Canes Venatici I
Canes Venatici I or CVn I is a dwarf spheroidal galaxy situated in the Canes Venatici constellation and discovered in 2006 in the data obtained by Sloan Digital Sky Survey.[4] It is one of the most distant known satellites of the Milky Way as of 2011 together with Leo I and Leo II.[4] The galaxy is located at a distance of about 220 kpc from the Sun and is moving away from the Sun at a velocity of about 31 km/s.[6] It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical (ratio of axes ~ 2.5:1) shape with the half-light radius of about 550 pc.[4][5]
| Canes Venatici Dwarf Galaxy[1] | |
|---|---|
| Observation data (J2000 epoch) | |
| Constellation | Canes Venatici |
| Right ascension | 13h 28m 03.5s[1] |
| Declination | +33° 33′ 21″[1] |
| Distance | 711 ± 33 kly (218 ± 10 kpc) [2] 685+23 −16 kly (210+7 −5 kpc)[3] |
| Apparent magnitude (V) | 13.9 ± 0.5[4] |
| Characteristics | |
| Type | dSph |
| Apparent size (V) | 17.8 ± 0.8′[5] |
| Other designations | |
| CVn Dwarf Galaxy,[1] PGC 4689223 | |
CVn I is a relatively faint satellite of the Milky Way—its integrated luminosity is about 230,000 times that of the Sun (absolute visible magnitude of about −8.6).[5] However, its mass is about 27 million solar masses, which means that the galaxy's mass to light ratio is around 220. A high mass to light ratio implies that CVn I is predominately made up of dark matter.[6]
The stellar population of CVn I consists mainly of old stars formed more than 10 billion years ago. The metallicity of these old stars is also very low at [Fe/H] ≈ −2.08 ± 0.02, which means that they contain 110 times less heavy elements than the Sun.[7] There are also about 60 RR Lyrae stars.[3] The galaxy also contains a small fraction of younger (1–2 billion years old) more metal-rich ([Fe/H] ≈ −1.5) stars, which account for about 5% of its mass and 10% of its light. These younger stars are concentrated in the center of the galaxy.[2] There is currently no star formation in CVn I and the measurements have so far failed to detect neutral hydrogen in it—the upper limit is 30,000 solar masses.[8]
References edit
- ^ a b c d "NAME CVn I dSph". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2011-11-21.
- ^ a b Martin, N. F.; Coleman, M. G.; De Jong, J. T. A.; Rix, H. W.; Bell, E. F.; Sand, D. J.; Hill, J. M.; Thompson, D.; Burwitz, V.; Giallongo, E.; Ragazzoni, R.; Diolaiti, E.; Gasparo, F.; Grazian, A.; Pedichini, F.; Bechtold, J. (2008). "A Deep Large Binocular Telescope View of the Canes Venatici I Dwarf Galaxy". The Astrophysical Journal. 672 (1): L13–L16. arXiv:0709.3365. Bibcode:2008ApJ...672L..13M. doi:10.1086/525559. S2CID 14614201.
- ^ a b Kuehn, C.; Kinemuchi, K.; Ripepi, V.; Clementini, G.; Dall'Ora, M.; Di Fabrizio, L.; Rodgers, C. T.; Greco, C.; Marconi, M.; Musella, I.; Smith, H. A.; Catelan, M. R.; Beers, T. C.; Pritzl, B. J. (2008). "Variable Stars in the Newly Discovered Milky Way Dwarf Spheroidal Satellite Canes Venatici I". The Astrophysical Journal. 674 (2): L81. arXiv:0709.3281. Bibcode:2008ApJ...674L..81K. doi:10.1086/529137. S2CID 118674121.
- ^ a b c d Zucker, D. B.; Belokurov, V.; Evans, N. W.; Wilkinson, M. I.; Irwin, M. J.; Sivarani, T.; Hodgkin, S.; Bramich, D. M.; Irwin, J. M.; Gilmore, G.; Willman, B.; Vidrih, S.; Fellhauer, M.; Hewett, P. C.; Beers, T. C.; Bell, E. F.; Grebel, E. K.; Schneider, D. P.; Newberg, H. J.; Wyse, R. F. G.; Rockosi, C. M.; Yanny, B.; Lupton, R.; Smith, J. A.; Barentine, J. C.; Brewington, H.; Brinkmann, J.; Harvanek, M.; Kleinman, S. J.; Krzesinski, J. (2006). "A New Milky Way Dwarf Satellite in Canes Venatici". The Astrophysical Journal. 643 (2): L103. arXiv:astro-ph/0604354. Bibcode:2006ApJ...643L.103Z. doi:10.1086/505216. S2CID 119421888.
- ^ a b c Martin, N. F.; De Jong, J. T. A.; Rix, H. W. (2008). "A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites". The Astrophysical Journal. 684 (2): 1075–1092. arXiv:0805.2945. Bibcode:2008ApJ...684.1075M. doi:10.1086/590336. S2CID 17838966.
- ^ a b Simon, J. D.; Geha, M. (2007). "The Kinematics of the Ultra-faint Milky Way Satellites: Solving the Missing Satellite Problem". The Astrophysical Journal. 670 (1): 313–331. arXiv:0706.0516. Bibcode:2007ApJ...670..313S. doi:10.1086/521816. S2CID 9715950.
- ^ Kirby, E. N.; Simon, J. D.; Geha, M.; Guhathakurta, P.; Frebel, A. (2008). "Uncovering Extremely Metal-Poor Stars in the Milky Way's Ultrafaint Dwarf Spheroidal Satellite Galaxies". The Astrophysical Journal. 685 (1): L43–L46. arXiv:0807.1925. Bibcode:2008ApJ...685L..43K. doi:10.1086/592432. S2CID 3185311.
- ^ Grcevich, J.; Putman, M. E. (2009). "H I in Local Group Dwarf Galaxies and Stripping by the Galactic Halo". The Astrophysical Journal. 696 (1): 385–395. arXiv:0901.4975. Bibcode:2009ApJ...696..385G. doi:10.1088/0004-637X/696/1/385.
External links edit
- The Universe within 500000 light-years The Satellite Galaxies (Atlas of the Universe)
- Two New Galaxies Orbiting the Milky Way (Ken Croswell) April 19, 2006
- Strange satellite galaxies revealed around Milky Way Kimm Groshong (New Scientist) 17:00 24 April 2006
- New Milky Way companions found: SDSS-II first to view two dim dwarf galaxies (SDSS) May 8, 2006
- Astronomers Find Two New Milky Way Companions (SpaceDaily) May 10, 2006