NGC 6946: A Laboratory for Studying the Diversity of SNR Evolution
Abstract
We propose Spitzer IRS spectral mapping of a sample of fifteen supernova remnants (SNRS) in the nearby, face-on spiral galaxy NGC6946. Selected from deep NIR imaging of the shock-sensitive emission lines [FeII] 1.644um and H2 2.121um, the SNRs are predominately located in the spiral arms where core-collapse SNe trace the ongoing massive star formation. The SNR sample represents a set of evolutionary 'snapshots', following the earliest stages of a remnants life, t ~ few years, through the adiabatic expansion phase and into the radiative 'snow-plow' phase, t ~ 10^5 years. We will use our 'snapshot' sample to study how the interaction between SNe and their birth clouds evolve from the earliest stages to the relatively mature phase in which the remnant settles back into the ISM. With our IRS spectral maps keyed to the location of shocked-gas based on [FeII] 1.644um emission, we will detect and measure the most important shock diagnostic lines, density and temperature sensitive ionic lines, and the major PAH broad emission bands. In combination with an extensive body of ancillary xray-to-radio data and models, our Spitzer data will allow us to: 1) investigate the properties of the ISM within and surrounding SNRs, comparing across a diverse range in SNR age, gas density, radiation field and metallicity conditions, 2) test different shock and photoionization models that are optimized for fast shocks, slow shocks, radiation field, grain destruction, dust to gas coupling, and metal enrichment; (3) infer the supernova rate of NGC6946, which can be compared with other starburst galaxies and with the Milky Way, and (4) study the ULX 'hypernova' candidate 'MF16' and its birth environment, comparing the strength and broadening of the H2 lines relative to the sample SNRs and HII regions.
- Publication:
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Spitzer Proposal
- Pub Date:
- March 2008
- Bibcode:
- 2008sptz.prop50362J