اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدLookback time and Chandra constrains on cosmological parameters
37
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
In this paper we combine the WMAP7 with lookback time and Chandra gas fraction data to constrain the main cosmological parameters and the equation of state for the dark energy. We find that the lookback time is a good measurement that can improve the determination of the equation of state for the dark energy with regard to other external data sets. We conclude that larger lookback time data set will further improve our determination of the cosmological parameters.
قيم البحث
اقرأ أيضاً
In this manuscript of the habilitation `a diriger des recherches (HDR), the author presents some of his work over the last ten years. The main topic of this thesis is cosmic shear, the distortion of images of distant galaxies due to weak gravitationa
l lensing by the large-scale structure in the Universe. Cosmic shear has become a powerful probe into the nature of dark matter and the origin of the current accelerated expansion of the Universe. Over the last years, cosmic shear has evolved into a reliable and robust cosmological probe, providing measurements of the expansion history of the Universe and the growth of its structure. I review the principles of weak gravitational lensing and show how cosmic shear is interpreted in a cosmological context. Then I give an overview of weak-lensing measurements, and present observational results from the Canada-France Hawaii Lensing Survey (CFHTLenS), as well as the implications for cosmology. I conclude with an outlook on the various future surveys and missions, for which cosmic shear is one of the main science drivers, and discuss promising new weak cosmological lensing techniques for future observations.
General relativistic corrections to the galaxy power spectrum appearing at the horizon scale, if neglected, may induce biases on the measured values of the cosmological parameters. In this paper, we study the impact of general relativistic effects on
non standard cosmologies such as scenarios with a time dependent dark energy equation of state, with a coupling between the dark energy and the dark matter fluids or with non-Gaussianities. We then explore whether general relativistic corrections affect future constraints on cosmological parameters in the case of a constant dark energy equation of state and of non-Gaussianities. We find that relativistic corrections on the power spectrum are not expected to affect the foreseen errors on the cosmological parameters nor to induce large biases on them.
This is a review article for The Review of Particle Physics 2020 (aka the Particle Data Book). It forms a compact review of knowledge of the cosmological parameters at the end of 2019. Topics included are Parametrizing the Universe; Extensions to the
standard model; Probes; Bringing observations together; Outlook for the future.
Upcoming galaxy surveys will allow us to probe the growth of the cosmic large-scale structure with improved sensitivity compared to current missions, and will also map larger areas of the sky. This means that in addition to the increased precision in
observations, future surveys will also access the ultra-large scale regime, where commonly neglected effects such as lensing, redshift-space distortions and relativistic corrections become important for calculating correlation functions of galaxy positions. At the same time, several approximations usually made in these calculations, such as the Limber approximation, break down at those scales. The need to abandon these approximations and simplifying assumptions at large scales creates severe issues for parameter estimation methods. On the one hand, exact calculations of theoretical angular power spectra become computationally expensive, and the need to perform them thousands of times to reconstruct posterior probability distributions for cosmological parameters makes the approach unfeasible. On the other hand, neglecting relativistic effects and relying on approximations may significantly bias the estimates of cosmological parameters. In this work, we quantify this bias and investigate how an incomplete modeling of various effects on ultra-large scales could lead to false detections of new physics beyond the standard $Lambda$CDM model. Furthermore, we propose a simple debiasing method that allows us to recover true cosmologies without running the full parameter estimation pipeline with exact theoretical calculations. This method can therefore provide a fast way of obtaining accurate values of cosmological parameters and estimates of exact posterior probability distributions from ultra-large scale observations.
We construct empirical models of star-forming galaxy evolution assuming that individual galaxies evolve along well-known scaling relations between stellar mass, gas mass and star formation rate following a simple description of chemical evolution. We
test these models by a comparison with observations and with detailed Magneticum high resolution hydrodynamic cosmological simulations. Galaxy star formation rates, stellar masses, gas masses, ages, interstellar medium and stellar metallicities are compared. It is found that these simple lookback models capture many of the crucial aspects of galaxy evolution reasonably well. Their key assumption of a redshift dependent power law relationship between galaxy interstellar medium gas mass and stellar mass is in agreement with the outcome of the complex Magneticum simulations. Star formation rates decline towards lower redshift not because galaxies are running out of gas, but because the fraction of the cold ISM gas, which is capable of producing stars, becomes significantly smaller. Gas accretion rates in both model approaches are of the same order of magnitude. Metallicity in the Magneticum simulations increases with the ratio of stellar mass to gas mass as predicted by the lookback models. The mass metallicity relationships agree and the star formation rate dependence of these relationships is also reproduced. We conclude that these simple models provide a powerful tool for constraining and interpreting more complex models based on cosmological simulations and for population synthesis studies analyzing integrated spectra of stellar populations.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
