Optical Imaging and Spectroscopy of the Galactic Supernova Remnant 3C 58 (G130.7+3.1)

Abstract

We present a comprehensive imaging and spectroscopic survey of optical emission knots associated with the young Galactic supernova remnant 3C 58. H images show hundreds of clumpy filaments and knots arranged in a complex structure covering a nearly circular area roughly 400 00 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 À1 , respectively, forming a thick shell, and the other showing jvj 250 km s À1. High-velocity knots (jvj ! 500 km s À1) 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]/H line emission ratios, suggesting enhanced N/H. In contrast, the slower expanding knot population shows much lower [N ii]/H 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 00 and 2.0 00 , implying proper motions of 0.02 00 Y0.07 00 yr À1. These values agree with previous estimates but are much less than the %0.2 00 yr À1 expected if 3C 58 were associated with historic guest star of 1181 CE. Subject headingg s: ISM: individual (3C 58)-ISM: kinematics and dynamics-supernova remnants