Astron. Astrophys. 359, 316-336 (2000)

Multi-wavelength observations and modelling of shock-cloud interaction regions in the Vela Supernova Remnant

F. Bocchino  ^{*  1}, A. Maggio ¹, S. Sciortino ¹ and J. Raymond <sup>2

1</sup> Osservatorio Astronomico di Palermo "G.S. Vaiana", Palazzo dei Normanni, 90134 Palermo, Italy
² Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA

Received 12 November 1999 / Accepted 22 April 2000

Abstract

We present optical photometric and spectrophotometric observations of two selected filaments near the North rim of the Vela supernova remnant also observed in UV with the International Ultraviolet Explorer, and in X-rays with the ROSAT PSPC detector. From the optical data, we have derived spatially-resolved () profiles of several emission lines across the filaments, which allowed us to resolve the post-shock region. Starting from model-independent line ratio diagnostics, we have estimated densities ( cm^-3), temperatures ( K), pressures ( dyne cm^-2) and ambient magnetic fields ( µG) in the post-shock flow. We have also found clear evidence of a relative displacement between the X-ray emission, the emission in the H line and the emission in the [O III] line. We have compared the measured displacement, the width of the filaments in H and [O III], and the peak values of selected line ratios with the predictions of a radiative shock model which describes in detail the structure of the post-shock region. Shock models with velocities around km sec^-1 are shown to be consistent with the optical and UV observations if we assume that the direction of propagation is tilted with respect to the line of sight. The layout of the X-ray and optical emission of the filament and their thermodynamical properties strongly suggest that the shock is travelling along increasing density gradient.

Key words: shock waves ISM: clouds ISM: individual objects: Vela SNR ISM: structure ISM: supernova remnants ultraviolet: ISM

* Present address: ESA/ESTEC, Astrophysic Division, P.O. Box 299, 2200 AG Noordwijk, The Netherlands

Send offprint requests to: fbocchin@estec.esa.nl

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Contents

• 1. Introduction
• 2. Selection of the targets
• 3. The data
  • 3.1. Optical observations
  • 3.2. UV observations
• 4. Analysis and results
  • 4.1. Optical photometry
  • 4.2. Optical spectrophotometry
    • 4.2.1. Absolute flux distributions
    • 4.2.2. Normalized fluxes
    • 4.2.3. Line ratios
  • 4.3. UV data
• 5. Discussion
  • 5.1. Spatial correlation between optical and X-ray emission
  • 5.2. Interpretation of the optical and UV emission
• 6. A radiative shock model for the high density phase
  • 6.1. Model parameters
  • 6.2. Simulations
  • 6.3. Model results
  • 6.4. Comparison with observations
    • 6.4.1. Shock velocity and density estimates based on UV data
    • 6.4.2. Comparison of flux distributions
• 7. Summary and Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 2000

Online publication: June 30, 2000
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