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TITLE A Redshift Survey of the Nearby Galaxy Cluster A2107: Global Rotation of the Cluster and Its Connection to Large-scale Structures in the Universe
KIAS AUTHORS Park, Changbom,Song, Hyunmi,Hwang, Ho Seong
ABSTRACT We study the rotational motion of the galaxy cluster A2107 at redshift z = 0.04 and its connection to nearby largescale structures using a large amount of spectroscopic redshift data. By combining 978 new redshifts from the MMT/Hectospec observations with data in the literature, we construct a large sample of 1968 galaxies with measured redshifts at clustercentric radius R < 60'. Our sample has high (80%) and spatially uniform completeness at r -band apparent magnitude mr,(Petro,0) < 19.1. We first apply the caustic method to the sample and identify 285 member galaxies of A2107 at R < 60'. Then the rotation amplitude and the position angle of the rotation axis are measured. We find that the member galaxies show strong global rotation at R < 20' (v(rot)/ sigma(v) similar to 0.6) with a significance of >3.8 sigma, which is confirmed by two independent methods. The rotation becomes weaker in outer regions. There are at least five filamentary structures that are connected to the cluster and that consist of known galaxy groups. These structures are smoothly connected to the cluster, which seem to be inducing the global rotation of the cluster through inflow of galaxies.
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