Properties of Optically Selected Supernova Remnant Candidates in M33
  Narrow band images covering strong emission lines are efficient to survey
supernova remnants (SNRs) in nearby galaxies. Using the narrow band images
provided by the Local Group Galaxy Survey we searched for SNRs in M33. Culling
the objects with enhanced [SII]/Ha and round morphology in the
continuum-subtracted Ha and [SII] images, we produce a list of 199 sources.
Among them 79 are previously unknown. Their progenitor and morphology types
were classified. A majority of the sample (170 objects) are likely remnants of
core-collapse SNe, and 29 are remnants of Type Ia SNe. The cumulative size
distribution of these objects is found to be similar to that of the M31
remnants derived in the similar way. We obtain a power law slope, a = 2.38 +
0:05. Thus a majority of the sources are considered to be in the Sedov-Taylor
phase, consistent with previous findings. The histogram of the emission line
ratio ([SII]/Ha) of the remnants has two concentrations at [SII]/Ha ~0.55 and
~0.8, as in M31. Interestingly Lx (and L20cm) of the compact center-bright
objects are correlated with their optical luminosity. The remnants with X-ray
emission have brighter optical surface brightness and smaller diameters than
those without X-ray emission.
