We present new radio observations of the massive and X-ray luminous galaxy cluster MACS J0417.5–1154, at 1.387 GHz and 18 GHz, from the Giant Metrewave Radio Telescope (GMRT) and the Australia Telescope Compact Array (ATCA) respectively. We estimate diffuse emission in the central region of the cluster at 1.387 GHz and 18 GHz. We combine these data with previously published results and present the spectrum of diffuse emission from 76 MHz to 18 GHz. This is possibly a unique study of the radio halo emission in galaxy cluster over this wide range of frequencies. Such studies lay the prospects of future studies with radio telescopes with wide-range of frequencies like the Square Kilometre Array (SKA). Our 1.387 GHz data, with $$2^{\prime \prime }$$2″ angular resolution, provides a better estimate of point source emission than previous L-band observations, which is crucial, given the claim of sharp steepening of the radio halo spectrum at 0.61 GHz reported earlier. We find that the spectrum of the radio halo has a spectral index fit up to 18 GHz, and yields a spectral index between 76 MHz and 18 GHz that fits the available data better than earlier L-band observations. We discuss possible reasons for the peculiar spectral characteristics of the diffuse emission.

中文翻译：

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集群 MACSJ0417.5-1154 从 76 MHz 到 18 GHz 的漫发射研究

我们分别展示了巨型米波射电望远镜 (GMRT) 和澳大利亚望远镜紧凑阵列 (ATCA) 在 1.387 GHz 和 18 GHz 下对大质量和 X 射线发光星系团 MACS J0417.5-1154 的新无线电观测。我们估计在 1.387 GHz 和 18 GHz 的集群中心区域的漫射发射。我们将这些数据与之前公布的结果相结合，并展示了从 76 MHz 到 18 GHz 的漫发射频谱。这可能是对星系团在如此宽的频率范围内的射电晕发射的独特研究。这些研究为未来使用具有广泛频率范围的射电望远镜（如平方公里阵列 (SKA)）进行研究奠定了前景。我们的 1.387 GHz 数据，具有 $$2^{\prime \prime }$$2″ 角分辨率，与之前的 L 波段观测相比，它提供了对点源发射的更好估计，这一点至关重要，因为之前报道的 0.61 GHz 无线电晕频谱急剧陡峭。我们发现无线电晕的频谱具有高达 18 GHz 的频谱指数，并且在 76 MHz 和 18 GHz 之间产生的频谱指数比早期的 L 波段观测更适合可用数据。我们讨论了漫射发射特殊光谱特性的可能原因。