Herschel Studies of Supernova Remnants

Cas A PACS Image
Figure 1. A composite PACS image of the Cas A supernova remnant, made from 70um (blue), 100um (green) and 160um (red) images.

As a result of ground-based submillimetre observations, large quantities of dust have been deduced to be present in many high-redshift galaxies. Due to the young ages of these galaxies, this dust has often been interpreted as having originated in the ejecta of core-collapse supernovae (CCSNe) from massive stars. Models have predicted that each CCSN could form up to 0.1-1 solar masses of dust in its ejecta, which could be sufficient to account for the dust observed at high redshifts and might also provide a significant source of dust in the local Universe. However, direct observational evidence that CCSNe synthesise such large amounts of dust is scarce. In addition to our Spitzer mid-infrared programme which has studied the mid-infrared dust emission from extragalactic CCSNe during the first few years after their outburst, we are collaborating in a Herschel Key Project to determine the amounts of dust present within several young (less than 1000 years old) Galactic supernova remnants, via far-infrared and submillimetre photometric imaging with Herschel's PACS and SPIRE instruments.

Imaging photometry of the young CCSN supernova remnant Cassiopeia A, which exploded about 400 years ago, has been obtained in six bands between 70um and 500um with the PACS and SPIRE instruments, with angular resolutions ranging from 6 to 37" (see Figure 2). In the outer regions of the Cas A remnant, the 70-um PACS image resembles the published 24-um image Spitzer image, with the emission attributed to the same warm dust component, located in the reverse shock region. At longer wavelengths, the three SPIRE bands are increasingly dominated by emission from cold interstellar dust knots and filaments, particularly across the central, western and southern parts of the remnant. Nonthermal emission from the northern part of the remnant becomes prominent at 500 um.

Cas A SPIRE Image
Figure 2. Images of the Cas A supernova remnant taken with PACS (70, 100 and 160um) and with SPIRE (250, 350 and 500um).

We have estimated and subtracted the contributions from the nonthermal, warm dust and cold interstellar dust components. Following these subtractions, we resolve for the first time a cool (~35 K) dust component, emitting at 70-160 um, that is located interior to the reverse shock region (see Figure 3), with a mass that we estimate as 0.075 solar masses. More details can be found in the paper by Barlow et al. (2010) in the Herschel Special Issue of A&A.

Cas A Multi-wavelength Montage
Figure 3. Images of the Cas A supernova remmant at multiple wavelengths. The 70 and 100um images (right hand side) show the 35K cool dust component that is found to be emitting at these wavelengths.

  For further information, please contact Prof. Mike Barlow (mjb AT star.ucl.ac.uk).

Page last modified on 10 aug 10 17:08 by Michael Barlow