Summary
Sextans B (also known as UGC 5373 and DDO 70) is an irregular galaxy that may be part of the Local Group, or lie just beyond it. Sextans B is 4.44 million light-years away from Earth and thus is one of the most distant members of the Local Group, if it is indeed a member. It forms a pair with its neighbouring galaxy Sextans A.[4] It is a type Ir IV–V galaxy according to the galaxy morphological classification scheme.[5] Sextans B may also be gravitationally associated with the galaxies NGC 3109 and the Antlia Dwarf.[6]
| Sextans B | |
|---|---|
 | |
| Observation data (J2000 epoch) | |
| Constellation | Sextans |
| Right ascension | 10h 00m 00.1s[1] |
| Declination | +05° 19′ 56″[1] |
| Redshift | 300 ± 0 km/s[1] |
| Distance | 4.44 ± 0.23 Mly (1.36 ± 0.07 Mpc)[2][3] |
| Apparent magnitude (V) | 11.9[1] |
| Characteristics | |
| Type | ImIV–V[1] |
| Apparent size (V) | 5.1′ × 3.5′[1] |
| Other designations | |
| UGC 5373,[1] PGC 28913,[1] DDO 70,[1] Sex B[1] | |
Sextans B has a uniform stellar population,[7] but the interstellar medium in it may be inhomogeneous.[8] Its mass is estimated to be about 2×108 times the mass of the Sun, of which 5.5×107 is in the form of atomic hydrogen.[7] Star formation in the galaxy seems to have proceeded in distinct periods of low intensity, separated by shorter periods of no activity.[7] The existence of Cepheid variables in the galaxy implies that Sextans B contains at least some young stars.[5] The metallicity of Sextans B is very low, with a value of approximately Z = 0.001.[7] Sextans B is receding from the Milky Way with a speed of approximately 300 kilometres per second (190 mi/s),[8] and probably lies just outside the edge of the Local Group, so as its neighbour Sextans A.[9]
Five planetary nebulae have been identified in Sextans B, which is one of the smallest galaxies where planetary nebulae have been observed. These appear point-like and can be identified by their spectral emission lines.[10] It also contains a massive globular cluster.[11]
References edit
- ^ a b c d e f g h i j "NASA/IPAC Extragalactic Database". Results for Sex B. Retrieved 2006-12-13.
- ^ I. D. Karachentsev; V. E. Karachentseva; W. K. Hutchmeier; D. I. Makarov (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal. 127 (4): 2031–2068. Bibcode:2004AJ....127.2031K. doi:10.1086/382905.
- ^ Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6. S2CID 120973010.
- ^ Sandage, Allan; Carlson, George (July 1985). "The brightest stars in nearby galaxies. V – Cepheids and the brightest stars in the dwarf galaxy Sextans B compared with those in Sextans A". Astronomical Journal. 90: 1019–1026. Bibcode:1985AJ.....90.1019S. doi:10.1086/113809.
- ^ a b van den bergh, Sidney (2000). The galaxies of the Local Group. University of Cambridge. p. 265. ISBN 978-0-521-65181-3.
- ^ van den Bergh, Sidney (1999). "Stellar Content of Local Group Galaxies – An Introduction". The Stellar Content of Local Group Galaxies. 192: 3. Bibcode:1999IAUS..192....3V.
- ^ a b c d Tosi, M; Greggio, L.; Marconi, G.; Focardi, P. (September 1991). "Star formation in dwarf irregular galaxies – Sextans B". Astronomical Journal. 102: 951–974. Bibcode:1991AJ....102..951T. doi:10.1086/115925.
- ^ a b Kniazev, Alexei Y.; Grebel, Eva K.; Pustilnik, Simon A.; Pramskij, Alexander G.; Zucker, Daniel B. (October 2005). "Spectrophotometry of Sextans A and B: Chemical Abundances of H II Regions and Planetary Nebulae". Astronomical Journal. 130 (4): 1558–1573. arXiv:astro-ph/0502562. Bibcode:2005AJ....130.1558K. doi:10.1086/432931. S2CID 14176608.
- ^ Alloin, Danielle M.; Gieren, Wolfgang (2000). Stellar candles for the extragalactic distance scale. University of Cambridge. p. 265. ISBN 978-3-540-20128-1.
- ^ Magrini, L.; Corradi, R. L. M.; Walton, N. A.; Zijlstra, A. A.; Pollacco, D. L.; Walsh, J. R.; Perinotto, M.; Lennon, D. J.; Greimel, R. (2002). "The Local Group Census: Planetary nebulae in Sextans B". Astronomy & Astrophysics. 386 (3): 869–873. arXiv:astro-ph/0202516. Bibcode:2002A&A...386..869M. doi:10.1051/0004-6361:20020296. S2CID 16954005.
- ^ Sharina, M.E.; Puzia, T. H.; Krylatyh, A. S. (September 2009). "A globular cluster in the dwarf galaxy Sextans B". Astrophysical Bulletin. 62 (3): 209–216. arXiv:0704.3908. Bibcode:2007AstBu..62..209S. doi:10.1134/S1990341307030029. S2CID 119588326.
External links edit
- Sextans B on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images