Substructure in clusters and central galaxy peculiar velocities

Abstract

view Abstract Citations (148) References (66) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Substructure in Clusters and Central Galaxy Peculiar Velocities Bird, Christina M. Abstract Formation theories for central dominant galaxies in clusters require them to be located at the minimum of the cluster gravitational potential. However, 32% (8 out of 25) of the clusters with more than 50 measured redshifts have central galaxies with significant velocity offsets (with respect to other cluster members). By studying their velocity distributions and correlations between velocity and position, I show that the presence of a large peculiar velocity is strongly correlated with the presence of substructure in these massive systems. About 85% (21 of 25) of all well studied clusters show some evidence for substructure, in contrast to the 30%-40% found when using only galaxy or gas distributions. The correlation between substructure and central galaxy location verifies the hypothesis of Merritt [ApJ, 289, 18(1985)] and Tremaine (Dynamics and Interactions of Galaxies, edited by R. Wielen (Springer, Berlin) (1990), p. 394] that high peculiar velocities are indicative of recent merger events between less massive systems of galaxies. Dynamical friction should act quickly to pull the central galaxy, the most massive discrete object in a cluster, to the minimum of the potential. The less massive galaxies retain information about their primordial subclusters for a longer period of time. I use an objective partitioning algorithm to assign cluster galaxies to their host subclumps. When galaxies are allocated in this fashion to their subclusters, 75% of the significant velocity offsets are eliminated. Only 2 out of the 25 clusters have central galaxies which are not centrally located when substructure is considered in the analysis. Publication: The Astronomical Journal Pub Date: May 1994 DOI: 10.1086/116973 arXiv: arXiv:astro-ph/9402058 Bibcode: 1994AJ....107.1637B Keywords: Astronomy; Galactic Clusters; Galactic Evolution; Position (Location); Star Formation; Substructures; Velocity Distribution; Correction; Kurtosis; Numerical Analysis; Robustness (Mathematics); Skewness; Astronomy; GALAXIES: CLUSTERING; GALAXIES: INTERACTIONS; GALAXIES: KINEMATICS AND DYNAMICS; Astrophysics E-Print: 40 pages (text, figures and tables) full text sources arXiv | ADS | data products NED (49) SIMBAD (24)