Balmer-dominated Spectra of Nonradiative Shocks in the Cygnus Loop, RCW 86, and Tycho Supernova Remnants

By P. Ghavamian, J. C. Raymond, R. Smith, P. Hartigan. 2000

177 citations recorded by the source corpus.

We present an observational and theoretical study of the optical emission from nonradiative shocks in three supernova remnants: the Cygnus Loop, RCW 86, and Tycho. The spectra of these shocks are dominated by collisionally excited hydrogen Balmer lines, which have both a broad component caused by proton-neutral charge exchange and a narrow component caused by excitation of cold neutrals entering the shock. In each remnant, we have obtained the broad-to-narrow flux ratios of the Hα and Hβ lines and measured the Hα broad component width. A new numerical shock code computes the broad and narrow Balmer line emission from nonradiative shocks in partially neutral gas. The Balmer line fluxes are sensitive to Lyman line trapping and the degree of electron-proton temperature equilibration. The code calculates the density, temperature, and size of the postshock ionization layer and uses a Monte Carlo simulation to compute narrow Balmer line enhancement from Lyman line trapping. The initial fraction of the shock energy allocated to the electrons and protons (the equilibration) is a free parameter. Our models show that variations in electron-proton temperature equilibration and Lyman line trapping can reproduce the observed range of broad-to-narrow ratios. The results give 80%-100% equilibration in nonradiative portions of the northeast Cygnus Loop (vS ~ 300 km s-1), 40%-50% equilibration in nonradiative portions of RCW 86 (vS ~ 600 km s-1), and ≲20% equilibration in Tycho (vS ~ 2000 km s-1). Our results suggest an inverse correlation between magnetosonic Mach number and equilibration in the observed remnants.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/207aa9dc110872298351b44c38a17a0f0cd53bd4

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In Astronomy and Astrophysics

1. D. Maoz
2. F. Mannucci
3. G. Nelemans
4. C. Badenes
5. C. Rakowski
6. U. Hwang
7. J. Hughes
8. P. Slane

In Nuclear and High Energy Physics

1. D. Maoz
2. G. Nelemans
3. C. Badenes
4. F. Mannucci
5. C. Rakowski
6. U. Hwang
7. P. Slane
8. J. Laming

Citations in the corpus

• Observational Clues to the Progenitors of Type Ia Supernovae (2013, background): “On the other hand, this remnant, which is in an OB association, has traditionally been considered a CC SN (e.g. Ghavamian et al. 2001).”
• Cosmic-Ray Acceleration at the Forward Shock in Tycho’s Supernova Remnant: Evidence from Chandra X-Ray Observations (2005, background): “Optical observations reveal thin Balmer-dominated filaments in the north and east of the remnant (Smith et al. 1991; Ghavamian et al. 2001).”
• Constraints on the Physics of Type Ia Supernovae from the X-Ray Spectrum of the Tycho Supernova Remnant (2005, background): “In Ghavamian et al. (2001), the spectrum of the brightest knot in the eastern rim (knot g from Kamper & van den Bergh 1978) was examined in detail, yielding a velocity between 1940 and 2300 km s 1 for the forward shock.”
• The optical emission nebulae in the vicinity of WR 48 (Θ Mus): true Wolf–Rayet ejecta or unconnected supernova remnant? (2009, methodology): “The observations were made as part of our spectroscopic follow-up programme of new optical SNR candidates (as example, see filaments similarity in Blair et al. 1999; Ghavamian et al. 2001.”
• A Physical Relationship between Electron-Proton Temperature Equilibration and Mach Number in Fast Collisionless Shocks (2006, methodology): “In this paper we draw together observed values of (Te/Tp)0 and vS measured in five Balmer-dominated SNRs, including several previously unpublished measurements from the SNR RCW 86.”