力学模拟的输出。最后，我们讨论了我们的结果与之前的工作不一致的可能原因。
We study the properties of magnetic fields in the circumgalactic medium (CGM) of z < 1 galaxies by correlating Faraday rotation measures (RMs) of ∼1000 high-redshift radio sources with the foreground galaxy number density estimated from the DESI Legacy Imaging Surveys. This method enables us to extract signals of RMs contributed by intervening gas around multiple galaxies. Our results show that there is no detectable correlation between the distribution of RMs and the number of foreground galaxies, contrary to several previous results. Utilizing the non-detection signals, we estimate 3σ upper limits to the RMs from the CGM of $\sim \!20 \rm \ rad\, m^{-2}$ within 50 kpc and $\sim \!10 \rm \ rad \, m^{-2}$ at separations of 100 kpc. By adopting a column density distribution of ionized gas obtained from absorption-line measurements, we further estimate the strengths of coherent magnetic fields parallel to the line of sight of $\lt \rm 2 \ \mu G$ in the CGM. We show that the estimated upper limits of RMs and magnetic field strengths are sufficient to constrain outputs of recent galaxy magnetohydrodynamic simulations. Finally, we discuss possible causes for the inconsistency between our results and previous works.