Understanding the environment of a supernova explosion and its<br /><br /><br />
consequent evolution is crucial in understanding the Galactic<br /><br /><br />
ecology. The diverse characteristics of supernova remnants (SNRs) <br /><br /><br />
reflect the nature of the progenitor star, of the explosion itself, <br /><br /><br />
and of the ambient medium. In this talk, I will present observational <br /><br /><br />
studies of two Galactic SNRs, Tycho and IC 443, focusing on <br /><br /><br />
their interaction with the ambient medium.<br /><br /><br />
From observations of Tycho, we discovered a thin (<10^17 cm) <br /><br /><br />
shock precursor, whose primary candidate is a cosmic ray (CR) precursor. <br /><br /><br />
The observed properties of the precursor suggest efficient <br /><br /><br />
CR acceleration in Tycho. IC 443 is the first and most studied SNR <br /><br /><br />
interacting with molecular clouds. Our results indicate that the remnant<br /><br /><br />
is interacting with small (~1arc min) isolated molecular clouds, which are likely to be<br /><br /><br />
remnants of the parental molecular clouds destroyed during the pre-SN evolution.<br /><br /><br />
From the line characteristics of shocked molecular clumps, we study <br /><br /><br />
an evolution of shocked molecular clumps. <br /><br /><br />