Halo concentrations and weak-lensing number counts in dark energy cosmologies

¹ Max-Planck-Institut für Astrophysik, PO Box 1317, 85741 Garching, Germany
² Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA
³ Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
⁴ SISSA/ISAS, via Beirut 4, 34014 Trieste, Italy

Corresponding author: M. Bartelmann, msb@mpa-garching.mpg.de

Received: 1 July 2002
Accepted: 16 September 2002

Abstract

We study the effects of a dark energy component with equation of state with constant on the formation of Cold Dark Matter (CDM) haloes. We find two main effects: first, haloes form earlier as w increases, and second, the amplitude of the dark-matter power spectrum gets reduced in order to remain compatible with the large scale Cosmic Microwave Background (CMB) anisotropies. These effects counteract. Using recipes derived from numerical simulations, we show that haloes are expected to be up to ~50% more concentrated in CDM models with quintessence compared to ΛCDM models, the maximum increase being reached for . For larger w, the amplitude of the power spectrum decreases rapidly and makes expected halo concentrations decrease. Halo detections through weak gravitational lensing are highly sensitive to halo concentrations. We show that weak-lensing halo counts with the aperture-mass technique increase by a factor of ~2 as w is increased from -1 to -0.6, offering a new method for constraining the nature of dark energy.