The Nature of the Young Supernova Remnant S8 in the Dwarf Galaxy IC 1613
Abstract
We present subarcsecond optical images and low- to moderate-resolution spectra of the compact, X-ray, and optically bright supernova remnant known as S8 in the nearby dwarf galaxy IC 1613. Deep Hα images of the remnant show a sharply defined crescent-shaped nebula, while narrow passband images reveal a coincident and unexpectedly bright continuum nebulosity exhibiting a size and morphology like that seen for the remnant's line emissions. Low-dispersion spectra covering 3600-9000 Šshow numerous low-ionization line emissions such as [O I] and [Fe II], along with higher-ionization emission lines including He II and optical coronal lines [Fe VIII], [Fe X], [Fe XI], and [Fe XIV]. This suggests the presence of a wide range of shock velocities from ∼50 to over 350 km s-1, corresponding to preshock densities of ∼1-30 cm-3. Higher-resolution spectra indicate an expansion velocity around 180 km s-1 with an ∼45 km s-1 wide central cavity. The Hα emission spans rest-frame velocities of +120 to -240 km s-1, and we estimate a total nebula mass of 119 ± 34 M⊙. We conclude that S8 is a relatively young supernova remnant (≃2700-4400 yr) exhibiting properties remarkably like those seen in the young LMC remnant N49, including age, physical size, shock velocities, filament densities, optical line strengths, X-ray and optical luminosities, and coronal line and continuum emissions.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2020
- DOI:
- 10.3847/1538-4357/abb243
- arXiv:
- arXiv:2008.08690
- Bibcode:
- 2020ApJ...902...19F
- Keywords:
-
- Emission nebulae;
- Interstellar medium;
- Supernova remnants;
- Optical observation;
- Spectral line identification;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 19 pages, 6 figures, and 5 tables. Accepted for publication in ApJ