Dynamics & Chemical Abundances in Young SNR
 
An Honours Project Proposed by: Michael A. Dopita & Ralph Sutherland, ANU
 
Objectives
To observe Young Supernova Remnants (YSNR) in order to directly test theories of nucleosynthesis in massive stars, draw conclusions on the mixing of material during the supernova explosion, derive dynamical ages and to search for evidence of the “jet ejection” expected if these objects were associated with a Gamma-Ray Burst, even when this was not aligned with the line of sight.
Note: This project is available only if the data collection can be done at the start of 2009.
Background
The oxygen-rich supernova remnants (YSNR) are a rare class of objects in which it is possible to see the material ejected from within the precursor star. The analysis of the chemical abundances of such remnants represents a rare opportunity to directly test theories of nucleosynthesis in massive stars. Up to the present, only a handful of such objects are known, mostly in the Galaxy and the Magellanic Clouds. The most famous of these is Cass A (Chevalier & Kirshner, 1978) for which detailed HST proper-motion data has recently been obtained (Fesen et al. 2006a,b). A second Galactic example is G292.0+1.8 (Goss et al. 1979, Murdin & Clark 1979). Two more are known in the LMC, N132D(Danziger & Dennefeld 1976), 0540-69.3 (Mathewson et al 1980) and 1E0102.2-7219 in the SMC ( Dopita, Tuohy & Mathewson 1981). For the Magellanic Cloud SNR, high resolution narrow-band images have been obtained by Morse et al. (1996). These clearly show filaments with a wide range of abundance and excitation conditions, indicative of poor mixing during the supernova explosion.
In these YSNR, the material ejected by the star is excited into emission as it passes through the reverse shock of the blast wave, and is shocked by the increased gas and ram pressure of the surrounding ISM. The shock characteristics of such oxygen-rich material are very different from those of normal radiative shocks, and the theory necessary to deal with such shocks has been fully developed by Ralph Sutherland as part of his PhD thesis work. We will use the same methods of analysis to determine the chemical abundances and shock conditions in the filaments.
Proposed Observations & Analysis
We propose to use the new Wide Field Spectrograph (WiFeS) on the 2.3m telescope at Siding Spring to observe four oxygen-rich and one nitrogen and oxygen enriched remnant: N132D and 0540-69.3 in the Large Magellanic Cloud (LMC), and 1E 0102.2-7219 in the Small Magellanic Cloud (SMC). and G292.0 + 1.8 and Puppis A in the Galaxy. The YSNR in the LMC and SMC are ideally matched to the field of view of WiFeS as Figure 1, below clearly demonstrates. We need to detect the faintest lines in the optical spectrum with good signal to noise, which implies a S/N > 20 in the nebular continuum, log(F) ~ 10-16 erg cm-2 s-1 arc sec-2 Å-1, or exposure times of ~1-2 Hr per spatial aperture. For the LMC and SMC remnants, full spatial coverage is sought, but for the Galactic remnants, only a few filaments will be studied.
In addition to these objects, we also propose to observe the shocked ring of ejecta around SN1987A. Here the blast wave has just reached a pre-existing ring of material, originally photo-ionized by the UV flash of the supernova event, and for which the chemical abundances are already well known. We will begin a monitoring program of the radiative shocks that are eating into this material, driven by the blast wave of the explosion. This program will continue beyond the end of this project in order to monitor the time evolution of these shocks.
The objectives of our observations are to provide spatially-resolved spectrophotometry with the aim of investigating the chemical abundances of the ejecta, and the degree to which chemical mixing may have occurred in the supernova event itself. In addition, we aim to investigate the 3-D dynamical structure of the ejecta, with the objective of searching for evidence of the “jets” associated with the Gamma-Ray burst which may have occurred at the the moment of explosion. The modelling of the spectrophotometric data will be done using the MAPPINGS V code, using a methodology similar to that described in Ralph Sutherland’s (1994) thesis (Sutherland & Dopita, 1995).
 
 
Figure 1.     An [O III] plus H-Alpha 2.3m image of the oxygen-rich supernova remnant in the SMC.
        The WiFeS aperture is shown superimposed as a yellow oblong.
 
        Table 1: Target Oxygen Rich SNR
 
SNR    
R.A.  (J2000.0)
Dec  (J2000.0)
#Pointings
0102.2-7219
01 04 01.4
-72 01 54
2
N132D
05 25 01.4
 -60 38 31    
4
SN 1987A    
05 35 28.0
-60 16 11
1
0540-69.3    
05 40 08.1
-69 20 00
4
Puppis A
08 23 43.0
-43 09 45
6
G292.0+1.8
11 24 44.0
 -59 16 02
2
 
 
References
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