The incidence and evolution of Active Galactic Nuclei in 2865 COSMOS radio sources

使用甚长基线干涉测量（VLBI）技术的观测传统上针对精心挑选的样品，以研究其特性和环境的特定方面。这种情况部分是由于足够亮的光源的相对稀疏（或者更确切地说是缺乏灵敏度）造成的，但主要是由于对分散在宽视场中的多个光源进行成像的固有技术困难。在过去几年中，这两个方面都发生了重大变化，使观测者能够用VLBI图像补充敏感的广域射电观测。我们已经在甚长基线阵列上获得了276小时的观测时间，对COSMOS调查中发现的所有2865个射电天体进行了成像。观测将使用我们与该领域其他工作人员在以前的宽场VLBI观测中开发的新的相关和校准技术。由于COSMOS 2 sq-deg场中所有已知的无线电发射器都是目标，没有其他选择，数据将首次产生各种星系中通量受限的VLBI检测对象的样本。此外，我们可以访问VLBA的200小时数据，以在100平方度区域内对FIRST（20厘米无线电天空的微弱图像）调查的所有源进行成像。这些数据集将使VLBI无线电源的调查从Jy级低于100 μ Jy。该项目的主要科学目标是研究放射性活动星系核的发生率和影响。我们将（i）确定哪些对象主机紧凑的核心;（ii）确定这些对象如何影响其宿主星系的星星的形成;和（iii）调查吸积模式的变化作为红移的函数。此外，我们预计调查数据的额外意外用例和后续观察的输入将产生重大影响。COSMOS领域拥有无与伦比的光学，红外，X射线和光谱覆盖范围，通过与COSMOS项目成员的合作，我们可以获得数据。

Observations using the Very Long Baseline Interferometry (VLBI) technique traditionally target carefully selected samples, to study particular aspects of their properties and surroundings. This situation is caused partly by the relative sparsity of sufficiently bright sources (or rather a lack of sensitivity), but mostly by the inherent technical difficulties of imaging multiple sources scattered across wide fields. Both aspects have undergone significant changes in the past few years, allowing observers to complement sensitive, wide-area radio observations with VLBI images. We have acquired 276h of observing time at the Very Long Baseline Array, to image all 2865 radio objects found in the COSMOS survey. The observations are going to use the new correlation and calibration techniques that we have developed with other workers in the field in previous wide-field VLBI observations. Since all known radio emitters in the COSMOS 2 sq-deg field are targeted, without other selection applied, the data will yield, for the first time, a sample of flux-limited, VLBI-detected objects in a large variety of galaxies. Furthermore, we have access to 200h of data from the VLBA to image all sources from the FIRST (Faint Images of the Radio Sky at Twenty Centimeters) survey in a 100 sq-deg region. Together these data sets will allow the investigation of VLBI radio sources from the Jy level to below 100 uJy. The main scientific goal of this project is to study the incidence and impact of radio-emitting AGN. We will (i) determine which objects host compact cores; (ii) determine how these objects affect the star formation in their host galaxies; and (iii) investigate the changes in accretion modes as a function of redshift. Furthermore, we anticipate significant input for additional, unexpected use cases of the survey data and input for follow-up observations. The COSMOS field has unrivalled optical, IR, X-ray, and spectroscopic coverage, and through a collaboration with members of the COSMOS project we have access to the data.