Boötes II (dwarf galaxy)

Bootes II Dwarf Galaxy^[1]
Observation data (J2000 epoch)
Constellation	Bootes
Right ascension	13^h 58^m 00^s^[1]
Declination	12° 51′ 00″^[1]
Distance	136 ± 7 kly (42 ± 2 kpc)^[2]^[3]
Type	dSph^[4]
Apparent dimensions (V)	8.0+2.2 −2.8′^[2]
Apparent magnitude (V)	15.8 ± 0.5^[4]
Other designations
Boo II,^[2] PGC 4713552

Bootes II or Boo II is a dwarf spheroidal galaxy situated in the Bootes constellation and discovered in 2007 in the data obtained by Sloan Digital Sky Survey.^[4] The galaxy is located at the distance of about 42 kpc from the Sun and moves towards the Sun with the speed of 120 km/s.^[4]^[5] It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately round shape with the half-light radius of about 51 pc.^[2]^{[note 1]}

Bootes II is one of the smallest and faintest satellites^{[note 2]} of the Milky Way—its integrated luminosity is about 1,000 times that of the Sun (absolute visible magnitude of about −2.7), which is much lower than the luminosity of the majority of globular clusters.^[2] However the mass of the galaxy is substantial corresponding to the mass to light ratio of more than 100.^[3]

The stellar population of Bootes II consists mainly of moderately old stars formed 10–12 billion years ago.^[5] The metallicity of these old stars is low at [Fe/H]=−1.8, which means that they contain 80 times less heavy elements than the Sun.^[3]^[5] Currently there is no star formation in Bootes II. The measurements have so far failed to detect any neutral hydrogen in it—the upper limit is only 86 solar masses.^[6]

Bootes II is located only 1.5 degrees (~1.6 kpc) away from another dwarf galaxy—Boötes I,^[4] although they are unlikely to be physically associated because they move in opposite directions relative to the Milky Way. Their relative velocity—about 200 km/s is too high. It is more likely associated with the Sagittarius Stream and, therefore, with the Sagittarius Dwarf Elliptical Galaxy (SagDEG). Bootes II may be either a satellite galaxy of SagDEG or one of its star clusters torn from the main galaxy 4–7 billion years ago.^[5]

Notes

^ Other sources give the half-light radius of about 36 pc.^[3]
^ Only Segue 1, Segue 2 and Willman 1 are fainter.^[2]

References

^ ^a ^b ^c "SIMBAD Astronomical Database". Results for Bootes II. Retrieved 2010-02-13.
^ ^a ^b ^c ^d ^e ^f Martin, Nicolas F.; de Jong, Jelte T. A.; Rix, Hans-Walter (September 2008). "A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites". The Astrophysical Journal 684 (2): 1075. Bibcode:2008ApJ...684.1075M. doi:10.1086/590336.
^ ^a ^b ^c ^d Walsh, S.M.; Willman, B.; Sand, D.; et al. (2008). "Boötes II ReBoöted: An MMT/MegaCam Study of an Ultrafaint Milky Way Satellite". The Astrophysical Journal 688 (1): 245–253. Bibcode:2008ApJ...688..245W. arXiv:0712.3054. doi:10.1086/592076.
^ ^a ^b ^c ^d ^e Walsh, S.M.; Jerjen, H.; Willman, B. (June 2007). "A Pair of Boötes: A New Milky Way Satellite". The Astrophysical Journal 662 (2): L83–L86. Bibcode:2007ApJ...662L..83W. arXiv:0705.1378. doi:10.1086/519684.
^ ^a ^b ^c ^d Koch, Andreas; Wilkinson; Kleyna, Jan T.; et al. (January 2009). "A Spectroscopic Confirmation of the Bootes II Dwarf Spheroidal". The Astrophysical Journal 690 (1): 453–462. Bibcode:2009ApJ...690..453K. arXiv:0809.0700. doi:10.1088/0004-637X/690/1/453.
^ Grcevich, Jana; Putman, Mary E. (May 2009). "H I in Local Group Dwarf Galaxies and Stripping by the Galactic Halo". The Astrophysical Journal 696 (1): 385. Bibcode:2009ApJ...696..385G. doi:10.1088/0004-637X/696/1/385.

The Milky Way

Location

Milky Way → Milky Way subgroup → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe
Each arrow (→) may be read as "within" or "part of".

Galactic core

Spiral arms

Satellite galaxies

Magellanic Clouds	Large Magellanic Cloud Small Magellanic Cloud Magellanic Stream Magellanic Bridge

Sagittarius Spheroidal	Sagittarius Stream Boötes II Coma Berenices Messier 54 Palomar 12 Segue 1 Segue 2 Terzan 7

Dwarfs	Boötes I Boötes III Canes Venatici I Canes Venatici II Canis Major Carina Draco Fornax Hercules Leo I Leo II Leo IV Leo V Phoenix Pisces I Pisces II Sculptor Sextans Ursa Major I Ursa Major II Ursa Minor

Other	Monoceros Ring Virgo Stream Koposov I Koposov II Segue 3 Willman 1

Andromeda–Milky Way collision

Astronomy portal

Categories

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.

Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.

By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Boötes II (dwarf galaxy)