OPTICAL SPECTROSCOPY OF SUPERNOVA REMNANTS IN M81 AND M82
- Astronomy Program, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul 151-742 (Korea, Republic of)
- Korea Astronomy and Space Science Institute, Daejeon, 305-348 (Korea, Republic of)
We present spectroscopy of 28 supernova remnant (SNR) candidates as well as one H ii region in M81 and two SNR candidates in M82. Twenty-six of the M81 candidates turn out to be genuine SNRs, and two in M82 may be shocked condensations in the galactic outflow or SNRs. The distribution of [N ii]/Hα ratios of M81 SNRs is bimodal. M81 SNRs are divided into two groups in the spectral line ratio diagrams: an [O iii]-strong group and an [O iii]-weak group. The latter are larger and may have faster shock velocities. [N ii]/Hα ratios of the SNRs show a strong correlation with [S ii]/Hα ratios. They show a clear radial gradient in their [N ii]/Hα and [S ii]/Hα ratios: dLog ([N ii]/Hα)/dLog R = −0.018 ± 0.008 dex kpc{sup −1} and dLog ([S ii]/Hα)/dLog R = −0.016 ± 0.008 dex kpc{sup −1}, where R is the deprojected galactocentric distance. We estimate the nitrogen and oxygen abundances of the SNRs from comparison with shock-ionization models. We obtain a value for the nitrogen radial gradient of dLog(N/H)/dLog R= −0.023 ± 0.009 dex kpc{sup −1}, and find little evidence for an oxygen gradient. This nitrogen abundance shows a gradient that is a few times flatter than those of the planetary nebulae and H ii regions. We find that five SNRs are matched with X-ray sources. Their X-ray hardness colors are consistent with thermal SNRs.
- OSTI ID:
- 22522458
- Journal Information:
- Astrophysical Journal, Vol. 804, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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