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Boötes II Dwarf Galaxy [1]
Observation data ( J2000 epoch)
Constellation Boötes
Right ascension13h 58m 00s [1]
Declination+12° 51′ 00″ [1]
Distance136 ± 7 kly (42 ± 2 kpc) [2] [3]
Apparent magnitude (V)15.8 ± 0.5 [4]
Characteristics
TypedSph [4]
Apparent size (V)8.0+2.2
−2.8′ [2]
Other designations
Boo II, [2] PGC 4713552

Boötes II or Boo II is a dwarf spheroidal galaxy situated in the constellation Boötes 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]

Boötes 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 Boötes 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 Boötes II. The measurements have so far failed to detect any neutral hydrogen in it—the upper limit is only 86 solar masses. [6]

Boötes 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). Boötes 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

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

References

  1. ^ a b c "NAME Boötes II". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-02-13.
  2. ^ 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): 1075–1092. arXiv: 0805.2945. Bibcode: 2008ApJ...684.1075M. doi: 10.1086/590336. S2CID  17838966.
  3. ^ 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. arXiv: 0712.3054. Bibcode: 2008ApJ...688..245W. doi: 10.1086/592076. S2CID  244191.
  4. ^ 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. arXiv: 0705.1378. Bibcode: 2007ApJ...662L..83W. doi: 10.1086/519684. S2CID  17830926.
  5. ^ a b c d Koch, Andreas; Wilkinson, Mark I.; Kleyna, Jan T.; et al. (January 2009). "A Spectroscopic Confirmation of the Boötes II Dwarf Spheroidal". The Astrophysical Journal. 690 (1): 453–462. arXiv: 0809.0700. Bibcode: 2009ApJ...690..453K. doi: 10.1088/0004-637X/690/1/453. S2CID  14365307.
  6. ^ 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): 385–395. arXiv: 0901.4975. Bibcode: 2009ApJ...696..385G. doi: 10.1088/0004-637X/696/1/385.


Retrieved from " https://en.wikipedia.org/?title=Boötes_II&oldid=1157007734"
From Wikipedia, the free encyclopedia
Boötes II Dwarf Galaxy [1]
Observation data ( J2000 epoch)
Constellation Boötes
Right ascension13h 58m 00s [1]
Declination+12° 51′ 00″ [1]
Distance136 ± 7 kly (42 ± 2 kpc) [2] [3]
Apparent magnitude (V)15.8 ± 0.5 [4]
Characteristics
TypedSph [4]
Apparent size (V)8.0+2.2
−2.8′ [2]
Other designations
Boo II, [2] PGC 4713552

Boötes II or Boo II is a dwarf spheroidal galaxy situated in the constellation Boötes 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]

Boötes 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 Boötes 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 Boötes II. The measurements have so far failed to detect any neutral hydrogen in it—the upper limit is only 86 solar masses. [6]

Boötes 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). Boötes 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

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

References

  1. ^ a b c "NAME Boötes II". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-02-13.
  2. ^ 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): 1075–1092. arXiv: 0805.2945. Bibcode: 2008ApJ...684.1075M. doi: 10.1086/590336. S2CID  17838966.
  3. ^ 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. arXiv: 0712.3054. Bibcode: 2008ApJ...688..245W. doi: 10.1086/592076. S2CID  244191.
  4. ^ 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. arXiv: 0705.1378. Bibcode: 2007ApJ...662L..83W. doi: 10.1086/519684. S2CID  17830926.
  5. ^ a b c d Koch, Andreas; Wilkinson, Mark I.; Kleyna, Jan T.; et al. (January 2009). "A Spectroscopic Confirmation of the Boötes II Dwarf Spheroidal". The Astrophysical Journal. 690 (1): 453–462. arXiv: 0809.0700. Bibcode: 2009ApJ...690..453K. doi: 10.1088/0004-637X/690/1/453. S2CID  14365307.
  6. ^ 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): 385–395. arXiv: 0901.4975. Bibcode: 2009ApJ...696..385G. doi: 10.1088/0004-637X/696/1/385.


Retrieved from " https://en.wikipedia.org/?title=Boötes_II&oldid=1157007734"

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