IC 10
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Irregular Galaxy IC 10. |
|
| Observation data: J2000 epoch | |
|---|---|
| Constellation: | Cassiopeia |
| Right ascension: | 00h 20m 17.3s[1] |
| Declination: | +59° 18′ 14″[1] |
| Redshift: | -348 ± 1 km/s[1] |
| Distance: | 2.2 ± 0.2 Mly (660 ± 60 kpc)[2] |
| Type: | dIrr IV/BCD[1] |
| Apparent dimensions (V): | 6′.8 × 5′.9[1] |
| Apparent magnitude (V): | 10.4 ± 0.2[citation needed] |
| Notable features: | starburst galaxy |
| Other designations | |
| UGC 192,[1] PGC 1305[1] | |
| See also: Galaxy, List of galaxies | |
IC 10 is an irregular galaxy in the constellation Cassiopeia. It was discovered by Lewis Swift in 1889.[3] Nicholas U. Mayall was the first to suggest that the object is extragalactic in 1935. Edwin Hubble suspected it might belong to the Local Group of galaxies, but its status remained uncertain for decades. Radial velocity of the galaxy was measured in 1962, which strengthened the assumption.[3] Finally, in 1996, based on direct Cepheid distance measurements, it was demonstrated to be a true member of the group. Despite its closeness, the galaxy is rather difficult to study because it lies near the plane of the Milky Way and is therefore heavily obscured by interstellar matter.[4]
Apparent distance between IC 10 and the Andromeda Galaxy is about the same as the apparent distance between the Andromeda Galaxy and the Triangulum Galaxy, which suggests that IC 10 may belong to the M31 subgroup.[4]
IC 10 the only known starburst galaxy in the Local Group of galaxies. It has many more Wolf-Rayet stars per square kiloparsec (5.1 stars/kpc²) compared to the Large Magellanic Cloud (2.0 stars/kpc²) and Small Magellanic Cloud (0.9 stars/kpc²). Although the galaxy has similar luminosity to the SMC, it is considerably smaller. The higher oxygen level in the galaxy compared to the SMC suggests that the star formation activity has continued for a longer time period. The evolutionary status of the Wolf-Rayet stars suggests that they all formed in a relatively short timespan. Ratio between two types of Wolf-Rayet stars in IC 10 is very different from the ratio in other galaxies in the Local Group, which may be somehow due the starburst nature of the galaxy. Currently the galaxy produces stars at the speed of 0.04–0.08 MSun per year, which means that the gas supply in the galaxy can last only a few thousand million years.[4]
The galaxy has a huge envelope of hydrogen gas, apparent size measuring 68′ × 80′, which is by far larger than the apparent size of the galaxy in visible light (5.5′ × 7.0′). IC 10 is also unusual in the respect that the visible part of the galaxy seems to rotate different direction than the outer envelope.[4] It has a H II nucleus.[5]
[edit] References
- ^ a b c d e f g NASA/IPAC Extragalactic Database. Results for IC 10. Retrieved on 2007-03-15.
- ^ 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.
- ^ a b IC 10. SEDS Messier Database. Retrieved on 2006-05-15.
- ^ a b c d Van den Bergh, Sidney (2000). Galaxies of the Local Group, 1st edition, Cambridge University Press. ISBN 0-521-65181-6.
- ^ Ho, Luis C.; Alexei V. Filippenko & Wallace L. W. Sargent (October 1997), "A Search for 'Dwarf' Seyfert Nuclei. III. Spectroscopic Parameters and Properties of the Host Galaxies", Astrophysical Journal Supplement 112: 315
