NGC 185


NGC 185

Dwarf Elliptical Galaxy NGC 185
Observation data (J2000 epoch)
Constellation Cassiopeia
Right ascension 00h 38m 58.0s[1]
Declination +48° 20′ 15″[1]
Redshift -202 ± 3 km/s[1]
Distance 2.05 ± 0.13 Mly (630 ± 40 kpc)[2][3][4][a]
Type dSph/dE3[1]
Apparent dimensions (V) 11′.7 × 10′.0[1]
Apparent magnitude (V) 10.1[1]
Notable features satellite galaxy of the
Andromeda Galaxy
Other designations
UGC 396,[1] PGC 2329[1]
See also: Galaxy, List of galaxies

NGC 185 is a dwarf elliptical galaxy about 2.08 million light-years away in the constellation Cassiopeia. NGC 185 is a satellite galaxy of the famous Andromeda Galaxy (M31) and was discovered by William Herschel on November 30, 1787. Unlike most dwarf elleptical galaxies, NGC 185 actually contains young stellar clusters and star formation proceeded at a low rate until the recent past. NGC 185 has an active galactic nucleus (AGN) and is classified as a type 2 Seyfert galaxy.[5]

Contents

Distance measurements

At least two techniques have been used to measure distances to NGC 185. The surface brightness fluctuations distance measurement technique estimates distances to spiral galaxies based on the graininess of the appearance of their bulges. The distance measured to NGC 185 using this technique is 2.08 ± 0.15 Mly (640 ± 50 kpc).[2] However, NGC 185 is close enough that the tip of the red giant branch (TRGB) method may be used to estimate its distance. The estimated distance to NGC 185 using this technique is 2.02 ± 0.2 Mly (620 ± 60 kpc).[3][4] Averaged together, these distance measurements give a distance estimate of 2.05 ± 0.13 Mly (630 ± 40 kpc).[a]

Star formation

Martínez-Delgado, Aparicio, & Gallart (1999) looked into the star formation history of NGC 185 and found that the majority of star formation in NGC 185 happened at early times. In the last ~1 Gyr, stars have only formed near the center of this galaxy. Walter Baade discovered young blue objects within this galaxy in 1951, but these have turned out to be star clusters and not individual stars. A supernova remnant near the center was also discovered by Martínez-Delgado et al.[6]

See also

Notes

  1. average(640 ± 50, 620 ± 60) = ((640 + 620) / 2) ± ((502 + 602)0.5 / 2) = 630 ± 40

References

  1. ^ a b c d e f g h "NASA/IPAC Extragalactic Database". Results for NGC 185. Retrieved on 2006-11-29.
  2. ^ a b J. L. Tonry, A. Dressler, J. P. Blakeslee, E. A. Ajhar, A. B. Fletcher, G. A. Luppino, M. R. Metzger, C. B. Moore (2001). "The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances". Astrophysical Journal 546 (2): 681–693. doi:10.1086/318301. 
  3. ^ 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. 
  4. ^ a b 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. 
  5. ^ Ho, Luis C.; Filippenko, Alexei V. & Sargent, Wallace L. W. (October 1997), “A Search for 'Dwarf' Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies”, The Astrophysical Journal Supplement Series 112: 315, doi:10.1086/313041, <http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997ApJS..112..315H> 
  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, doi:10.1086/316548, <http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000PASP..112..529V> 


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