Tucana Dwarf

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.

Tucana Dwarf
Tucana Dwarf by HST
Observation data (J2000 epoch)
ConstellationTucana
Right ascension22h 41m 49.0s[1]
Declination−64° 25′ 12″[1]
Redshift130 ± ? km/s[1]
Distance3.2 Mly
Apparent magnitude (V)15.7[1]
Characteristics
TypedE4[1]
Apparent size (V)2.9′ × 1.2′[1]
Other designations
PGC 69519[1]

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]

References
  1. "NASA/IPAC Extragalactic Database". Results for Tucana Dwarf. Retrieved 2006-11-29.
  2. 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. 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. 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: 55–62. arXiv:2207.02229. Bibcode:2023MNRAS.520...55S. doi:10.1093/mnras/stad085.
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