NGC 4449
| NGC 4449 | |
|---|---|
.jpg) A Hubble Space Telescope (HST) image of NGC 4449. |
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| Observation data (J2000 epoch) | |
| Constellation | Canes Venatici[1] |
| Right ascension | 12h 28m 11.9s[2] |
| Declination | +44° 05′ 40″[2] |
| Redshift | 207 ± 4 km/s[2] |
| Distance | ~12 Mly (~ 3.6 Mpc)[2] |
| Type | IBm[2] |
| Apparent dimensions (V) | 6′.2 × 4′.4[2] |
| Apparent magnitude (V) | 10.0[2] |
| Other designations | |
| UGC 7592,[2] PGC 40973,[2] Caldwell 21 | |
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See also: Galaxy, List of galaxies |
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NGC 4449 (also known as Caldwell 21) is an irregular galaxy in the constellation Canes Venatici. It is located about 12 million light-years away, part of the M94 Group (the Canes Venatici I Group), a galaxy group relatively close to the Local Group containing the Milky Way.
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Characteristics [edit]
This well-studied galaxy is similar in size and brightness, and often compared to, the Milky Way's satellite galaxy, the Large Magellanic Cloud (LMC).[3] NGC 4449 has a general bar shape, also characteristic of the LMC, with scattered young blue star clusters.
Starburst galaxy [edit]
Unlike the Large Magellanic Cloud, however, NGC 4449 is considered a starburst galaxy due to its high rate of star formation (twice the one of the LMC)[4] and includes several massive and young star clusters,[5][6] one of them in the galaxy's center.[7]
Near the bottom (of the Hubble photo) is the pinkish glow of atomic hydrogen gas, the telltale tracer of massive star forming regions.
NGC 4449 is surrounded by a large envelope of neutral hydrogen that extends over an area of 75 arc minutes −14 times larguer than the optical diameter of the galaxy- that show distorsions and irregularities likely caused by interactions with nearby galaxies.[8]
Interactions with nearby galaxies are thought to have influenced star formation in NGC 4449 and, in fact, in 2012 two small galaxies have been discovered interacting with this galaxy: a very low surface brightness dwarf spheroidal with just the same stellar mass than that present of NGC 4449's halo but much more massive (between 10 times and 5 times less than it) due to the presence of dark matter that is merging with NGC 4449[9] and a highly flattened globular cluster with two tails of young stars that may be the nucleus of a gas-rich galaxy being disrupted and absorbed by NGC 4449.[10]
External links [edit]
- Astronomy Picture of the Day – May 3, 2007, 10 July 2007, and 25 February 2011
- NGC 4449 on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
References [edit]
- ^ R. W. Sinnott, editor (1988). The Complete New General Catalogue and Index Catalogue of Nebulae and Star Clusters by J. L. E. Dreyer. Sky Publishing Corporation and Cambridge University Press. ISBN 0-933346-51-4.
- ^ a b c d e f g h i "NASA/IPAC Extragalactic Database". Results for NGC 4449. Retrieved 2007-07-13.
- ^ Karachentsev, Igor D.; Karachentseva, Valentina E.; Huchtmeier, Walter K.; Makarov, Dmitry I. (2003). "A Catalog of Neighboring Galaxies". The Astronomical Journal 127 (4): 2031–2068. Bibcode:2004AJ....127.2031K. doi:10.1086/382905.
- ^ Annibali, F.; Aloisi, A.; Mack, J.; Tosi, M.; van der Marel, R. P.; Angeretti, L.; Leitherer, C.; Sirianni, M. (2008). "Starbursts in the Local Universe: New Hubble Space Telescope Advanced Camera for Surveys Observations of the Irregular Galaxy NGC 4449". The Astronomical Journal 135 (5): 1900–1916. Bibcode:2008AJ....135.1900A. doi:10.1088/0004-6256/135/5/1900.
- ^ Reines, Amy E.; Johnson, Kelsey E.; Goss, W. M. (2008). "Emerging Massive Star Clusters Revealed: High-Resolution Imaging of NGC 4449 from the Radio to the Ultraviolet". The Astronomical Journal 135 (6): 2222–2239. Bibcode:2008AJ....135.2222R. doi:10.1088/0004-6256/135/6/2222.
- ^ Larsen, Søren S.; Brodie, Jean P.; Hunter, Deidre A. (2004). "Dynamical Mass Estimates for Five Young Massive Stellar Clusters". The Astronomical Journal 128 (5): 2295–2305. Bibcode:2004AJ....128.2295L. doi:10.1086/424538.
- ^ Böker, Torsten; van der Marel, Roeland P.; Mazzuca, Lisa; Rix, Hans-Walter; Rudnick, Gregory; Ho, Luis C.; Shields, Joseph C. (2001). "A Young Stellar Cluster in the Nucleus of NGC 4449". The Astronomical Journal 121 (3): 1473–1481. Bibcode:2001AJ....121.1473B. doi:10.1086/319415.
- ^ Bajaja, E.; Huchtmeier, W. K.; Klein, U. (1994). "The extended HI halo in NGC 4449". Astronomy and Astrophysics 285: 385–388. Bibcode:1994A&A...285..385B.
- ^ Martínez-Delgado, David; Romanowsky, Aaron J.; Gabany, R. Jay; Annibali, Francesca; Arnold, Jacob A.; Fliri, Jürgen; Zibetti, Stefano; van der Marel, Roeland P.; Rix, Hans-Walter; Chonis, Taylor S.; Carballo-Bello, Julio A.; Aloisi, Alessandra; Macciò, Andrea V.; Gallego-Laborda, J.; Brodie, Jean P.; Merrifield, Michael R. (2012). "Dwarfs Gobbling Dwarfs: A Stellar Tidal Stream around NGC 4449 and Hierarchical Galaxy Formation on Small Scales". The Astrophysical Journal Letters 748 (2). Bibcode:2012ApJ...748L..24M. doi:10.1088/2041-8205/748/2/L24. Unknown parameter
|article id=ignored (help) - ^ Annibali, F.; Tosi, M.; Aloisi, A.; van der Marel, R. P.; Martinez-Delgado, D. (2012). "Cluster 77 in NGC 4449: The Nucleus of a Satellite Galaxy Being Transformed into a Globular Cluster?". The Astrophysical Journal Letters 745 (1). Bibcode:2012ApJ...745L...1A. doi:10.1088/2041-8205/745/1/L1. Unknown parameter
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