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arXiv 2202.04607astro-ph.COastro-ph.GA
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宇宙网细丝中的磁场强度

Magnetic field strength in cosmic web filaments

E. Carretti, V. Vacca, S. P. O'Sullivan, G. H. Heald, C. Horellou, H. J. A. Rottgering, A. M. M. Scaife, T. W. Shimwell, A. Shulevski, C. Stuardi, T. Vernstrom

摘要:

我们使用来自LOFAR两米巡天数据发布2(LoTSS DR 2)的144 MHz旋转测量(RM)目录来测量低密度环境中河外RM(RRM:剩余RM)和源的偏振分数($p$)随红移的演化。我们还通过与NRAO VLA Sky Survey RM目录的交叉匹配在1.4 GHz处进行了相同的测量。我们发现,RRM与红移是平坦的,在144 MHz,但是,一旦红移校正,它显示出在高意义的演变。此外,$p$随着红移而演化,在$z\sim2$处减少$\sim$ 8倍。比较144-MHz和1.4-GHz的数据,我们发现,所观察到的RRM和$p$是最有可能有一个起源本地的源在1.4-GHz的,而宇宙网丝的起源是在144-MHz的青睐。如果我们将整个信号归因于细丝,我们推断每细丝的平均静止帧RRM为RRM_{0,f} = 0.71 \pm 0.07 rad m^{-2},每细丝的磁场为B_f = 32 \pm 3 nG。这与基于同步辐射叠加的互补方法获得的估计一致,并且如果原始磁场被天体物理源场播种放大,则与宇宙学模拟一致。对RRM_{0,f}的测量支持了暗条中存在扩散重子气体的说法。我们还估计了丝条磁湍流的保守上限σ_{ RRM_{0,f} } =0.039 \pm 0.001 rad m^{-2},认为有序磁场分量在丝条中占主导地位.

英文摘要:

We used the Rotation Measure (RM) catalogue derived from the LOFAR Two-metre Sky Survey Data Release 2 (LoTSS DR2) at 144-MHz to measure the evolution with redshift of the extragalactic RM (RRM: Residual RM) and the polarization fraction ($p$) of sources in low density environments. We also measured the same at 1.4-GHz by cross-matching with the NRAO VLA Sky Survey RM catalogue. We find that RRM versus redshift is flat at 144-MHz, but, once redshift-corrected, it shows evolution at high significance. Also $p$ evolves with redshift with a decrement by a factor of $\sim$8 at $z\sim2$. Comparing the 144-MHz and 1.4-GHz data, we find that the observed RRM and $p$ are most likely to have an origin local to the source at 1.4-GHz, while a cosmic web filament origin is favoured at 144-MHz. If we attribute the entire signal to filaments, we infer a mean rest frame RRM per filament of RRM_{0,f} = 0.71 \pm 0.07 rad m^{-2} and a magnetic field per filament of B_f = 32 \pm 3 nG. This is in agreement with estimates obtained with a complementary method based on synchrotron emission stacking, and with cosmological simulations if primordial magnetic fields are amplified by astrophysical source field seeding. The measurement of an RRM_{0,f} supports the presence of diffuse baryonic gas in filaments. We also estimated a conservative upper limit of the filament magnetic turbulence of σ_{ RRM_{0,f}} =0.039 \pm 0.001 rad m^{-2}, concluding that the ordered magnetic field component dominates in filaments.

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