Canes Venatici I (dwarf galaxy)

Short description: Galaxy in constellation Canes Venatici

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

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]

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 dominated by the 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

1. ↑ 1.0 1.1 1.2 1.3 "NAME CVn I dSph". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=NAME+CVn+I+dSph.
2. ↑ 2.0 2.1 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. et al. (2008). "A Deep Large Binocular Telescope View of the Canes Venatici I Dwarf Galaxy". The Astrophysical Journal 672 (1): L13–L16. doi:10.1086/525559. Bibcode: 2008ApJ...672L..13M.
3. ↑ 3.0 3.1 Kuehn, C.; Kinemuchi, K.; Ripepi, V.; Clementini, G.; Dall'Ora, M.; Di Fabrizio, L.; Rodgers, C. T.; Greco, C. et al. (2008). "Variable Stars in the Newly Discovered Milky Way Dwarf Spheroidal Satellite Canes Venatici I". The Astrophysical Journal 674 (2): L81. doi:10.1086/529137. Bibcode: 2008ApJ...674L..81K.
4. ↑ 4.0 4.1 4.2 4.3 Zucker, D. B.; Belokurov, V.; Evans, N. W.; Wilkinson, M. I.; Irwin, M. J.; Sivarani, T.; Hodgkin, S.; Bramich, D. M. et al. (2006). "A New Milky Way Dwarf Satellite in Canes Venatici". The Astrophysical Journal 643 (2): L103. doi:10.1086/505216. Bibcode: 2006ApJ...643L.103Z.
5. ↑ 5.0 5.1 5.2 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. doi:10.1086/590336. Bibcode: 2008ApJ...684.1075M.
6. ↑ 6.0 6.1 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. doi:10.1086/521816. Bibcode: 2007ApJ...670..313S.
7. ↑ 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. doi:10.1086/592432. Bibcode: 2008ApJ...685L..43K.
8. ↑ 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. doi:10.1088/0004-637X/696/1/385. Bibcode: 2009ApJ...696..385G.

## External links

* 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

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Coordinates:  13h 28m 03.5s, +33° 33′ 21″

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