Topic
Cosmology
About: Cosmology is a research topic. Over the lifetime, 18004 publications have been published within this topic receiving 631028 citations. The topic is also known as: physical cosmology & cosmologies.
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TL;DR: In this paper, the tomographic cosmic shear signal in Kilo Degree Survey (KiDS) data was combined with the galaxy-matter cross-correlation signal of galaxies from the Galaxies And Mass Assembly (GAMA) survey determined with KiDS weak lensing, and the angular correlation function of the same GAMA galaxies.
Abstract: We present cosmological parameter constraints from a joint analysis of three cosmological probes: the tomographic cosmic shear signal in ˜450 deg2 of data from the Kilo Degree Survey (KiDS), the galaxy-matter cross-correlation signal of galaxies from the Galaxies And Mass Assembly (GAMA) survey determined with KiDS weak lensing, and the angular correlation function of the same GAMA galaxies. We use fast power spectrum estimators that are based on simple integrals over the real-space correlation functions, and show that they are practically unbiased over relevant angular frequency ranges. We test our full pipeline on numerical simulations that are tailored to KiDS and retrieve the input cosmology. By fitting different combinations of power spectra, we demonstrate that the three probes are internally consistent. For all probes combined, we obtain S_8≡ σ _8 √{Ω _m/0.3}=0.800_{-0.027}^{+0.029}, consistent with Planck and the fiducial KiDS-450 cosmic shear correlation function results. Marginalising over wide priors on the mean of the tomographic redshift distributions yields consistent results for S8 with an increase of 28% in the error. The combination of probes results in a 26% reduction in uncertainties of S8 over using the cosmic shear power spectra alone. The main gain from these additional probes comes through their constraining power on nuisance parameters, such as the galaxy intrinsic alignment amplitude or potential shifts in the redshift distributions, which are up to a factor of two better constrained compared to using cosmic shear alone, demonstrating the value of large-scale structure probe combination.
223 citations
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TL;DR: Cluster lensing as mentioned in this paper is a powerful geometric tool to study the geometry of the universe and the formation and evolution of galaxies, as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer.
Abstract: Clusters of galaxies are the most recently assembled, massive, bound structures in the Universe As predicted by General Relativity, given their masses, clusters strongly deform space-time in their vicinity Clusters act as some of the most powerful gravitational lenses in the Universe Light rays traversing through clusters from distant sources are hence deflected, and the resulting images of these distant objects therefore appear distorted and magnified Lensing by clusters occurs in two regimes, each with unique observational signatures The strong lensing regime is characterized by effects readily seen by eye, namely, the production of giant arcs, multiple-images, and arclets The weak lensing regime is characterized by small deformations in the shapes of background galaxies only detectable statistically Cluster lenses have been exploited successfully to address several important current questions in cosmology: (i) the study of the lens(es) - understanding cluster mass distributions and issues pertaining to cluster formation and evolution, as well as constraining the nature of dark matter; (ii) the study of the lensed objects - probing the properties of the background lensed galaxy population - which is statistically at higher redshifts and of lower intrinsic luminosity thus enabling the probing of galaxy formation at the earliest times right up to the Dark Ages; and (iii) the study of the geometry of the Universe - as the strength of lensing depends on the ratios of angular diameter distances between the lens, source and observer, lens deflections are sensitive to the value of cosmological parameters and offer a powerful geometric tool to probe Dark Energy In this review, we present the basics of cluster lensing and provide a current status report of the field
222 citations
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TL;DR: In this article, the authors cross-correlate the cosmic microwave background temperature anisotropies observed by the Wilkinson Microwave Anisotropy Probe (WMAP) with the projected distribution of extended sources in the Two Micron All Sky Survey (2MASS).
Abstract: We cross-correlate the cosmic microwave background temperature anisotropies observed by the Wilkinson Microwave Anisotropy Probe (WMAP) with the projected distribution of extended sources in the Two Micron All Sky Survey (2MASS). By modeling the theoretical expectation for this signal, we extract the signatures of dark energy [integrated Sachs-Wolfe effect (ISW)], hot gas [thermal Sunyaev-Zeldovich (SZ) effect], and microwave point sources in the cross-correlation. Our strongest signal is the thermal SZ, at the $3.1--3.7\ensuremath{\sigma}$ level, which is consistent with the theoretical prediction based on observations of x-ray clusters. We also see the ISW signal at the $2.5\ensuremath{\sigma}$ level, which is consistent with the expected value for the concordance $\ensuremath{\Lambda}\mathrm{CDM}$ cosmology, and is an independent signature of the presence of dark energy in the Universe. Finally, we see the signature of microwave point sources at the $2.7\ensuremath{\sigma}$ level.
222 citations
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TL;DR: In this article, a controlled set of high-resolution cosmological simulations to quantify the effect of baryons on weak-lensing signal at scales corresponding to multipole moments 100 < l < 10,000 was used.
Abstract: Future weak-lensing measurements of cosmic shear will reach such high accuracy that second-order effects in weak-lensing modeling, such as the influence of baryons on structure formation, become important. We use a controlled set of high-resolution cosmological simulations to quantify this effect by comparing pure N-body dark matter runs with corresponding hydrodynamic simulations, carried out both in nonradiative form and in dissipative form with cooling and star formation. In both hydrodynamic simulations, the clustering of the gas is suppressed while that of dark matter is boosted at scales k > 1 h Mpc(-1). Despite this counterbalance between dark matter and gas, the clustering of the total matter is suppressed by up to 1% at 1 h Mpc(-1) less than or similar to k less than or similar to 10 h Mpc(-1), while for k approximate to 20 h Mpc(-1) it is boosted, up to 2% in the nonradiative run and 10% in the run with star formation. The stellar mass formed in the latter is highly biased relative to the dark matter in the pure N-body simulation. Using our power spectrum measurements to predict the effect of baryons on the weak-lensing signal at scales corresponding to multipole moments 100 < l < 10,000, we find that baryons may change the lensing power spectrum by less than 0.5% at l < 1000, but by 1% to 10% at 1000 < l < 10,000. The size of the effect exceeds the predicted accuracy of future lensing power spectrum measurements and will likely be detected. Precise determinations of cosmological parameters with weak lensing, and studies of small-scale fluctuations and clustering, therefore rely on properly including baryonic physics.
222 citations
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TL;DR: In this paper, the authors show that the detection of acoustic oscillations in both upcoming cosmic microwave background (CMB) satellite experiments and large-redshift surveys can yield 5% determinations of H --> 0 and? -->m, an order-of-magnitude improvement over CMB data alone.
Abstract: We show that the detection of acoustic oscillations in both upcoming cosmic microwave background (CMB) satellite experiments and large-redshift surveys can yield 5% determinations of H -->0 and ? -->m, an order-of-magnitude improvement over CMB data alone. CMB anisotropies provide the sound horizon at recombination as a standard ruler. For reasonable baryon fractions, this scale is imprinted on the galaxy power spectrum as a series of spectral features. Measuring these features in redshift space determines the Hubble constant, which in turn yields ? -->m once combined with CMB data. Since the oscillations in both power spectra are frozen-in at recombination, this test is insensitive to low-redshift cosmology.
222 citations