Far UV and Optical Emissions from Three Very Large Supernova Remnants Located at Unusually High Galactic Latitudes. (arXiv:2102.12599v2 [astro-ph.HE] UPDATED)

Far UV and Optical Emissions from Three Very Large Supernova Remnants Located at Unusually High Galactic Latitudes. (arXiv:2102.12599v2 [astro-ph.HE] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Fesen_R/0/1/0/all/0/1">Robert A. Fesen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Drechsler_M/0/1/0/all/0/1">Marcel Drechsler</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weil_K/0/1/0/all/0/1">Kathryn E. Weil</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Strottner_X/0/1/0/all/0/1">Xavier Strottner</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Raymond_J/0/1/0/all/0/1">John C. Raymond</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rupert_J/0/1/0/all/0/1">Justin Rupert</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Milisavljevic_D/0/1/0/all/0/1">Dan Milisavljevic</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Subrayan_B/0/1/0/all/0/1">Bhagya M. Subrayan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cicco_D/0/1/0/all/0/1">Dennis di Cicco</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Walker_S/0/1/0/all/0/1">Sean Walker</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mittelman_D/0/1/0/all/0/1">David Mittelman</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ludgate_M/0/1/0/all/0/1">Mathew Ludgate</a>

Galactic supernova remnants (SNRs) with angular dimensions greater than a few
degrees are relatively rare, as are remnants located more than ten degrees off
the Galactic plane. Here we report a UV and optical investigation of two
previously suspected SNRs more than ten degrees in both angular diameter and
Galactic latitude. One is a proposed remnant discovered in 2008 through 1420
MHz polarization maps near Galactic coordinates $l$ = 353, $b$ = $-$34. GALEX
far UV (FUV) and H$alpha$ emission mosaics show the object’s radio emission
coincident with a 11 x 14 degree shell of UV filaments which surrounds a
diffuse H$alpha$ emission ring. Another proposed high latitude SNR is the 20 x
26 degree Antlia nebula (G275.5+18.4) discovered in 2002 through low-resolution
all-sky H$alpha$ and ROSAT soft X-ray emissions. GALEX UV and H$alpha$
mosaics along with optical spectra indicate the presence of shocks throughout
the Antlia nebula with estimated shock velocities of 70 to over 100 km
s$^{-1}$, and we present evidence that it has collided with the northeast rim
of the Gum Nebula. We find both of these nebulae are bona fide SNRs with ages
less than 10$^{5}$ yr despite their unusually large angular dimensions. Using
FUV and optical spectra and images, we also report finding an apparent new,
high latitude SNR (G249.7+24.7) 4.5 degrees in diameter based on its UV and
optical emission properties. We find this remnant’s distance to be less than
400 pc based on the detection of red and blue Na I absorption features in the
spectra of two background stars.

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