Sextans B

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Galaxy
Sextans B
{{{Card text}}}
Hubble shot
Hubble shot
AladinLite
Constellation sextant
Position
equinox :  J2000.0 , epoch : J2000.0
Right ascension 10 h 00 m 00.1 s
declination + 05 ° 19 ′ 56 ″
Appearance
Morphological type (d) In the IV-V  
Brightness  (visual) 11.9 likes
Angular expansion 5 ′, 1 × 3 ′, 5
Physical data
Affiliation Local group  
Radial velocity (301 ± 1) km / s  
distance (4,440,000 ± 230,000) Lj /
(1,360,000 ± 70,000) pc
Dimensions 2 × 10 8 M ☉
history
Catalog names
UGC  5373 • PGC  28913 • MCG  + 01-26-005 • DDO 70

Sextans B is an irregular dwarf galaxy of the Ir IV-V type in the constellation Sextans .

Together with the dwarf galaxy Sextans A , it forms a pair on the outer edge of the local group . The galaxy is also showing signs of gravitational binding to the NGC-3109 subgroup .

properties

Sizes

Sextans B is located at a distance of about 1360 k pc from our solar system and is moving away from our sun at a speed of about 301 km / s . It is one of the most distant galaxies in the Local Group.

composition

The dwarf galaxy has a uniform star population , but its interstellar medium is relatively inhomogeneous. The mass of sextans B is estimated to be about 2 × 10 8 M ⊙ , with a proportion of 5.5 × 10 7 M ⊙ of atomic hydrogen .

Star formation

The star formation of the galaxy shows different periods of low activity, interrupted by periods of no activity. However, the existence of variable Cepheid stars in sextans B also indicates current, if only minor, star formation.

Metallicity

The metallicity of sextans B is relatively low. So far, five planetary nebulae have been identified in the dwarf galaxy. It is one of the smallest galaxies in which this could be observed so far. Due to the distance of sextans B , they appear as point sources, but can be identified based on their spectral emission lines . A massive globular star cluster could also be assigned to this dwarf galaxy .

Individual evidence

  1. ↑ a b c d e f NASA / IPAC Extragalactic Database . In: Results for Sex B . Retrieved December 13, 2006.
  2. ↑ SIMBAD Astronomical Database . In: Results for Sextans B . Retrieved February 7, 2010.
  3. ↑ ID Karachentsev, VE Karachentseva, WK Hutch Meier, DI Makarov: A Catalog of Neighboring Galaxies . In: Astronomical Journal . 127, No. 4, 2004, pp. 2031-2068. bibcode : 2004AJ .... 127.2031K . doi : 10.1086 / 382905 .
  4. ↑ Karachentsev, ID; Kashibadze, OG: Masses of the local group and of the M81 group estimated from distortions in the local velocity field . In: Astrophysics . 49, No. 1, 2006, pp. 3-18. bibcode : 2006Ap ..... 49 .... 3K . doi : 10.1007 / s10511-006-0002-6 .
  5. ↑ a b Sidney van den bergh: The galaxies of the Local Group . University of Cambridge, 2000, ISBN 978-0-521-65181-3 , p. 265.
  6. ^ Allan Sandage, Carlson, George: The brightest stars in nearby galaxies. V - Cepheids and the brightest stars in the dwarf galaxy Sextans B Compared with Those in sextans a . In: Astronomical Journal . 90, July 1985, pp. 1019-1026. bibcode : 1985AJ ..... 90.1019S . doi : 10.1086 / 113809 .
  7. ^ Sidney van den Bergh: Stellar Content of Local Group Galaxies - An Introduction . In: The stellar content of Local Group galaxies . 192, 1999, p. 3. bibcode : 1999IAUS..192 .... 3V .
  8. ↑ a b Alexei Y. Kniazev, Grebel, Eva K., Pustilnik, Simon A., Pramskij, Alexander G., Zucker, Daniel B .: Spectrophotometry of Sextans A and B: Chemical Abundances of H II Regions and Planetary Nebulae . In: Astronomical Journal . 130, No. 4, October 2005, pp. 1558-1573. arxiv : astro-ph / 0502562 . bibcode : 2005AJ .... 130.1558K . doi : 10.1086 / 432931 . Retrieved November 28, 2010.
  9. ^ Danielle M. Alloin, Gieren, Wolfgang: Stellar candles for the extragalactic distance scale . University of Cambridge, 2000, ISBN 978-3-540-20128-1 , p. 265.
  10. ↑ a b c d M Tosi, Greggio, L., Marconi, G., Focardi, P .: Star formation in dwarf irregular galaxy - Sextans B . In: Astronomical Journal . 102, September 1991, pp. 951-974. bibcode : 1991AJ .... 102..951T . doi : 10.1086 / 115925 .
  11. ↑ L. Magrini, RLM Corradi, NA Walton, AA Zijlstra, DL Pollaco, JR Walsh, M. Perinotto, DJ Lennon, R. Greimel: The Local Group Census: planetary nebulae in Sextans B . arxiv : astro-ph / 0202516v1 .
  12. ↑ ME Sharina, Puzia, TH; Krylatyh, AS: A Globular Cluster in Sextans B . In: Astronomy and Astrophysics . 62, No. 3, September 2009, pp. 209-216. arxiv : 0704.3908 . bibcode : 2007AstBu..62..209S . doi : 10.1134 / S1990341307030029 .

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