High dynamic range VLBI observations of NGC 6251
1986; IOP Publishing; Volume: 305; Linguagem: Inglês
10.1086/164283
ISSN1538-4357
AutoresDayton L. Jones, S. C. Unwin, A. C. S. Readhead, W. L. W. Sargent, G. A. Seielstad, R. Simon, R. C. Walker, John M. Benson, R. A. Perley, A. H. Bridle, I. I. K. Pauliny‐Toth, J. D. Romney, A. Witzel, P. N. Wilkinson, L. Bååth, R. S. Booth, D. N. Fort, John Galt, R. L. Mutel, R. P. Linfield,
Tópico(s)GNSS positioning and interference
Resumoview Abstract Citations (53) References (35) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS High Dynamic Range VLBI Observations of NGC 6251 Jones, Dayton L. ; Unwin, S. C. ; Readhead, A. C. S. ; Sargent, W. L. W. ; Seielstad, G. A. ; Simon, R. S. ; Walker, R. C. ; Benson, J. M. ; Perley, R. A. ; Bridle, A. H. ; Pauliny-Toth, I. I. K. ; Romney, J. ; Witzel, A. ; Wilkinson, P. N. ; Baath, L. B. ; Booth, R. S. ; Fort, D. N. ; Galt, J. A. ; Mutel, R. L. ; Linfield, R. P. Abstract The large radio galaxy NGC 6251 has been observed with an 11-telescope VLBI array, including the full VLA, at 18 cm. High-dynamic-range maps of both the VLBI-scale and VLA-scale radio structure from these observations, as well as hybrid maps from earlier VLBI experiments at 6 and 13 cm, are presented. The 18-cm VLBI hybrid map has an unusually high dynamic range of about 300 to 1 (ratio of the peak brightness to five times the rms noise level) and is limited by thermal noise rather than calibration errors. A lower limit of 80 to 1 for the ratio of jet/counterjet brightness at parsec scales can be set. This is the strongest such limit produced by VLBI observations of any source to date. If the absence of a detectable counterjet is caused by relativistic beaming, then the jet must be aligned within 45 deg of the line of sight. The VLA map shows a complex structure along the previously detected kiloparsec-scale counterjet. The physical conditions in the inner few parsecs of the NGC 6251 jet and their relation to the conditions in the extraordinarily long and well collimated kiloparsec-scale jets are discussed, and it is shown that both small-scale and large-scale morphology can be explained in terms of a simple model and relativistic beaming. Publication: The Astrophysical Journal Pub Date: June 1986 DOI: 10.1086/164283 Bibcode: 1986ApJ...305..684J Keywords: Galactic Nuclei; Radio Jets (Astronomy); Radio Sources (Astronomy); Very Long Base Interferometry; X Ray Astronomy; Circular Polarization; Data Reduction; Doppler Effect; Signal To Noise Ratios; Thermal Noise; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 6251; GALAXIES: JETS; GALAXIES: NUCLEI; INTERFEROMETRY; RADIO SOURCES: GALAXIES full text sources ADS | data products SIMBAD (6) NED (5)
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