Submillimetre (submm) observations of Cas A seemed to provide the first evidence for large (∼2 M ⊙) quantities of colder dust manufactured in the SN explosion ( Dunne et al. 2007), for example the maximum warm dust mass inferred for Cas A from Spitzer data is 0.03–0.05 M ⊙ ( Rho et al. 2006 Williams, Chu & Gruendl 2006 Blair et al. #CASSIOPEIA SEARCH REMOVAL ISO#Observations from mid-/far-infrared (IR) satellites ( IRAS, ISO and Spitzer) detect only warm dust and find orders of magnitude less than predicted by theory ( Dwek et al. 2003 Bianchi & Schneider 2007) and, if true, this can account for the dust observed at high redshift ( Morgan & Edmunds 2003 Dwek, Galliano & Jones 2007).Įvidence for this quantity of dust forming in young SNe in the local Universe has been scant and controversial. Theory predicts that each Type II SNe should produce ∼0.1–1 M ⊙ of dust ( Todini & Ferrara 2001 Nozawa et al. Type II supernovae (SNe) are good candidates for these dust factories as they evolve to a dust-producing phase in only a few hundred Myr and contain a high abundance of heavy elements. 2007, 2008), at a time when the Universe was only ∼1 Gyr old, suggest that a rapid mechanism for dust production must operate. 2003 Priddey, Ivison & Isaak 2008 Wang et al. The large quantities of dust seen in high-redshift quasars and galaxies ( Priddey et al. Supernovae: individual: Cassiopeia A, dust, extinction, supernova remnants, submillimetre 1 INTRODUCTION The inferred dust polarization fraction is unprecedented ( f pol∼ 30 per cent) which, coupled with the brief time-scale available for grain alignment (<300 yr), suggests that supernova dust differs from that seen in other Galactic sources (where f pol= 2−7 per cent) or that a highly efficient grain alignment process must operate in the environment of a supernova remnant. This is supported by the presence of both polarized and unpolarized dust emission in the north of the remnant where there is no contamination from foreground molecular clouds. No known mechanism would vary the synchrotron polarization in this way and so we attribute the excess polarized submm flux to cold dust within the remnant, providing fresh evidence that cosmic dust can form rapidly. The orientation is consistent with that of the magnetic field in Cas A, implying that the polarized submm emission is associated with the remnant. In this paper, we present new data which show that the submm emission from Cas A is polarized at a level significantly higher than that of its synchrotron emission. Submillimetre (submm) 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. If Type II supernovae – the evolutionary end points of short-lived, massive stars – produce a significant quantity of dust (>0.1 M ⊙) then they can explain the rest-frame far-infrared emission seen in galaxies and quasars in the first Gyr of the Universe.
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