scholarly journals The effect of photometric redshift uncertainties on galaxy clustering and baryonic acoustic oscillations

2018 ◽  
Vol 477 (3) ◽  
pp. 3892-3909 ◽  
Author(s):  
Jonás Chaves-Montero ◽  
Raúl E Angulo ◽  
Carlos Hernández-Monteagudo
Keyword(s):  
Acoustic Oscillations ◽  
Galaxy Clustering ◽  
Photometric Redshift ◽  
Baryonic Acoustic Oscillations

scholarly journals Suppressing cosmic variance with paired-and-fixed cosmological simulations: average properties and covariances of dark matter clustering statistics

2020 ◽  
Vol 496 (3) ◽  
pp. 3862-3869 ◽  
Author(s):  
Anatoly Klypin ◽  
Francisco Prada ◽  
Joyce Byun
Keyword(s):  
Dark Matter ◽  
Power Spectrum ◽  
Initial Conditions ◽  
Cosmological Parameters ◽  
Average Density ◽  
Covariance Matrices ◽  
Acoustic Oscillations ◽  
Galaxy Clustering ◽  
The Mean ◽  
Statistical Noise

ABSTRACT Making cosmological inferences from the observed galaxy clustering requires accurate predictions for the mean clustering statistics and their covariances. Those are affected by cosmic variance – the statistical noise due to the finite number of harmonics. The cosmic variance can be suppressed by fixing the amplitudes of the harmonics instead of drawing them from a Gaussian distribution predicted by the inflation models. Initial realizations also can be generated in pairs with 180○ flipped phases to further reduce the variance. Here, we compare the consequences of using paired-and-fixed versus Gaussian initial conditions on the average dark matter clustering and covariance matrices predicted from N-body simulations. As in previous studies, we find no measurable differences between paired-and-fixed and Gaussian simulations for the average density distribution function, power spectrum, and bispectrum. Yet, the covariances from paired-and-fixed simulations are suppressed in a complicated scale- and redshift-dependent way. The situation is particularly problematic on the scales of Baryon acoustic oscillations where the covariance matrix of the power spectrum is lower by only $\sim 20{{\ \rm per\ cent}}$ compared to the Gaussian realizations, implying that there is not much of a reduction of the cosmic variance. The non-trivial suppression, combined with the fact that paired-and-fixed covariances are noisier than from Gaussian simulations, suggests that there is no path towards obtaining accurate covariance matrices from paired-and-fixed simulations – result, that is theoretically expected and accepted in the field. Because the covariances are crucial for the observational estimates of galaxy clustering statistics and cosmological parameters, paired-and-fixed simulations, though useful for some applications, cannot be used for the production of mock galaxy catalogues.

scholarly journals A divergence-free parametrization of deceleration parameter for scalar field dark energy

2016 ◽  
Vol 25 (03) ◽  
pp. 1650032 ◽  
Author(s):  
Abdulla Al Mamon ◽  
Sudipta Das
Keyword(s):  
Dark Energy ◽  
Deceleration Parameter ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Frw Universe ◽  
Potential Term ◽  
Type Ia ◽  
De Formula ◽  
Divergence Free ◽  
Baryonic Acoustic Oscillations

In this paper, we have considered a spatially flat FRW universe filled with pressureless matter and dark energy (DE). We have considered a phenomenological parametrization of the deceleration parameter [Formula: see text] and from this, we have reconstructed the equation-of-state (EoS) for DE [Formula: see text]. This divergence-free parametrization of the deceleration parameter is inspired from one of the most popular parametrization of the DE EoS given by Barboza and Alcaniz [see E. M. Barboza and J. S. Alcaniz, Phys. Lett. B 666 (2008) 415]. Using the combination of datasets (Type Ia Supernova (SN Ia) + Hubble + baryonic acoustic oscillations/cosmic microwave background (BAO/CMB)), we have constrained the transition redshift [Formula: see text] (at which the universe switches from a decelerating to an accelerating phase) and have found the best fit value of [Formula: see text]. We have also compared the reconstructed results of [Formula: see text] and [Formula: see text] and have found that the results are compatible with a [Formula: see text]CDM universe if we consider SN Ia + Hubble data, but inclusion of BAO/CMB data makes [Formula: see text] and [Formula: see text] incompatible with [Formula: see text]CDM model. The potential term for the present toy model is found to be functionally similar to a Higgs potential.

scholarly journals Quintessence and tachyon dark energy in interaction with dark matter: Observational constraints and model selection

2020 ◽  
Vol 29 (08) ◽  
pp. 2050057
Author(s):  
Sandro M. R. Micheletti
Keyword(s):  
Field Theory ◽  
Dark Energy ◽  
Scalar Fields ◽  
Coupling Constants ◽  
Observational Constraints ◽  
Acoustic Oscillations ◽  
Distance Information ◽  
New Agegraphic Dark Energy ◽  
Text Model ◽  
Baryonic Acoustic Oscillations

We derive two field theory models of interacting dark energy, one in which dark energy is associated with the quintessence and another in which it is associated with the tachyon. In both, instead of choosing arbitrarily the potential of scalar fields, these are specified implicitly by imposing that the dark energy fields must behave as the new agegraphic dark energy. The resulting models are compared with the Pantheon supernovae sample, CMB distance information from Planck 2015 data, baryonic acoustic oscillations (BAO) and Hubble parameter data. For comparison, the noninteracting case and the [Formula: see text] model also are considered. By use of the AIC and BIC criteria, we have obtained strong evidence in favor of the two interacting models, and the coupling constants are nonvanishing at more than [Formula: see text] confidence level.

scholarly journals THE ΛCDM GROWTH RATE OF STRUCTURE REVISITED

2012 ◽  
Vol 21 (07) ◽  
pp. 1250064 ◽  
Author(s):  
SPYROS BASILAKOS
Keyword(s):  
Growth Rate ◽  
Growth Index ◽  
Acoustic Oscillations ◽  
Growth Data ◽  
Microwave Background ◽  
Shift Parameter ◽  
Likelihood Analysis ◽  
Type Ia ◽  
Supernovae Type Ia ◽  
Baryonic Acoustic Oscillations

We re-examine the growth index of the concordance Λ cosmology in the light of the latest 6dF and WiggleZ data. In particular, we investigate five different models for the growth index γ, by comparing their cosmological evolution using observational data of the growth rate of structure formation at different redshifts. Performing a joint likelihood analysis of the recent supernovae type Ia data, the Cosmic Microwave Background shift parameter, Baryonic Acoustic Oscillations and the growth rate data, we determine the free parameters of the γ(z) parametrizations and we statistically quantify their ability to represent the observations. We find that the addition of the 6dF and WiggleZ growth data in the likelihood analysis improves significantly the statistical results. As an example, considering a constant growth index we find Ωm0 = 0.273 ± 0.011 and [Formula: see text].

scholarly journals Large-scale structure studies with AGN in the eROSITA/SRG All-Sky Survey

2013 ◽  
Vol 9 (S304) ◽  
pp. 422-425
Author(s):  
Alexander Kolodzig ◽  
Marat Gilfanov ◽  
Gert Hütsi ◽  
Rashid Sunyaev
Keyword(s):  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Full Potential ◽  
Acoustic Oscillations ◽  
X Ray ◽  
Bias Factor ◽  
Sky Survey ◽  
First Time ◽  
Baryonic Acoustic Oscillations

AbstractThe four-year X-ray all-sky survey (eRASS) of the eROSITA telescope aboard the Spektrum-Roentgen-Gamma satellite will detect ~ 3 million active galactic nuclei (AGN) with a median redshift of z≈1. We show that this unprecedented AGN sample, complemented with redshift information, will supply us with outstanding opportunities for large-scale structure research. For the first time with a sample of X-ray selected AGN, it will become possible to perform detailed redshift- and luminosity-resolved studies of the linear bias factor, and to convincingly detected baryonic acoustic oscillations (BAOs). To exploit the full potential of the eRASS AGN sample, photometric and spectroscopic surveys of large areas and a sufficient depth will be needed.

Sign in / Sign up

Export Citation Format

Share Document