The radio structure of ultra-high-energy synchrotron-peak BL Lacs
The radio structure of ultra-high-energy synchrotron-peak BL Lacs
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DOI：
10.1111/j.1365-2966.2012.21366.x
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发表时间：
2012-05
影响因子：
4.8
通讯作者：
Zhongzu Wu;D. Jiang;M. Gu
中科院分区：
文献类型：
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作者：
Zhongzu Wu;D. Jiang;M. Gu
我们给出了欧洲甚长基线干涉网(EVN)和多元无线电干涉仪网络(MERLIN)对9个超高能同步波峰BL Lacs(UHBL)的5 GHz观测结果，这些超高能BLLacs由Nieppola等人工作的所有对数为？(？峰/赫兹)和gt；20的BLLac组成。结合现有的甚长基线阵列(VLBA)档案数据，调查了这些震源的无线电结构。我们发现，在五个震源中检测到了核喷流结构，而在PC尺度上，有四个震源只有一个致密的核心。所有源的核心都显示出较高的亮温(平均值和中值为log？(Tb/K)11)，这意味着在所有源中都可能存在束流效应。当有多历元甚长基线干涉测量数据时，我们发现两个源(2E0414+0057和EXO 0706.1+5913)的核心或总通量密度没有显著变化，2E0414+0057也没有明显的自行运动，而EXO 0706.1+5913可能有超光速运动。通过比较弧秒尺度上VLBI总通量与核心通量的比率，发现我们的源没有Giroletti等人典型的高频峰值BLLac天体(HBL)那么紧凑。结合我们的所有结果，我们认为超高频层的喷流中可能存在束流效应，但它可能比典型的高压层的弱。此外，通过比较红移和射电光度的分布，我们发现UHBL可能是具有相似喷流功率的较少多普勒波束的HBL版本。这些结果与我们以前工作的预期很好地一致。
We present the results of European Very Long Baseline Interferometry Network (EVN) and Multi-Element Radio Linked Interferometer Network (MERLIN) 5-GHz observations of nine ultra-high-energy synchrotron-peak BL Lacs (UHBLs), consisting of all BL Lacs with log?(?peak/Hz) > 20 from the work of Nieppola et al. The radio structure was investigated for these sources, in combination with available Very Long Baseline Array (VLBA) archive data. We found that a corejet structure is detected in five sources, while four sources only have a compact core at the pc scale. The cores of all sources show high brightness temperature (with mean and median values log?(Tb/K) 11), which implies that the beaming effect is likely present in all sources. When multi-epoch Very Long Baseline Interferometry (VLBI) data are available, we find no significant variations for either core or total flux density in two sources (2E 0414+0057 and EXO 0706.1+5913) and no evident proper motion in 2E 0414+0057, while superluminal motion is likely detected in EXO 0706.1+5913. Our sources are found to be less compact than the typical high-frequency peaked BL Lac objects (HBLs) of Giroletti et al., by comparing the ratio of the VLBI total flux and the core flux at the arcsec scale. Combining all our results, we propose that the beaming effect might be present in the jets of UHBLs; however, it is likely weaker than that for typical HBLs. Moreover, we found by comparing the distributions of redshift and radio luminosity that UHBLs could be less Doppler-beamed versions of HBLs with similar jet power. These results are in good consistence with the expectations of our previous work.