论文标题
VLBI观察palomar绿色类星体I：parsec-cale形态
VLBI Observations of a sample of Palomar-Green quasars I: parsec-scale morphology
论文作者
论文摘要
我们在低红移（$ z <0.5 $）处观察到20个Palomar-Green（PG）类星体，总磁通密度> 1 MJY，其中包括4个Radio-Loud-quasars（RLQ）和16个Radio-Quiet Quasars（RQQS），使用非常长的基线阵列（VLBA（VLBA））为5 GHz。在VLBA图像中清楚地检测到了十个RQQ，并且在其中八个中鉴定出一个紧凑的无线电芯，表明在此磁通密度限制的RQQ样品中，活动的银河核（AGN）相关的无线电发射的流行率。我们样本中的RQQS和RLQs的部门为$ \ sim $ 30〜mjy。 RQQ的无线电发射似乎是恒星形成和与AGN相关活性的组合的结果。我们样本中的所有RQQ的5 GHz通量密度比为非常大的数组（VLA）A-Array与D-array $ f _ {\ rm c} = S _ {\ rm a}^{\ rm a}^{\ rm vla}/s _带有$ f_a $（vlba和vla磁通密度比$ s^{\ rm vlba}/s _ {\ rm a}^{\ rm vla}）> 0.2 $ verus $ f_a <0.2 $的RQQS <rm vlba}/s _ {\ rm a}^{\ rm a}^{\ rm vla}）<0.2 $在形式，平稳度，且总且总且总且总且且总且且总且且总且且总且且总且总且总且总且总且总差异。 RQQS的$ f _ {\ rm a} $系统地低于RLQ，这可能是由于10s rqqs的扩展喷气机或RQQ的遗物射流到100s parsecs中，这些parsecs在VLBA图像中已解决。未来的较大样品，尤其是在添加了毫克分辨率的毫克分辨率的无线电图像以下，总磁通密度低于1 mjy，可以测试本文的结论，并有助于理解RQQ的无线电发射机制，以及RQQS和RQQS和RLQS之间的二分法和物理连接。
We observed 20 Palomar-Green (PG) quasars at low redshift ($z<0.5$) with total flux density > 1 mJy, including 4 radio-loud quasars (RLQs) and 16 radio-quiet quasars (RQQs), using the Very Long Baseline Array (VLBA) at 5 GHz. Ten RQQs are clearly detected in the VLBA images, and a compact radio core is identified in eight of them, indicating the prevalence of active galactic nucleus (AGN)-related radio emission in this flux-density-limited RQQ sample. The RQQs and RLQs in our sample have a division at $\sim$30~mJy. The radio emission from RQQs appears to be the result of a combination of star formation and AGN-associated activities. All RQQs in our sample have a 5 GHz flux density ratio of Very Large Array (VLA) A-array to D-array $f_{\rm c} = S_{\rm A}^{\rm VLA}/S_{\rm D}^{\rm VLA}$ above 0.2. The RQQs with $f_a$ (VLBA and VLA flux density ratio $S^{\rm VLBA}/S_{\rm A}^{\rm VLA}) > 0.2$ versus $f_a < 0.2$ show significant differences in morphology, compactness and total flux density. $f_{\rm a}$ of RQQs is systematically lower than that of RLQs, probably due to the extended jets or relic jets of RQQs on 10s to 100s parsecs which are resolved out in VLBA images. Future larger samples, especially with the addition of milli-arcsec resolution radio images of RQQs with total flux densities below 1 mJy, can test the conclusions of this paper and contributes to the understanding of the radio emission mechanism of RQQs, and the dichotomy and physical connection between RQQs and RLQs.
