arXiv subjects

R. F. L. Holanda

Publications and source records attributed to R. F. L. Holanda.

77 records · Page 5Linked to original sources

arXiv2011

Cosmic Distance Duality Relation and the Shape of Galaxy Clusters

Observations in the cosmological domain are heavily dependent on the validity of the cosmic distance-duality (DD) relation, D_L(z) (1 + z)^{2}/D_{A}(z) = 1, an exact result required by the Etherington reciprocity theorem where D_L(z) and D_A(z) are, respectively, the luminosity and angular diameter distances. In the limit of very small redshifts D_A(z) = D_L(z) and this ratio is trivially satisfied. Measurements of Sunyaev-Zeldovich effect (SZE) and X-rays combined with the DD relation have been used to determine D_A(z)from galaxy clusters. This combination offers the possibility of testing the validity of the DD relation, as well as determining which physical processes occur in galaxy clusters via their shapes. We use WMAP (7 years) results by fixing the conventional LCDM model to verify the consistence between the validity of DD relation and different assumptions about galaxy cluster geometries usually adopted in the literature. We assume that $η$ is a function of the redshift parametrized by two different relations: η(z) = 1 + η_{0}z, and η(z)=1 + η_{0}z/(1+z), where η_0 is a constant parameter quantifying the possible departure from the strict validity of the DD relation. In order to determine the probability density function (PDF) of η_{0}, we consider the angular diameter distances from galaxy clusters recently studied by two different groups by assuming elliptical (isothermal) and spherical (non-isothermal) $β$ models. The strict validity of the DD relation will occur only if the maximum value of η_{0} PDF is centered on η_{0}=0. It was found that the elliptical $β$ model is in good agreement with the data, showing no violation of the DD relation (PDF peaked close to η_0=0 at 1-sigma), while the spherical (non-isothermal) one is only marginally compatible at 3-sigma.

astro-ph.CO↗

arXiv2010

Are Galaxy Clusters Suggesting an Accelerating Universe?

The present cosmic accelerating stage is discussed through a new kinematic method based on the Sunyaev- Zel'dovich effect (SZE) and X-ray surface brightness data from galaxy clusters. By using the SZE/X-ray data from 38 galaxy clusters in the redshift range $0.14 \leq z \leq 0.89 $ [Bonamente et al., Astrop. J. {\bf 647}, 25 (2006)] it is found that the present Universe is accelerating and that the transition from an earlier decelerating to a late time accelerating regime is relatively recent. The ability of the ongoing Planck satellite mission to obtain tighter constraints on the expansion history through SZE/X-ray angular diameters is also discussed. Our results are fully independent on the validity of any metric gravity theory, the possible matter- energy contents filling the Universe, as well as on the SNe Ia Hubble diagram from which the presenting accelerating stage was inferred.

astro-ph.CO↗

arXiv2010

Testing the Distance-Duality Relation with Galaxy Clusters and Type Ia Supernovae

In this letter we propose a new and model-independent cosmological test for the distance-duality (DD) relation, η=D_{L}(z)(1+z)^{-2}/D_{A}(z)=1, where D_{L} and D_{A} are, respectively, the luminosity and angular diameter distances. For $D_L$ we consider two sub-samples of SNe type Ia taken from Constitution data (2009) whereas $D_A$ distances are provided by two samples of galaxy clusters compiled by De Fillipis et al. (2005) and Bonamente et al. (2006) by combining Sunyaev-Zeldovich effect (SZE) and X-ray surface brightness. The SNe Ia redshifts of each sub-sample were carefully chosen to coincide with the ones of the associated galaxy cluster sample (Δz<0.005) thereby allowing a direct test of DD relation. Since for very low redshifts, D_{A}(z) \approxeq D_{L}(z), we have tested the DD relation by assuming that $η$ is a function of the redshift parametrized by two different expressions: η(z) = 1 + η_{0}z and η(z) = 1 + η_{0}z/(1+z), where η_0 is a constant parameter quantifying a possible departure from the strict validity of the reciprocity relation (η_0=0). In the best scenario (linear parametrization) we obtain η_{0} = -0.28^{+ 0.44}_{- 0.44} (2σ$, statistical + systematic errors) for de Fillipis et al. sample (eliptical geometry), a result only marginally compatible with the DD relation. However, for Bonamente et al. sample (spherical geometry) the constraint is η_{0} = -0.42^{+ 0.34}_{- 0.34} (3σ$, statistical + systematic errors) which is clearly incompatible with the duality-distance relation.

astro-ph.CO↗

arXiv2010

Constraining H0 in General Dark Energy Models from Sunyaev-Zeldovich/X-ray Technique and Complementary Probes

In accelerating dark energy models, the estimates of H0 from Sunyaev-Zel'dovich effect (SZE) and X-ray surface brightness of galaxy clusters may depend on the matter content (Omega_M), the curvature (Omega_K) and the equation of state parameter (w). In this article, by using a sample of 25 angular diameter distances from galaxy clusters obtained through SZE/X-ray technique, we constrain H_0 in the framework of a general LCDM models (free curvature) and a flat XCDM model with equation of state parameter, w=p_x/ρ_x (w=constant). In order to broke the degeneracy on the cosmological parameters, we apply a joint analysis involving the baryon acoustic oscillations (BAO) and the CMB Shift Parameter signature. By neglecting systematic uncertainties, for nonflat LCDM cosmologies we obtain $H_0=73.2^{+4.3}_{-3.7}$ km s$^{-1}$ Mpc$^{-1}$ (1sigma) whereas for a flat universe with constant equation of state parameter we find $H_0=71.4^{+4.4}_{-3.4}$ km s$^{-1}$ Mpc$^{-1}$ (1$σ$). Such results are also in good agreement with independent studies from the Hubble Space Telescope key project and recent estimates based on Wilkinson Microwave Anisotropy Probe, thereby suggesting that the combination of these three independent phenomena provides an interesting method to constrain the Hubble constant. In particular, comparing these results with a recent determination for a flat LCDM model using only the SZE technique and BAO [Cunha et al. MNRAS 379, L1 2007], we see that the geometry has a very weak influence on H0 estimates for this combination of data.

astro-ph.CO↗

arXiv2009

Are Galaxy Clusters Suggesting an Accelerating Universe Independent of SNe Ia and Gravity Metric Theory?

A kinematic method to access cosmic acceleration based exclusively on the Sunyaev-Zel'dovich effect (SZE) and X-ray surface brightness data from galaxy clusters is proposed. By using the SZE/X-ray data from 38 galaxy clusters [Bonament et al., Astrop. J. 647, 25 (2006)], we find that the present Universe is accelerating and that the transition from an earlier decelerating to a late time accelerating regime occurred relatively recent. Such results are fully independent on the validity of any metric gravity theory, the possible matter-energy contents filling the Universe, as well as on the SNe type Ia Hubble diagram from which the present acceleration was inferred. The ability of the ongoing Planck satellite mission to obtain tighter constraints on the expansion history through SZE/X-ray angular diameters is also discussed. Two simple simulations of future Planck data suggest that such technique will be competitive with supernova data besides being complementary to it.

astro-ph.CO↗