Forbidden Line Emission from Type Ia Supernova Remnants Containing Balmer-Dominated Shells

Abstract

Balmer-dominated shells in supernova remnants (SNRs) are produced by collisionless shocks advancing into a partially neutral medium, and are most frequently associated with Type Ia supernovae. We have analyzed Hubble Space Telescope (HST) images and VLT/MUSE or AAT/WiFeS observations of five Type Ia SNRs containing Balmer-dominated shells in the LMC: 0509-67.5, 0519-69.0, N103B, DEM L71, and 0548-70.4. Contrary to expectations, we find bright forbidden line emission from small dense knots embedded in four of these SNRs. The electron densities in some knots are higher than 10${}^4$ cm${}^{-3}$. The size and density of these knots are not characteristic for interstellar medium (ISM) -- they most likely originate from a circumstellar medium (CSM) ejected by the SN progenitor. Physical property variations of dense knots in the SNRs appear to reflect an evolutionary effect. The recombination timescales for high densities are short, and HST images of N103B taken 3.5 yr apart already show brightness changes in some knots. VLT/MUSE observations detect [Fe XIV] line emission from reverse shocks into SN ejecta as well as forward shocks into the dense knots. Faint [O III] line emission is also detected from the Balmer shell in 0519-69.0, N103B, and DEM L71. We exclude the postshock origin because the [O III] line is narrow. For the preshock origin, we considered three possibilities: photoionization precursor, cosmic ray precursor, and neutral precursor. We conclude that the [O III] emission arises from oxygen that has been photoionized by [He II] $\lambda$304 photons and is then collisionally excited in a shock precursor heated mainly by cosmic rays.

20 pages, 2 tables, 14 figures, accepted for publication in The Astrophysical Journal (ApJ)

References in corpus (8)

• Array Programming with NumPy
• The NumPy array: a structure for efficient numerical computation
• Resolved shock structure of the Balmer-dominated filaments in Tycho's supernova remnant: Cosmic-ray precursor?
• The Destruction of the Circumstellar Ring of SN 1987A
• Spitzer Observations of the Type Ia Supernova Remnant N103B: Kepler's Older Cousin?
• Physical Structures of the Type Ia Supernova Remnant N103B
• Balmer filaments in Tycho's supernova remnant: an interplay between cosmic-ray and broad-neutral precursors
• Imagery and UV Spectroscopy of the LMC Supernova Remnant N103B Using HST

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• Evidence for a Dense, Inhomogeneous Circumstellar Medium in the Type Ia SNR 0519-69.0
• Locating the CSM Emission within the Type Ia Supernova Remnant N103B
• A First-look at Spatially-resolved Infrared Supernova Remnants in M33 with JWST
• Helium emission from Balmer-dominated shocks in Type Ia supernova remnants provides constraints to their progenitor systems