EDP Sciences
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Volume 416, Number 3, March IV 2004
Page(s) 853 - 864
Section Cosmology (including clusters of galaxies)
DOI http://dx.doi.org/10.1051/0004-6361:20031757

A&A 416, 853-864 (2004)
DOI: 10.1051/0004-6361:20031757

Numerical study of halo concentrations in dark-energy cosmologies

K. Dolag1, M. Bartelmann2, F. Perrotta3, 4, C. Baccigalupi3, 4, L. Moscardini5, M. Meneghetti1 and G. Tormen1

1  Dipartimento di Astronomia, Università di Padova, Italy
2  Max-Planck-Institut für Astrophysik, PO Box 1317, 85741 Garching, Germany
3  SISSA, Trieste, Italy
4  Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
5  Dipartimento di Astronomia, Università di Bologna, Italy

(Received 18 August 2003 / Accepted 2 December 2003 )

We study the concentration parameters, their mass dependence and redshift evolution, of dark-matter halos in different dark-energy cosmologies with constant and time-variable equation of state, and compare them with "standard" $\Lambda$CDM and OCDM models. We find that previously proposed algorithms for predicting halo concentrations can be well adapted to dark-energy models. When centred on the analytically expected values, halo concentrations show a log-normal distribution with a uniform standard deviation of ~0.2. The dependence of averaged halo concentrations on mass and redshift permits a simple fit of the form $(1+z)\,c=c_0\,(M/M_0)^\alpha$, with $\alpha\approx-0.1$ throughout. We find that the cluster concentration depends on the dark energy equation of state at the cluster formation redshift $z_{\rm coll}$ through the linear growth factor $D_+(z_{\rm coll})$. As a simple correction accounting for dark-energy cosmologies, we propose scaling c0 from $\Lambda$CDM with the ratio of linear growth factors, $c_0\rightarrow
c_0\,D_+(z_{\rm coll})/D_{+,~\Lambda{\rm CDM}}(z_{\rm coll})$ .

Key words: galaxies: clusters: general -- galaxies: halos -- cosmology: theory

Offprint request: K. Dolag, kdolag@pd.astro.it

© ESO 2004

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