Radial velocity dependence in the spatial orientations of galaxies in and around the local supercluster

Abstract

We study the radial velocity dependence in the spatial orientations of 10 562 spiral galaxies that have radial velocity <5000 km s −1 . The inclination angle and intrinsic flatness of galaxy are used to covert two-dimensional given parameters into three-dimensional spin vectors of the galaxy. We have performed Kolmogorov–Smirnov, Kuiper and Fourier tests in order to examine non-random effects in the expected isotropic distributions. The galaxies that have radial velocities 1500 to 2000 and 3000 to 3500 km s −1 show preferred alignments in both the two- and three-dimensional analysis. The possible explanations of the results will be discussed. The origin of the angular momentum and the Hubble recessional velocity of galaxies is closely related to the physics of the early universe. The dynamical ‘fossil’ nature of the alignment of rotational axes of galaxies in superclusters provides us with the information on the formation process of galaxy at the early epoch (Djorgovski 1987). There have been contradictory theoretical models predicting various galaxy cluster formation scenarios. The ‘pancake model’ (Doroshkevich 1973; Shandarin 1974) predicts that the angular momentum of galaxies tends to lie within the cluster plane whereas the ‘primordial vorticity model’ (Ozernoy 1978) says that the angular momentum of galaxies tends to be oriented perpendicular the cluster plane. The ‘hierarchy model’ (Peebles 1969) predicts that the direction of angular momentum is entirely random. According to this scenario, galaxies were first formed and then obtained their angular momentum by tidal forces while they were gathering gravitationally to form a cluster with no dissipation. Lee & Pen (2002) found the observational evidence for the alignment of galaxy spin axes with the local tidal share field. Their result is consistent with the linear tidal-torque model based on gravitational instability. In an analytical study, Lee (2004) concluded a large-scale coherence in the orientation of galaxies in the two-dimensional sheet-like structures in the frame of the tidal-torque theory. Godlowski (1994) studied the dependence of galaxy alignment on radial velocity (RV) of 2227 galaxies in the local supercluster (LSC) and found anisotropy for the galaxies that have RVs 1000 to 1500 km s −1 . He concluded the dominance of Virgo cluster