Sagittarius Dwarf Irregular Galaxy

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SagDIG. Courtesy of NASA/ESA
Observation data (J2000 epoch)
Constellation Sagittarius
Right ascension 19h 29m 59.0s[1]
Declination -17° 40′ 41″[1]
Redshift -79 ± 1 km/s[1]
Distance 3.39 ± 0.23 Mly (1.04 ± 0.07 Mpc)[2][3]
Type IB(s)m[1] V (Dwarf irregular galaxy)
Apparent dimensions (V) 2′.9 × 2′.1[1]
Apparent magnitude (V) 15.5[1]
Other designations
Sagittarius Dwarf Irregular,[1] SGR Dwarf,[1]
ESO594-G004,[1] PGC 63287,[1] Kowal's Object[1]
See also: Galaxy, List of galaxies

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

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

SagDIG is a much more luminous galaxy than Aquarius Dwarf and it has been through a prolonged star formation (Momany et al. 2005). 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 Gyr for the dominant population.[5]

[edit] References

  1. ^ a b c d e f g h i j k NASA/IPAC Extragalactic Database. Results for Sagittarius Dwarf Irregular. Retrieved on 2007-03-15.
  2. ^ I. D. Karachentsev, V. E. Karachentseva, W. K. Hutchmeier, D. I. Makarov (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal 127: 2031-2068. 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. doi:10.1007/s10511-006-0002-6. 
  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, <http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000PASP..112..529V> 
  5. ^ 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, <http://adsabs.harvard.edu/abs/2007A%26A...475..467G>