Observational Evidence of Dust Evolution in Supernova Remnants: Size Redistribution Toward Larger Grains in Early Sedov Phase

Abstract: Recent observations have revealed that dust is widespread and abundant in galaxies up to $z\,{\backsimeq}\,8$, significantly influencing their appearance and spectral properties. In the early Universe, dust is thought to form primarily in supernova (SN) ejecta, but also undergoes destruction by the reverse shock. Studying dust in local supernova remnants (SNRs) of different sizes and ages thus provides key constraints on dust formation and evolution during cosmic dawn. Using the newly released 3D $R_{\rm V}$ map, we derived local $R_{\rm V} \equiv A_{\rm V}/E(B-V)$ values for dust in 14 Galactic SNRs in the early Sedov phase and their surrounding interstellar medium (ISM). For the first time, we detect a moderately strong positive correlation between the difference in SNR and ISM $R_{\rm V}$ ($\Delta R_{\rm V}$) and SNR radius ($R_{\rm SNR}$), with a Spearman coefficient of $r_{\rm s}\,{=}\,0.62\,{\pm}\,0.14$. This trend offers direct observational evidence for a redistribution of dust grain sizes toward larger grains during SN shock processing, consistent with theoretical models. Our findings provide essential observational constraints on dust size evolution in SNRs and important implications for understanding the rapid enrichment and survival of dust in the early Universe.