The Ultraviolet Spectrum of the Liner NGC 4579

Details The Ultraviolet Spectrum of the Liner NGC 4579 The Ultraviolet Spectrum of the Liner NGC 4579

Nov 1996

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996aj....112.1829b&link_type=abstract

Astronomical Journal v.112, p.1829

Astronomy and Astrophysics

Astronomy

41

Galaxies: Individual: Ngc 4579, Galaxies: Active, Galaxies: Nuclei

Scientific paper

We present a Hubble Space Telescope ultraviolet spectrum of the LINER nucleus of NGC 4579, spanning the wavelength range 1160-3270 A. The data reveal a low-excitation spectrum of narrow (FWHM ~1200 km s^-1^) and broad (FWHM ~ 6600 km s^-1^) emission lines, which provide new diagnostics of the physical conditions within the emission-line regions. A featureless ultraviolet continuum is detected unambiguously, with fnu) is proportional to ν^-1.0^ over the range 1300-2200 A and ν^-2.4^ over 2200-3000 A. The 2200 A continuum flux is a factor of 3.3 lower than the value reported by Maoz et al. (1995) based on an HST image taken 19 months earlier; this is the first time that UV variability has been discovered in a LINER. The predictions of fast shock models are incompatible with the narrow-line spectrum, because the high-excitation lines produced in fast shocks are weak or absent in NGC 4579. Models of a single slab of gas photoionized by a power-law spectrum do not reproduce the observed line ratios well either, and it appears that the narrow-line region cannot be characterized by a unique value of the ionization parameter. We argue that the narrow-line region is photoionized by the central UV/X-ray source, and that more sophisticated photoionization calculations, incorporating the effects of density and/or ionization stratification and different continuum shapes, can yield results in better agreement with the data.

Affiliated with

Also associated with

No associations

Rating

The Ultraviolet Spectrum of the Liner NGC 4579 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with The Ultraviolet Spectrum of the Liner NGC 4579, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The Ultraviolet Spectrum of the Liner NGC 4579 will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1146146