arXiv 0706.08992007-06-06astro-ph

$z = 4.4$ QSO BRI 1335-0417的高灵敏度阵列观测

High Sensitivity Array Observations of the $z = 4.4$ QSO BRI 1335-0417

E. Momjian, C. L. Carilli, D. A. Riechers, F. Walter

备注：: 13 pages, 3 figures, AJ accepted
发表信息：: Astron.J.134:694-697,2007
DOI：: 10.1086/519840

摘要：

本文给出了$z=4.4$类星体BRI 1335- 0417射电连续辐射的灵敏的相位参考VLBI结果。使用高灵敏度阵列（HSA）在1.4 GHz下进行观测。我们在$189 \times 113$ mas（$1.25 \times 0.75$ kpc）分辨率下的灵敏VLBI图像显示BRI 1335- 0417的连续发射，总通量密度为$208 \pm 46 μ$ Jy，与VLA测量的通量密度一致。在半高宽处源的尺寸为$255 \times 138$ mas（$1.7 \times 0.9$ kpc），导出的本征亮度温度为$\sim 3.5\times 10^4$ K。在VLBI全分辨率（$32 \times 7$ mas，$211 \times 46$ pc）下，没有探测到连续辐射，点源的上限为34 $μ$ Jy束$^{-1}$，或本征亮度温度的上限为$5.6\times 10^5$ K。在至少4.5 $σ$的射电连续辐射探测中，最高的角分辨率是$53 \times 27$ mas（$0.35 \times 0.18$ kpc）。在此分辨率下，图像显示BRI 1335- 0417中的连续特征，在FWHM下尺寸为$64 \times 35$ mas（$0.42 \times 0.23$ kpc），固有亮度温度为$\sim 2\times 10^5$ K。观测到的1.4 GHz连续谱源的范围和由此导出的亮温表明，BRI 1335- 0417的射电辐射（因此推测是远红外辐射）是由一个主要的星暴提供动力的，其大质量恒星形成率为几千个M_{\odot} { \rm yr}^{-1} $. Moreover, the absence of any compact high-brightness temperature source suggests that there is no radio-loud AGN in this $ z=4.4$类星体。

英文摘要：

We present sensitive phase-referenced VLBI results on the radio continuum emission from the $z=4.4$ QSO BRI 1335--0417. The observations were carried out at 1.4 GHz using the High Sensitivity Array (HSA). Our sensitive VLBI image at $189 \times 113$ mas ($1.25 \times 0.75$ kpc) resolution shows continuum emission in BRI 1335--0417 with a total flux density of $208 \pm 46 μ$Jy, consistent with the flux density measured with the VLA. The size of the source at FWHM is $255 \times 138$ mas ($1.7 \times 0.9$ kpc) and the derived intrinsic brightness temperature is $\sim 3.5\times 10^4$ K. No continuum emission is detected at the full VLBI resolution ($32 \times 7$ mas, $211 \times 46$ pc), with a 4$σ$ point source upper limit of 34 $μ$Jy beam$^{-1}$, or an upper limit to the intrinsic brightness temperature of $5.6\times 10^5$ K. The highest angular resolution with at least a 4.5$σ$ detection of the radio continuum emission is $53 \times 27$ mas ($0.35 \times 0.18$ kpc). At this resolution, the image shows a continuum feature in BRI 1335--0417 with a size of $64 \times 35$ mas ($0.42 \times 0.23$ kpc) at FWHM, and intrinsic brightness temperature of $\sim 2\times 10^5$ K. The extent of the observed continuum sources at 1.4 GHz and the derived brightness temperatures show that the radio emission (and thus presumably the far-infrared emission) in BRI 1335--0417 is powered by a major starburst, with a massive star formation rate of order a few thousand M_{\odot} {\rm yr}^{-1}$. Moreover, the absence of any compact high-brightness temperature source suggests that there is no radio-loud AGN in this $z=4.4$ QSO.

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