Peculiar Velocities of Galaxies Just Beyond the Local Group

被引:20
作者
Anand, Gagandeep S. [1 ]
Tully, R. Brent [1 ]
Rizzi, Luca [2 ]
Shaya, Edward J. [3 ]
Karachentsev, Igor D. [4 ]
机构
[1] Univ Hawaii, Inst Astron, 2680 Woodlawn Dr, Honolulu, HI 96822 USA
[2] WM Keck Observ, 65-1120 Mamalahoa Highway, Kamuela, HI 96743 USA
[3] Univ Maryland, Astron Dept, College Pk, MD 20743 USA
[4] Special Astrophys Observ, Nizhniy Arkhyz 369167, Karachai Cherke, Russia
关键词
galaxies: distances and redshifts; galaxies: stellar content; Hertzsprung-Russell and C-M diagrams; large-scale structure of universe; RED GIANT BRANCH; DWARF GALAXIES; DISTANCE; STELLAR; TIP; ORION; DYNAMICS;
D O I
10.3847/1538-4357/ab24e5
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
The Milky Way lies in a thin plane, the Local Sheet, a part of a wall bounding the Local Void lying toward the north supergalactic pole. Galaxies with accurate distances both above and below this supergalactic equatorial plane have systematically negative peculiar velocities. The interpretation of this situation is that the Local Void is expanding, giving members of the Local Sheet deviant velocities toward the south supergalactic pole. The few galaxies within the void are evacuating the void. Galaxies in a filament in the supergalactic south are not feeling the expansion so their apparent motion toward us is mainly a reflex of our motion. The model of the local velocity field was uncertain because the apex of our motion away from the Local Void lies in obscurity near the Galactic plane. Here, results of Hubble Space Telescope infrared observations are reported that find tip of the red giant branch distances to four obscured galaxies. All the distances are similar to 7 Mpc, revealing that these galaxies are part of a continuous filamentary structure passing between the north and south Galactic hemispheres and sharing the same kinematic signature of peculiar velocities toward us. A fifth galaxy nearby in projection, GALFA-DW4, has an ambiguous distance. If nearby at similar to 3 Mpc, this galaxy has an anomalous velocity away from us of +348 km s(-1). Alternatively, perhaps the resolved stars are on the asymptotic giant branch and the galaxy is beyond 6 Mpc whence the observed velocity would not be unusual.
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页数:11
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