Crater_2_Dwarf Latitude and Longitude:

Sky map 11h 49m 14.4s, −18° 24′ 46.8″
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Crater 2
Observation data ( J2000.0 epoch)
Constellation Crater [1]
Right ascension11h 49m 14.400s
177.310°±0.03° [1]
Declination−18° 24′ 46.80″
−18.413°±0.03° [1]
Heliocentric radial velocity88 km/s [2]
Galactocentric velocity-74 km/s [2]
Distance383,000  ly (117.5  kpc) [1]
Apparent magnitude (V)12.15 mag [1]
Absolute magnitude (V)−8.2±0.1 mag [1]
Characteristics
Type dSph [1]
Apparent size (V)62.4 (rh=31.2 ± 2.5 ) [1]
6,950  ly (2,132  pc)
rh=1066pc ± 84pc [1]
Notable features4th largest satellite
galaxy to Milky Way [1]

Crater 2 is a low-surface-brightness dwarf satellite galaxy of the Milky Way, [1] located approximately 380,000 ly from Earth. Its discovery in 2016 revealed significant gaps in astronomers' understanding of galaxies possessing relatively small half-light diameters and suggested the possibility of many undiscovered dwarf galaxies orbiting the Milky Way. [3] Crater 2 was identified in imaging data from the VST ATLAS survey. [3]

The galaxy has a half-light radius of ~1100  pc, making it the fourth largest satellite of the Milky Way. [1] It has an angular size about double of that of the moon. [3] [4] Despite the large size, Crater 2 has a surprisingly low surface brightness, implying that it is not very massive. [5] In addition, its velocity dispersion is also low, suggesting it may have formed in a halo of low dark matter density. [6] Alternatively, it may be a result of tidal interactions with it and larger galaxies, such as the Milky Way and the Large Magellanic Cloud, [5] but according to some simulations, this would not explain the relatively large size. [6] This unusually low velocity dispersion was predicted using Modified Newtonian Dynamics, an alternative to the dark matter hypothesis. [7] This prediction was later confirmed by observations. [8]

See also

References

  1. ^ a b c d e f g h i j k l Torrealba, G.; Koposov, S. E.; Belokurov, V.; Irwin, M. (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. arXiv: 1601.07178. Bibcode: 2016MNRAS.459.2370T. doi: 10.1093/mnras/stw733.
  2. ^ a b Kashibadze, Olga G.; Karachentsev, Igor D. (2018). "Cosmic flow around local massive galaxies". Astronomy & Astrophysics. 609: A11. arXiv: 1709.09420. Bibcode: 2018A&A...609A..11K. doi: 10.1051/0004-6361/201731645. S2CID  55486336.
  3. ^ a b c Croswell, Ken (14 April 2016). "Never-before-seen galaxy spotted orbiting the Milky Way". New Scientist. Retrieved 14 April 2016.
  4. ^ Howard, Jacqueline (2016-04-16). "Elusive Dwarf Galaxy Found Orbiting Our Milky Way". Huffington Post. Retrieved 2016-04-19.
  5. ^ a b Ji, Alexander P.; Koposov, Sergey E.; Li, Ting S.; Erkal, Denis; Pace, Andrew B.; Simon, Joshua D.; Belokurov, Vasily; Cullinane, Lara R.; Da Costa, Gary S.; Kuehn, Kyler; Lewis, Geraint F.; MacKey, Dougal; Shipp, Nora; Simpson, Jeffrey D.; Zucker, Daniel B.; Hansen, Terese T.; Bland-Hawthorn, Joss; S5 Collaboration (2021). "Kinematics of Antlia 2 and Crater 2 from the Southern Stellar Stream Spectroscopic Survey (S 5)". The Astrophysical Journal. 921 (1): 32. arXiv: 2106.12656. Bibcode: 2021ApJ...921...32J. doi: 10.3847/1538-4357/ac1869. S2CID  235624056.{{ cite journal}}: CS1 maint: numeric names: authors list ( link)
  6. ^ a b Borukhovetskaya, Alexandra; Navarro, Julio F.; Errani, Raphaël; Fattahi, Azadeh (2022). "Galactic tides and the Crater II dwarf spheroidal: A challenge to LCDM?". Monthly Notices of the Royal Astronomical Society. 512 (4): 5247–5257. arXiv: 2112.01540. Bibcode: 2022MNRAS.512.5247B. doi: 10.1093/mnras/stac653.
  7. ^ McGaugh, Stacy S. (2016-11-14). "MOND Prediction for the Velocity Dispersion of the 'Feeble Giant' Crater II". The Astrophysical Journal. 832 (1): L8. arXiv: 1610.06189. Bibcode: 2016ApJ...832L...8M. doi: 10.3847/2041-8205/832/1/L8. ISSN  2041-8213. S2CID  51764960.
  8. ^ Caldwell, Nelson; Walker, Matthew G.; Mateo, Mario; Olszewski, Edward W.; Koposov, Sergey; Belokurov, Vasily; Torrealba, Gabriel; Geringer-Sameth, Alex; Johnson, Christian I. (2017-04-10). "Crater 2: An Extremely Cold Dark Matter Halo". The Astrophysical Journal. 839 (1): 20. arXiv: 1612.06398. Bibcode: 2017ApJ...839...20C. doi: 10.3847/1538-4357/aa688e. hdl: 10150/623952. ISSN  1538-4357. S2CID  119422981.

External links