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14 October 2024 |
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On The Origin of the Local Group's Peculiar Velocity | | Dale D. Kocevski
; Harald Ebeling
; | | Date: |
5 Oct 2005 | | Subject: | astro-ph | | Abstract: | We aim to settle the debate regarding the fraction of the Local Group’s peculiar velocity that is induced by structures beyond the Great Attractor by calculating the dipole anisotropy of the largest, all-sky, truly X-ray selected cluster sample compiled to date. The sample is the combination of the REFLEX catalog in the southern hemisphere, the eBCS sample in the north, and the CIZA survey in the Galactic plane. The composite REFLEX+eBCS+CIZA sample overcomes many of the problems inherent to previous galaxy and cluster catalogs which limited their effectiveness in determining the origin of the Local Group’s motion. From the dipole anisotropy present in the cluster distribution we determine that 44% of the Local Group’s peculiar velocity is due to infall into the GA region, while 56% is in the form of a large-scale flow induced by more distant overdensities between 130 and 180 h^-1 Mpc away. In agreement with previous analyses, we find that the Shapley supercluster is the single overdensity most responsible for the increase in the dipole amplitude beyond 130 h^-1 Mpc, generating 30.4% of the large-scale contribution. We find that numerous groupings and loose associations of clusters at roughly the same distance as the Shapley region induce a significant acceleration on the Local Group. These include the well known Horologium-Reticulum concentration, as well as newly noted associations centered on Abell 3667 and Abell 3391 and a string of CIZA clusters near C1410 which may trace an extension of the Shapley complex into the Zone of Avoidance. We also note that the large-scale anisotropy measured in the cluster distribution near 150 h^-1 Mpc may be due to an observed underdensity of clusters in the northern hemisphere near this distance. (abridged) | | Source: | arXiv, astro-ph/0510106 | | Services: | Forum | Review | PDF | Favorites | |
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