Sculptor Dwarf Galaxy

The Sculptor Dwarf Galaxy (also known as Sculptor Dwarf Elliptical Galaxy or the Sculptor Dwarf Spheroidal Galaxy, and formerly as the Sculptor System) 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.[4][5] 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.[6]

For the nearby irregular galaxy within the constellation Sculptor, see Sculptor Dwarf Irregular Galaxy.
Sculptor Dwarf Elliptical Galaxy
Observation data (J2000 epoch)
ConstellationSculptor
Right ascension01h 00m 09.3s[1]
Declination−33° 42′ 33″[1]
Redshift110 ± 1 km/s[1]
Distance290 ± 30 kly (90 ± 10 kpc)[2][3]
Apparent magnitude (V)10.1[1]
Characteristics
TypeE[1]
Apparent size (V)39′.8 × 30′.9[1]
Other designations
Sculptor Dwarf Spheroidal,[1] PGC 3589,[1] MCG-06-03-015

Metallicity

The metallicity of Sculptor dwarf appears to be broken up into two distinct groups, one with [Fe/H] = −2.3 and the other with [Fe/H] = −1.5.[7] Similar to many of the other Local Group galaxies, the older metal-poor segment appears more extended than the younger metal-rich segment.[8] Using cosmological numerical simulations, it has been recently argued that Sculptor's two distinct stellar populations would be the tell-tale sign of a past merger between Sculptor and another small dwarf galaxy companion.[9]

The Sculptor Dwarf is home to the most metal-poor star outside of the Milky Way, known as AS0039, with a metallicity of [Fe/H] = −4.11. Unlike other known metal-poor stars, it has a low carbon abundance and an unusual ratio of alpha elements, suggesting it may have been formed in the aftermath of a Population III star hypernova.[10]

Measurements

Using both Hubble Space Telescope and Gaia observations 12 years apart, about 100 stars in the galaxy were mapped accurately, and 3D motions of about 10 of those stars enable trajectories to be mapped as well.[11]

References
  1. "NASA/IPAC Extragalactic Database". Results for PGC 3589. Retrieved 2006-12-03.
  2. I. D. Karachentsev; V. E. Karachentseva; W. K. Hutchmeier; D. I. Makarov (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal (abstract). 128 (4): 2031–2068. Bibcode:2004AJ....127.2031K. doi:10.1086/382905.
  3. Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics. 49 (1): 3–18. Bibcode:2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6. S2CID 120973010.
  4. Shapley, H., (1938) Harvard Bull. 908.
  5. Shapley H (1938). "Two Stellar Systems of a New Kind". Nature. 142 (3598): 715–6. Bibcode:1938Natur.142..715S. doi:10.1038/142715b0. S2CID 4071472.
  6. Astronomers Detect Dust Around a Primitive Star, Shedding New Light on Universe’s Origins Newswise, Retrieved on January 19, 2008.
  7. S.R. Majewski; et al. (20 July 1999). "An Internal Second-Parameter Problem in the Sculptor Dwarf Spheroidal Galaxy". The Astrophysical Journal. 520 (1): L33–L36. arXiv:astro-ph/9905238. Bibcode:1999ApJ...520L..33M. doi:10.1086/312133. S2CID 14523540.
  8. 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.
  9. Benítez-Llambay, A.; Navarro, J. F.; Abadi, M. G.; Gottlöber, S.; Yepes, G.; Hoffman, Y.; Steinmetz, M. (2016-02-21). "Mergers and the outside-in formation of dwarf spheroidals". Monthly Notices of the Royal Astronomical Society. 456 (2): 1185–1194. doi:10.1093/mnras/stv2722. hdl:10486/684610. ISSN 0035-8711.
  10. Skúladóttir, Ása; Salvadori, Stefania; Amarsi, Anish M.; Tolstoy, Eline; Irwin, Michael J.; Hill, Vanessa; Jablonka, Pascale; Battaglia, Giuseppina; Starkenburg, Else; Massari, Davide; Helmi, Amina; Posti, Lorenzo (2021). "Zero-metallicity Hypernova Uncovered by an Ultra-metal-poor Star in the Sculptor Dwarf Spheroidal Galaxy". The Astrophysical Journal Letters. 915 (2): 8. arXiv:2106.11592. Bibcode:2021ApJ...915L..30S. doi:10.3847/2041-8213/ac0dc2. S2CID 235593020. L30.
  11. Hubble and Gaia team up to measure 3D stellar motion with record-breaking precision
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