NGC 185

NGC 185
NGC185 (with nearby stars removed) Dwarf Spheroidal 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] LEDA 2329, Caldwell 18
See also: Galaxy, List of galaxies

NGC 185 (also known as Caldwell 18) is a dwarf spheroidal galaxy about 2.08 million light-years away in the constellation Cassiopeia. It is a member of the Local group, and is a satellite galaxy of the Andromeda Galaxy (M31).^[5] NGC 185 was discovered by William Herschel on November 30, 1787, and he cataloged it "H II.707".^[5] John Herschel observed the object again in 1833 when he cataloged it as "h 35", and then in 1890 when he cataloged it as "GC 90" within his General Catalogue of Nebulae and Clusters.^[5] NGC 185 was first photographed between 1898 and 1900 by James Edward Keeler with the Crossley Reflector of Lick Observatory.^[5] Unlike most dwarf elliptical galaxies, NGC 185 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.^[6]

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 galaxies based on the graininess of their appearance. 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).^{[Note 1]}

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 formed only 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.^[7]

See also

• Andromeda's satellite galaxies

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. http://nedwww.ipac.caltech.edu/. Retrieved 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. arXiv:astro-ph/0011223. Bibcode 2001ApJ...546..681T. 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 (4): 2031–2068. Bibcode 2004AJ....127.2031K. 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. Bibcode 2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6. 
5. ^ ^{a b c d} "SEDS — NGC 185". http://spider.seds.org/spider/LG/n0185.html. 
6. ^ 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: pp. 315. doi:10.1086/313041. http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1997ApJS..112..315H. 
7. ^ 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. 

External links

• NGC 185 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images

Coordinates: 00^h 38^m 58.0^s, +48° 20′ 15″