Andromeda XVIII

Andromeda XVIII
Andromeda XVIII
	DSS image of Andromeda XVIII
Observation data (J2000 epoch)
Constellation	Andromeda
Right ascension	00h 02m 14.5s
Declination	+45° 05′ 20″
Heliocentric radial velocity	−337.2 km/s
Distance	4,420 ± 290 kly (1,355 ± 88 kpc)
Group or cluster	Local Group
Apparent magnitude (V)	15.50 ± 0.24
Absolute magnitude (V)	−10.41 ± 0.28
Characteristics
Type	dSph
Mass	4.2×106 ± 0.3×106 M☉
Half-light radius (physical)	325 ± 24
Other designations
	PGC 5056918

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]}

References

^ ^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.
^ ^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.
^ ^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.
^ 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.
^ "NAME Andromeda XVIII". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 19 September 2017.

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[McConnachie-1] 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.

[Kvasova-2] 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.

[Makarova-3] 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.

[Collins-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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v t e Andromeda Galaxy
Location	Andromeda Galaxy → Andromeda subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each → may be read as "within" or "part of".	Andromeda Galaxy
Satellite galaxies	M32 M110 NGC 185 NGC 147 Andromeda I Andromeda II Andromeda III Andromeda IV* Andromeda V Andromeda VI Andromeda VII Andromeda VIII Andromeda IX Andromeda X Andromeda XI Andromeda XII Andromeda XIII Andromeda XIV Andromeda XV Andromeda XVI Andromeda XVII Andromeda XVIII Andromeda XIX Andromeda XX Andromeda XXI Andromeda XXII Andromeda XXIII Andromeda XXIV Andromeda XXV Andromeda XXVI Andromeda XXVII Andromeda XXVIII Andromeda XXIX Triangulum subgroup* *It is uncertain whether these are companion galaxies of the Andromeda Galaxy
Catalogued stars	AE Andromedae AF Andromedae M31-RV
Other	Andromeda–Milky Way collision S Andromedae Mayall II M32p NGC 206 3XMM J004232.1+411314
Category

See also

References