Pisces Overdensity

Last updated
Pisces Overdensity
Observation data (J2000 epoch)
Constellation Pisces
Right ascension 23h 19m 00s [1]
Declination +00° 00′ 00″ [1]
Distance 260  kly (80  kpc) [2]
Absolute magnitude  (V)−10.35 [3]
Characteristics
Type dIrr/dSph [3]
Apparent size  (V)~1° [4]
Other designations
Pisces Plume [1]

The Pisces Overdensity is a clump of stars in the Milky Way's halo, which may be a disrupted dwarf spheroidal galaxy. [5] It is situated in the Pisces constellation and was discovered in 2009 by analysis of distribution of RR Lyrae stars in the data obtained by the Sloan Digital Sky Survey's data. [2] The galaxy is located at the distance of about 80 kpc from the Sun and moves towards it with a speed of about 75 km/s. [4]

The Pisces Overdensity is one of the faintest satellites of the Milky Way. [5] Its mass is estimated to be at least 105 Solar masses. [2] However it has a large size of about several degrees (around 1 kpc) and may be in a transitional phase between a gravitationally bound galaxy and completely unbound system. [4] The Pisces Overdensity is located near the plane, where the Magellanic Clouds lie. There may exist a connection between the Magellanic Stream and this galaxy. [2]

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">Messier 2</span> Globular cluster in the constellation Aquarius

Messier 2 or M2 is a globular cluster in the constellation Aquarius, five degrees north of the star Beta Aquarii. It was discovered by Jean-Dominique Maraldi in 1746, and is one of the largest known globular clusters.

<span class="mw-page-title-main">Canis Major Overdensity</span> Disputed galaxy located near the constellation Canis Major

The Canis Major Overdensity or Canis Major Dwarf Galaxy is a disputed dwarf irregular galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major.

The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup, which is part of the local galaxy cluster, the Local Group.

<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.

Canes Venatici I or CVn I is a dwarf spheroidal galaxy situated in the Canes Venatici constellation and discovered in 2006 in the data obtained by Sloan Digital Sky Survey. It is one of the most distant known satellites of the Milky Way as of 2011 together with Leo I and Leo II. The galaxy is located at a distance of about 220 kpc from the Sun and is moving away from the Sun at a velocity of about 31 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical shape with the half-light radius of about 550 pc.

Segue 1 is a dwarf spheroidal galaxy or globular cluster situated in the Leo constellation and discovered in 2006 by Sloan Digital Sky Survey. It is located at a distance of about 23 kpc from the Sun and moves away from the Sun with the velocity of about 206 km/s. Segue 1 has a noticeably elongated shape with the half-light radius of about 30 pc. This elongation may be caused by the tidal forces acting from the Milky Way galaxy if Segue 1 is being tidally disrupted now.

<span class="mw-page-title-main">Leo IV (dwarf galaxy)</span> Galaxy in the constellation Leo

Leo IV is a dwarf spheroidal galaxy situated in the Leo constellation, discovered in 2006 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 160 kpc from the Sun and moves away from the Sun with the velocity of about 130 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately round shape with the half-light radius of about 130 pc.

Leo V is a dwarf spheroidal galaxy situated in the Leo constellation and discovered in 2007 in the data obtained by the Sloan Digital Sky Survey. The galaxy is located at a distance of about 180 kpc from the Sun and moves away from the Sun with the velocity of about 173 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately spherical shape with the half-light radius of about 130 pc.

Coma Berenices or Com is a dwarf spheroidal galaxy situated in the Coma Berenices constellation and discovered in 2006 in data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 44 kpc from the Sun and moves away from the Sun with the velocity of about 98 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical shape with the half-light radius of about 70 pc.

Boötes II or Boo II is a dwarf spheroidal galaxy situated in the constellation Boötes and discovered in 2007 in the data obtained by Sloan Digital Sky Survey. The galaxy is located at the distance of about 42 kpc from the Sun and moves towards the Sun with the speed of 120 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately round shape with the half-light radius of about 51 pc.

<span class="mw-page-title-main">Hercules (dwarf galaxy)</span> Dwarf spheroidal galaxy in the constellation Hercules

Hercules, or Her, is a dwarf spheroidal galaxy situated in the Hercules constellation and discovered in 2006 in data obtained by the Sloan Digital Sky Survey. The galaxy is located at a distance of about 140 kpc from the Sun and moves away from the Sun with a velocity of about 45 km/s. It is classified as a dwarf spheroidal galaxy (dSph). It has a noticeably elongated shape with a half-light radius of about 350 pc. The cause of this elongation is under debate. Some studies have found a gradient of velocities across the galaxy's body and a faint stellar stream associated with the galaxy, suggesting that the elongation may be caused by tidal forces acting from the Milky Way galaxy. However, other studies failed to find a velocity gradient or an associated stellar stream, suggesting that it is not being tidally disrupted.

Boötes III is an overdensity in the Milky Way's halo, which may be a disrupted dwarf spheroidal galaxy. It is situated in the constellation Boötes and was discovered in 2009 in the data obtained by Sloan Digital Sky Survey. The galaxy is located at the distance of about 46 kpc from the Sun and moves away from it at the speed of about 200 km/s. It has an elongated shape with the radius of about 0.5 kpc. The large size and an irregular shape may indicate that Boötes III in a transitional phase between a gravitationally bound galaxy and completely unbound system.

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 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.

Galaxy X is a postulated dark satellite dwarf galaxy of the Milky Way Galaxy. If it exists, it would be composed mostly of dark matter and interstellar gas with few stars. Its proposed location is some 90 kpc (290 kly) from the Sun, behind the disk of the Milky Way, and some 12 kpc (39 kly) in extent. Galactic coordinates would be (l= -27.4°,b=-1.08°).

<span class="mw-page-title-main">NGC 5053</span> Globular cluster in the constellation Coma Berenices

NGC 5053 is the New General Catalogue designation for a globular cluster in the northern constellation of Coma Berenices. It was discovered by German-British astronomer William Herschel on March 14, 1784 and cataloged as VI-7. In his abbreviated notation, he described it as, "an extremely faint cluster of extremely small stars with resolvable nebula 8 or 10′ diameter, verified by a power of 240, beyond doubt". Danish-Irish astronomer John Louis Emil Dreyer reported in 1888 that the cluster appeared, "very faint, pretty large, irregular round shape, growing very gradually brighter at the middle".

References

  1. 1 2 3 "NAME Pisces Overdensity". SIMBAD . Centre de données astronomiques de Strasbourg.
  2. 1 2 3 4 Watkins, L. L.; et al. (2009), "Substructure revealed by RR Lyraes in SDSS Stripe 82", Monthly Notices of the Royal Astronomical Society , 398 (4): 1757–70, arXiv: 0906.0498 , Bibcode:2009MNRAS.398.1757W, doi: 10.1111/j.1365-2966.2009.15242.x , S2CID   14409027.
  3. 1 2 Boyer, Martha L; Skillman, Evan D; Van Loon, Jacco Th; Gehrz, Robert D; Woodward, Charles E (2009). "Aspitzerstudy of Asymptotic Giant Branch Stars. Iii. Dust Production and Gas Return in Local Group Dwarf Irregular Galaxies". The Astrophysical Journal. 697 (2): 1993. arXiv: 0903.3871 . Bibcode:2009ApJ...697.1993B. doi:10.1088/0004-637X/697/2/1993. S2CID   12162514.
  4. 1 2 3 Kollmeier, Juna A.; et al. (2009), "Spectroscopic Confirmation of the Pisces Overdensity", The Astrophysical Journal Letters, 705 (2): L158–L162, arXiv: 0908.1381 , Bibcode:2009ApJ...705L.158K, doi:10.1088/0004-637X/705/2/L158, S2CID   9825846.
  5. 1 2 Belokurov, V.; et al. (2010), "Big fish, small fish: Two New Ultra-Faint Satellites of the Milky Way", The Astrophysical Journal Letters, 712 (1): L103–106, arXiv: 1002.0504 , Bibcode:2010ApJ...712L.103B, doi:10.1088/2041-8205/712/1/L103, S2CID   29195107.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.