Willman 1

Willman 1 is an ultralight dwarf galaxy, possibly also a globular cluster . It is named after Beth Willman of Haverford College , the lead author of a study based on data from the Sloan Digital Sky Survey . The galaxy is a satellite of the Milky Way and about 120 k pc away. Willman 1 has an elliptical shape with a half-light radius of about 25 pc and a heliocentric escape velocity of approximately −13 km / s.

properties

Stand of the Year 2011 is Willman 1 the zweitlichtschwächste known dwarf galaxy by Segue 1 . It is only a 10 millionth of the luminosity of the Milky Way. The galaxy has an absolute magnitude of −3 mag. Observations suggest that it has a mass of 400,000 M _⊙ . This leads to a mass-luminosity ratio of around 800, which implies that this galaxy is dominated by dark matter . However, it is difficult, especially with such faint objects, to estimate the total mass of the system, since a stable gravitationally bound system is always assumed as the basis for calculation, which is not always the case with galaxies that are currently exposed to the external influence of tidal forces .

Willman 1 is primarily composed of older stars that formed more than 10 billion years ago. The metallicity of these stars is correspondingly low with [Fe / H] ≈ −2.1, which is equivalent to the fact that they contain about 110 times less heavy elements than our sun .

Individual evidence

↑ ^a ^b ^c ^d ^e Beth Willman, Michael R. Blanton, Andrew A. West, Julianne J. Dalcanton, David W. Hogg, Donald P. Schneider, Nicholas Wherry, Brian Yanny u. a .: A New Milky Way Companion: Unusual Globular Cluster or Extreme Dwarf Satellite? . In: The Astronomical Journal . 129, No. 6, 2005, pp. 2692-2700. arxiv : astro-ph / 0410416 . bibcode : 2005AJ .... 129.2692W . doi : 10.1086 / 430214 .
^ ^A ^b N. F. Martin, JTA De Jong, HW Rix: A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites. The Astrophysical Journal 684 (2) p. 1075, 2008, doi: 10.1086 / 590336 .
↑ ^a ^b ^c ^d ^e ^f Beth Willman, Marla Geha, Jay Strader, Louie Strigari, Josh Simon, Evan Kirby, Ho West, Warres Nhung and others: Willman 1 — A Probable Dwarf Galaxy with an Irregular Kinematic Distribution . In: AJ . 142, No. 4, October 2011, p. 128. arxiv : 1007.3499 . bibcode : 2011AJ .... 142..128W . doi : 10.1088 / 0004-6256 / 142/4/128 .
↑ (15.2 ± 0.4) likes apparent brightness - 5 * log ₁₀ ((38,000 ± 7,000) pc / 10 pc) → −2.7 likes absolute brightness
↑ NED Results for SDSS J1049 + 5103 . Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. January 9, 2007. Retrieved December 28, 2012.
^ NF Martin, JTA De Jong, HW Rix: A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites. The Astrophysical Journal 684 (2) p. 1075, 2008, doi: 10.1086 / 590336 .

[Willmanetal2005-1] Beth Willman, Michael R. Blanton, Andrew A. West, Julianne J. Dalcanton, David W. Hogg, Donald P. Schneider, Nicholas Wherry, Brian Yanny u. a .: A New Milky Way Companion: Unusual Globular Cluster or Extreme Dwarf Satellite? . In: The Astronomical Journal . 129, No. 6, 2005, pp. 2692-2700. arxiv : astro-ph / 0410416 . bibcode : 2005AJ .... 129.2692W . doi : 10.1086 / 430214 .

[Martin2008-2] A ^b N. F. Martin, JTA De Jong, HW Rix: A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites. The Astrophysical Journal 684 (2) p. 1075, 2008, doi: 10.1086 / 590336 .

[Willmanetal2011-3] ↑ ^a ^b ^c ^d ^e ^f Beth Willman, Marla Geha, Jay Strader, Louie Strigari, Josh Simon, Evan Kirby, Ho West, Warres Nhung and others: Willman 1 — A Probable Dwarf Galaxy with an Irregular Kinematic Distribution . In: AJ . 142, No. 4, October 2011, p. 128. arxiv : 1007.3499 . bibcode : 2011AJ .... 142..128W . doi : 10.1088 / 0004-6256 / 142/4/128 .

[4] (15.2 ± 0.4) likes apparent brightness - 5 * log ₁₀ ((38,000 ± 7,000) pc / 10 pc) → −2.7 likes absolute brightness

[5] NED Results for SDSS J1049 + 5103 . Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. January 9, 2007. Retrieved December 28, 2012.

[6] NF Martin, JTA De Jong, HW Rix: A Comprehensive Maximum Likelihood Analysis of the Structural Properties of Faint Milky Way Satellites. The Astrophysical Journal 684 (2) p. 1075, 2008, doi: 10.1086 / 590336 .