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A strong radio brightening at the jet base of M87 during the elevated very-high-energy γ-ray state in 2012

Published online by Cambridge University Press:  24 March 2015

K. Hada ,
M. Giroletti ,
M. Kino ,
G. Giovannini ,
F. D' Ammando ,
C. C. Cheung ,
M. Beilicke ,
H. Nagai ,
A. Doi  and
K. Akiyama
...Show all authors
K. Hada
Affiliation:
INAF Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna, Italy email: kazuhiro.hada@nao.ac.jp Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan
M. Giroletti
Affiliation:
INAF Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna, Italy email: kazuhiro.hada@nao.ac.jp
M. Kino
Affiliation:
Korea Astronomy and Space Science Institute, 776 Daedukdae-ro, Yusong, Daejon 305-348, Korea Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara 252-5210, Japan
G. Giovannini
Affiliation:
INAF Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna, Italy email: kazuhiro.hada@nao.ac.jp Dipartimento di Fisica e Astronomia, Università di Bologna, via Ranzani 1, I-40127 Bologna, Italy
F. D' Ammando
Affiliation:
INAF Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna, Italy email: kazuhiro.hada@nao.ac.jp
C. C. Cheung
Affiliation:
Space Science Division, Naval Research Laboratory, Washington, DC 20375, USA
M. Beilicke
Affiliation:
Physics Department and McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130, USA
H. Nagai
Affiliation:
Physics Department and McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130, USA
A. Doi
Affiliation:
Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara 252-5210, Japan
K. Akiyama
Affiliation:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
M. Honma
Affiliation:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
K. Niinuma
Affiliation:
Department of Astronomical Science, The Graduate University for Advanced Studies (SOKENDAI), 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
C. Casadio
Affiliation:
Instituto de Astrofisica de Andalucia, CSIC, Apartado 3004, 18080 Granada, Spain
M. Orienti
Affiliation:
INAF Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna, Italy email: kazuhiro.hada@nao.ac.jp
H. Krawczynski
Affiliation:
Physics Department and McDonnell Center for the Space Sciences, Washington University, St. Louis, MO 63130, USA
J. L. Gómez
Affiliation:
Instituto de Astrofisica de Andalucia, CSIC, Apartado 3004, 18080 Granada, Spain
S. Sawada-Satoh
Affiliation:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan
S. Koyama
Affiliation:
Mizusawa VLBI Observatory, National Astronomical Observatory of Japan, Osawa, Mitaka, Tokyo 181-8588, Japan Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo, Sagamihara 252-5210, Japan Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
A. Cesarini
Affiliation:
Department of Physics, University of Trento, I38050, Povo, Trento, Italy
S. Nakahara
Affiliation:
Faculty of Science, Kagoshima University, 1-21-35 Korimoto, Kagoshima, Kagoshima 890-0065, Japan
M. A. Gurwell
Affiliation:
Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA
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Abstract

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The nearby radio galaxy M87 offers a unique opportunity for exploring the connection between γ-ray production and jet formation at an unprecedented linear resolution. However, the origin and location of the γ-rays in this source is still elusive. Based on previous radio/TeV correlation events, the unresolved jet base (radio core) and the peculiar knot HST-1 at >120 pc from the nucleus are proposed as candidate site(s) of γ-ray production. Here we report our intensive, high-resolution radio monitoring observations of the M87 jet with the VLBI Exploration of Radio Astrometry (VERA) and the European VLBI Network (EVN) from February 2011 to October 2012. During this period, an elevated level of the M87 flux is reported at TeV with VERITAS. We detected a remarkable flux increase in the radio core with VERA at 22/43 GHz coincident with the VHE activity. Meanwhile, HST-1 remained quiescent in terms of its flux density and structure at radio. These results strongly suggest that the TeV γ-ray activity in 2012 originates in the jet base within 0.03 pc (projected) from the central supermassive black hole.

Keywords

galaxies: activegalaxies: individual (M87)galaxies: jets
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 10 , Issue S313: Extragalactic jets from every angle , September 2014 , pp. 340 - 345
Copyright
Copyright © International Astronomical Union 2015 

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