  In order to better characterize the rich supernova remnant (SNR) population
of M83 (NGC 5236), we have obtained high-resolution (about 85 km/s) spectra of
119 of the SNRs and SNR candidates in M83 with Gemini/GMOS, as well as new
spectra of the young SNRs B12-174a and SN1957D. Most of the SNRs and SNR
candidates have [S II]:H{\alpha} ratios that exceed 0.4. Combining these
results with earlier studies we have carried out with MUSE and at lower
spectroscopic resolution with GMOS, we have confirmed a total of 238 emission
nebulae to be SNRs on the basis of their [S II]:H{\alpha} ratios, about half of
which have emission lines that show velocity broadening greater than 100 km/s,
providing a kinematic confirmation that they are SNRs and not H II regions.
Looking at the entire sample, we find a strong correlation between velocity
widths and the line ratios of [O I]{\lambda}6300:H{\alpha}, [N
II]{\lambda}6584:H{\alpha} and [S II]{\lambda}{\lambda}6716,6731:H{\alpha}. The
density-sensitive [S II]{\lambda}6716:{\lambda}6731 line ratio is strongly
correlated with SNR diameter, but not with the velocity width. We discuss these
results in the context of previously published shock models.
