Scutum Supershell
 | This article contains an excessive amount of intricate detail. (September 2026) |
| Nebula | |
|---|---|
| Superbubble | |
 Location of the Scutum Supershell on a map | |
| Observation data: J2000 epoch | |
| Right ascension | 18h 42m 00s[1] |
| Declination | −18° 00′ 00″[1] |
| Distance | ~11,000 ly |
| Constellation | Scutum and Sagittarius |
| Physical characteristics | |
| Radius | ~472 ly |
| Designations | GS 018–04+44[1] |
Scutum Supershell (also known as Scutum Superbubble) is a giant expanding bubble of hot gas and hydrogen in space. It is located ~11,000 ly away from the earth inside the Scutum-Centaurus Arm of the Milky Way. The superbubble is formed by exploding stars and strong cosmic winds. It was discovered by astronomer Matthew B. Callaway and his colleagues in 1999.[2]
Physical Structure
[edit]Scutum supershell is large and has a diameter of approximately 290 pc and extends about 400 pc from the galactic plane, which was derived from a kinematic distance of 3.3 kpc calculated from using D.P. Clemen's formula.[3] Because the superbubble is not cleary distinguishable, a radius of ~29 pc is estimated. Studies indicate that the infrared emission shows the presence of molecular hydrogen in the high column density regions.[4] The infrared emissions 100 μm and 60 μm are the main emission lines in infrared with a surface brightness 6.23 MJy sr⁻¹ and 1.64 MJy sr⁻¹ respectively. The scutum supershell interior has an X-ray luminosity of ~6–8 x 10 ergs s⁻¹, ~1–4 x 10³⁶ ergs s⁻¹ for the blown out top, and ~0.3–17 x 10³⁶ ergs s⁻¹ for the high-latitude feature, these values come from a much more difficult method of determining X-ray luminosity.[2]
Scutum supershell is mostly visible through H I, with the top of the shell appearing to be blown away, leaving a column of neutral hydrogen and superheated gas pouring directly into the galactic plane at l = 18° and lying between b = -9° and b = -12°, which created a high-latitude cloud that has a distance of ~630 pc from the galactic plane. The high-latitude cloud has an estimated X-ray luminosity of ~1³⁶ ergs s⁻¹. The high-latitude cloud was formed through supernova remnants, H II regions, and OB associations.[5] Two O-type Blue giant stars HD 175754 (O8II(n)((f))p)[6] and HD 175876 (O6.5III(n)(f))[6] most likely formed in this very cloud and were ejected from it, or formed recently at their current distance.[7][2] The Far Ultraviolet Spectroscopic Explorer (FUSE) detected highly ionized absorption lines like O IV, Si IV, and C IV near the blowout spot.[5]
H II regions S45 and S55 are H II regions that dominate the Hα emissions with the brightest Hα feature located in S45 which lies at +20 km s⁻¹. The close proximity of S45 causes some confusion regarding membership in the superbubble. S55 is most likely in the superbubble, as it has an H I column density of 1.21 x 10²² cm⁻¹ using conversion ratio from Diplas & Savage.[8][9][2]
The galactic worms GW 14.9-1.6 and GW 16.9-3.8 are elongated vertical filamentary structures of neutral hydrogen (H I) that form the walls of the superbubble. GW 16.9-3.8 influences the rightmost edge of the bow-shock Hα emission and overlaps with [S II] line emission, 4.85 GHz radio, and both 60μm and 100μm infrared emissions.[10] Simulations show that the outflow and bow-shock are likely formed by many supernovae events.[10] X-ray binary LS 5039 is also speculated as the contributing event from the supernova or hypernova and formation of a magnetar or black hole in the system.[10]
References
[edit]- 1 2 3 "NAME Scutum Supershell". simbad.cds.unistra.fr.
- 1 2 3 4 Callaway, B.; Tufte, L.; Benjamin, A.; Savage, D.; Haffner, L. (April 2000). "Observational Evidence of Supershell Blowout in GS 018-04+44: The Scutum Supershell". The Astrophysical Journal. 532 (2): 943–969. Bibcode:2000ApJ...532..943C. doi:10.1086/308601.
- ↑ Clemens, D. P. (August 1985). "Massachusetts-Stony Brook Galactic plane CO survey: the galactic disk rotation curve". The Astrophysical Journal. 295 (422–436): 422. Bibcode:1985ApJ...295..422C. doi:10.1086/163386.
- ↑ Odegard, N.; Reach, T.; Wall, F. (November 1998). "Infrared Excess and Molecular Clouds: A Comparison of New Surveys of Far-Infrared and H I 21 Centimeter Emission at High Galactic Latitudes". The Astrophysical Journal. 507 (2): 507–525. arXiv:astro-ph/9802169. Bibcode:1998ApJ...507..507R. doi:10.1086/306357.
- 1 2 Sterling, N. C.; Savage, B. D.; Richter, P.; Fabian, D.; Sembach, K. R. (November 2001). "FUSE Observations of O VI Overlying the Scutum Supershell". The Astrophysical Journal. 567: 954–362. arXiv:astro-ph/0111226. doi:10.1086/338421.
- 1 2 Sota, A.; Apellániz, J. Maíz; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J. (2014-02-25). "The Galactic O-Star Spectroscopic Survey (Gosss). Ii. Bright Southern Stars". The Astrophysical Journal Supplement Series. 211 (1): 10. arXiv:1312.6222. Bibcode:2014ApJS..211...10S. doi:10.1088/0067-0049/211/1/10. ISSN 0067-0049.
- ↑ Savage, D.; Sembach, R.; Howk, J. (February 2001). "STIS and GHRS Observations of Warm and Hot Gas Overlying the Scutum Supershell (GS 018-04+44)". The Astrophysical Journal. 547 (2): 907–921. Bibcode:2001ApJ...547..907S. doi:10.1086/318411.
- ↑ Diplas, A.; Savage, B. D. (May 1994). "An IUE Survey of Interstellar H i Lyman-Alpha Absorption. II. Interpretations". The Astrophysical Journal. 427: 274. Bibcode:1994ApJ...427..274D. doi:10.1086/174139.
- ↑ Cardelli, A.; Clayton, C.; Mathis, S. (October 1989). "The Relationship between Infrared, Optical, and Ultraviolet Extinction". The Astrophysical Journal. 345: 245. Bibcode:1989ApJ...345..245C. doi:10.1086/167900.
- 1 2 3 Alsulami, R.; Einecke, S.; Rowell, G. P.; McGee, P. K.; Filipović, M. D.; Seitenzahl, I. R.; Stupar, M.; Collins, T.; Fukui, Y. (2024-10-21). "Investigating Unusual H$α$ Features towards the Scutum Supershell". Publications of the Astronomical Society of Australia. 41 e098. arXiv:2410.15712. Bibcode:2024PASA...41...98A. doi:10.1017/pasa.2024.99.