Open AccessThe pairwise velocity dispersion of galaxies: effects of non‐radial motions
Author(s) -
Del Popolo A.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04621.x
Subject(s) - physics , velocity dispersion , astrophysics , galaxy , redshift , radial velocity , universe , distortion (music) , virial theorem , correlation function (quantum field theory) , quantum mechanics , stars , dielectric , amplifier , optoelectronics , cmos
I discuss the effect of non‐radial motions on the small‐scale peculiar pairwise velocity dispersions (PVD) of galaxies in a cold dark matter (CDM) model and calculate the PVD for the SCDM model by means of the refined cosmic virial theorem (CVT), taking account of non‐radial motions by means of the Del Popolo & Gambera model. I compare the results of the present model with the data from Davis & Peebles, the IRAS value at 1 h −1 Mpc of Fisher et al. and Marzke et al. I show that while the SCDM model disagrees with the observed values, as pointed out by several authors, taking account of non‐radial motions produces smaller values for the PVD. At r≤1 h −1 Mpc the result is in agreement with Bartlett & Blanchard. In the light of this last paper, the result may be also read as a strong dependence of the CVT prediction on the model chosen to describe the mass distribution around galaxies, suggesting that the CVT cannot be taken as a direct evidence for a low‐density Universe. Similarly to what is shown by Del Popolo & Gambera and Del Popolo et al., the agreement of our model to the observational data is because of a scale‐dependent bias induced by the presence of non‐radial motions. As the assumptions on which CVT is based have been questioned by several authors, I also calculated the PVD using the redshift distortion in the redshift‐space correlation function, ξ z ( r p , π), and compared it with the PVD measured from the Las Campanas Redshift Survey by Jing et al. The result confirms that non‐radial motions influence the PVD making them agree better with the observed data.