We search for far-infrared ( FIR ) counterparts of known supernova remnants ( SNRs ) in the Galactic plane ( 10 ^ { \circ } < \mid l \mid < 60 ^ { \circ } ) at 70 – 500 \mu m using the Herschel Infrared Galactic Plane Survey ( Hi-GAL ) .
Of 71 sources studied , we find that 29 ( 41 % ) SNRs have a clear FIR detection of dust emission associated with the SNR .
Dust from 8 of these is in the central region , and 4 indicate pulsar wind nebulae ( PWNe ) heated ejecta dust .
A further 23 have dust emission in the outer shell structures which is potentially related to swept up material .
Many Galactic SNe have dust signatures but we are biased towards detecting ejecta dust in young remnants and those with a heating source ( shock or PWN ) .
We estimate the dust temperature and mass contained within three PWNe , G11.2 - 0.3 , G21.5 - 0.9 , and G29.7 - 0.3 using modified blackbody fits .
To more rigorously analyse the dust properties at various temperatures and dust emissivity index \beta , we use point process mapping ( PPMAP ) .
We find significant quantities of cool dust ( at 20-40 K ) with dust masses of M _ { d } = 0.34 \pm 0.14 M _ { \odot } , M _ { d } = 0.29 \pm 0.08 M _ { \odot } , and M _ { d } = 0.51 \pm 0.13 M _ { \odot } for G11.2 - 0.3 , G21.5 - 0.9 , and G29.7 - 0.3 respectively .
We derive the dust emissivity index for the PWN ejecta dust in G21.5 - 0.3 to be \beta = 1.4 \pm 0.5 compared to dust in the surrounding medium where \beta = 1.8 \pm 0.1 .