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Andromeda XVIII

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Andromeda XVIII
DSS image of Andromeda XVIII
Observation data (J2000 epoch)
ConstellationAndromeda
Right ascension00h 02m 14.5s[1]
Declination+45° 05′ 20″[1]
Heliocentric 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]

It was announced in 2010 that the orbiting galaxies lie close to a plane running through M31's center.[citation needed]

See also

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References

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  1. ^ a b c McConnachie, Alan W; Huxor, Avon; Martin, Nicolas F; Irwin, Mike J; Chapman, Scott C; Fahlman, Gregory; Ferguson, Annette M. N; Ibata, Rodrigo A; Lewis, Geraint F; Richer, Harvey; Tanvir, Nial R (2008). "A Trio of New Local Group Galaxies with Extreme Properties". The Astrophysical Journal. 688 (2): 1009. arXiv:0806.3988. Bibcode:2008ApJ...688.1009M. doi:10.1086/591313. S2CID 16950090.
  2. ^ a b 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. arXiv:2404.11804. Bibcode:2024ApJ...972..180K. doi:10.3847/1538-4357/ad55f0.
  3. ^ a b c 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. arXiv:1609.09706. Bibcode:2017MNRAS.464.2281M. doi:10.1093/mnras/stw2502. S2CID 119275751.
  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; Peñarrubia, Jorge; Arimoto, Nobuo; Casey, Caitlin M; Ferguson, Annette M. N; Koch, Andreas; McConnachie, Alan W; Tanvir, Nial (2013). "A Kinematic Study of the Andromeda Dwarf Spheroidal System". The Astrophysical Journal. 768 (2): 172. arXiv:1302.6590. Bibcode:2013ApJ...768..172C. doi:10.1088/0004-637X/768/2/172. S2CID 67749084.
  5. ^ "NAME Andromeda XVIII". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 19 September 2017.


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