IC 1613 (object 1613 in the Index Catalogues (IC), also known as Caldwell 51) is an irregular dwarf galaxy, visible in the constellation Cetus near the star 26 Ceti.[5] It was discovered in 1906 by Max Wolf,[6] and is approaching Earth at 234 km/s.
IC 1613 | |
---|---|
Observation data (J2000 epoch) | |
Constellation | Cetus |
Right ascension | 01h 04m 47.8s[2] |
Declination | +02° 07′ 04″[2] |
Redshift | −234±1 km/s[2] |
Distance | 2.38±0.07 Mly (730±20 kpc)[3][4] |
Apparent magnitude (V) | 9.9[2] |
Characteristics | |
Type | IB(s)m[2] |
Apparent size (V) | 16.2′ × 14.5′[2] |
Other designations | |
UGC 668,[2] DDO 8,[2] PGC 3844,[2] Caldwell 51 |
IC 1613 is a member of the Local Group.[7] It has played an important role in the calibration of the Cepheid variable period-luminosity relation for estimating distances.[8] Other than the Magellanic Clouds, it is one of the few Local Group dwarf irregular galaxy where RR Lyrae-type variables have been observed; this factor, along with an unusually low abundance of interstellar dust both within IC 1613 and along the line of sight enable especially accurate distance estimates.[7][9]
In 1999, Cole et al.[7] used the Hubble Space Telescope to find that the dominant population of this galaxy has an age of ~7 Gyr. Using its Hess diagram, they found that its evolutionary history may be similar to that of the Pegasus Dwarf Irregular Galaxy. Both galaxies are classified as Ir V in the DDO system. Also in 1999, Antonello et al. found five cepheids of Population II in IC 1613, giving self-evident support for the existence of a very old stellar population component of IC 1613. In 1999, King, Modjaz, & Li discovered the first nova ever detected in IC 1613.[10]
IC 1613 contains a WO star known as DR1, which might be the only Wolf–Rayet star in the galaxy,[11][12] although a candidate WC+O binary, SPIRITS14bqe, has been found.[13] The galaxy also contains a Luminous Blue Variable candidate,[14] and a rich population of OB-type[15] stars and OB associations.[16]
There are many faint galaxies close to IC 1613, 14 of which are catalogued as members of a yet-unnamed galaxy cluster located at z≈0.20.[17]
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