连接 Abell 85 星系团中迷你晕与凤凰的射电桥
A radio bridge connecting the minihalo and phoenix in the Abell 85 cluster
AI总结:
研究利用 700 MHz uGMRT 与 MeerKAT L 波段观测,在 Abell 85 中确认中心迷你晕并发现连接其与外围射电凤凰的约220 kpc射电桥,提出湍流再加速与激波后湍流的可能成因。
摘要:
星系团位于宇宙纤维结构的节点处,因此存在大量流体动力学活动。然而,冷核星系团被认为是相对弛豫的系统,没有太多并合活动。Abell 85 星系团是一个独特案例:该星系团同时拥有冷核和多个正在进行的并合过程。在本工作中,我们使用作为 MGCLS 一部分而开展的 Abell 85 的 700 MHz uGMRT 观测以及 MeerKAT L 波段观测。我们在 700 MHz 下再次确认了星系团中心存在一个迷你晕,该迷你晕最近在 MGCLS 中被发现。此外,我们发现了一座连接中心迷你晕与外围射电凤凰的射电桥。在 700 MHz 下,该射电桥的平均表面亮度、尺寸和流量密度分别约为 0.14 μJy/arcsec²、220 kpc 和 4.88 mJy,其谱指数为 α₇₀₀^1.28 = −0.92。尽管种子相对论性电子的起源仍不清楚,但星系团内介质(ICM)中螺旋式晃荡气体引起的湍流再加速,以及与凤凰形成相关的向外传播并合激波产生的激波后湍流,可能共同导致了这座射电桥。
英文摘要:
Galaxy clusters are located at the nodes of cosmic filaments and therefore host a lot of hydrodynamical activity. However, cool core clusters are considered to be relatively relaxed systems without much merging activity. The Abell 85 cluster is a unique example where the cluster hosts both a cool core and multiple ongoing merging processes. In this work, we used 700 MHz uGMRT as well as MeerKAT L-band observations, carried out as part of the MGCLS, of the Abell 85. We reconfirm the presence of a minihalo in the cluster centre at 700MHz that was recently discovered in MGCLS. Furthermore, we discovered a radio bridge connecting the central minihalo and the peripheral radio phoenix. The mean surface brightness, size and flux density of the bridge at 700 MHz is found to be $\sim 0.14\ μ$Jy/arcsec$^2$, $\sim 220$ kpc and $\sim 4.88$ mJy, respectively, with a spectral index of $α_{700}^{1.28} = -0.92$. Although the origin of the seed relativistic electrons is still unknown, turbulent re-acceleration caused by both the spiralling sloshing gas in the intracluster medium (ICM) and the post-shock turbulence from the outgoing merging shock associated with the phoenix formation may be responsible for the bridge.
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