XMM-Newton XMM-LSS  

Index - ... - Scientific Goals - Simulations (1/3) - Simulations (2/3) - ...

4. Simulations (1/3)

4.1 - The 3D cluster distribution

In order to produce an accurate estimate of the cluster distribution that this survey should observe, we have used the Hubble Volume simulations performed by the Virgo consortium. These simulations examined a sufficiently large region of space (2-3 gigaparsecs) with enough resolution that we can directly measure the masses and distributions of simulated clusters. As part of that work, the distribution of particles was recorded on the past light cone of an observer at z = 0. Using the cluster catalogue extracted from these Hubble Volume Lightcone Simulations, we have computed survey wedge diagrammes for 2 cosmologies: CDM (lambda-dominated universe) and CDM (critical density universe). We have applied the survey selection function using the appropriate L(z)-T-M relations. Results are presented in Fig. 3, 4, 5 & 6.

Since open cosmologies are currently favored by (among others observations) the non-evolution of the galaxy cluster X-ray luminosity function out to z ~ 0.8, we have computed the expected correlation function from the simulated cluster population obtained for the CDM model (Fig. 4). Results are presented in Fig. 7 & 8.

Given these results, we conclude that it will be possible to measure the correlation length with a high degree of accuracy in 2 redshift bins.

(Note that owing to observed lack of evolution of the cluster luminosity function out to z ~ 0.8, there may be even less evolution than predicted by the CDM model.)

LCDM_wedge_fig1.ps.gz (gzipped Postscript, 133691 bytes)

Figure 3: The distribution of galaxy clusters for the CDM model from the Hubble Volume Simulation Lightcone for a 8 x 8 sq.deg area (the opening angle of the wedge has been blown up, for display purpose). One sees clearly the effect of evolution beyond z > 1: fewer massive clusters are present. The number of clusters in the 0 < z < 0.4 and 0.4 < z < 1 redshift bins are indicated in brackets. Cosmological parameters: 0 = 0.3, = 0.7, h = 0.7.

LCDM_wedge_fig2.ps.gz (gzipped Postscript, 25748 bytes)

Figure 4: Same as above, but folded with the X-ray survey selection function.

tCDM_wedge_fig1.ps.gz (gzipped Postscript, 24600 bytes)

Figure 5: Same as Fig. 3, but for a CDM cosmology: evolution is much stronger for this high density universe. Cosmological parameters: 0 = 1, = 0, h = 0.5.

tCDM_wedge_fig2.ps.gz (gzipped Postscript, 14058 bytes)

Figure 6: Same as Fig. 4, but for a CDM cosmology.

LCDM_near_10ks_fig1.ps.gz (gzipped Postscript, 4908 bytes)

Figure 7: The cluster correlation function for the 0 < z < 0.4 redhsift bin, for the CDM model, with the survey selection function (see Fig.4 - the number of objects are given in that figure). The line shows the best fit for = (r/r0). Associated error ellipses on the correlation length and the exponent (significance levels: 68.3% (1 d.o.f.), 68.3%. (2 d.o.f.), 99%. (1 d.o.f.). The simulations show that it will be possible to measure r0 with an accuracy better than 10%.

LCDM_dist_10ks_fig1.ps.gz (gzipped Postscript, 4935 bytes)

Figure 8: Same as above, but for the 0.4 < z < 1 redhsift bin.

4.2 - Simulated XMM images of cosmic filaments

Index - ... - Scientific Goals - Simulations (1/3) - Simulations (2/3) - ...
Web Pages : Alain Detal, Oct 2001.