The mass function of galaxies based on correlated velocity structure (original) (raw)
1990, Monthly Notices of the Royal Astronomical Society
Summary This paper introduces a new approach to the calculation of the galactic mass multiplicity function based on the probability of correlated velocity structures existing on a given spatial scale. The correlations are supposed to have developed during a protogalactic era of virialized structures, before which time the density evolution had already become non-linear. We determine the density index empirically in this paper, although it may eventually be related to a spectrum of initial fluctuations. The subsequent non-linear dynamics are dealt with explicitly using a continuum model with tidal interactions simulated by an effective shear viscosity. Our predictions for the (unnormalized) mass function and for the large-scale velocity correlations between galaxies are deduced relatively directly from the ‘cosmic von Karman-Howarth’ equation implicit in our basic model. Our predictions are in good agreement with existing data. The first part of our paper offers a summary and a criti...
Related papers
Non-Gaussian velocity distributions - the effect on virial mass estimates of galaxy groups
Monthly Notices of The Royal Astronomical Society, 2011
We present a study of 9 galaxy groups with evidence for non-Gaussianity in their velocity distributions out to 4R200. This sample is taken from 57 groups selected from the 2PIGG catalog of galaxy groups. Statistical analysis indicates that non-Gaussian groups have masses significantly higher than Gaussian groups. We also have found that all non-Gaussian systems seem to be composed of multiple velocity modes. Besides, our results indicate that multimodal groups should be considered as a set of individual units with their own properties. In particular, we have found that the mass distribution of such units are similar to that of Gaussian groups. Our results reinforce the idea of non-Gaussian systems as complex structures in the phase space, likely corresponding to secondary infall aggregations at a stage before virialization. The understanding of these objects is relevant for cosmological studies using groups and clusters through the mass function evolution.
The pairwise velocity dispersion of galaxies: effects of non-radial motions
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 21 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 21 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, j z (r p , p), 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.
Loading Preview
Sorry, preview is currently unavailable. You can download the paper by clicking the button above.