论文标题

研究方向效应考虑使用VLA观测值考虑的无线电大型类星体样本的角度分辨率

Investigating orientation effects considering angular resolution for a sample of radio-loud quasars using VLA observations

论文作者

Maithil, Jaya, Runnoe, Jessie C., Brotherton, Michael S., Wardle, John F., Wills, Beverley J., DiPompeo, Michael, De Breuck, Carlos

论文摘要

无线电核心优势测量是射流方向的指标,有时依赖于大区域调查的核心通量密度测量值,例如二十cm(第一)的无线电天空的微弱图像,它们的角度分辨率仅为5''。这样的低分辨率调查通常无法从扩展发射中解析核心,从而导致错误的测量。我们专注于研究119种无线电类星体样本的分辨率效果。我们从NSF的Karl G. Jansky获得了连续观测,在A-Array中以0.2'的分辨率在10 GHz处非常大的阵列(VLA)。我们的测量结果表明,在首先,即使考虑到核心变异性后,核心通量测量确实在系统上也很高。对于少数类星体,10 GHz图像揭示了扩展功能,而第一个图像显示了点源。我们发现,对于具有较小角尺寸的类星体,分辨率效果更为突出。我们进一步计算了两个无线电核心优势参数R5100用于与该样品进行统计取向研究。我们还介绍了74 MHz和1.4 GHz之间的光谱能分布,我们用来测量这些类星体扩展发射的光谱指数。我们的结果从经验上证实,确定无线电核心优势需要高空间分辨率数据。我们强调了与频率和分辨率的选择相关的实际问题,并在核心和扩展通量密度的测量中。

Radio core dominance measurements, an indicator of jet orientation, sometimes rely on core flux density measurements from large-area surveys like Faint Images of the Radio Sky at Twenty cm (FIRST) that have an angular resolution of only 5''. Such low-resolution surveys often fail to resolve cores from the extended emission resulting in an erroneous measurement. We focus on investigating this resolution effect for a sample of 119 radio-loud quasars. We obtained continuum observations from NSF's Karl G. Jansky Very Large Array (VLA) at 10 GHz in A-array with a 0.2'' resolution. Our measurements show that at FIRST spatial resolution, core flux measurements are indeed systematically high even after considering the core-variability. For a handful of quasars, 10 GHz images reveal extended features, whereas the FIRST image shows a point source. We found that the resolution effect is more prominent for quasars with smaller angular sizes. We further computed two radio core dominance parameters R & R5100 for use in statistical orientation investigations with this sample. We also present the spectral energy distributions between 74 MHz and 1.4 GHz, which we used to measure the spectral index of the extended emission of these quasars. Our results empirically confirm that determination of radio core dominance requires high-spatial resolution data. We highlight the practical issues associated with the choice of frequency and resolution in the measurement of core and extended flux densities.

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