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Segue 1

January 01, 1970

Segue 1 is a dwarf spheroidal galaxy or globular cluster situated in the Leo constellation and discovered in 2006 by Sloan Digital Sky Survey.[2] It is located at a distance of about 23 kpc (about 75,000 light years) from the Sun and moves away from the Sun with the velocity of about 206 km/s.[2][5] Segue 1 has a noticeably elongated (ratio of axes ~ 2:1) shape with the half-light radius of about 30 pc.[2][4] This elongation may be caused by the tidal forces acting from the Milky Way galaxy if Segue 1 is being tidally disrupted now.[6]

Segue 1
Observation data (J2000 epoch)
ConstellationLeo
Right ascension10h 07m 04s[1]
Declination16° 04′ 55″[1]
Distance75 ± 6.5 kly (23 ± 2 kpc)[2]
Apparent magnitude (V)13.8 ± 0.5[2]
Characteristics
TypedSph or GC[1][2]
Mass/Light ratio3400 (V)[3] M☉/L☉
Apparent size (V)8.8′[4]
Other designations
Segue 1, PGC 4713559

The name is due to the fact that it was found by the SEGUE program, the Sloan Extension for Galactic Understanding and Exploration.

Properties edit

Segue 1 is one of the smallest and faintest satellites of the Milky Way—its integrated luminosity is about 300 times that of the Sun (absolute visible magnitude of about −1.5),[note 1] which is much smaller than the luminosity of a typical globular cluster.[2][4] Observations indicate its mass is about 600,000 solar masses, which means that Segue's 1 mass to light ratio is around 3400.[3] Segue 1 had the highest known mass-to-light ratio of any observed galaxy as of 2011.[3] A high mass to light ratio implies that Segue 1 may be dominated by dark matter. It is difficult, however, to estimate the mass of such faint objects due to significant foreground contamination, which inflates the velocity dispersion. In addition, any mass estimate is based on an implicit assumption that an object is gravitationally bound, which may not be true if the object is in a process of disruption.[6]

The stellar population of Segue 1 consists mainly of old stars formed more than 12 billion years ago.[6] The metallicity of these old stars is also very low at [Fe/H] ≈ −2.5 ± 0.8, which means that they contain 300 times less heavy elements than the Sun.[3] Currently there is no star formation in Segue 1. Measurements have so far failed to detect neutral hydrogen in it—the upper limit is 13 solar masses.[7] There is an estimate of roughly 1000 stars within the object. Of these, 7 have been found to be in the red giant stage of their life. The chemical composition of Segue 1 indicates no substantial chemical evolution has occurred since the galaxy formed, supporting the idea that it may be a surviving first galaxy that experienced only one burst of star formation, a fossil galaxy from the early universe.[8][9][10][11]

Segue 1 is located in the middle of the Sagittarius Stream and at approximately the same distance from the Sun. It may once have been a globular cluster of the Sagittarius Dwarf Elliptical Galaxy, which was later stripped from it by the tidal forces acting from the Milky Way galaxy.[6] However, more recent studies concluded that Segue 1 is not actually associated with the Sagittarius stream and that it is not being tidally disrupted.[3][12] If Segue 1 is a galaxy it may have been a satellite of the Sagittarius Dwarf Elliptical Galaxy in the past.[5]

Notes edit

  1. ^ From other sources the absolute magnitude is from −3 to −1.6.[2][6]

References edit

  1. ^ a b c "NAME Segue 1". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-03-13.
  2. ^ a b c d e f g h Belokurov, V.; Zucker, D. B.; Evans, N. W.; Kleyna, J. T.; Koposov, S.; Hodgkin, S. T.; Irwin, M. J.; Gilmore, G.; Wilkinson, M. I.; Fellhauer, M.; Bramich, D. M.; Hewett, P. C.; Vidrih, S.; De Jong, J. T. A.; Smith, J. A.; Rix, H. ‐W.; Bell, E. F.; Wyse, R. F. G.; Newberg, H. J.; Mayeur, P. A.; Yanny, B.; Rockosi, C. M.; Gnedin, O. Y.; Schneider, D. P.; Beers, T. C.; Barentine, J. C.; Brewington, H.; Brinkmann, J.; Harvanek, M.; Kleinman, S. J. (2007). "Cats and Dogs, Hair and a Hero: A Quintet of New Milky Way Companions". The Astrophysical Journal. 654 (2): 897–906. arXiv:astro-ph/0608448. Bibcode:2007ApJ...654..897B. doi:10.1086/509718. S2CID 18617277.
  3. ^ a b c d e Simon, J. D.; Geha, M.; Minor, Q. E.; Martinez, G. D.; Kirby, E. N.; Bullock, J. S.; Kaplinghat, M.; Strigari, L. E.; Willman, B.; Choi, P. I.; Tollerud, E. J.; Wolf, J. (2011). "A Complete Spectroscopic Survey of the Milky Way Satellite Segue 1: The Darkest Galaxy". The Astrophysical Journal. 733 (1): 46. arXiv:1007.4198. Bibcode:2011ApJ...733...46S. doi:10.1088/0004-637X/733/1/46. S2CID 28622194.
  4. ^ a b c 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. arXiv:0805.2945. Bibcode:2008ApJ...684.1075M. doi:10.1086/590336. S2CID 17838966.
  5. ^ a b Geha, Marla; Willman, Beth; Simon, Joshua D.; Strigari, Louis E.; Kirby, Evan N.; Law, David R.; Strader, Jay (2009). "The Least-Luminous Galaxy: Spectroscopy of the Milky Way Satellite Segue 1". The Astrophysical Journal. 692 (2): 1464–1475. arXiv:0809.2781. Bibcode:2009ApJ...692.1464G. doi:10.1088/0004-637X/692/2/1464. S2CID 8894302.
  6. ^ a b c d e Niederste-Ostholt, M.; Belokurov, V.; et al. (2009). "The Origin of Segue 1". Monthly Notices of the Royal Astronomical Society. 398 (4): 1771–1781. arXiv:0906.3669. Bibcode:2009MNRAS.398.1771N. doi:10.1111/j.1365-2966.2009.15287.x. S2CID 12798677.
  7. ^ 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. arXiv:0901.4975. Bibcode:2009ApJ...696..385G. doi:10.1088/0004-637X/696/1/385.
  8. ^ "Nearby galaxy is a 'fossil' from the early universe". Science Daily. 1 May 2014.
  9. ^ . 2014-05-11. Archived from the original on May 14, 2014. Retrieved 2018-09-21.
  10. ^ Frebel, Anna; Simon, Joshua D.; Kirby, Evan N. (April 2014). "Segue 1: An Unevolved Fossil Galaxy from the Early Universe". The Astrophysical Journal. 786 (1): 74. arXiv:1403.6116. Bibcode:2014ApJ...786...74F. doi:10.1088/0004-637X/786/1/74. hdl:1721.1/94556. ISSN 0004-637X. S2CID 56011623.
  11. ^ SEGUE 1: AN UNEVOLVED FOSSIL GALAXY FROM THE EARLY UNIVERSE
  12. ^ Martinez, G. D.; Minor, Q. E.; Bullock, J.; Kaplinghat, M.; Simon, J. D.; Geha, M. (2011). "A Complete Spectroscopic Survey of the Milky Way Satellite Segue 1: Dark Matter Content, Stellar Membership, and Binary Properties from a Bayesian Analysis". The Astrophysical Journal. 738 (1): 55. arXiv:1008.4585. Bibcode:2011ApJ...738...55M. doi:10.1088/0004-637X/738/1/55. S2CID 118674090.

External links edit

  • . W.M. Keck Observatory. Archived from the original on 10 March 2016. Retrieved 4 November 2011.

January 01, 1970
segue, dwarf, spheroidal, galaxy, globular, cluster, situated, constellation, discovered, 2006, sloan, digital, survey, located, distance, about, about, light, years, from, moves, away, from, with, velocity, about, noticeably, elongated, ratio, axes, shape, wi. Segue 1 is a dwarf spheroidal galaxy or globular cluster situated in the Leo constellation and discovered in 2006 by Sloan Digital Sky Survey 2 It is located at a distance of about 23 kpc about 75 000 light years from the Sun and moves away from the Sun with the velocity of about 206 km s 2 5 Segue 1 has a noticeably elongated ratio of axes 2 1 shape with the half light radius of about 30 pc 2 4 This elongation may be caused by the tidal forces acting from the Milky Way galaxy if Segue 1 is being tidally disrupted now 6 Segue 1Observation data J2000 epoch ConstellationLeoRight ascension10h 07m 04s 1 Declination16 04 55 1 Distance75 6 5 kly 23 2 kpc 2 Apparent magnitude V 13 8 0 5 2 CharacteristicsTypedSph or GC 1 2 Mass Light ratio3400 V 3 M L Apparent size V 8 8 4 Other designationsSegue 1 PGC 4713559 The name is due to the fact that it was found by the SEGUE program the Sloan Extension for Galactic Understanding and Exploration Contents 1 Properties 2 Notes 3 References 4 External linksProperties editSegue 1 is one of the smallest and faintest satellites of the Milky Way its integrated luminosity is about 300 times that of the Sun absolute visible magnitude of about 1 5 note 1 which is much smaller than the luminosity of a typical globular cluster 2 4 Observations indicate its mass is about 600 000 solar masses which means that Segue s 1 mass to light ratio is around 3400 3 Segue 1 had the highest known mass to light ratio of any observed galaxy as of 2011 3 A high mass to light ratio implies that Segue 1 may be dominated by dark matter It is difficult however to estimate the mass of such faint objects due to significant foreground contamination which inflates the velocity dispersion In addition any mass estimate is based on an implicit assumption that an object is gravitationally bound which may not be true if the object is in a process of disruption 6 The stellar population of Segue 1 consists mainly of old stars formed more than 12 billion years ago 6 The metallicity of these old stars is also very low at Fe H 2 5 0 8 which means that they contain 300 times less heavy elements than the Sun 3 Currently there is no star formation in Segue 1 Measurements have so far failed to detect neutral hydrogen in it the upper limit is 13 solar masses 7 There is an estimate of roughly 1000 stars within the object Of these 7 have been found to be in the red giant stage of their life The chemical composition of Segue 1 indicates no substantial chemical evolution has occurred since the galaxy formed supporting the idea that it may be a surviving first galaxy that experienced only one burst of star formation a fossil galaxy from the early universe 8 9 10 11 Segue 1 is located in the middle of the Sagittarius Stream and at approximately the same distance from the Sun It may once have been a globular cluster of the Sagittarius Dwarf Elliptical Galaxy which was later stripped from it by the tidal forces acting from the Milky Way galaxy 6 However more recent studies concluded that Segue 1 is not actually associated with the Sagittarius stream and that it is not being tidally disrupted 3 12 If Segue 1 is a galaxy it may have been a satellite of the Sagittarius Dwarf Elliptical Galaxy in the past 5 Notes edit From other sources the absolute magnitude is from 3 to 1 6 2 6 References edit a b c NAME Segue 1 SIMBAD Centre de donnees astronomiques de Strasbourg Retrieved 2010 03 13 a b c d e f g h Belokurov V Zucker D B Evans N W Kleyna J T Koposov S Hodgkin S T Irwin M J Gilmore G Wilkinson M I Fellhauer M Bramich D M Hewett P C Vidrih S De Jong J T A Smith J A Rix H W Bell E F Wyse R F G Newberg H J Mayeur P A Yanny B Rockosi C M Gnedin O Y Schneider D P Beers T C Barentine J C Brewington H Brinkmann J Harvanek M Kleinman S J 2007 Cats and Dogs Hair and a Hero A Quintet of New Milky Way Companions The Astrophysical Journal 654 2 897 906 arXiv astro ph 0608448 Bibcode 2007ApJ 654 897B doi 10 1086 509718 S2CID 18617277 a b c d e Simon J D Geha M Minor Q E Martinez G D Kirby E N Bullock J S Kaplinghat M Strigari L E Willman B Choi P I Tollerud E J Wolf J 2011 A Complete Spectroscopic Survey of the Milky Way Satellite Segue 1 The Darkest Galaxy The Astrophysical Journal 733 1 46 arXiv 1007 4198 Bibcode 2011ApJ 733 46S doi 10 1088 0004 637X 733 1 46 S2CID 28622194 a b c 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 arXiv 0805 2945 Bibcode 2008ApJ 684 1075M doi 10 1086 590336 S2CID 17838966 a b Geha Marla Willman Beth Simon Joshua D Strigari Louis E Kirby Evan N Law David R Strader Jay 2009 The Least Luminous Galaxy Spectroscopy of the Milky Way Satellite Segue 1 The Astrophysical Journal 692 2 1464 1475 arXiv 0809 2781 Bibcode 2009ApJ 692 1464G doi 10 1088 0004 637X 692 2 1464 S2CID 8894302 a b c d e Niederste Ostholt M Belokurov V et al 2009 The Origin of Segue 1 Monthly Notices of the Royal Astronomical Society 398 4 1771 1781 arXiv 0906 3669 Bibcode 2009MNRAS 398 1771N doi 10 1111 j 1365 2966 2009 15287 x S2CID 12798677 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 arXiv 0901 4975 Bibcode 2009ApJ 696 385G doi 10 1088 0004 637X 696 1 385 Nearby galaxy is a fossil from the early universe Science Daily 1 May 2014 Fossil Galaxy Provides a Window Into the Early Universe 2014 05 11 Archived from the original on May 14 2014 Retrieved 2018 09 21 Frebel Anna Simon Joshua D Kirby Evan N April 2014 Segue 1 An Unevolved Fossil Galaxy from the Early Universe The Astrophysical Journal 786 1 74 arXiv 1403 6116 Bibcode 2014ApJ 786 74F doi 10 1088 0004 637X 786 1 74 hdl 1721 1 94556 ISSN 0004 637X S2CID 56011623 SEGUE 1 AN UNEVOLVED FOSSIL GALAXY FROM THE EARLY UNIVERSE Martinez G D Minor Q E Bullock J Kaplinghat M Simon J D Geha M 2011 A Complete Spectroscopic Survey of the Milky Way Satellite Segue 1 Dark Matter Content Stellar Membership and Binary Properties from a Bayesian Analysis The Astrophysical Journal 738 1 55 arXiv 1008 4585 Bibcode 2011ApJ 738 55M doi 10 1088 0004 637X 738 1 55 S2CID 118674090 External links edit Found Heart of Darkness W M Keck Observatory Archived from the original on 10 March 2016 Retrieved 4 November 2011 Retrieved from https en wikipedia org w index php title Segue 1 amp oldid 1220470058, wikipedia, wiki, book, books, library,

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