arXiv subjects

Gert Huetsi

Publications and source records attributed to Gert Huetsi.

14 recordsLinked to original sources

arXiv2015

What can we learn from higher multipole power spectra of galaxy distribution in redshift space?

We investigate a potential of the higher multipole power spectra of the galaxy distribution in redshift space as a cosmological probe on halo scales. Based on the fact that a halo model explains well the multipole power spectra of the luminous red galaxy (LRG) sample in the Sloan Digital Sky Survey (SDSS), we focus our investigation on the random motions of the satellite LRGs that determine the higher multipole spectra at large wavenumbers. We show that our theoretical model fits the higher multipole spectra at large wave numbers from N-body numerical simulations and we apply these results for testing the gravity theory and the velocity structure of galaxies on the halo scales. In this analysis, we use the multipole spectra P_4(k) and P_6(k) on the small scales of the range of wavenumber 0.3<k/[h{Mpc}^{-1}]<0.6, which is in contrast to the usual method of testing gravity by targeting the linear growth rate on very large scales. We demonstrate that our method could be useful for testing gravity on the halo scales.

astro-ph.CO↗

arXiv2014

Combining clustering and abundances of galaxy clusters to test cosmology and primordial non-Gaussianity

We present the clustering of galaxy clusters as a useful addition to the common set of cosmological observables. The clustering of clusters probes the large-scale structure of the Universe, extending galaxy clustering analysis to the high-peak, high-bias regime. Clustering of galaxy clusters complements the traditional cluster number counts and observable-mass relation analyses, significantly improving their constraining power by breaking existing calibration degeneracies. We use the maxBCG galaxy clusters catalogue to constrain cosmological parameters and cross-calibrate the mass-observable relation, using cluster abundances in richness bins and weak-lensing mass estimates. We then add the redshift-space power spectrum of the sample, including an effective modelling of the weakly non-linear contribution and allowing for an arbitrary photometric redshift smoothing. The inclusion of the power spectrum data allows for an improved self-calibration of the scaling relation. We find that the inclusion of the power spectrum typically brings a $\sim 50$ per cent improvement in the errors on the fluctuation amplitude $σ_8$ and the matter density $Ω_{\mathrm{m}}$. Finally, we apply this method to constrain models of the early universe through the amount of primordial non-Gaussianity of the local type, using both the variation in the halo mass function and the variation in the cluster bias. We find a constraint on the amount of skewness $f_{\mathrm{NL}} = 12 \pm 157 $ ($1σ$) from the cluster data alone.

astro-ph.CO↗

arXiv2010

Deconvolution of window effect in galaxy power spectrum analysis

We develop a new method for deconvolving the smearing effect of the survey window in the analysis of the galaxy multipole power spectra from a redshift survey. This method is based on the deconvolution theorem, and is compatible with the use of the fast Fourier transform. It is possible to measure the multipole power spectra deconvolved from the window effect efficiently. Applying this method to the luminous red galaxy sample of the Sloan Digital Sky Survey data release 7 as well as mock catalogues, we demonstrate how the method works properly. Using this deconvolution technique, the amplitude of the multipole power spectrum is corrected. Besides, the covariance matrices of the deconvolved power spectra get quite close to the diagonal form. This is also advantageous in the study of the BAO signature.

astro-ph.CO↗

arXiv2010

Constraint on the cosmological f(R) model from the multipole power spectrum of the SDSS luminous red galaxy sample and prospects for a future redshift survey

A constraint on the viable f(R) model is investigated by confronting theoretical predictions with the multipole power spectrum of the luminous red galaxy sample of the Sloan Digital Sky survey data release 7. We obtain a constraint on the Compton wavelength parameter of the f(R) model on the scales of cosmological large-scale structure. A prospect of constraining the Compton wavelength parameter with a future redshift survey is also investigated. The usefulness of the redshift-space distortion for testing the gravity theory on cosmological scales is demonstrated.

astro-ph.CO↗

arXiv2009

Constraint on the growth factor of the cosmic structure from the damping of the baryon acoustic oscillation signature

We determine a constraint on the growth factor by measuring the damping of the baryon acoustic oscillations in the matter power spectrum using the Sloan Digital Sky Survey luminous red galaxy sample. The damping of the BAO is detected at the one sigma level. We obtain σ_8D_1(z=0.3) = 0.42^{+0.34}_{-0.28} at the 1σstatistical level, where σ_8 is the root mean square overdensity in a sphere of radius 8h^{-1}Mpc and D_1(z) is the growth factor at redshift z. The above result assumes that other parameters are fixed and the cosmology is taken to be a spatially flat cold dark matter universe with the cosmological constant.

astro-ph.CO↗

arXiv2009

Power spectrum of the maxBCG sample: detection of acoustic oscillations using galaxy clusters

We use the direct Fourier method to calculate the redshift-space power spectrum of the maxBCG cluster catalog -- currently by far the largest existing galaxy cluster sample. The total number of clusters used in our analysis is 12,616. After accounting for the radial smearing effect caused by photometric redshift errors and also introducing a simple treatment for the nonlinear effects, we show that currently favored low matter density "concordance" LCDM cosmology provides a very good fit to the estimated power. Thanks to the large volume (~0.4 h^{-3}Gpc^{3}), high clustering amplitude (linear effective bias parameter b_{eff} ~3x(0.85/sigma_8)), and sufficiently high sampling density (~3x10^{-5} h^{3}Mpc^{-3}) the recovered power spectrum has high enough signal to noise to allow us to find evidence (~2 sigma CL) for the baryonic acoustic oscillations (BAO). In case the clusters are additionally weighted by their richness the resulting power spectrum has slightly higher large-scale amplitude and smaller damping on small scales. As a result the confidence level for the BAO detection is somewhat increased: ~2.5 sigma. The ability to detect BAO with relatively small number of clusters is encouraging in the light of several proposed large cluster surveys.

astro-ph.CO↗

arXiv2009

Constraints on leptonically annihilating Dark Matter from reionization and extragalactic gamma background

The PAMELA, Fermi and HESS experiments (PFH) have shown anomalous excesses in the cosmic positron and electron fluxes. A very exciting possibility is that those excesses are due to annihilating dark matter (DM). In this paper we calculate constraints on leptonically annihilating DM using observational data on diffuse extragalactic gamma-ray background and measurements of the optical depth to the last-scattering surface, and compare those with the PFH favored region in the m_{DM} - <σ_A v> plane. Having specified the detailed form of the energy input with PYTHIA Monte Carlo tools we solve the radiative transfer equation which allows us to determine the amount of energy being absorbed by the cosmic medium and also the amount left over for the diffuse gamma background. We find that the constraints from the optical depth measurements are able to rule out the PFH favored region fully for the τ^{-}+τ^{+} annihilation channel and almost fully for the μ^{-}+μ^{+} annihilation channel. It turns out that those constraints are quite robust with almost no dependence on low redshift clustering boost. The constraints from the gamma-ray background are sensitive to the assumed halo concentration model and, for the power law model, rule out the PFH favored region for all leptonic annihilation channels. We also find that it is possible to have models that fully ionize the Universe at low redshifts. However, those models produce too large free electron fractions at z > ~100 and are in conflict with the optical depth measurements. Also, the magnitude of the annihilation cross-section in those cases is larger than suggested by the PFH data.

astro-ph.CO↗

arXiv2009

Confronting the damping of the baryon acoustic oscillations with observation

We investigate the damping of the baryon acoustic oscillations in the matter power spectrum due to the quasinonlinear clustering and redshift-space distortions by confronting the models with the observations of the Sloan Digital Sky Survey luminous red galaxy sample. The chi-squared test suggests that the observed power spectrum is better matched by models with the damping of the baryon acoustic oscillations rather than the ones without the damping.

astro-ph.CO↗

arXiv2008

The cluster-galaxy cross-spectrum: an additional probe of cosmological and halo parameters

There are several wide field galaxy and cluster surveys planned for the nearest future, e.g. BOSS, WFMOS, ADEPT, Hetdex, SPT, eROSITA. In the simplest approach one would analyze these independently, thus neglecting the extra information provided by the cluster-galaxy cross-pairs. In this paper we have focused on the possible synergy between these surveys by investigating the amount of information encoded in the cross-pairs. We present a model for the cluster-galaxy cross-spectrum within the Halo Model framework. To assess the gain in performance due to inclusion of the cluster-galaxy cross-pairs we carry out a Fisher matrix analysis for a BOSS-like galaxy redshift survey targeting luminous red galaxies and a hypothetical mass-limited cluster redshift survey with a lower mass threshold of 1.7x10^14 M_sun/h over the same volume. On small scales cluster-galaxy cross-spectrum probes directly density profile of the halos, instead of the density profile convolved with itself, as is the case for the galaxy power spectrum. Due to this different behavior, adding information from the cross-pairs helps to tighten constraints on the halo occupation distribution. By inclusion of the cross-pairs a factor of ~2 stronger constraints are obtained for sigma_8, while the improvement for the dark energy figure-of-merit is somewhat weaker: an increase by a factor of 1.4.

astro-ph↗

arXiv2008

Testing general relativity with the multipole spectra of the SDSS luminous red galaxies

As a test of general relativity on cosmological scales, we measure the γparameter for the growth rate of density perturbations using the redshift-space distortion of the luminous red galaxies in the Sloan Digital Sky Survey (SDSS). Assuming the cosmological constant model, which matches the results of the WMAP experiment, we find γ=0.62+1.8(σ_8-0.8) \pm 0.11 at 1-sigma confidence level, which is consistent with the prediction of general relativity, γ\simeq0.55\sim0.56. Rather high value of σ_8(\geq0.87) is required to be consistent with the prediction of the cosmological DGP model, γ\simeq0.68.

astro-ph↗

arXiv2007

Power spectrum of the maxBCG cluster sample: new evidence for the acoustic features

We use the direct Fourier method to calculate the redshift-space power spectrum of the maxBCG cluster catalog (Koester et al. 2007) -- currently by far the largest existing galaxy cluster sample. The total number of clusters used in our analysis is 12,616. After accounting for the radial smearing effect caused by photometric redshift errors and also introducing a simple treatment for the nonlinear effects, we show that currently favored low matter density ``concordance'' LambdaCDM cosmology provides a very good fit to the estimated power. Thanks to the large volume (~ 0.4 h^{-3} Gpc^3), high clustering amplitude (linear effective bias parameter b_{eff} ~ 3x(0.85/sigma_8)), and sufficiently high sampling density (~ 3x10^{-5} h^{3} Mpc^{-3}) the recovered power spectrum has high enough signal to noise to allow us to find weak evidence (~ 2sigma CL) for the acoustic features. These results are encouraging in light of the several proposed large cluster surveys. In case we use the photometric redshift errors as suggested in Koester et al. (2007) we are left with the excess large-scale power which has previously been noticed by several other authors.

astro-ph↗

arXiv2006

Power spectrum of the SDSS luminous red galaxies: constraints on cosmological parameters

In this paper we determine the constraints on cosmological parameters using the CMB data from the WMAP experiment together with the recent power spectrum measurement of the SDSS Luminous Red Galaxies (LRGs). Specifically, we focus on spatially flat, low matter density models with adiabatic Gaussian initial conditions. The spatial flatness is achieved with an additional quintessence component whose equation of state parameter w_eff is taken to be independent of redshift. Throughout most of the paper we do not allow any massive neutrino contribution and also the influence of the gravitational waves on the CMB is taken to be negligible. The analysis is carried out separately for two cases: (i) using the acoustic scale measurements as presented in Hütsi (2006), (ii) using the full SDSS LRG power spectrum and its covariance matrix. We are able to obtain a very tight constraint on the Hubble constant: H_0 = 70.8 ^{+2.1}_{-2.0} km/s/Mpc, which helps in breaking several degeneracies between the parameters and allows us to determine the low redshift expansion law with much higher accuracy than available from the WMAP + HST data alone. The positive deceleration parameter q_0 is found to be ruled out at 5.5 σconfidence level. Finally, we extend our analysis by investigating the effects of relaxing the assumption of spatial flatness and also allow for a contribution from massive neutrinos.

astro-ph↗

arXiv2005

Acoustic oscillations in the SDSS DR4 Luminous Red Galaxy sample power spectrum

We calculate the redshift-space power spectrum of the Sloan Digital Sky Survey (SDSS) Data Release 4 (DR4) Luminous Red Galaxy (LRG) sample, finding evidence for a full series of acoustic features down to the scales of \sim 0.2 hMpc^{-1}. This corresponds up to the 7th peak in the CMB angular power spectrum. The acoustic scale derived, (105.4 \pm 2.3) h^{-1}Mpc, agrees very well with the ``concordance'' model prediction and also with the one determined via the analysis of the spatial two-point correlation function by Eisenstein et al. (2005). The models with baryonic features are favored by 3.3 σover their ``smoothed-out'' counterparts without any oscillatory behavior.

astro-ph↗

arXiv2005

Acoustic oscillations in the SDSS Luminous Red Galaxy sample power spectrum

We calculate the redshift-space power spectrum of the Sloan Digital Sky Survey (SDSS) Luminous Red Galaxy (LRG) sample, finding evidence for a full series of acoustic features down to the scales of ~0.25 h Mpc^{-1}. This corresponds up to the 9. peak in the CMB angular power spectrum. The acoustic scale derived, (107.8 +- 4.3) h^{-1}Mpc (k < 0.2 h Mpc^{-1}), agrees very well with the ``concordance'' model prediction and also with the one determined via the analysis of the spatial two-point correlation function by Eisenstein et al.(2005). This is not only an independent confirmation of Eisenstein et al.(2005) results made with different methods and software but also, according to our knowledge, the first determination of the power spectrum of the SDSS LRG sample. By calculating the two-point correlation function using the smooth cubic spline model fitted to the observed bandpowers and comparing with the results of the direct determination we demonstrate the consistency of our results.

astro-ph↗