MASS INHOMOGENEITIES AND THE ANGULAR SIZE-REDSHIFT RELATION

2004 ◽  
Vol 13 (07) ◽  
pp. 1309-1313 ◽  
Author(s):  
JAILSON S. ALCANIZ ◽  
JOSÉ A. S. LIMA ◽  
RAIMUNDO SILVA
Keyword(s):  
Dark Energy ◽  
Angular Size ◽  
Matter Density ◽  
Radio Sources ◽  
Density Parameter ◽  
Energy Component ◽  
Dark Energy Component ◽  
Smoothness Parameter ◽  
Best Fit ◽  
Size Data

We investigate the influence of mass inhomogeneities on the angular size-redshift test through a statistical analysis of angular size data for a large sample of milliarcsecond radio sources. The results are based on flat models driven by nonrelativistic matter plus a dark energy component in the form of a relic cosmological constant. To model the mass inhomogeneities we use the Zeldovich–Kantowski distance formula (also known as Dyer–Roeder distance redshift relation) which is characterized by the smoothness parameter α. Marginalizing over the characteristic angular size l and assuming a Gaussian prior on the matter density parameter, i.e., Ωm=0.35±0.07, the best fit model occurs at Ωm=0.35 and α=0.8. For an analysis without priors and minimizing χ2 for the parameters l, Ωm and α we find that a conventional homogeneous scenario (α=1) with Ωm=0.2 and D=22.6h-1 pc constitutes the best fit model for the present angular size data.

scholarly journals Cosmological constraints from higher redshift gamma-ray burst, H ii starburst galaxy, and quasar (and other) data

2020 ◽  
Vol 501 (1) ◽  
pp. 1520-1538
Author(s):  
Shulei Cao ◽  
Joseph Ryan ◽  
Narayan Khadka ◽  
Bharat Ratra
Keyword(s):  
Dark Energy ◽  
Gamma Ray ◽  
Angular Size ◽  
Acoustic Oscillation ◽  
Matter Density ◽  
Joint Analysis ◽  
Starburst Galaxy ◽  
Density Parameter ◽  
Gamma Ray Burst ◽  
Cosmological Constraints

ABSTRACT We use higher redshift gamma-ray burst (GRB), H ii starburst galaxy (H iiG), and quasar angular size (QSO-AS) measurements to constrain six spatially flat and non-flat cosmological models. These three sets of cosmological constraints are mutually consistent. Cosmological constraints from a joint analysis of these data sets are largely consistent with currently accelerating cosmological expansion and with cosmological constraints derived from a combined analysis of Hubble parameter (H(z)) and baryon acoustic oscillation (BAO, with Planck-determined baryonic matter density) measurements. A joint analysis of the H(z) + BAO + QSO-AS + H iiG + GRB data provides fairly model-independent determinations of the non-relativistic matter density parameter $\Omega _{\rm m_0}=0.313\pm 0.013$ and the Hubble constant $H_0=69.3\pm 1.2\, \rm {km \, s^{-1} \, Mpc^{-1}}$. These data are consistent with the dark energy being a cosmological constant and with spatial hypersurfaces being flat, but they do not rule out mild dark energy dynamics or a little spatial curvature. We also investigate the effect of including quasar flux measurements in the mix and find no novel conclusions.

scholarly journals OBSERVATIONAL CONSTRAINTS ON THE GENERALIZED CHAPLYGIN GAS

2009 ◽  
Vol 18 (13) ◽  
pp. 2007-2022 ◽  
Author(s):  
SERGIO DEL CAMPO ◽  
J. R. VILLANUEVA
Keyword(s):  
Dark Energy ◽  
Cosmological Model ◽  
Chaplygin Gas ◽  
Observational Constraints ◽  
Energy Component ◽  
Generalized Chaplygin Gas ◽  
Astronomical Data ◽  
Astronomical Observations ◽  
Dark Energy Component ◽  
Two Parameters

In this paper we study a quintessence cosmological model in which the dark energy component is considered to be the generalized Chaplygin gas and the curvature of the three-geometry is taken into account. Two parameters characterize this sort of fluid: ν and α. We use different astronomical data for restricting these parameters. It is shown that the constraint ν ≲ α agrees well enough with the astronomical observations.

scholarly journals Cosmological constraints from H ii starburst galaxy apparent magnitude and other cosmological measurements

2020 ◽  
Vol 497 (3) ◽  
pp. 3191-3203 ◽  
Author(s):  
Shulei Cao ◽  
Joseph Ryan ◽  
Bharat Ratra
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Angular Size ◽  
Hubble Constant ◽  
Joint Analysis ◽  
Apparent Magnitude ◽  
Starburst Galaxy ◽  
Density Parameter ◽  
Acoustic Oscillations ◽  
Combined Data

ABSTRACT We use H ii starburst galaxy apparent magnitude measurements to constrain cosmological parameters in six cosmological models. A joint analysis of H ii galaxy, quasar angular size, baryon acoustic oscillations peak length scale, and Hubble parameter measurements result in relatively model-independent and restrictive estimates of the current values of the non-relativistic matter density parameter $\Omega _{\rm m_0}$ and the Hubble constant H0. These estimates favour a 2.0–3.4σ (depending on cosmological model) lower H0 than what is measured from the local expansion rate. The combined data are consistent with dark energy being a cosmological constant and with flat spatial hypersurfaces, but do not strongly rule out mild dark energy dynamics or slightly non-flat spatial geometries.

GRAVITATIONAL LENSING CONSTRAINT ON THE COSMIC EQUATION OF STATE

2003 ◽  
Vol 12 (05) ◽  
pp. 953-962 ◽  
Author(s):  
DEEPAK JAIN ◽  
ABHA DEV ◽  
N. PANCHAPAKESAN ◽  
S. MAHAJAN ◽  
V. B. BHATIA
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Gravitational Lensing ◽  
Energy Component ◽  
Distance Measurements ◽  
Dark Energy Component ◽  
Highly Sensitive ◽  
Type Ia ◽  
Image Separation ◽  
Ia Supernovae

Recent redshift-distance measurements of Type Ia supernovae (SNe Ia) at cosmological distances suggest that two-third of the energy density of the universe is dominated by dark energy component with an effective negative pressure. This dark energy component is described by the equation of state px= wρx(w ≥ - 1). We use gravitational lensing statistics to constrain the equation of state of this dark energy. We use n(Δθ), the image separation distribution function of lensed quasars, as a tool to probe w. We find that for the observed range of Ωm~ 0.2–0.4, w should lie between -0.8 ≤ w ≤ -0.4 in order to have five lensed quasars in a sample of 867 optical quasars. This limit is highly sensitive to lens and Schechter parameters and the evolution of galaxies.

scholarly journals Radio Galaxy Redshift–Angular Size Data Constraints on Dark Energy

2003 ◽  
Vol 584 (2) ◽  
pp. 577-579 ◽  
Author(s):  
Silviu Podariu ◽  
Ruth A. Daly ◽  
Matthew P. Mory ◽  
Bharat Ratra
Keyword(s):  
Dark Energy ◽  
Radio Galaxy ◽  
Angular Size ◽  
Galaxy Redshift ◽  
Data Constraints ◽  
Size Data

scholarly journals The Flux Density-Angular Size Distribution for Extragalactic Radio Sources

1977 ◽  
Vol 74 ◽  
pp. 125-132 ◽  
Author(s):  
G. Swarup ◽  
C. R. Subrahmanya
Keyword(s):  
Size Distribution ◽  
Flux Density ◽  
Angular Size ◽  
Evolutionary Model ◽  
Radio Sources ◽  
Extragalactic Radio Sources ◽  
Size Evolution ◽  
Theoretical Predictions ◽  
Best Fit ◽  
Remarkable Agreement

The median values of angular sizes of weak extragalactic radio sources, the flux densities of which lie in the range of about 0. 3 to 5 Jy at 327 MHz, have been determined for a new sample of 119 sources observed during 1973-74, and agree well with the value of about 10 arc sec determined earlier by Swarup (1975). For 8 different flux density ranges, the angular size distribution for the All-sky, 3CR and Ooty radio sources have been compared with theoretical predictions based on the evolutionary model by Kapahi (1975) and show a remarkable agreement with his model except that the best fit is found for a linear size evolution proportional to (l+z)−1.

scholarly journals Novel null-test for the Λ cold dark matter model with growth-rate data

2015 ◽  
Vol 24 (06) ◽  
pp. 1550045 ◽  
Author(s):  
Savvas Nesseris ◽  
Domenico Sapone
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Statistical Tests ◽  
Cosmological Parameters ◽  
Accelerated Expansion ◽  
Late Time ◽  
Energy Component ◽  
Dark Energy Component ◽  
Standard Cosmological Model ◽  
Flrw Universe

Current and upcoming surveys will measure the cosmological parameters with an extremely high accuracy. The primary goal of these observations is to eliminate some of the currently viable cosmological models created to explain the late-time accelerated expansion (either real or only inferred). However, most of the statistical tests used in cosmology have a strong requirement: the use of a model to fit the data. Recently there has been an increased interest on finding tests that are model independent, i.e. to have a function that depends entirely on observed quantities and not on the model, see for instance [C. Clarkson, B. Bassett and T. H. C. Lu, Phys. Rev. Lett.101 (2008) 011301, arXiv:0712.3457 [astro-ph]]. In this paper, we present an alternative consistency check at the perturbative level for a homogeneous and isotropic Universe filled with a dark energy component. This test makes use of the growth of matter perturbations data and it is able to detect a deviation from the standard cosmological model, which could later be attributed to a clustering dark energy component, a tension in the data or a modification of gravity, within the framework of a Friedmann–Lemaître–Robertson–Walker (FLRW) universe.

scholarly journals THERMODYNAMIC OF THE GHOST DARK ENERGY UNIVERSE

2012 ◽  
Vol 27 (31) ◽  
pp. 1250182 ◽  
Author(s):  
CHAO-JUN FENG ◽  
XIN-ZHOU LI ◽  
XIAN-YONG SHEN
Keyword(s):  
Dark Energy ◽  
Vacuum Energy ◽  
Hawking Temperature ◽  
Frw Universe ◽  
Energy Component ◽  
Ghost Dark Energy ◽  
Dark Energy Component ◽  
Acceleration Of The Universe ◽  
The Universe ◽  
Friedmann Robertson Walker

Recently, the vacuum energy of the QCD ghost in a time-dependent background is proposed as a kind of dark energy candidate to explain the acceleration of the Universe. In this model, the energy density of the dark energy is proportional to the Hubble parameter H, which is the Hawking temperature on the Hubble horizon of the Friedmann–Robertson–Walker (FRW) Universe. In this paper, we generalized this model and chose the Hawking temperature on the so-called trapping horizon, which will coincide with the Hubble temperature in the context of flat FRW Universe dominated by the dark energy component. We study the thermodynamics of Universe with this kind of dark energy and find that the entropy-area relation is modified, namely, there is another new term besides the area term.

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