Astronomy:Satellite galaxies of the Milky Way

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Short description: Galaxies bound to the Milky Way

The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup, which is part of the local galaxy cluster, the Local Group.[1]

There are 61 small galaxies confirmed to be within 420 kiloparsecs (1.4 million light-years) of the Milky Way,[2] but not all of them are necessarily in orbit, and some may themselves be in orbit of other satellite galaxies. The only ones visible to the naked eye are the Large and Small Magellanic Clouds, which have been observed since prehistory. Measurements with the Hubble Space Telescope in 2006 suggest the Magellanic Clouds may be moving too fast to be orbiting the Milky Way.[3] Of the galaxies confirmed to be in orbit, the largest is the Sagittarius Dwarf Elliptical Galaxy, which has a diameter of 2.6 kiloparsecs (8,500 ly)[4] or roughly a twentieth that of the Milky Way.

Characteristics

Satellite galaxies that orbit from 1,000 ly (310 pc) of the edge of the disc of the Milky Way Galaxy to the edge of the dark matter halo of the Milky Way at 980,000 ly (300 kpc) from the center of the galaxy,[lower-alpha 1] are generally depleted in hydrogen gas compared to those that orbit more distantly. This is because of their interactions with the dense hot gas halo of the Milky Way that strip cold gas from the satellites. Satellites beyond that region still retain copious quantities of gas.[5][6]

List

The Milky Way's satellite galaxies include the following:[7][2]

Name Diameter (kpc) Distance
(kpc) 		Absolute visual magnitude Type Discovered
Large Magellanic Cloud 4 48.5 −18.1 SBm prehistoric
Antlia 2 2.9 130 −8.5 Irr? 2018
Sagittarius Dwarf 2.6 20 −13.5 E 1994
Crater II 2.2 117.5 −8.2 dSph 2016 [8]
Small Magellanic Cloud 2 61 −16.8 Irr prehistoric
Canes Venatici I 1.1 220 −8.6 dSph 2006
Canis Major Dwarf 1.5 8 −14.4 Irr 2003
Boötes III 1.0 46 −5.75 dSph? 2009
Sculptor Dwarf 0.8 90 −11.1 dE3 1937
Draco Dwarf 0.7 80 −8.8 dE0 1954
Hercules 0.7 135 −6.6 dSph 2006
Leo II 0.7 210 −9.8 dE0 1950
Fornax Dwarf 0.6 140 −13.4 dE2 1938
−7.1 dSph 2015 [9][10]
Sextans Dwarf Spheroidal 0.5 90 −9.3 dE3 1990
Carina Dwarf Spheroidal 0.5 100 −9.1 dE3 1977
Leo I 0.5 250 −12.0 dE3 1950
Ursa Minor Dwarf 0.4 60 −8.8 dE4 1954
Leo T 0.34 420 −8.0 dSph/dIrr 2006
Aquarius II 0.32 108 −4.2 dSph 2016 [11]
Boötes I 0.30 60 −6.3 dSph 2006
Canes Venatici II 0.30 155 −4.9 dSph 2006
Leo IV 0.30 160 −5.8 dSph 2006
Tucana IV 0.25 48 −3.5 dSph 2015 [12]
Columba I 0.21 182 −4.5 dSph 2015 [12]
Ursa Major II Dwarf 0.20 30 −4.25 dG D 2006
Grus II 0.19 53 −3.9 dSph 2015 [12]
Cetus III 0.18 251 −2.4 dSph? 2017 [13]
Coma Berenices 0.14 42 −4.1 dSph 2006
Hydra II 0.14 128 −4.8 dSph 2015 [14]
Reticulum III 0.13 92 −3.3 dSph 2015 [12]
Pisces II 0.12 180 −5.0 dSph 2010
Pegasus III 0.11 215 −3.4 dSph 2015 [15][16]
Hydrus I 0.10 28 −4.7 dSph 2018 [17]
Boötes II 0.10 42 −2.7 dSph 2007
Tucana III 0.09 25 −2.4 dSph 2015 [12]
Virgo I 0.09 91 −0.3 dSph? 2016 [13]
Horologium II 0.09 78 −2.6 dSph 2015 [18]
Sagittarius II 0.08 67 −5.2 dSph 2015 [19]
Leo V 0.08 180 −5.2 dSph 2007
Triangulum II 0.07 30 −1.8 dSph 2015
Segue 2 0.07 35 −2.5 dSph 2007
Segue 1 0.06 23 −1.5 dSph 2007
Draco II 0.04 20 −2.9 dSph 2015 [19]
Tucana V 0.03 55 −1.6 dSph 2015 [12]
Cetus II 0.03 30 0.0 dSph? 2015 [12]
Reticulum II 0.064 30 −3.6 dSph 2015 [9][10]
Tucana II 0.33 70 −3.9 dSph 2015 [9][10]
Pisces Overdensity 1.5 80 −13 dSph? 2009
DES 1 0.02 82 −3.05 GC 2016 [20]
Eridanus III 0.028 90 −2.4 dSph?[lower-alpha 2] 2015 [9][10]
Horologium I 0.06 100 −3.5 dSph?[lower-alpha 2] 2015 [9][10]
Kim 2/Indus I 0.074 100 −3.5 GC 2015 [9][10]
Phoenix II 0.0521 100 −3.7 dSph?[lower-alpha 2] 2015 [9][10]
Ursa Major I Dwarf 0.64 100 −5.5 dG D 2005
Pictoris I 0.058 115 −3.7 dSph?[lower-alpha 2] 2015 [9][10]
Grus I 0.12 120 −3.4 dSph 2015 [9]
Pegasus IV 0.082 90 −4.25 dSph 2022 [21]
Carina II 0.182 36 −4.5 dSph 2018 [22]
Carina III 0.06 28 −2.4 GC? 2018 [22]
Boötes IV 0.28 209 −4.53 dSph 2019 [23]
Centaurus I 0.076 116 −5.55 dSph 2020 [24]
Pictor II 0.046 46 −3.2 dSph 2016 [25]
Willman 1 0.02 38 −2.53 dSph 2018 [26]
Ursa Major III 0.003 10 +2.2 dSph 2023

Map with clickable regions

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Streams

The Sagittarius Dwarf Spheroidal Galaxy is currently in the process of being consumed by the Milky Way and is expected to pass through it within the next 100 million years. The Sagittarius Stream is a stream of stars in polar orbit around the Milky Way leeched from the Sagittarius Dwarf. The Virgo Stellar Stream is a stream of stars that is believed to have once been an orbiting dwarf galaxy that has been completely distended by the Milky Way's gravity.

See also

Notes

  1. ↑ The distance to edge of the dark matter halo of the galaxy from its center is the virial radius of a galaxy, Rvir
  2. ↑ 2.0 2.1 2.2 2.3 May be a globular cluster instead

References

  1. ↑ David G. Turner (15 August 2013). "An Eclectic View of our Milky Way Galaxy". Canadian Journal of Physics 92 (9): 959–963. September 2013. doi:10.1139/cjp-2013-0429. Bibcode: 2014CaJPh..92..959T. 
  2. ↑ 2.0 2.1 A. Drlica-Wagner (2020). "The Astrophysical Journal | Milky Way Satellite Census. I. The Observational Selection Function for Milky Way Satellites in DES Y3 and Pan-STARRS DR1". The Astrophysical Journal 893 (1): 47. doi:10.3847/1538-4357/ab7eb9. 
  3. ↑ "Press release: Magellanic Clouds May Be Just Passing Through". Harvard University. January 9, 2007. https://www.cfa.harvard.edu/news/2007-02. 
  4. ↑ Karachentsev, I. D.; Karachentseva, V. E.; Hutchmeier, W. K.; Makarov, D. I. (2004). "A Catalog of Neighboring Galaxies". The Astronomical Journal 127 (4): 2031–2068. doi:10.1086/382905. Bibcode: 2004AJ....127.2031K. 
  5. ↑ "Milky Way Ransacks Nearby Dwarf Galaxies". SpaceDaily. 17 October 2014. http://www.spacedaily.com/reports/Milky_Way_Ransacks_Nearby_Dwarf_Galaxies_Stripping_All_Traces_of_Star_Forming_Gas_999.html. 
  6. ↑ "Milky Way ransacks nearby dwarf galaxies". ScienceDaily. 15 October 2014. https://www.sciencedaily.com/releases/2014/10/141015152552.htm. 
  7. ↑ Sjölander, Nils. "Milky Way satellite galaxies". http://www.astro.uu.se/~ns/mwsat.html. 
  8. ↑ Torrealba, G.; Koposov, S.E.; Belokurov, V.; Irwin, M. (13 April 2016). "The feeble giant. Discovery of a large and diffuse Milky Way dwarf galaxy in the constellation of Crater". Monthly Notices of the Royal Astronomical Society 459 (3): 2370–2378. doi:10.1093/mnras/stw733. Bibcode: 2016MNRAS.459.2370T. 
  9. ↑ 9.0 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 Koposov, Sergey E.; Belokurov, Vasily; Torrealba, Gabriel; Evans, N. Wyn (10 March 2015). "Beasts of the Southern Wild. Discovery of a large number of ultra faint satellites in the vicinity of the Magellanic Clouds". The Astrophysical Journal 805 (2): 130. doi:10.1088/0004-637X/805/2/130. Bibcode: 2015ApJ...805..130K. 
  10. ↑ 10.0 10.1 10.2 10.3 10.4 10.5 10.6 10.7 DES Collaboration (10 March 2015). "Eight New Milky Way companions discovered in first-year Dark Energy Survey data". The Astrophysical Journal 807 (1): 50. doi:10.1088/0004-637X/807/1/50. Bibcode: 2015ApJ...807...50B. 
  11. ↑ Torrealba, G.; Koposov, S.E.; Belokurov, V.; Irwin, M.; Collins, M.; Spencer, M.; Ibata, R.; Matteo, M. et al. (2016). "At the survey limits: Discovery of the Aquarius 2 dwarf galaxy in the VST ATLAS and the SDSS data". Monthly Notices of the Royal Astronomical Society 463 (1): 712–722. doi:10.1093/mnras/stw2051. Bibcode: 2016MNRAS.463..712T. 
  12. ↑ 12.0 12.1 12.2 12.3 12.4 12.5 12.6 Drlica-Wagner, A. (4 November 2015). "Eight ultra-faint galaxy candidates discovered in Year Two of the Dark Energy Survey". The Astrophysical Journal 813 (2): 109. doi:10.1088/0004-637X/813/2/109. Bibcode: 2015ApJ...813..109D. 
  13. ↑ 13.0 13.1 Homma, Daisuke; Chiba, Masashi; Okamoto, Sakurako; Komiyama, Yutaka; Tanaka, Masayuki; Tanaka, Mikito; Ishigaki, Miho N.; Hayashi, Kohei et al. (2017-04-19). "Searches for New Milky Way Satellites from the First Two Years of Data of the Subaru/Hyper Suprime-Cam Survey: Discovery of Cetus III". Publications of the Astronomical Society of Japan 70: S18. doi:10.1093/pasj/psx050. Bibcode: 2018PASJ...70S..18H. 
  14. ↑ Martin, Nicolas F. (23 April 2015). "Hydra II: A faint and compact Milky Way dwarf galaxy found in the survey of the Magellanic stellar history". The Astrophysical Journal Letters 804 (1): L5. doi:10.1088/2041-8205/804/1/L5. Bibcode: 2015ApJ...804L...5M. 
  15. ↑ Kim, Dongwon; Jerjen, Helmut; Mackey, Dougal; Da Costa, Gary S.; Milone, Antonino P. (12 May 2015). "A hero's dark horse: Discovery of an ultra-faint Milky Way satellite in Pegasus". The Astrophysical Journal Letters 804 (2): L-44. doi:10.1088/2041-8205/804/2/L44. Bibcode: 2015ApJ...804L..44K. 
  16. ↑ Kim, Dongwon; Jerjen, Helmut; Geha, Marla; Chiti, Anirudh; Milone, Antonino P.; Mackey, Dougal; da Costa, Gary; Frebel, Anna et al. (2016). "Portrait of a dark horse: Photometric properties and kinematics of the ultra-faint Milky Way satellite Pegasus III". The Astrophysical Journal 833 (1): 16. doi:10.3847/0004-637X/833/1/16. Bibcode: 2016ApJ...833...16K. 
  17. ↑ Koposov, Sergey E.; Walker, Matthew G.; Belokurov, Vasily; Casey, Andrew R.; Geringer-Sameth, Alex; Mackey, Dougal; Da Costa, Gary; Erkal, Denis et al. (2018-10-01). "Snake in the Clouds: a new nearby dwarf galaxy in the Magellanic bridge*" (in en). Monthly Notices of the Royal Astronomical Society 479 (4): 5343–5361. doi:10.1093/mnras/sty1772. ISSN 0035-8711. 
  18. ↑ Kim, Dongwon; Jerjen, Helmut (28 July 2015). "Horologium II: A second ultra-faint Milky Way satellite in the Horologium constellation". The Astrophysical Journal Letters 808 (2): L-39. doi:10.1088/2041-8205/808/2/L39. Bibcode: 2015ApJ...808L..39K. 
  19. ↑ 19.0 19.1 Laevens, B.P.M; Martin, N.F.; Bernard, E.J.; Schlafly, E.F.; Sesar, B. (1 November 2015). "Sagittarius II, Draco II and Laevens 3: Three new Milky Way satellites discovered in the PAN-STARRS 1 3π survey". The Astrophysical Journal 813 (1): 44. doi:10.1088/0004-637X/813/1/44. Bibcode: 2015ApJ...813...44L. 
  20. ↑ Luque, E. (9 February 2016). "Digging deeper into Southern skies: A compact Milky Way companion discovered in first-year Dark Energy Survey data". Monthly Notices of the Royal Astronomical Society 458 (1): 603–612. doi:10.1093/mnras/stw302. Bibcode: 2016MNRAS.458..603L. 
  21. ↑ Cerny, W. et al. (2023). "Pegasus IV: Discovery and Spectroscopic Confirmation of an Ultra-faint Dwarf Galaxy in the Constellation Pegasus". The Astrophysical Journal 942 (2): 111. doi:10.3847/1538-4357/aca1c3. Bibcode: 2023ApJ...942..111C. 
  22. ↑ 22.0 22.1 Torrealba, G.; Belokurov, V.; Koposov, S. E.; Bechtol, K.; Drlica-Wagner, A.; Olsen, K. A. G.; Vivas, A. K.; Yanny, B. et al. (2018-01-22). "Discovery of two neighbouring satellites in the Carina constellation with MagLiteS". Monthly Notices of the Royal Astronomical Society 475 (4): 5085–5097. doi:10.1093/mnras/sty170. 
  23. ↑ Homma (2019). "Boötes. IV. A new Milky Way satellite discovered in the Subaru Hyper Suprime-Cam Survey and implications for the missing satellite problem". Publications of the Astronomical Society of Japan 71 (5). doi:10.1093/pasj/psz076. https://academic.oup.com/pasj/article-abstract/71/5/94/5539816. 
  24. ↑ Mau (2020). "Two Ultra-faint Milky Way Stellar Systems Discovered in Early Data from the DECam Local Volume Exploration Survey". The Astrophysical Journal 890 (2): 136. doi:10.3847/1538-4357/ab6c67. Bibcode: 2020ApJ...890..136M. 
  25. ↑ Drlica-Wagner (2016). "An Ultra-Faint Galaxy Candidate Discovered in Early Data from the Magellanic Satellites Survey". The Astrophysical Journal 833 (1): L5. doi:10.3847/2041-8205/833/1/L5. Bibcode: 2016ApJ...833L...5D. 
  26. ↑ Muñoz (2018). "A MegaCam Survey of Outer Halo Satellites. III. Photometric and Structural Parameters". The Astrophysical Journal 860 (1): 66. doi:10.3847/1538-4357/aac16b. Bibcode: 2018ApJ...860...66M. 

Further reading

  • K. Spekkens; N. Urbancic; B. S. Mason; B. Willman; J. E. Aguirre (30 September 2014). "The Dearth of Neutral Hydrogen in Galactic Dwarf Spheroidal Galaxies". The Astrophysical Journal Letters 795 (1): L5. 13 October 2014. doi:10.1088/2041-8205/795/1/L5. Bibcode: 2014ApJ...795L...5S. 



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