Andromeda XXI

Andromeda XXI
Andromeda XXI
Observation data
Constellation	Andromeda
Right ascension	23h 54m 47.7s
Declination	+42° 28′ 15″
Distance	859 ± 51 kiloparsecs (2.80 ± 0.17 Mly)
Apparent magnitude (V)	9.9 ± 0.6
Characteristics
Type	dSph
Notable features	Satellite galaxy; of Andromeda
Other designations
	Andromeda XXI, And XXI, And 21

Andromeda XXI (And 21, And XXI) is a moderately bright dwarf spheroidal galaxy about 859 ± 51 kiloparsecs (2.80 ± 0.17 Mly) away from the Sun in the constellation Andromeda. It is the fourth largest Local Group dwarf spheroidal galaxy.

This large satellite of the Andromeda Galaxy (M31) has a half-light radius of nearly 1 kpc.^[2]

The discovery arose from the first year data of a photometric survey of the M31/M33 subgroupings of the Local Group by the Pan-Andromeda Archaeological Survey (PAndAS). This survey was conducted with the Megaprime/MegaCam wide-field camera mounted on the Canada-France-Hawaii Telescope.

Andromeda XXI appears as a spatial overdensity of stars. It has red giant branches at the distance of M31/M33, and follows metal-poor, [Fe/H]=-1.8 when plotted in a color-magnitude diagram.

Although moderately bright (M_V=-9.9 ± 0.6), it has low surface brightness. This indicates that numerous relatively luminous M31 satellites remain undiscovered.

References

^ ^a ^b "NAME Andromeda XXI". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2 April 2011.
^ ^a ^b Nicolas F. Martin, Alan W. McConnachie, Mike Irwin, Lawrence M. Widrow, Annette M. N. Ferguson, Rodrigo A. Ibata, John Dubinski, Arif Babul, Scott Chapman, Mark Fardal, Geraint F. Lewis, Julio Navarro, R. Michael Rich; "PAndAS' cubs: discovery of two new dwarf galaxies in the surroundings of the Andromeda and Triangulum galaxies"; The Astrophysical Journal, Volume 705, Issue 1, pp. 758-765 (2009); doi:10.1088/0004-637X/705/1/758; Bibcode:2009ApJ...705..758M; arXiv:0909.0399;

[SIMBAD-1] "NAME Andromeda XXI". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2 April 2011.

[ApJ-705-1-758-765-2] Nicolas F. Martin, Alan W. McConnachie, Mike Irwin, Lawrence M. Widrow, Annette M. N. Ferguson, Rodrigo A. Ibata, John Dubinski, Arif Babul, Scott Chapman, Mark Fardal, Geraint F. Lewis, Julio Navarro, R. Michael Rich; "PAndAS' cubs: discovery of two new dwarf galaxies in the surroundings of the Andromeda and Triangulum galaxies"; The Astrophysical Journal, Volume 705, Issue 1, pp. 758-765 (2009); doi:10.1088/0004-637X/705/1/758; Bibcode:2009ApJ...705..758M; arXiv:0909.0399;

[1]

[2]

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