Andromeda I

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Andromeda I
Andromeda I.jpg
Observation data (J2000 epoch)
Constellation Andromeda
Right ascension 00h 45m 39.8s[1]
Declination +38° 02′ 28″[1]
Redshift -368 ± 11 km/s[1]
Distance 2.40 ± 0.08 Mly (735 ± 23 kpc)[2][3][4]
Type E3 pec?[1]
Apparent dimensions (V) 2′.5 × 2′.5[1]
Apparent magnitude (V) 13.6[1]
Notable features satellite galaxy of M31
Other designations
And I,[2] Anon 0043+37,[1] PGC 2666[1]
See also: Galaxy, List of galaxies

Andromeda I is a dwarf spheroidal galaxy(dSph)[5] about 2.40[4] 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.[6] As of 2005, it is the closest known dSph companion to M31[7] at an estimated projected distance of ~40[4] kpc.

Andromeda I was discovered by Sidney van den Bergh[8] in 1970 with the Mount Palomar Observatory 48-inch telescope.[5] Further study of Andromeda I was done by the WFPC2 camera of the Hubble Space Telescope. This found that the horizontal branch stars, like other dwarf spheroidal galaxies were predominantly red.[9] From this, and the abundance of blue horizontal branch stars, along with 99 RR Lyrae stars detected in 2005,[7] lead to the conclusion there was an extended epoch of star formation. The estimated age is approximately 10 Gyr. The Hubble telescope also found a globular cluster in Andromeda I, being the least luminous galaxy where such a cluster was found.[10]

Andromeda I by HST

[edit] See also

[edit] External links

[edit] References

  1. ^ a b c d e f g h "NASA/IPAC Extragalactic Database". Results for Andromeda I. http://nedwww.ipac.caltech.edu/. Retrieved 2008-01-21. 
  2. ^ a b 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, http://adsabs.harvard.edu/abs/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, http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2006Ap.....49....3K 
  4. ^ a b c McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A.; Lewis, G. F.; Tanvir, N. (May 2004), "Determining the location of the tip of the red giant branch in old stellar populations: M33, Andromeda I and II", Monthly Notices of the Royal Astronomical Society 350 (1): 250, doi:10.1111/j.1365-2966.2004.07637.x, http://adsabs.harvard.edu/abs/2004MNRAS.350..243M 
  5. ^ a b van den Bergh, Sydney (January 1972), "Search for Faint Companions to M31", Astrophysical Journal 171: L31, doi:10.1086/180861, http://adsabs.harvard.edu/abs/1972ApJ...171L..31V 
  6. ^ Andromeda I, Students for the Exploration and Development of Space (SEDS), July 25, 2001, http://www.seds.org/~spider/spider/LG/and1.html 
  7. ^ a b Pritzl, Barton J.; Armandroff, Taft E.; Jacoby, George H.; Da Costa, G. S. (May 2005), "The Dwarf Spheroidal Companions to M31: Variable Stars in Andromeda I and Andromeda III", The Astronomical Journal 129 (5): 2232–2256, doi:10.1086/428372, http://adsabs.harvard.edu/abs/2005AJ....129.2232P 
  8. ^ McConnachie, A. W.; Irwin, M. J.; Ferguson, A. M. N.; Ibata, R. A.; Lewis, G. F.; Tanvir, N. (2005). "Distances and metallicities for 17 Local Group galaxies". Monthly Notices of the Royal Astronomical Society 356 (4): 979–997. doi:10.1111/j.1365-2966.2004.08514.x. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2005MNRAS.356..979M. 
  9. ^ Da Costa, G. S.; Armandroff, T. E.; Caldwell, Nelson; Seitzer, Patrick (December 1996), "The Dwarf Spheroidal Companions to M31: WFPC2 Observations of Andromeda I", Astronomical Journal 112: 2576, doi:10.1086/118204, http://adsabs.harvard.edu/abs/1996AJ....112.2576D 
  10. ^ Grebel, E. K.; Dolphin, A. E.; Guhathakurta, P. (September 18-23, 2000), Abstracts of Contributed Talks and Posters presented at the Annual Scientific Meeting of the Astronomische Gesellschaft, "Discovery of a Globular Cluster in M31's Dwarf Spheroidal Companion Andromeda I", Astronomische Gesellschaft Abstract Series (Bremen) 17, http://adsabs.harvard.edu/cgi-bin/nph-bib_query?2000AGM....17..P61G 

Coordinates: Sky map 00h 45m 39.8s, +38° 02′ 28″


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