Local Sheet

Nearby extragalactic region of space

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	0 Mly (0 Mpc)
See also: Galaxy group, Galaxy cluster, List of galaxy groups and clusters

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]

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.

Galaxies in the "Council of Giants"^[4]
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.

References

^ ^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". 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. {{cite journal}}: Unknown parameter |agency= ignored (help)