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Detection of compact ultraviolet nuclear emission in liner galaxiesLow-ionization nuclear emission-line regions (LINERs), which exist in a large fraction of galaxies, may be the least luminous manifestation of quasar activity. As such, they may make possible the study of the active galactic nucleus (AGN) phenomenon in the nearest galaxies. The nature of LINERs has, however, remained controversial because an AGN-like nonstellar continuum source has not been directly observed in them. We report the detection of bright (greater than or approximately = 2 x 10(exp -16) ergs/s/sq cm/A), unresolved (full width at half maximum (FWHM) less than or approximately = 0.1 sec) point sources of UV (approximately 2300 A) emission in the nuclei of nine nearby galaxies. The galaxies were imaged using the Faint Object Camera (FOC) on the Hubble Space Telescope (HST), and seven of them are from a complete sample of 110 nearby galaxies that was observed with HST. Ground-based optical spectroscopy reveals that five of the nuclei are LINERs, three are starburst nuclei, and one is a Seyfert nucleus. The observed UV flux in each of the five LINERs implies an ionizing flux that is sufficient to account to the observed emission lines through photoionization. The detection of a strong UV continuum in the LINERs argues against shock excitation as the source of the observed emission lines, and supports the idea that photoionization excites the lines in at least some objects of this class. We have analyzed ground-based spectra for most of the northern-hemisphere galaxies in the HST sample and find that 26 of them are LINERs, among which only the above five LINERs have a detected nuclear UV source.
Document ID
19950041402
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Maoz, Dan
(Tel-Aviv Univ. Tel-Aviv, Israel)
Filippenko, Alexei V.
(Univ. of California, Berkeley, CA United States)
Ho, Luis C.
(Univ. of California, Berkeley, CA United States)
Rix, Hans-Walter
(Inst. for Advanced Study, Princeton, NJ United States)
Bahcall, John N.
(Inst. for Advanced Study, Princeton, NJ United States)
Schneider, Donald P.
(Inst. for Advanced Study, Princeton, NJ United States)
Macchetto, F. Duccio
(Space Telescope Science Inst. Baltimore, MD, United States)
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
95A73001
Funding Number(s)
CONTRACT_GRANT: NAG5-1618
CONTRACT_GRANT: NSF AST-89-57063
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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