Tucana Dwarf

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Tucana Dwarf
Tucana Dwarf Hubble WikiSky.jpg
Tucana Dwarf by HST
Observation data (J2000 epoch)
Constellation Tucana
Right ascension 22h 41m 49.0s [1]
Declination −64° 25′ 12″ [1]
Redshift 130 ± ? km/s [1]
Distance 3.2 Mly
Apparent magnitude  (V)15.7 [1]
Characteristics
Type dE4 [1]
Apparent size  (V)2.9′ × 1.2′ [1]
Other designations
PGC 69519 [1]

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.

Contents

Properties

The Tucana Dwarf is a dwarf spheroidal galaxy of type dE5. [2] It contains only old stars, formed in a single star formation era around the time the Milky Way's globular clusters formed. [3] It is not experiencing any current star formation, unlike other isolated dwarf galaxies. [4]

The Tucana Dwarf does not contain very much neutral hydrogen gas. [5] It has a metallicity of -1.8, a significantly low number. There is no significant spread in metallicity throughout the galaxy. [3] There does not seem to be any substructure to the stellar distribution in the galaxy. [3]

Location

The Tucana Dwarf is located in the constellation Tucana. It is about 870 kiloparsecs (2,800 kly) away, [6] on the opposite side of the Milky Way galaxy to most of the other Local Group galaxies and is therefore important for understanding the kinematics and formation history of the Local Group, [2] as well as the role of environment in determining how dwarf galaxies evolve. It is isolated from other galaxies, [2] and located near the edge of the Local Group, [3] around 1,100 kiloparsecs (3,600 kly) from the barycentre of the Local Group—the second most remote of all member galaxies after the Sagittarius Dwarf Irregular Galaxy. [6]

The Tucana Dwarf galaxy is one of only two dwarf spheroidal galaxies in the Local Group not located near the Milky Way or the Andromeda Galaxy. [7] It is thought to have approached the Andromeda Galaxy about 11 billion years ago, which ejected the galaxy far away to its current position; such galaxies are called "backsplash galaxies". [8]

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<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">Sagittarius Dwarf Spheroidal Galaxy</span> Satellite galaxy of the Milky Way

The Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), also known as the Sagittarius Dwarf Elliptical Galaxy, is an elliptical loop-shaped satellite galaxy of the Milky Way. It contains four globular clusters in its main body, with the brightest of them—NGC 6715 (M54)—being known well before the discovery of the galaxy itself in 1994. Sgr dSph is roughly 10,000 light-years in diameter, and is currently about 70,000 light-years from Earth, travelling in a polar orbit at a distance of about 50,000 light-years from the core of the Milky Way. In its looping, spiraling path, it has passed through the plane of the Milky Way several times in the past. In 2018 the Gaia project of the European Space Agency showed that Sgr dSph had caused perturbations in a set of stars near the Milky Way's core, causing unexpected rippling movements of the stars triggered when it moved past the Milky Way between 300 and 900 million years ago.

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

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

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<span class="mw-page-title-main">Dwarf spheroidal galaxy</span> Low-luminosity galaxy of old stars & little dust

A dwarf spheroidal galaxy (dSph) is a term in astronomy applied to small, low-luminosity galaxies with very little dust and an older stellar population. They are found in the Local Group as companions to the Milky Way and as systems that are companions to the Andromeda Galaxy (M31). While similar to dwarf elliptical galaxies in appearance and properties such as little to no gas or dust or recent star formation, they are approximately spheroidal in shape and generally have lower luminosity.

<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">Sculptor Dwarf Galaxy</span> Dwarf spheroidal Galaxy in the constellation Sculptor

The Sculptor Dwarf Galaxy is a dwarf spheroidal galaxy that is a satellite of the Milky Way. The galaxy lies within the constellation Sculptor. It was discovered in 1937 by American astronomer Harlow Shapley using the 24-inch Bruce refractor at Boyden Observatory. The galaxy is located about 290,000 light-years away from the Solar System. The Sculptor Dwarf contains only 4 percent of the carbon and other heavy elements in our own galaxy, the Milky Way, making it similar to primitive galaxies seen at the edge of the universe.

<span class="mw-page-title-main">Wolf–Lundmark–Melotte</span> Irregular galaxy in the Local Group

The Wolf–Lundmark–Melotte Galaxy (WLM) is a barred irregular galaxy discovered in 1909 by Max Wolf, located on the outer edges of the Local Group. The discovery of the nature of the galaxy was accredited to Knut Lundmark and Philibert Jacques Melotte in 1926. It is in the constellation Cetus.

<span class="mw-page-title-main">Ursa Minor Dwarf</span> Dwarf spheroidal galaxy

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

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<span class="mw-page-title-main">Palomar 12</span> Globular cluster in the constellation Capricornus

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<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.

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

The Antlia Dwarf is a dwarf spheroidal/irregular galaxy. It lies about 1.3 Mpc from Earth in the constellation Antlia. It is the fourth and faintest member of the nearby Antlia-Sextans Group of galaxies. The galaxy contains stars of all ages, contains significant amounts of gas, and has experienced recent star formation. The Antlia Dwarf is believed to be tidally interacting with the small barred spiral galaxy NGC 3109.

References

  1. 1 2 3 4 5 6 7 "NASA/IPAC Extragalactic Database". Results for Tucana Dwarf. Retrieved 2006-11-29.
  2. 1 2 3 Lavery, Russell J.; Mighell, Kenneth J. (January 1992). "A new member of the Local Group - The Tucana dwarf galaxy". The Astronomical Journal . 103 (1): 81–84. Bibcode:1992AJ....103...81L. doi:10.1086/116042.
  3. 1 2 3 4 Saviane, I.; Held, E. V.; Piotto, G. (November 1996). "CCD photometry of the Tucana dwarf galaxy". Astronomy and Astrophysics. 315: 40–51. arXiv: astro-ph/9601165 . Bibcode:1996A&A...315...40S.
  4. ↑ van den Bergh, Sidney (June 1994). "The evolutionary history of low-luminosity local group dwarf galaxies". The Astrophysical Journal . 428: 617–619. Bibcode:1994ApJ...428..617V. doi:10.1086/174270.
  5. ↑ Oosterloo, T.; Da Costa, G. S.; Staveley-Smith, L. (November 1996). "HI Observations of the Tucana Dwarf Elliptical Galaxy". The Astronomical Journal . 112 (5): 1969–1974. Bibcode:1996AJ....112.1969O. doi: 10.1086/118155 .
  6. 1 2 van den Bergh, Sidney (April 2000). "Updated Information on the Local Group". The Publications of the Astronomical Society of the Pacific . 112 (770): 529–536. arXiv: astro-ph/0001040 . Bibcode:2000PASP..112..529V. doi:10.1086/316548. S2CID   1805423.
  7. ↑ Fraternali, F.; Tolstoy, E.; Irwin, M. J.; Cole, A. A. (May 2009). "Life at the periphery of the Local Group: the kinematics of the Tucana dwarf galaxy". Astronomy and Astrophysics . 499 (1): 121–128. arXiv: 0903.4635 . Bibcode:2009A&A...499..121F. doi:10.1051/0004-6361/200810830. S2CID   18698184.
  8. ↑ Santos-Santos, Isabel M. E.; Navarro, Julio F.; McConnachie, Alan (2023). "The Tucana dwarf spheroidal: A distant backsplash galaxy of M31?". Monthly Notices of the Royal Astronomical Society. 520 (1): 55–62. arXiv: 2207.02229 . Bibcode:2023MNRAS.520...55S. doi: 10.1093/mnras/stad085 .
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