Astrophys. J., 804, 63 (2015/May-1)
Optical spectroscopy of supernova remnants in M81 and M82.
LEE M.G., SOHN J., LEE J.H., LIM S., JANG I.S., KO Y., KOO B.-C., HWANG N., KIM S.C. and PARK B.-G.
Abstract (from CDS):
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 and dLog ([S ii]/Hα)/dLog R = -0.016±0.008 dex/kpc, 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, 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.
galaxies: abundances - galaxies: individual: (M81, M82) - galaxies: ISM - galaxies: spiral
Tables 1-2: [LSL2015] LNN (Nos L01-L06), [LSL2015] M81HII-L1 N=1, [LSL2015] M82-LN (Nos L1-L2).
erratum vol. 842, art. 69 (2017)
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