Type IIP supernovae ( SNe IIP ) are the most common class of core-collapse SNe .
They often show rapid increase of polarization degree in the late phase .
This time evolution is generally believed to originate from the emergence of an inner aspherical core , while an effect of polarized-scattered echoes by circumstellar ( CS ) dust around the SN may also substantially contribute to this polarization feature .
In this study , we examine the effects of the scatted echoes on the SN polarization through radiative transfer simulations for various geometry and amount of CS dust .
It has been found that asymmetrically-distributed CS dust , which is generally inferred for red supergiants , could reproduce the observed polarization features .
We have applied our results to SNe 2004dj and 2006ov , deriving the geometry and amount of CS dust to explain their observed polarization features in this scenario .
For both SNe , the blob-like or bipolar distribution of CS dust rather than the disk-like distribution is favored .
The derived dust mass M _ { \mathrm { dust } } in the blob model ( the bipolar CS dust model ) for SNe 2004dj and 2006ov are \sim 7.5 \times 10 ^ { -4 } M _ { \odot } ( \sim 8.5 \times 10 ^ { -4 } M _ { \odot } ) and \sim 5.2 \times 10 ^ { -4 } M _ { \odot } ( \sim 1.3 \times 10 ^ { -3 } M _ { \odot } ) , respectively .
Even in the case where this process would not play a dominant role in the observed polarization signals , this effect should in principle contribute to it , the strength of which depends on the nature of CS dust .
Therefore , this effect must be taken into account in discussing multi-dimensional structure of an SN explosion through polarimetric observations .