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The nuclear spectrum of M 87

  • Z. I. Tsvetanov
  • G. F. Hartig
  • H. C. Ford
  • G. A. Kriss
  • M. A. Dopita
  • L. L. Dressel
  • R. J. Harms
Conference paper
Part of the Lecture Notes in Physics book series (LNP, volume 530)

Abstract

The nuclear spectrum of M 87 covering the Lyα-Hα wavelength range was obtained with the HST Faint Object Spectrograph (FOS) trough a 0″.21 aperture. Contrary to some previous claims, a single power law (F v v −α ) can not reproduce the observed continuum shape and at least a broken power law is required for a good fit (α=1.75 and 1.41 shortward and longward of the break at ∼4500 Å). We detect a set of broad (FWHM ∼ 400 km s−1) absorption lines arising in the gas associated with M 87. These are only lines from neutral and very low ionization species blueshifted by ∼150 km s−1 relative to the M 87 systemic velocity, indicating a net gas outflow and turbulence. The excitation sensitive emission line ratios suggest that shocks may be the dominant energy supplier.

The nuclear source in M 87 is significantly variable. From the FOS target acquisition data, we have established that the flux from the optical nucleus varies by a factor ∼2 on time scales of ∼2.5 months and by as much as 25% over 3 weeks, and remains unchanged (≤ 2.5%) on time scales of ∼ 1 day. These time scales limit the physical size of the emitting region to a few hundred gravitational radii. The variability, combined with other observed spectral properties, strongly suggest that M 87 is intrinsically of BL Lac type but is viewed at an angle too large to reveal the classical BL Lac properties.

Keywords

Black Hole Absorption Line Host Galaxy Gaseous Disk Systemic Velocity 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer-Verlag 1999

Authors and Affiliations

  • Z. I. Tsvetanov
    • 1
  • G. F. Hartig
    • 2
  • H. C. Ford
    • 1
    • 2
  • G. A. Kriss
    • 1
  • M. A. Dopita
    • 3
  • L. L. Dressel
    • 4
  • R. J. Harms
    • 4
  1. 1.Johns Hopkins UniversityBaltimoreUSA
  2. 2.Space Telescope Science InstituteBaltimoreUSA
  3. 3.Mount Stromlo and Siding Spring ObservatoriesAustralia
  4. 4.RJH Scientific, 5904 Richmond HighwayAlexandriaUSA

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