The Local Sheet in astronomy is a nearby extragalactic region of space 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 is only 40 km⋅s−1 in the radial direction.[2] Nearly 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] The Local Sheet forms a wall of galaxies delineating one boundary of the Local Void.[5]
| Local Sheet | |
|---|---|
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| 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 | 0 Mly (0 Mpc) |
A significant component of the mean velocity of the galaxies in the Local Sheet appears as the result of the gravitational attraction of the Virgo Cluster of galaxies, resulting in a peculiar motion ~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 so-called 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.
| Catalog ID | Name | Constellation | Distance (Mly) | Stellar mass * |
|---|---|---|---|---|
| NGC 253 | Sculptor Galaxy | Sculptor | 11 | 10.805 |
| 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 | 11.169 |
| NGC 4945 | Centaurus | 12 | 10.528 | |
| ESO 97-G13 | Circinus Galaxy | Circinus | 14 | 10.559 |
* The mass is given as the logarithm (base unspecified) of the mass in solar masses.
See also
edit- Local Void, the Local Sheet defining the wall of galaxies at one end of the void
- Supergalactic coordinate system, the coordinate system taking the Local Sheet, the Supergalactic Plane, as its X–Y bases
References
edit- ^ a b c d "Milky Way amidst a 'Council of Giants'". Science Daily. 11 March 2014.
- ^ 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. S2CID 14738309.
- ^ 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, vol. 244, pp. 146–151, arXiv:0708.0864, Bibcode:2008IAUS..244..146T, doi:10.1017/S1743921307013932, S2CID 119643726
- ^ a b c d McCall, Marshall L. (29 April 2013). "A Council of Giants". Monthly Notices of the Royal Astronomical Society. 440 (1) (published 10 March 2014): 405–426. arXiv:1403.3667. Bibcode:2014MNRAS.440..405M. doi:10.1093/mnras/stu199.
- ^ Shaya, Ed J.; Tully, R. Brent (December 2013). "The Formation of the Local Group Planes of Galaxies". Royal Astronomical Society (Monthly Notices of the Royal Astronomical Society). 436 (3). Oxford University Press: 2096–2119. arXiv:1307.4297. Bibcode:2013MNRAS.436.2096S. doi:10.1093/mnras/stt1714.
