Program: GN-2014B-Q-83

As the host to more recorded supernovae (nine in the past century) than any other galaxy, \ngal\ is a unique venue for studying young (and old) supernova remnants (SNRs). Using deep emission-line images of \ngal\ we obtained from WIYN, we have identified 148 new emission nebulae through their high \sii:\ha\ ratios, indicating that they are strong SNR candidates. This is over 5 times as many as have previously been identified, yet of the 175 total objects, only 6 have been spectroscopically confirmed. We propose multislit spectroscopy from GMOS-N to study the majority of those with no spectra to date. Some 26 are essentially unresolved in our images (diameters $\lesssim 1\arcsec$ = 27 pc at \ngal) and hence probably are relatively young. Several are also coincident with soft X-ray sources (a further indicator of youthful vigor) and have strong \oiii\ emission. Some may be rare, ejecta-dominated core-collapse SNRs akin to Cas A, where ``fresh" nucleosynthesis products can be seen. Only spectroscopy, to look for {\em broad} emission lines from fast-moving ejecta, can confirm this. We will include spectra of two of the nine recorded SNe in \ngal---the first late-time spectrum of SN\,2004et, and the first of SN\,1980K with high signal-to-noise---adding to the extremely small number of spectra for SNRs only a few decades old. Finally we will use the \nii:\ha\ ratio in a large number of ISM-dominated SNRs to map the N abundance and its gradient across the disk of \ngal, and we will use archival {\em HST} images to identify the stellar environments that produced the SNe whose remnants we see today.