Detection of Extensive Optical Emission from the Extremely Radio Faint Galactic Supernova Remnant G182.4+4.3. (arXiv:1905.08901v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Fesen_R/0/1/0/all/0/1">Robert Fesen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Neustadt_J/0/1/0/all/0/1">Jack Neustadt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+How_T/0/1/0/all/0/1">Thomas How</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Black_C/0/1/0/all/0/1">Christine Black</a>
Wide-field Halpha images of the radio faint Galactic supernova remnant
G182.4+4.2 reveal a surprisingly extensive and complex emission structure, with
an unusual series of broad and diffuse filaments along the remnant’s
southwestern limb. Deep [O III] 5007 images reveal no appreciable remnant
emission with the exception of a single filament coincident with the
westernmost of the broad southwest filaments. The near total absence of [O III]
emission suggests the majority of the remnant’s optical emission arises from
relatively slow shocks (<70 km/s), consistent with little or no associated
X-ray emission. Low-dispersion optical spectra of several regions in the
remnant's main emission structure confirm a lack of appreciable [O III]
emission and indicate [S II]/Halpha line ratios of 0.73 - 1.03, consistent with
a shock-heated origin. We find G182.4+4.2 to be a relatively large (d~50 pc at
4 kpc) and much older (age ~40 kyr) supernova remnant than previously
estimated, whose weak radio and X-ray emissions are related to its age, low
shock velocity, and location in a low density region some 12 kpc out from the
Galactic centre.
Wide-field Halpha images of the radio faint Galactic supernova remnant
G182.4+4.2 reveal a surprisingly extensive and complex emission structure, with
an unusual series of broad and diffuse filaments along the remnant’s
southwestern limb. Deep [O III] 5007 images reveal no appreciable remnant
emission with the exception of a single filament coincident with the
westernmost of the broad southwest filaments. The near total absence of [O III]
emission suggests the majority of the remnant’s optical emission arises from
relatively slow shocks (<70 km/s), consistent with little or no associated
X-ray emission. Low-dispersion optical spectra of several regions in the
remnant’s main emission structure confirm a lack of appreciable [O III]
emission and indicate [S II]/Halpha line ratios of 0.73 – 1.03, consistent with
a shock-heated origin. We find G182.4+4.2 to be a relatively large (d~50 pc at
4 kpc) and much older (age ~40 kyr) supernova remnant than previously
estimated, whose weak radio and X-ray emissions are related to its age, low
shock velocity, and location in a low density region some 12 kpc out from the
Galactic centre.
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