Andromeda XVIII

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Andromeda XVIII
Andromeda XVIII.jpg
DSS image of Andromeda XVIII
Observation data (J2000 epoch)
Constellation Andromeda
Right ascension 00h 02m 14.5s [1]
Declination +45° 05′ 20″ [1]
Heliocentric radial velocity −326.2 ± 2.7 [2]
Distance 4,420 ± 290  kly (1,355 ± 88  kpc)
Group or cluster Local Group
Apparent magnitude  (V)15.50 ± 0.24 [3]
Absolute magnitude  (V)−10.41 ± 0.28 [3]
Characteristics
Type dG [1]
Mass 4.2×106 ± 0.3×106 [3]   M☉
Half-light radius  (physical)325 ± 24 [2]
Other designations
PGC  5056918 [4]

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

See also

Related Research Articles

<span class="mw-page-title-main">Local Group</span> Group of galaxies that includes the Milky Way

The Local Group is the galaxy group that includes the Milky Way, where Earth is located. It has a total diameter of roughly 3 megaparsecs (10 million light-years; 9×1019 kilometres), and a total mass of the order of 2×1012 solar masses (4×1042 kg). It consists of two collections of galaxies in a "dumbbell" shape; the Milky Way and its satellites form one lobe, and the Andromeda Galaxy and its satellites constitute the other. The two collections are separated by about 800 kiloparsecs (3×10^6 ly; 2×1019 km) and are moving toward one another with a velocity of 123 km/s. The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster. The exact number of galaxies in the Local Group is unknown as some are occluded by the Milky Way; however, at least 80 members are known, most of which are dwarf galaxies.

<span class="mw-page-title-main">Andromeda Galaxy</span> Barred spiral galaxy in the Local Group

The Andromeda Galaxy is a barred spiral galaxy and is the nearest major galaxy to the Milky Way. It was originally named the Andromeda Nebula and is cataloged as Messier 31, M31, and NGC 224. Andromeda has a D25 isophotal diameter of about 46.56 kiloparsecs (152,000 light-years) and is approximately 765 kpc (2.5 million light-years) from Earth. The galaxy's name stems from the area of Earth's sky in which it appears, the constellation of Andromeda, which itself is named after the princess who was the wife of Perseus in Greek mythology.

<span class="mw-page-title-main">Pegasus Dwarf Spheroidal Galaxy</span> Dwarf spheroidal galaxy in the constellation Pegasus

The Pegasus Dwarf Spheroidal is a dwarf spheroidal galaxy about 2.7 million light-years away in the constellation Pegasus. The Pegasus Dwarf is a member of the Local Group and a satellite galaxy of the Andromeda Galaxy (M31).

<span class="mw-page-title-main">Pegasus Dwarf Irregular Galaxy</span> Dwarf irregular galaxy in the constellation of Pegasus

The Pegasus Dwarf Irregular Galaxy is a dwarf irregular galaxy in the direction of the constellation Pegasus. It was discovered by A. G. Wilson in the 1950s. The Pegasus Dwarf is a companion of the Andromeda Galaxy in the Local Group.

<span class="mw-page-title-main">Andromeda I</span> Dwarf galaxy in the constellation Andromeda

Andromeda I is a dwarf spheroidal galaxy (dSph) about 2.40 million light-years away in the constellation Andromeda. Andromeda I is part of the local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It is roughly 3.5 degrees south and slightly east of M31. As of 2005, it is the closest known dSph companion to M31 at an estimated projected distance of ~40 kpc or ~150,000 light-years.

<span class="mw-page-title-main">Tucana Dwarf</span> Dwarf galaxy in the constellation Tucana

The Tucana Dwarf Galaxy is a dwarf galaxy in the constellation Tucana. It was discovered in 1990 by R.J. Lavery of Mount Stromlo Observatory. It is composed of very old stars and is very isolated from other galaxies. Its location on the opposite side of the Milky Way from other Local Group galaxies makes it an important object for study.

<span class="mw-page-title-main">Pisces Dwarf</span>

The Pisces Dwarf, also known as Pisces I, is an irregular dwarf galaxy that is part of the Local Group. The galaxy, taking its name from the constellation Pisces where it appears, is suspected of being a satellite galaxy of the Triangulum Galaxy (M33). It displays a blueshift, as it is approaching the Milky Way at 287 km/s. It may be transition-type galaxy, somewhere between dwarf spheroidal and dwarf irregular. Alternatively, it may be a rare, but statistically acceptable, version of one of the two types.

Andromeda IX is a dwarf spheroidal satellite of the Andromeda Galaxy. It was discovered in 2004 by resolved stellar photometry from the Sloan Digital Sky Survey (SDSS), by Zucker et al. (2004). At the time of its discovery, it was the galaxy with the lowest known surface brightness, ΣV ≃ 26.8mags arcsec−2 and the faintest galaxy known from its intrinsic absolute brightness.

<span class="mw-page-title-main">Andromeda II</span> Dwarf spheroidal galaxy in the constellation Andromeda

Andromeda II is a dwarf spheroidal galaxy about 2.22 Mly away in the constellation Pisces. While part of the Local Group, it is not quite clear if it is a satellite of the Andromeda Galaxy or the Triangulum Galaxy.

Andromeda III is a dwarf spheroidal galaxy about 2.44 million light-years away in the constellation Andromeda. It is part of the Local Group and is a satellite galaxy of the Andromeda Galaxy (M31). The galaxy was discovered by Sidney van den Bergh on photographic plates taken in 1970 and 1971.

<span class="mw-page-title-main">Andromeda IV</span> Isolated irregular dwarf galaxy in the constellation of Andromeda

Andromeda IV is an isolated irregular dwarf galaxy. The moderate surface brightness, a very blue color, low current star formation rate and low metallicity are consistent with it being a small (background) dwarf irregular galaxy, perhaps similar to Local Group dwarfs such as IC 1613 and Sextans A. Arguments based on the observed radial velocity and the tentative detection of the RGB tip suggest that it lies well outside the confines of the Local Group.

Andromeda V is a dwarf spheroidal galaxy about 2.52 Mly away in the constellation Andromeda.

<span class="mw-page-title-main">Cetus Dwarf</span> Galaxy in the constellation Cetus

Cetus Dwarf is a dwarf spheroidal galaxy. It lies approximately 2.46 Million light-years from Earth. It is an isolated galaxy of the Local Group, which also contains the Milky Way. All of the most readily observable stars in the galaxy are red giants.

Pisces II is a dwarf spheroidal galaxy situated in the Pisces constellation and discovered in 2010 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 180 kpc (kiloparsecs) from the Sun. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elongated shape with the half-light radius of about 60 pc and ratio of the axis of about 5:3.

Andromeda 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. 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 XXII is a low surface brightness dwarf spheroidal galaxy about 940–1,033 kiloparsecs away from the Sun in the constellation Pisces, of the Local Group.

Andromeda XIX is a satellite galaxy of the Andromeda Galaxy (M31), a member of the Local Group, like the Milky Way Galaxy. Andromeda XIX is considered "the most extended dwarf galaxy known in the Local Group", and has been shown to have a half-light radius of 1.7 kiloparsec (kpc). It was discovered by the Canada–France–Hawaii Telescope, and is thought to be a dwarf galaxy.

References

  1. 1 2 3 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. 1 2 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.
  3. 1 2 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.
  4. ↑ "NAME Andromeda XVIII". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 19 September 2017.


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