Astronomy:Sagittarius Dwarf Irregular Galaxy

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Short description: Dwarf galaxy in the constellation of Sagittarius


SagDIG
SagDIG.jpg
Observation data (J2000 epoch)
ConstellationSagittarius
Right ascension 19h 29m 59.0s[1]
Declination−17° 40′ 41″[1]
Redshift−79±1 km/s[1]
Distance3.39±0.23 Mly (1.04±0.07 Mpc)[2][3]
Apparent magnitude (V)15.5[1]
Characteristics
TypeIB(s)m[1] V (Dwarf irregular galaxy)
Apparent size (V)2.9′ × 2.1′[1]
Other designations
Sagittarius Dwarf Irregular,[1] SGR Dwarf,[1]
ESO594-G004,[1] PGC 63287,[1] Kowal's Object[1]

The Sagittarius Dwarf Irregular Galaxy (SagDIG) is a dwarf galaxy in the constellation of Sagittarius. (SagDIG should not be confused with the Sagittarius Dwarf Spheroidal Galaxy, SagDEG, a satellite galaxy of the Milky Way discovered decades later in the same constellation.) It lies about 3.4 million light-years away. It was discovered by Cesarsky et al. on a photographic plate taken for the ESO (B) Atlas on 13 June 1977 using the ESO 1 meter Schmidt telescope.

The SagDIG is thought to be the member of the Local Group most remote from the Local Group's barycenter. It is only slightly outside the zero-velocity surface of the Local Group.[4]

SagDIG is a much more luminous galaxy than the Aquarius Dwarf and it has been through a prolonged period of star formation.[5] This has resulted in it containing a rich intermediate-age population of stars. Twenty-seven candidate carbon stars have been identified inside SagDIG. Analysis shows that the underlying stellar population of SagDIG is metal-poor (at least [Fe/H] ≤ −1.3). Further, the population is young, with the most likely average age between 4 and 8 billion years for the dominant population.[6]

References

  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 "NASA/IPAC Extragalactic Database". Results for Sagittarius Dwarf Irregular. http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=Sagittarius+Dwarf+Irregular#ObjNo1. 
  2. ↑ Karachentsev, I.D.; Karachentseva, V.E.; Hutchmeier, W.K.; Makarov, D.I. (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal 127 (4): 2031–2068. doi:10.1086/382905. Bibcode: 2004AJ....127.2031K. 
  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. doi:10.1007/s10511-006-0002-6. Bibcode: 2006Ap.....49....3K. 
  4. ↑ 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. doi:10.1086/316548. Bibcode: 2000PASP..112..529V. 
  5. ↑ Momany et al. 2005.
  6. ↑ Gullieuszik, M.; Rejkuba, M.; Cioni, M. R.; Habing, H. J.; Held, E. V. (November 2007). "Near-infrared photometry of carbon stars in the Sagittarius dwarf irregular galaxy and DDO 210". Astronomy and Astrophysics 475 (2): 467–477. doi:10.1051/0004-6361:20066848. Bibcode: 2007A&A...475..467G. 

External links


Coordinates: Sky map 19h 29m 59.0s, −17° 40′ 41″



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