Resolving the base of the relativistic jet in M87 at 6$R_{\rm sch}$ resolution with global mm-VLBI
J. -Y. Kim, R. -S. Lu, T. P. Krichbaum, M. Bremer, J. A. Zensus, R. C. Walker, the M87 collaboration
备注：
8 pages, accepted for publication in the special issue of Galaxies, "Blazars through Sharp Multi-wavelength Eyes", edited by J. L. Gómez, A. P. Marscher, and S. G. Jorstad
M87 is one of the nearest radio galaxies with a central SMBH and a prominent relativistic jet. Due to its close distance to the observer and the large SMBH mass, the source is one of the best laboratories to obtain strong observational constraints on the theoretical models for the formation and evolution of the AGN jets. In this article, we present preliminary results from our ongoing observational study about the innermost jet of M87 at an ultra-high resolution of $\sim$50$μ$as achieved by the Global Millimeter-VLBI Array (GMVA). The data obtained between 2004 and 2015 clearly show limb-brightened jets at extreme resolution and sensitivity. Our preliminary analysis reveals that the innermost jet expands in an edge-brightened cone structure (parabolic shape) but with the jet expansion profile slightly different from the outer regions of the jet. Brightness temperatures of the VLBI core obtained from cm- to mm-wavelengths show a systematic evolution, which can be interpreted as the evolution as a function of distance from the BH. We also adopt an alternative imaging algorithm, BSMEM, to test reliable imaging at higher angular resolution than provided by the standard CLEAN method (i.e. super-resolution). A demonstration with a VLBA 7mm example data set shows consistent results with a near-in-time 3mm VLBI image. Application of the method to the 2009 GMVA data yields an image with remarkable fine-scale structures that have been never imaged before. We present a brief interpretation of the complexity in the structure.
A pilot VLBI study of the SQUAB quasar sample featuring multiple Gaia detections
Shanghai Astronomical Observatory, CAS（中国科学院上海天文台）；State Key Laboratory of Radio Astronomy and Technology（射电天文学与技术国家重点实验室）；CSIRO Space and Astronomy（澳大利亚联邦科学与工业研究组织空间与天文部）；School of Astronomy and Space Sciences, University of Chinese Academy of Sciences（中国科学院大学天文与空间科学学院）
The twin-jet system in the FRII radio galaxy 3C 452: A sub-parsec scale VLBI study
Max-Planck-Institut für Radioastronomie（马克斯·普朗克射电天文研究所）；Leiden Observatory, Leiden University（莱顿大学莱顿天文台）；Julius-Maximilians-Universität Würzburg（维尔茨堡朱利叶斯-马克西米利安大学）；INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（意大利国家天体物理研究所博洛尼亚空间科学与天体物理观测站）；INAF–Istituto di Radioastronomia（意大利国家天体物理研究所射电天文研究所）；Università degli Studi di Bologna（博洛尼亚大学）
