Astronomy:Andromeda XVIII

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Andromeda XVIII
DSS image of Andromeda XVIII
Observation data (J2000 epoch)
ConstellationAndromeda
Right ascension 00h 02m 14.5s[1]
Declination+45° 05′ 20″[1]
Helio radial velocity−337.2 km/s[2]
Distance4,420 ± 290 kly (1,355 ± 88 kpc)
Group or clusterLocal Group
Apparent magnitude (V)15.50 ± 0.24[3]
Absolute magnitude (V)−10.41 ± 0.28[3]
Characteristics
TypedSph[1]
Mass4.2×106 ± 0.3×106[3] M☉
Half-light radius (physical)325 ± 24[4]
Other designations
PGC 5056918[5]

Andromeda XVIII, discovered in 2008, is a dwarf spheroidal galaxy (has no rings, low luminosity, much dark matter, little gas or dust), which is a satellite of the Andromeda Galaxy (M31). It is one of the 14 known dwarf galaxies orbiting M31. It is relatively isolated, being about 1.8 million light-years (579 kpc) away. However, for an isolated dwarf galaxy it is also unusually quiescent. This suggests that Andromeda XVIII is a backsplash galaxy, a galaxy that once had a close orbital encounter with a more massive galaxy which stripped it of much of its star-forming matter. However, alternative hypotheses are also possible for Andromeda XVIII.[2]


See also

References

  1. ↑ 1.0 1.1 1.2 McConnachie, Alan W; Huxor, Avon; Martin, Nicolas F; Irwin, Mike J; Chapman, Scott C; Fahlman, Gregory; Ferguson, Annette M. N; Ibata, Rodrigo A et al. (2008). "A Trio of New Local Group Galaxies with Extreme Properties". The Astrophysical Journal 688 (2): 1009. doi:10.1086/591313. Bibcode: 2008ApJ...688.1009M. 
  2. ↑ 2.0 2.1 Kvasova, Kateryna A.; Kirby, Evan N.; Beaton, Rachael L. (2024). "Kinematics and Metallicity of the Dwarf Spheroidal Galaxy Andromeda XVIII". The Astrophysical Journal 972 (2): 180. doi:10.3847/1538-4357/ad55f0. Bibcode: 2024ApJ...972..180K. 
  3. ↑ 3.0 3.1 3.2 Makarova, L. N; Makarov, D. I; Karachentsev, I. D; Tully, R. B; Rizzi, L (2017). "Star formation history of And XVIII: a dwarf spheroidal galaxy in isolation". Monthly Notices of the Royal Astronomical Society 464 (2): 2281. doi:10.1093/mnras/stw2502. Bibcode: 2017MNRAS.464.2281M. 
  4. ↑ Collins, Michelle L. M; Chapman, Scott C; Rich, R. Michael; Ibata, Rodrigo A; Martin, Nicolas F; Irwin, Michael J; Bate, Nicholas F; Lewis, Geraint F et al. (2013). "A Kinematic Study of the Andromeda Dwarf Spheroidal System". The Astrophysical Journal 768 (2): 172. doi:10.1088/0004-637X/768/2/172. Bibcode: 2013ApJ...768..172C. 
  5. ↑ "NAME Andromeda XVIII". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NAME+Andromeda+XVIII. 




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