The large reservoirs of dust observed in some high redshift galaxies have been hypothesised to originate from dust produced by supernovae (SN). Theoretical models predict that core-collapse SN can be efficient dust producers (0.1-1 M☉) potentially responsible for most of the dust production in the early Universe. Observational evidence for this dust production efficiency is however currently limited to only a few remnants (e.g., SN 1987A, Cas A) that confirm this scenario. I will revisit the dust mass produced in the Crab Nebula relying on a spatially resolved analysis of its infrared to radio observations. The Crab's supernova dust mass is estimated to range between 0.024 and 0.054 M☉ (for amorphous carbon grains) with an average dust temperature Tdust of 42 K. This revised dust mass is up to ten times lower than some previous estimates, which can be attributed to our different interstellar dust corrections, lower submm fluxes, and higher dust temperatures. The dust is predominantly found in dense filaments south of the pulsar, with an average V band dust extinction of AV = 0.20-0.26 mag, consistent with recent optical dust extinction studies. The modelled synchrotron power-law spectrum is consistent with a radio spectral index αradio=-0.29, a spectral break long-wards of λbreak=1 mm, and an infrared spectral index αIR=-0.42. We have identified a millimetre excess emission in the Crab's spectrum, and argue that this mm-wave bump most likely results from the pile up of energetic electrons just below the spectral break in the Crab's central regions. We conclude that the Crab's efficient dust condensation (6-13%) is consistent with predictions from theoretical dust condensation models and provides further evidence for a scenario where supernovae provide non-negligible contributions to the interstellar dust budgets in galaxies.
Supernova Remnants: An Odyssey in Space after Stellar Death II
- Pub Date:
- June 2019