Angular momentum of galaxies within the local supercluster

Abstract

The various available scenarios for the galaxy origin predict different types of galactic angular momenta distributions within galactic superclusters. The random distribution of galaxy rotation axes is expected to occur within the hierarchical clustering picture (Dekel 1985), whereas some alignment is expected to arise in the fragmentation scenario. Within the latter model the perpendicular to the supercluster main plane orientation of galactic rotation axes conforms to the predictions of the turbulence model (Efstathiou & Silk 1983), while the alignment of galactic axes with that plane supports rather the adiabatic galaxy origin model (Shandarin 1974). The recently proposed “hedgehog model” predicts that the the galaxy planes should tend to be oriented perpendicular to direction oriented toward the superclus ter centre. Most of the papers published to date analyze the Local Superclus ter (e.g. Hawley & Peebles 1975; Kapranidis & Sullivan 1983; MacGillivray & Dood 1985) to conclude that galactic rotation axes are oriented in a random manner or, when some alignment was found, the rotation axes were preferably oriented perpendicularly to the supergalactic plane. In those papers however, the samples considered were selected according to magnitude limits so they could be contaminated by background objects. Moreover, using the equatorial coordinate system made the discussion of results very difficult. In this paper a method originally proposed by Jaaniste & Saar (1977) for investigating galactic angular momentum in the Local Supercluster (LSC) is applied to a sample of 2227 galaxies chosen according radial velocities from the UGC and ESO catalogues. We (Flip & Godlowski 1986; Godlowski 1993) introduced the important modifications and corrected for its inconsistencies and use sophisticated statistical method which had not been used in solv ing this problem before using supergalactic coordinate system. The method takes into account both the galactic image position angle and the inclination of the normal to the galaxy to the line-of sight. Another independent sample of galaxies taken from Tully's Nearby Galaxy Catalogue is also used. In the present paper, we find the distribution of galactic planes throughout LSC anisotropic. The planes tend to be oriented perpendicular to the Local Supercluster plane. The projection of galactic rotation axes on the LSC plane shows a tendency to point toward the Virgo Cluster centre. Differences between spiral and non-spiral galaxies are observed, with a weaker alignment for spirals. When we check our computation using independent sample taken from Tully's catalogue we obtain very similar results. Our results support the so called “pancake” galaxy formation scenario, but the “hedgehog model” is not excluded either because of differences distribution of edge-on galaxies.