EPJ Web of Conferences 61, 06004 (2013)
https://doi.org/10.1051/epjconf/20136106004

A sensitive study of the peculiar jet structure HST-1 in M87

¹ Instituto de Astrofísica de Andalucía, CSIC, Apartado 3004, 18080 Granada, Spain
² INAF Istituto di Radioastronomia, via Gobetti 101, 40129 Bologna, Italy
³ Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy
⁴ Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo, 181-8588, Japan
⁵ National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo, 181-8588, Japan
⁶ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁷ Departament d’Astronomia i Astrofisica, Universitat de València, Dr. Moliner 50, 46100 Burjassot, Valencia, Spain

^a e-mail: casadio@iaa.es

Published online: 9 December 2013

Abstract

To obtain a better understanding of the location and mechanisms for the production of the gamma-ray emission in jets of AGN we present a detailed study of the HST-1 structure, 0.8 arcsec downstream the jet ofM87, previously identified as a possible candidate for TeV emission. HST-1 shows a very peculiar structure with superluminal as well as possible stationary sub-components, and appears to be located in the transition from a parabolic to a conical jet shape, presumably leading to the formation of a recollimation shock. This scenario is supported by our new RHD simulations in which the interaction of a moving component with are collimation shock leads to the appearance of a new superluminal component. To discern whether HST-1 is produced by a recollimation shock or some other MHD instability, we present new polarimetric 2.2 and 5 GHz VLBA, as well as 15, 22 and 43 GHz JVLA observations obtained between November 2012 and March 2013.