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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
VLBI observations of the ultracompact radio nucleus of the galaxy M81
Astrophysical Journal, Volume 457, No. 2 PART I, Year 1996
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Description
VLBI observations of the nuclear region of the nearby spiral galaxy M81 reveal the smallest size yet for its core and that of any other extragalactic nucleus: 0.18 mas × 0.07 mas (700 AU × 300 AU) at 22.2 GHz. Images show no brightness structure outside the core region above the sensitivity limit of ∼2% of the peak brightness. The core is slightly asymmetric with its brightness falling off along its major axis toward the northeast. There has been no significant change in the size and orientation since the last VLBI observation of this source in 1981, giving a nominal expansion velocity of -60 ± 60 km s-1. The size varies with observing frequency, with the length of the major axis being proportional to v-0.8. The apparent position angle is also frequency dependent, and changes by 35° between 22.2 and 2.3 GHz, equivalent to such a change on a length scale from 700 to 4000 AU. These observations exclude a starburst or supernova origin of the core emission and instead argue for the core being an active galactic nucleus, perhaps with a bent jet, and with properties lying between those of Sgr A* and the cores of powerful radio galaxies and quasars. © 1996. The American Astronomical Society. All rights reserved.
Authors & Co-Authors
Bietenholz, Michael F.
Canada, Toronto
York University
Bartel, Norbert
United States, Socorro
National Radio Astronomy Observatory Socorro
Rupen, Michael P.
United States, Westford
Mit Haystack Observatory
Conway, John E.
Germany, Bonn
Max Planck Institute for Radio Astronomy
Beasley, Anthony J.
United States, Pasadena
California Institute of Technology
Romney, Jonathan D.
Italy, Rome
Consiglio Nazionale Delle Ricerche
Altunin, Valery I.
United States, Berkeley
University of California, Berkeley
Jones, Dayton L.
United States, Baltimore
Space Telescope Science Institute
Venturi, Tiziana
Canada, Ottawa
Natural Resources Canada
Umana, Grazia
United Kingdom, Macclesfield
Nuffield Radio Astronomy Laboratories
Weiler, Kurt W.
Canada, Toronto
York University
van Dyk, Schuyler D.
United States, Socorro
National Radio Astronomy Observatory Socorro
Panagia, Nino
United States, Westford
Mit Haystack Observatory
Cannon, Wayne H.
Germany, Bonn
Max Planck Institute for Radio Astronomy
Statistics
Citations: 42
Authors: 14
Affiliations: 12
Identifiers
Doi:
10.1086/176756
ISSN:
0004637X
Research Areas
Cancer
Environmental