The North Polar Spur: Detection of Nitrogen Enhancement with Suzaku
Abstract
We present Suzaku observations of the North Polar Spur (NPS), a region of enhanced soft X-ray and radio emission projected above the plane of the Galaxy, likely produced by combined supernovae and stellar winds from the nearby Sco-Cen OB association. The exceptional sensitivity and spectral resolution of the Suzaku/XIS below 1 keV allow unprecedented probing of low-energy spectral lines, and we have detected highly-ionized nitrogen toward the NPS for the first time. The best-fit emission model implies a hot (kT~0.3 keV), CIE plasma with an enhanced nitrogen abundance ratio of N/O = 4.0-0.5+0.4 solar. This N abundance is best explained by enrichment from stellar material that has been processed by AGB stars undergoing the CNO cycle. Due to the time required to develop AGB stars, we conclude that this enhancement cannot be caused by the Sco-Cen OB association, but may result from a previous enrichment episode in the solar neighborhood.
- Publication:
-
The Local Bubble and Beyond II
- Pub Date:
- August 2009
- DOI:
- 10.1063/1.3211821
- Bibcode:
- 2009AIPC.1156..241M
- Keywords:
-
- 95.80.+p;
- 98.58.Ca;
- 97.10.Me;
- 97.60.Bw;
- 98.35.Jk;
- Astronomical catalogs atlases sky surveys databases retrieval systems archives etc.;
- Interstellar dust grains;
- diffuse emission;
- infrared cirrus;
- Mass loss and stellar winds;
- Supernovae;
- Galactic center bar circumnuclear matter and bulge