Some aspects of the orientation of galaxies in clusters

Abstract

The analysis of Tully's groups of galaxies belonging to the Local Supercluster (LSC) was performed. In the 1975 Hawley and Peebles [D. I. Hawley, P. J. E. Peebles, Astron. J. 80, 477 (1975)] presented the method for investigations of the galaxies orientation in the large structures. In our previous papers [W. God lowski, P. Piwowarska, E. Panko, P. Flin, Astron. J. 723, 985 (2010); W. God lowski, Astrophys. J. 747, 7 (2012)] the statistical test proposed by Hawley and Peebles for the investigation of this problem was analyzed in detail and some improvements were suggested. On this basis the new method of the analysis of galactic alignment in clusters was proposed. Using this method, God lowski [W. God lowski, Acta Phys. Polon. B 42, 2323Polon. B 42, (2011] analyzed the orientation of galaxies inside Tully's groups founding no significant deviations from isotropy both in orientation of position angles and δD and η angles as well, giving the spatial orientation of galaxy planes. In the present paper we examined carefully and methodically the dependence of alignment in Tully's groups on the morphological type of galaxies. Moreover, we discussed the consequences of different approximation of "true shape" of the galaxies for different morphological types, a possible influence of this problem for the investigation of spatial orientation of galaxies. In addition, we discussed the implications of the obtained results for the theory of galaxy formation as well.

The investigations of anisotropy in the orientations of galaxies

“…In the case of analysing the distribution of the position angles all N 0,k are equal N 0 , which is also the mean number of galaxies per bin. It is easy to see that Function F is in this case is strictly related to ∆ 11 coefficient: F = 2∆ 11 (see [21,22] for details).…”

The Alignment of Galaxies in Structures – Review

“…The main reason for this is the fact that Tully, when calculating the angles of inclination of galaxies, assumed that the "true" ratio of the axes of galaxies is q 0 = 0.2. This is a very bad approximation, especially for non-spiral galaxies (Godłowski 2011b, Pajowska et al 2012 [219,220]. This work also shows that if instead of taking the values of the angles of inclination given in the Tully catalogue (1988), one calculates the angle of inclination from Holmberg's formula: cos 2 i = (q 2 − q 2 0 )/(1 − q 2 0 ), taking the values of q 0 for galaxies of different morphological types from the work Heidmann, Heidmann, de Vaucouleurs (1972) [221], it turns out that the surplus of galaxies with normals to their planes directed towards the line of sight, obtained by Godłowski and Ostrowski (1999) [218] disappears.…”