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Faint Object Camera imaging and spectroscopy of NGC 4151We describe ultraviolet and optical imaging and spectroscopy within the central few arcseconds of the Seyfert galaxy NGC 4151, obtained with the Faint Object Camera on the Hubble Space Telescope. A narrowband image including (O III) lambda(5007) shows a bright nucleus centered on a complex biconical structure having apparent opening angle approximately 65 deg and axis at a position angle along 65 deg-245 deg; images in bands including Lyman-alpha and C IV lambda(1550) and in the optical continuum near 5500 A, show only the bright nucleus. In an off-nuclear optical long-slit spectrum we find a high and a low radial velocity component within the narrow emission lines. We identify the low-velocity component with the bright, extended, knotty structure within the cones, and the high-velocity component with more confined diffuse emission. Also present are strong continuum emission and broad Balmer emission line components, which we attribute to the extended point spread function arising from the intense nuclear emission. Adopting the geometry pointed out by Pedlar et al. (1993) to explain the observed misalignment of the radio jets and the main optical structure we model an ionizing radiation bicone, originating within a galactic disk, with apex at the active nucleus and axis centered on the extended radio jets. We confirm that through density bounding the gross spatial structure of the emission line region can be reproduced with a wide opening angle that includes the line of sight, consistent with the presence of a simple opaque torus allowing direct view of the nucleus. In particular, our modelling reproduces the observed decrease in position angle with distance from the nucleus, progressing initially from the direction of the extended radio jet, through our optical structure, and on to the extended narrow-line region. We explore the kinematics of the narrow-line low- and high-velocity components on the basis of our spectroscopy and adopted model structure.
Document ID
19950041409
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Boksenberg, A.
(Royal Greenwich Observatory Cambridge, United Kingdom)
Catchpole, R. M.
(Royal Greenwich Observatory Cambridge, United Kingdom)
Macchetto, F.
(Space Telescope Science Institute, Baltimore, MD United States)
Albrecht, R.
(Space Telescope European Coordinating Facility Garching, Germany)
Barbieri, C.
(Osservatorio Astronomico Padova, Italy)
Blades, J. C.
(Space Telescope Science Institute, Baltimore, MD United States)
Crane, P.
(European Southern Observatory Garching, Germany)
Deharveng, J. M.
(CNRS Marseille, France)
Disney, M. J.
(Univ. College of Cardiff, Cardiff, Wales United Kingdom)
Jakobsen, P.
(ESTEC Noordwijk, Netherlands)
Date Acquired
August 16, 2013
Publication Date
February 10, 1995
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 440
Issue: 1
ISSN: 0004-637X
Subject Category
Astronomy
Accession Number
95A73008
Funding Number(s)
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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