从RACS发现的三个新的射电强$z\sim5.6$类星体的多波段性质
Multi-wavelength properties of three new radio-powerful $z\sim5.6$ quasi-stellar objects discovered from RACS
AI总结：
本研究通过多波段观测和光谱分析，识别了三个红移约5.6的射电强类星体，其中一个具有耀变体性质，并估算了中心黑洞质量与吸积率，有助于理解早期宇宙中喷流和超大质量黑洞的演化。
摘要：
我们展示了对三个新的$z\sim5.6$类星体（QSOs）的多波段研究，这些类星体是通过专门的 spectroscopic 观测识别出来的。这三个源是根据它们在快速ASKAP连续巡天（RACS）、暗能量巡天（DES）和全景巡天望远镜及快速响应系统（Pan-STARRS）巡天中报告的射电和光学/近红外性质而被选为高红移候选体的。这些是当前已知的$z>5.5$类星体中相对于其光学光度最为射电明亮的，具有$\rm R=S_{\rm 5GHz}/S_{\rm 4400A}>100$。在这项工作中，我们介绍了它们的识别过程，并基于公共巡天以及专门的射电和X射线观测中的探测，讨论了它们的多波段性质（从射电到X射线波段）。这三个源在相对强度和光谱形状方面呈现出广泛的性质范围，突显了多波段观测在准确刻画这些高红移天体中的重要性。特别是，从我们的分析中，我们发现了一个红移$z=5.61$的源呈现出清晰的耀变体性质（强烈的射电和X射线发射），使其成为目前已知的这一类天体中距离最远的之一。此外，通过对光学/近红外光度测量数据与吸积盘模型的拟合，以及对其中一个源的CIV宽发射线的分析，我们能够估算这些系统中中心黑洞的质量和吸积率，发现$\rm M_{\rm BH}\sim1-10\times10^9$~M$_\odot$，以$λ_{\rm Edd}\sim0.1-0.4$的速率吸积。对$z>5.5$射电类星体（如本文所报告的）的多波段表征，对于约束这类天体所承载的相对论性喷流和超大质量黑洞的演化至关重要。
英文摘要：
We present a multi-wavelength study of three new $z\sim5.6$ quasi-stellar objects (QSOs) identified from dedicated spectroscopic observations. The three sources were selected as high-$z$ candidates based on their radio and optical/near-infrared properties as reported in the Rapid ASKAP Continuum Survey (RACS), the Dark Energy Survey (DES), and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) survey. These are among the most radio-bright QSOs currently known at $z>5.5$, relative to their optical luminosity, having $\rm R=S_{\rm 5GHz}/S_{\rm 4400A}>100$. In this work, we present their identification, and we also discuss their multi-wavelength properties (from the radio to the X-ray band) based on detections in public surveys as well as in dedicated radio and X-ray observations. The three sources present a wide range of properties in terms of relative intensity and spectral shape, highlighting the importance of multi-wavelength observations in accurately characterising these high-$z$ objects. In particular, from our analysis we found one source at $z=5.61$ that presents clear blazar properties (strong radio and X-ray emission), making it one of the most distant currently known in this class. Moreover, from the fit of the optical/near-infrared photometric measurements with an accretion disc model as well as the analysis of the CIV broad emission line in one case, we were able to estimate the mass and accretion rate of the central black holes in these systems, finding $\rm M_{\rm BH}\sim1-10\times10^9$~M$_\odot$ accreting at a rate $λ_{\rm Edd}\sim0.1-0.4$. The multi-wavelength characterisation of radio QSOs at $z>5.5$, such as the ones reported here, is essential to constraining the evolution of relativistic jets and supermassive black holes hosted in this class of objects.
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