Astronomy and Astrophysics – Astronomy
Scientific paper
May 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997apj...480...43n&link_type=abstract
Astrophysical Journal v.480, p.43
Astronomy and Astrophysics
Astronomy
24
Cosmology: Theory, Cosmology: Dark Matter, Cosmology: Large-Scale Structure Of Universe, Methods: Numerical
Scientific paper
We present techniques for identifying and analyzing galaxy groups and apply them to large-scale particle-mesh (PM) N-body simulations of structure formation in three Omega 0 = 1 cosmological models: cold plus hot dark matter (CHDM), with Omega cold = 0.6, Omega nu = 0.3, and Omega baryon = 0.1 at bias b= sigma ^{-1}8=1.5 ; and two cold dark matter (CDM) models, at bias b = 1.5 and b = 1.0. Groups are identified with the adaptive friends-of-friends algorithm of Nolthenius. Our most important conclusions follow. The standard group M/L method gives Omega 0 ~= 0.08 for the CfA1 survey (for redshift link parameter V5 = 350), and, applied to our Omega 0 = 1 simulations, it gives Omega 0 ~= 0.12 for CHDM (V5 = 350) and Omega 0 ~= 0.35 for CDM (V5 = 600). This Omega bias appears to be even stronger at higher resolution. We show quantitatively how three different effects conspire to produce this large discrepancy, and we conclude that low observed Omega values need not argue for a low- Omega universe. Our preferred statistics of groups show promise in becoming powerful discriminators between Gaussian cosmological models, whose Omega nu differ and are robust against several methods for assigning luminosity to dark matter halos, and for merging CfA1 data. However, our latest results at higher resolution show such strong sensitivity to how massive over-mergers are broken up that more reliable ways of identifying luminous galaxies within large-scale simulations will be necessary before these statistics can provide reliable discrimination. When over-mergers are broken up, the median virial-to-DM mass Mvir/MDM of three-dimensional--selected groups is ~1 for all simulations. Groups with MDM > 1014 M&sun; appear virialized in all simulations. We measure global (not pairwise) velocity biases bv, similar to previous studies. Within three-dimensional--selected groups, CHDM and CDM with b = 1.5 show a stronger bias of bv = 0.7--0.8, while CDM with b = 1.0 shows groups of bv ~= 1.
Klypin Anatoly A.
Nolthenius Richard
Primack Joel R.
No associations
LandOfFree
Galaxy Groups, CDM/CHDM Cosmologies, and the Value of Omega 0 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Galaxy Groups, CDM/CHDM Cosmologies, and the Value of Omega 0, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Galaxy Groups, CDM/CHDM Cosmologies, and the Value of Omega 0 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-835842