标题： 利用uGMRT探测星系团之间的弥散射电源桥 显示英文标题

标题： Probing diffuse radio emission in bridges between galaxy clusters with uGMRT

摘要： 这项工作的主要目的是研究在相互作用星团对 Abell 0399-Abell 0401 和 Abell 21-PSZ2 G114.9 中发现的非热辐射性质，这两个系统都处于相互作用状态。 在这两种情况下，它们沿纤维状结构的连接得到了由普朗克卫星探测到的SZ效应的支持，在Abell 0399-Abell 0401的特殊情况下，140 MHz LOFAR观测已经确认了射电桥的存在。 在这里，我们分析了这两个系统的新的高灵敏度宽频带（250-500 MHz）uGMRT数据，并描述了一种注入程序，以限制Abell 0399-Abell 0401的谱指数以及Abell 21-PSZ2 G114.9之间的射电发射。 对于A399-A401对，我们在140 MHz和400 MHz之间以95%置信水平约束了桥接发射的陡峭谱指数为alpha > 2.2。 对于A21-PSZ2 G114.9对，我们使用两种不同方法对桥接发射的通量密度设定了上限，在383 MHz中心频率下，以95%置信水平得到保守值fu_1 < 260 mJy，基于目视检查和形态学标准得出较低值fu_2 < 125 mJy（80%置信水平）。 我们的工作对A399-A401桥接的谱提供了限制，这表明冲击加速并不是无线电发射的主要机制。 显示英文摘要

摘要： The main purpose of this work is to investigate the properties of the non-thermal emission in the interacting clusters pairs Abell 0399-Abell 0401 and Abell 21-PSZ2 G114.9, found in an interacting state. In both cases their connection along a filament is supported by SZ effect detected by the Planck satellite and, in the special case of Abell 0399-Abell 0401, the presence of a radio bridge has been already confirmed by LOFAR observations at 140MHz. Here, we analyse new high sensitivity wideband (250-500MHz) uGMRT data of these two systems and describe an injection procedure to place limits on the spectrum of Abell 0399-Abell 0401 and on the radio emission between Abell 21-PSZ2 G114.9. For the A399-A401 pair, we are able to constrain the steep spectral index of the bridge emission to be alpha>2.2 with a 95% confidence level between 140MHz and 400MHz. For the A21-PSZ2 G114.9 pair, we are able to place an upper limit on the flux density of the bridge emission with two different methods, finding at the central frequency of 383MHz a conservative value of fu_1<260mJy at 95% confidence level, and a lower value of fu_2<125mJy at 80% confidence level, based on visual inspection and a morphological criterion. Our work provides a constraint on the spectrum in the bridge A399-A401 which disfavours shock-acceleration as the main mechanism for the radio emission.