The Gamma-Ray Emitting Radio-Loud Narrow-Line Seyfert 1 Galaxy PKS 2004-447 II. The Radio View
The Gamma-Ray Emitting Radio-Loud Narrow-Line Seyfert 1 Galaxy PKS 2004-447 II. The Radio View
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DOI：
10.1051/0004-6361/201527404
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发表时间：
2015-09
影响因子：
6.5
通讯作者：
R. Schulz;A. Kreikenbohm;M. Kadler;R. Ojha;E. Ros;J. Stevens;P. G. Edwards;B. Carpenter;D. Elsasser;N. Gehrels;C. Grossberger;H. Hase;S. Horiuchi;J. Lovell;K. Mannheim;A. Markowitz;C. Muller;C. Phillips;C. Plotz;J. Quick;J. Trustedt;A. Tzioumis;J. Wilms
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文献类型：
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作者：
R. Schulz;A. Kreikenbohm;M. Kadler;R. Ojha;E. Ros;J. Stevens;P. G. Edwards;B. Carpenter;D. Elsasser;N. Gehrels;C. Grossberger;H. Hase;S. Horiuchi;J. Lovell;K. Mannheim;A. Markowitz;C. Muller;C. Phillips;C. Plotz;J. Quick;J. Trustedt;A. Tzioumis;J. Wilms
背景：Γ射线探测到的射电强窄线Seyfert 1（γ-NLS 1）星系构成了γ射线强活动星系核的一个小而有趣的样本。已知射电最强的γ-NLS 1，PKS 2004−447，位于南半球，由多波长监测计划TANAMI在射电区域进行监测。目的：我们的目标是首次详细研究PKS 2004−447的射电形态和长期射电光谱演化，这对于理解γ-NLS 1的射电性质的多样性至关重要。研究方法：TANAMI VLBI监测计划使用澳大利亚长基线阵列（LBA）和南极洲，智利，新西兰和南非的望远镜来监测南半球射电大声活动星系的喷流。澳大利亚望远镜紧凑阵列（ATCA）在四年的观测中获得了多个无线电频率的低分辨率无线电通量密度测量值。结果：TANAMI VLBI在8.4 GHz的图像显示了一个扩展的单侧喷流与占主导地位的紧凑VLBI核心。它的亮温与均分现象一致，但比其它γ-NLS 1低一个数量级，样品值变化超过两个数量级。我们发现了一种紧凑的形态，预计具有大规模的尺寸结论：PKS 2004 - 447似乎是γ-NLS 1样本的独特成员。它表现出类似耀变体的特征，例如平坦的无特征X射线光谱和以核心为主的单侧秒差距尺度喷流，并有相对论性光束的迹象。然而，这些数据也揭示了耀变体的非典型性质，例如与致密陡谱（CSS）天体一致的射电频谱和大尺度尺寸，这些天体通常与年轻的射电源有关。这些特征在所有的γ-NLS 1中是独一无二的，在γ射线强的活动星系核中也是极其罕见的。
Context: Γ-ray-detected radio-loud narrow-line Seyfert 1 (γ-NLS1) galaxies constitute a small but interesting sample of the γ-ray-loud AGN. The radio-loudest γ-NLS1 known, PKS 2004−447, is located in the southern hemisphere and is monitored in the radio regime by the multiwavelength monitoring programme TANAMI. Aims: We aim for the first detailed study of the radio morphology and long-term radio spectral evolution of PKS 2004−447, which are essential for understanding the diversity of the radio properties of γ-NLS1s. Methods: The TANAMI VLBI monitoring program uses the Australian Long Baseline Array (LBA) and telescopes in Antarctica, Chile, New Zealand, and South Africa to monitor the jets of radio-loud active galaxies in the southern hemisphere. Lower resolution radio flux density measurements at multiple radio frequencies over four years of observations were obtained with the Australia Telescope Compact Array (ATCA). Results: The TANAMI VLBI image at 8.4 GHz shows an extended one-sided jet with a dominant compact VLBI core. Its brightness temperature is consistent with equipartition, but it is an order of magnitude below other γ-NLS1s with the sample value varying over two orders of magnitude. We find a compact morphology with a projected large-scale size Conclusions: PKS 2004−447 appears to be a unique member of the γ-NLS1 sample. It exhibits blazar-like features, such as a flat featureless X-ray spectrum and a core-dominated, one-sided parsec-scale jet with indications for relativistic beaming. However, the data also reveal properties atypical for blazars, such as a radio spectrum and large-scale size consistent with compact-steep-spectrum (CSS) objects, which are usually associated with young radio sources. These characteristics are unique among all γ-NLS1s and extremely rare among γ-ray-loud AGN.