Volopas II or Boo II is a dwarf spheroidal galaxy located in the constellation Bootop and discovered in 2007 when processing data obtained by Sloan digital sky survey [2] . The galaxy is at a distance of about 42 kpc from the Sun and moves toward the Sun at a speed of 120 km / s [2] [5] . It has an approximately circular shape with a radius of about 51 pc and is classified as a dwarf spheroidal galaxy (dSph) [3] [note 1] .
Boots II [1] | |
---|---|
Galaxy | |
Research history | |
opening date | 2010.02.13 |
Designations | Boo II |
Observational data ( The Age of J2000 ) | |
Constellation | Bootes |
Right ascension | |
Declination | |
Specifications | |
Type of | dSph [2] |
Enters into | |
Redshift | |
Distance | 136 ± 7 thousand, sv. years (42 ± 2 thousand, pc ) [3] [4] |
Boots II is one of the smallest and dimest satellites [note 2] of the Milky Way - its integral luminosity is only 1000 times larger than the Sun (the absolute apparent magnitude is about −2.7 m ), which is significantly lower than the luminosity of most globular clusters [ 3] . However, the mass of the galaxy is significant, the mass to luminosity ratio is more than 100 M M / L ☉ [4] .
The stellar population of Bootes II consists mainly of moderately old stars that arose 10–12 billion years ago [5] . The metallicity of these old stars is at a low level [Fe / H] = −1.8 , which means that they contain 80 times less heavy elements than the Sun [4] [5] . Currently there is no star formation in Bootes II. Until now, the radio link of neutral hydrogen has not been found in the galaxy - the upper limit of the presence of neutral hydrogen is only 86 M ☉ [6] .
Boots II is located only 1.5 degrees ( ~ 1.6 kpc ) from another dwarf galaxy - Bootes I [2] , although they can hardly be physically connected because they move in opposite directions relative to the Milky Way. Their relative speed is too high, about 200 km / s . It is more likely that Bolop II is associated with the Sagittarius Flow and, therefore, with the Sagittarius Dwarf Elliptical Galaxy . Boots II can be either a SagDEG satellite galaxy, or one of its star clusters detached from the main galaxy 4-7 billion years ago [5] .
Notes
- ↑ Other sources give a radius of about 36 pc in half isophote. [four]
- ↑ Only Segue 1 , Segue 2 and Willman 1 are dimmer [3] .
Links
- ↑ SIMBAD Astronomical Database . Results for Bootes II . The appeal date is February 13, 2010. Archived May 31, 2013.
- ↑ 1 2 3 4 Walsh SM; Jerjen, H .; Willman, B. A New York Milky Way Satellite (Eng.) // The Astrophysical Journal. - 2007. - Vol. 662 , no. 2 - P. L83 — L86 . - DOI : 10.1086 / 519684 . - . - arXiv : 0705.1378 .
- ↑ 1 2 3 4 Martin Nicolas F. , de Jong Jelte TA , Rix Hans-Walter. The Milky Way Satellites // A Astrophysical Journal. - 2008. - September 10 ( v. 684 , № 2 ). - S. 1075-1092 . - ISSN 0004-637X . - DOI : 10.1086 / 590336 .
- ↑ 1 2 3 4 Walsh, SM; Willman, B .; Sand, D. et al. Boötes II ReBoöted: An MMT / MegaCam Milk Way Satellite Ultrafaint (Eng.) // The Astrophysical Journal: journal. - 2008. - Vol. 688 , no. 1 . - P. 245-253 . - DOI : 10.1086 / 592076 . - . - arXiv : 0712.3054 .
- ↑ 1 2 3 4 Koch, Andreas; Wilkinson, Mark I .; Kleyna, Jan T. et al. A Spectroscopic Confirmation of the Bootes II Dwarf Spheroidal (Eng.) // The Astrophysical Journal: journal. - 2009. - Vol. 690 , no. 1 . - P. 453-462 . - DOI : 10.1088 / 0004-637X / 690/1/453 . - . - arXiv : 0809.0700 .
- Ce Grcevich Jana , Putman Mary E. HI IN LOCAL GROUP DWARF GALAXIES AND STRIPPING BY THE GALACTIC HALO // The Astrophysical Journal. - 2009. - April 15 ( v. 696 , No. 1 ). - p . 385-395 . - ISSN 0004-637X . - DOI : 10.1088 / 0004-637X / 696/1/385 .