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D.S. Wong, J.S. Ulvestad, G.B. Taylor (NRAO), J.F. Gallimore (Bucknell Univ.)
The VLBA and phased-VLA were used to image Seyfert galaxy NGC~4151 at wavelengths of 3.6 and 6 cm, achieving resolutions of ~2 and 3 mas (0.16 and 0.24 pc) respectively. This marks the first time that this Seyfert has been imaged at 3.6 cm with VLBI.
At both wavelengths, two components (previously denoted as D and E) were identified. The brightness temperatures (~107-108 K) we calculated were consistent with non-thermal emission from D and E. There is no evidence for extended emission of a lower brightness temperature that might be associated with a nuclear torus. The spectral indices of the components and their subcomponents reveal no obvious flat-spectrum source, so the question of whether the nucleus is in component D or E remains unanswered. This is the second time that NGC 4151 has been imaged by the VLBA at 6 cm, enabling derivation of a tentative speed limit of \leq 0.07c on the parsec scale motion of component E with respect to component D.
NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. Further support for D. S. Wong was provided by NSERC of Canada.
The author(s) of this abstract have provided an email address for comments about the abstract: dianew@astro.columbia.edu