2008ApJS..174..379F

We present a comprehensive imaging and spectroscopic survey of optical emission knots associated with the young Galactic supernova remnant 3C 58. Hα images show hundreds of clumpy filaments and knots arranged in a complex structure covering a nearly circular area roughly 400" in diameter. A quite different emission structure is seen in [O III], where the brightest features are less clumpy and largely confined to the remnant's northwest quadrant. Measured radial velocities of over 450 knots reveal two distinct kinematic populations; one with average and peak expansion velocities of 770 and 1100 km/s, respectively, forming a thick shell, and the other showing|v|≤250 km/s. High-velocity knots (|v|≥500 km/s) exhibit a strong bipolar expansion pattern with redshifted and blueshifted knots located in northeastern and southwestern regions, respectively. These knots also show strong [N II]/Hα line emission ratios, suggesting enhanced N/H. In contrast, the slower expanding knot population shows much lower [N II]/Hα line ratios and likely represents circumstellar mass loss material from the 3C 58 progenitor. Proper-motion estimates using images spanning a 28 yr time interval suggest positional shifts of between 0.5" and 2.0", implying proper motions of 0.02"-0.07"/yr. These values agree with previous estimates but are much less than the ~0.2"/yr expected if 3C 58 were associated with historic guest star of 1181 CE.