Spectral analysis of spatially resolved 3C295 (sub-arcsecond resolution) with the International LOFAR Telescope
Spectral analysis of spatially resolved 3C295 (sub-arcsecond resolution) with the International LOFAR Telescope
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使用国际 LOFAR 望远镜对空间分辨 3C295（亚角秒分辨率）进行光谱分析
DOI：
10.1051/0004-6361/202141731
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发表时间：
2022
影响因子：
6.5
通讯作者：
Bonnassieux E
中科院分区：
文献类型：
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作者：
Bonnassieux E
3C 295是一个明亮、紧凑的陡谱源，具有132 MHz至15 GHz的综合射电频谱能量分布（SED）。然而，空间分辨光谱的研究一直受到限制，由于缺乏高分辨率的图像在低无线电频率。这些频率对于测量吸收过程和锚定无线电SED的整体光谱建模至关重要。本文利用国际低频阵列射线望远镜（LOFAR）对3C 295的观测资料，研究了它在132 MHz亚弧秒分辨率下的空间分辨光谱特性。将我们新的132 MHz观测与1.6、4.8和15 GHz的存档数据相结合，我们能够进行解析的无线电频谱分析。热点的光谱特性为低频平坦化提供了证据。与此相反，整个叶的光谱形状是一致的Jaffe-Perola光谱老化模型。使用每个组件的集成光谱信息，然后我们将低频吸收模型拟合到热点，发现自由-自由吸收和同步加速器自吸收模型都比标准幂律模型更好地拟合数据。虽然我们可以说在3C 295的热点中存在低频吸收，但未来在55 MHz下使用ILT的低频天线进行的观测可能使我们能够区分吸收的类型。
3C295 is a bright, compact steep spectrum source with a well-studied integrated radio spectral energy distribution (SED) from 132 MHz to 15 GHz. However, spatially resolved spectral studies have been limited due to a lack of high resolution images at low radio frequencies. These frequencies are crucial for measuring absorption processes, and anchoring the overall spectral modelling of the radio SED. In this paper, we use International LOw-Frequency ARray (LOFAR) Telescope (ILT) observations of 3C295 to study its spatially resolved spectral properties with sub-arcsecond resolution at 132 MHz. Combining our new 132 MHz observation with archival data at 1.6, 4.8, and 15 GHz, we are able to carry out a resolved radio spectral analysis. The spectral properties of the hotspots provides evidence for low frequency flattening. In contrast, the spectral shape across the lobes is consistent with a Jaffe-Perola spectral ageing model. Using the integrated spectral information for each component, we then fitted low-frequency absorption models to the hotspots, finding that both free-free absorption and synchrotron self-absorption models provide a better fit to the data than a standard power law. Although we can say there is low-frequency absorption present in the hotspots of 3C295, future observations with the Low Band Antenna of the ILT at 55 MHz may allow us to distinguish the type of absorption.