OPTICAL SPECTROSCOPY OF SUPERNOVA REMNANTS IN M81 AND M82

ABSTRACT 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...

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Bibliographic Details
Published in:The Astrophysical journal 2015-05, Vol.804 (1), p.1-22
Main Authors: Lee, Myung Gyoon, Sohn, Jubee, Lee, Jong Hwan, Lim, Sungsoon, Jang, In Sung, Ko, Youkyung, Koo, Bon-Chul, Hwang, Narae, Kim, Sang Chul, Park, Byeong-Gon
Format: Article
Language:English
Subjects:
ABSORPTION SPECTROSCOPY
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
COLOR
COMPARATIVE EVALUATIONS
Condensing
Correlation
CORRELATIONS
COSMIC X-RAY SOURCES
DIAGRAMS
ELEMENT ABUNDANCE
EMISSION SPECTROSCOPY
GALAXIES
galaxies: abundances
galaxies: individual (M81, M82)
galaxies: ISM
galaxies: spiral
Hardness
HYDROGEN
NITROGEN
OXYGEN
PLANETARY NEBULAE
Spectroscopy
SULFUR
SUPERNOVA REMNANTS
X RADIATION
X-ray sources
X-rays
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Summary:ABSTRACT 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]/H 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]/H ratios of the SNRs show a strong correlation with [S ii]/H ratios. They show a clear radial gradient in their [N ii]/H and [S ii]/H ratios: dLog ([N ii]/H )/dLog R = −0.018 0.008 dex kpc−1 and dLog ([S ii]/H )/dLog R = −0.016 0.008 dex kpc−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−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.
ISSN:0004-637X
1538-4357
1538-4357
DOI:10.1088/0004-637X/804/1/63