Cassiopeia A: dust factory revealed via submillimetre polarimetry
arXiv:0809.0887 · doi:10.1111/j.1365-2966.2009.14453.x
Abstract
If Type-II supernovae - the evolutionary end points of short-lived, massive stars - produce a significant quantity of dust (>0.1 M_sun) then they can explain the rest-frame far-infrared emission seen in galaxies and quasars in the first Gyr of the Universe. Submillimetre observations of the Galactic supernova remnant, Cas A, provided the first observational evidence for the formation of significant quantities of dust in Type-II supernovae. In this paper we present new data which show that the submm emission from Cas A is polarised at a level significantly higher than that of its synchrotron emission. The orientation is consistent with that of the magnetic field in Cas A, implying that the polarised submm emission is associated with the remnant. No known mechanism would vary the synchrotron polarisation in this way and so we attribute the excess polarised submm flux to cold dust within the remnant, providing fresh evidence that cosmic dust can form rapidly. This is supported by the presence of both polarised and unpolarised dust emission in the north of the remnant, where there is no contamination from foreground molecular clouds. The inferred dust polarisation fraction is unprecedented (f_pol ~ 30%) which, coupled with the brief timescale available for grain alignment (<300 yr), suggests that supernova dust differs from that seen in other Galactic sources (where f_pol=2-7%), or that a highly efficient grain alignment process must operate in the environment of a supernova remnant.
In press at MNRAS, 10 pages, print in colour
References in corpus (17)
- Radiative torques: Analytical Model and Basic Properties
- Tracing Magnetic Fields with Aligned Grains
- Dust Formation and Survival in Supernova Ejecta
- The Cassiopeia A Supernova was of Type IIB
- The Evolution of Dust in the Early Universe with Applications to the Galaxy SDSS J1148+5251
- Freshly Formed Dust in the Cassiopeia A Supernova Remnant as Revealed by the Spitzer Space Telescope
- Radiative torque alignment: Essential Physical Processes
- Thermal Emission from Warm Dust in the Most Distant Quasars
- A Spitzer Space Telescope Study of SN 2003gd: Still No Direct Evidence that Core-Collapse Supernovae are Major Dust Factories
- Subsonic Mechanical Alignment of Irregular Grains
- Dust Destruction in Type Ia Supernova Remnants in the Large Magellanic Cloud
- No cold dust within the supernova remnant Cassiopeia A
- Millimeter and Radio Observations of z~6 Quasars
- Magnetic fields in massive star forming regions
- Alignment of Dust with Magnetic Inclusions: Radiative Torques and Superparamagnetic Barnett and Nuclear Relaxation
- Environments of z>5 quasars: searching for protoclusters at submillimetre wavelengths
- Supernova Remnants in the Magellanic Clouds. VII. Infrared Emission from SNRs