Origin of Galactic Spurs: New Insight from Radio/X-Ray All-sky Maps
Abstract
In this study, we analyze giant Galactic spurs seen in both radio and X-ray all-sky maps to reveal their origins. We discuss two types of giant spurs: one is the brightest diffuse emission near the map's center, which is likely to be related to Fermi bubbles (NPSs/SPSs, north/south polar spurs, respectively), and the other is weaker spurs that coincide positionally with local spiral arms in our Galaxy (LAS, Local Arm spur). Our analysis finds that the X-ray emissions, not only from the NPS but also from the SPS, are closer to the Galactic center by ∼5° compared with the corresponding radio emission. Furthermore, larger offsets of 10°-20° are observed in the LASs; however, they are attributed to different physical origins. Moreover, the temperature of the X-ray emission is kT ≃ 0.2 keV for the LAS, which is systematically lower than those of the NPS and SPS (kT ≃ 0.3 keV) but consistent with the typical temperature of Galactic halo gas. We argue that the radio/X-ray offset and the slightly higher temperature of the NPS/SPS X-ray gas are due to the shock compression/heating of halo gas during a significant Galactic explosion in the past, whereas the enhanced X-ray emission from the LAS may be due to the weak condensation of halo gas in the arm potential or star formation activity without shock heating.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2021
- DOI:
- 10.3847/1538-4357/abdb31
- arXiv:
- arXiv:2101.03302
- Bibcode:
- 2021ApJ...908...14K
- Keywords:
-
- X-ray astronomy;
- Interstellar medium;
- Radio astronomy;
- Superbubbles;
- Spiral arms;
- 1810;
- 847;
- 1338;
- 1656;
- 1559;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 11 pages, 4 figures, accepted for publication in ApJ