Local Sheet

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Local Sheet
Observation data (Epoch )
Brightest member Local Group
Major axis 17 Mly (5 Mpc) [1]
Minor axis 1.5 Mly (0.5 Mpc) [1]
Redshift 0.00
Distance
(co-moving)
Mly (0 Mpc)
See also: Galaxy groups, Galaxy clusters, List of superclusters

The Local Sheet in astronomy is a nearby region of the observable universe where the Milky Way, the members of the Local Group and other galaxies share a similar peculiar velocity.[2] This region lies within a radius of about 7 Mpc (23 Mly),[3] 0.46 Mpc (1.5 Mly) thick,[1] and galaxies beyond that distance show markedly different velocities.[3] The Local Group has only a relatively small peculiar velocity of 66 km s−1 with respect to the Local Sheet. Typical velocity dispersion of galaxies within the Local Sheet is only 40 km s−1 in the radial direction.[2] All nearby bright galaxies belong to the Local Sheet.[1] The Local Sheet is part of the Local Volume and is in the Virgo Supercluster (Local Supercluster).[4]

A significant component of the mean velocity of the galaxies in the Local Sheet comes as the result of the gravitational attraction of the Virgo Cluster of galaxies. This results in a peculiar motion of about 185 km s−1 toward the cluster.[2] A second component is directed away from the center of the Local Void; an expanding region of space spanning an estimated 45 Mpc (150 Mly) that is only sparsely populated with galaxies.[3] This component has a velocity of 259 km s−1.[2] The Local Sheet is inclined 8° from the Local Supercluster (Virgo Supercluster).[4]

The Council of Giants is a ring of twelve large galaxies surrounding the Local Group in the Local Sheet, with a radius of 3.75 Mpc (12.2 Mly).[4] Ten of these are spirals, while the remaining two are ellipticals. The two ellipticals (Maffei 1 and Centaurus A) lie on opposite sides of the Local Group, and their formation may have prompted the development of the Local Group. The Local Sheet's own development outlines a concentration of dark matter in a filament.[1]

Galaxies in the "Council of Giants"
Catalog ID Name Constellation Distance (Mly) Mass *
PGC 9892 Maffei 1 Cassiopeia 11 10.928
PGC 10217 Maffei 2 Cassiopeia 11 10.493
IC 342   Camelopardalis 11 10.302
NGC 3031 M 81 Ursa Major 12 10.905
NGC 3034 M 82 Ursa Major 11 10.573
NGC 4736 M 94 Canes Venatici 15 10.458
NGC 4826 M 64 Coma Berenices 16 10.496
NGC 5236 M 83 Hydra 16 10.642
NGC 5128 Centaurus A Centaurus 11 10.528
NGC 4945   Centaurus 12 11.169
ESO 97-G13 Circinus Galaxy Circinus 14 10.559
NGC 253 Sculptor Galaxy Sculptor 11 10.805

* The mass is given as the logarithm of the mass in solar masses.

References[edit]

  1. ^ a b c d e "Milky Way amidst a 'Council of Giants'". Science Daily. 11 March 2014. 
  2. ^ a b c d Tully, R. Brent; Shaya, Edward J.; Karachentsev, Igor D.; Courtois, Hélène M.; Kocevski, Dale D.; Rizzi, Luca; Peel, Alan (March 2008). "Our Peculiar Motion Away from the Local Void". The Astrophysical Journal 676 (1): 184–205. arXiv:0705.4139. Bibcode:2008ApJ...676..184T. doi:10.1086/527428. 
  3. ^ a b c Tully, R. Brent (May 2008), "The Local Void is Really Empty", Dark Galaxies and Lost Baryons, Proceedings of the International Astronomical Union, IAU Symposium 244, pp. 146–151, arXiv:0708.0864, Bibcode:2008IAUS..244..146T, doi:10.1017/S1743921307013932 
  4. ^ a b c Marshall L. McCall (April 29, 2013). "A Council of Giants" (published 10 March 2014). arXiv:1403.3667. Bibcode:2014MNRAS.440..405M. doi:10.1093/mnras/stu199.