IC 1613 (also known asCaldwell 51) is anirregulardwarf galaxy located on the outskirts of theLocal group around 730 kiloparsecs fromEarth in theconstellation ofCetus near the star26 Ceti.[6] It has a low mass with its mass only being around 10^8 solar masses.[7] It has played an important role in the calibration of theCepheid variableperiod-luminosity relation for estimating distances.[8] Other than theMagellanic Clouds, it is one of the few Local Group dwarf irregular galaxy whereRR Lyrae-type variables have been observed; this factor, along with an unusually low abundance ofinterstellar dust both within IC 1613 and along the line of sight enable especially accurate distance estimates.[9][10] IC 1613 was discovered in 1906 byMax Wolf,[11] and is approachingEarth at 234 km/s.[9]
There are many faint galaxies close to IC 1613, 14 of which are catalogued as members of a yet-unnamedgalaxy cluster located at z≈0.20.[12]
The sky around IC 1613, with26 Ceti towards the bottom of the frame (south) and29 Ceti to the left (east)
It is one of the few irregular dwarf galaxies in the Local group where RR Lyrae-type variable stars have been observed. Others include the Magellanic Clouds. In 1999, Cole et al.[9] used theHubble Space Telescope (HST) to find that the dominantpopulation of this galaxy has an age of ~7 Gyr. Using itsHess diagram, they found that its evolutionary history may be similar to that of thePegasus Dwarf Irregular Galaxy. Both galaxies are classified as Ir V in the DDO system. Also in 1999, Antonello et al. found five cepheids ofPopulation 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 firstnova ever detected in IC 1613.[13]
Hubble image of the central part of IC 1613, showing the faint galaxies of a background galaxy cluster.
GHV-62024 is aO6-type star located in thisgalaxy that shows characteristics ofF-type stars. It has a fast rotation which likely causes strongCNO mixing, the products of which contaminate the stars surface.[20]
Many studies have studied theinterstellar medium of IC 1613 such as H l and H ll complexes. There has currently been one recognizedsupernova remnant (SNR) which has been namedS8. There may also be another remnant with a shell-like structure with a diameter of 55 parsecs.[21] S8 was first identified byAllan Sandage as emission nebula no. 8 in 1971. He used the 200-inchHale reflector.[22] A study using data from theMDM Observatory found that S8 is a very young supernova remnant. The nebula has an estimated mass of 119±34M☉ and an age between 2700 and 4400 years.[23]
^abSkillman, Evan D.; Hidalgo, Sebastian L.; Weisz, Daniel R.; Monelli, Matteo; Gallart, Carme; Aparicio, Antonio; Bernard, Edouard J.; Boylan-Kolchin, Michael; Cassisi, Santi; Cole, Andrew A.; Dolphin, Andrew E.; Ferguson, Henry C.; Mayer, Lucio; Navarro, Julio F.; Stetson, Peter B.; Tolstoy, Eline (15 April 2014). "The ACS LCID project. X. The star formation history of IC 1613: revisiting the over-cooling problem".The Astrophysical Journal.786 (1): 44.arXiv:1403.4609.Bibcode:2014ApJ...786...44S.doi:10.1088/0004-637X/786/1/44.
^abcCole, Andrew A.; Tolstoy, Eline; Gallagher, John S., III; Hoessel, John G.; Mould, Jeremy R.; Holtzman, Jon A.; Saha, Abhijit; Ballester, Gilda E.; Burrows, Christopher J.; Clarke, John T.; Crisp, David; Griffiths, Richard E.; Grillmair, Carl J.; Hester, Jeff J.; Krist, John E.; Meadows, Vikki; Scowen, Paul A.; Stapelfeldt, Karl R.; Trauger, John T.; Watson, Alan M.; Westphal, James R. (1999). "Stellar Populations at the Center of IC 1613".The Astronomical Journal.118 (4):1657–1670.arXiv:astro-ph/9905350.Bibcode:1999AJ....118.1657C.doi:10.1086/301042.S2CID17566586.
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Media related toIC 1613 at Wikimedia Commons
