scholarly journals Cross-correlating Planck with VST ATLAS LRGs: a new test for the ISW effect in the Southern hemisphere

2020 ◽  
Vol 493 (4) ◽  
pp. 4830-4844
Author(s):  
Behzad Ansarinejad ◽  
Ruari Mackenzie ◽  
Tom Shanks ◽  
Nigel Metcalfe
Keyword(s):  
Cold Dark Matter ◽  
High Redshift ◽  
Total Sample ◽  
Late Time ◽  
Microwave Background ◽  
Luminous Red Galaxies ◽  
Cosmic Microwave Background Temperature ◽  
History Of ◽  
Background Temperature ◽  
Red Galaxies

ABSTRACT The integrated Sachs–Wolfe (ISW) effect probes the late-time expansion history of the Universe, offering direct constraints on dark energy. Here, we present our measurements of the ISW signal at redshifts of $\bar{z}=0.35$, 0.55, and 0.68, using the cross-correlation of the Planck cosmic microwave background temperature map with ∼0.5 million luminous red galaxies (LRGs) selected from the VST ATLAS survey. We then combine these with previous measurements based on WMAP and similar SDSS LRG samples, providing a total sample of ∼2.1 million LRGs covering ∼12 000 deg2 of sky. At $\bar{z}=0.35$ and $\bar{z}=0.55$, we detect the ISW signal at 1.2σ and 2.3σ (or 2.6σ combined), in agreement with the predictions of lambda cold dark matter (ΛCDM). We verify these results by repeating the measurements using the BOSS LOWZ and CMASS, spectroscopically confirmed LRG samples. We also detect the ISW effect in three magnitude limited ATLAS + SDSS galaxy samples extending to z ≈ 0.4 at ∼2σ per sample. However, we do not detect the ISW signal at $\bar{z}=0.68$ when combining the ATLAS and SDSS results. Further tests using spectroscopically confirmed eBOSS LRGs at this redshift remain inconclusive due to the current low sky coverage of the survey. If the ISW signal is shown to be redshift dependent in a manner inconsistent with the predictions of ΛCDM, it could open the door to alternative theories such as modified gravity. It is therefore important to repeat the high-redshift ISW measurement using the completed eBOSS sample, as well as deeper upcoming surveys such as DESI and LSST.

scholarly journals Cosmology with relativistically varying physical constants

2020 ◽  
Vol 498 (3) ◽  
pp. 4481-4491
Author(s):  
Rajendra P Gupta
Keyword(s):  
Cold Dark Matter ◽  
Physical Constant ◽  
Einstein Equations ◽  
Local Conservation ◽  
Microwave Background ◽  
Dark Energy Density ◽  
Cosmic Microwave Background Temperature ◽  
Λcdm Model ◽  
Background Temperature ◽  
Age Of The Universe

ABSTRACT We have shown that the varying physical constant model is consistent with the recently published variational approach wherein Einstein equations are modified to include the variation of the speed of light c, gravitational constant G, and cosmological constant Λ using the Einstein–Hilbert action. The general constraint resulting from satisfying the local conservation laws and contracted Bianchi identities provides the freedom to choose the form of the variation of the constants as well as how their variations are related. When we choose ${\dot{G}}/G = 3\,\underset{\raise0.3em\hbox{$\smash{\scriptscriptstyle\cdot}$}}{\dot{c}} /c,\,c = {c_0}\,{\rm{exp}}\,[({a^\alpha} - 1)],\,G = {G_0}\,{\rm{exp}}\,[3({a^\alpha} - 1)]$, and ${\rm{\Lambda }} = {{\rm{\Lambda }}_0}\ \exp [ {( {{a^{ - \alpha }} - 1} )} ]$, where a is the scale factor and α = 1.8, we are able to show that the resulting model: (a) fits the supernova 1a observational data marginally better than the Lambda cold dark matter (ΛCDM) model; (b) determines the first peak in the power spectrum of the cosmic microwave background temperature anisotropies at a multipole value of $l = 217.3$; (c) calculates the age of the Universe as 14.1 Gyr; and (d) finds the BAO acoustic scale to be 145.2 Mpc. These numbers are within less than 3 per cent of the values derived using the ΛCDM model. Surprisingly, we find that the dark-energy density is negative in a Universe that has significant negative curvature and whose expansion is accelerating at a faster rate than that predicted by the ΛCDM model.

scholarly journals The evolution of the cosmic microwave background temperature

2011 ◽  
Vol 526 ◽  
pp. L7 ◽  
Author(s):  
P. Noterdaeme ◽  
P. Petitjean ◽  
R. Srianand ◽  
C. Ledoux ◽  
S. López
Keyword(s):  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature

scholarly journals Decaying Dark Energy in Light of the Latest Cosmological Dataset

Symmetry ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 372 ◽  
Author(s):  
Ivan de Martino
Keyword(s):  
Dark Energy ◽  
Cosmic Microwave Background ◽  
Parameter Space ◽  
Hubble Constant ◽  
Two Dimensions ◽  
Matter Density ◽  
Microwave Background ◽  
Energy Models ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature

Decaying Dark Energy models modify the background evolution of the most common observables, such as the Hubble function, the luminosity distance and the Cosmic Microwave Background temperature–redshift scaling relation. We use the most recent observationally-determined datasets, including Supernovae Type Ia and Gamma Ray Bursts data, along with H ( z ) and Cosmic Microwave Background temperature versus z data and the reduced Cosmic Microwave Background parameters, to improve the previous constraints on these models. We perform a Monte Carlo Markov Chain analysis to constrain the parameter space, on the basis of two distinct methods. In view of the first method, the Hubble constant and the matter density are left to vary freely. In this case, our results are compatible with previous analyses associated with decaying Dark Energy models, as well as with the most recent description of the cosmological background. In view of the second method, we set the Hubble constant and the matter density to their best fit values obtained by the Planck satellite, reducing the parameter space to two dimensions, and improving the existent constraints on the model’s parameters. Our results suggest that the accelerated expansion of the Universe is well described by the cosmological constant, and we argue that forthcoming observations will play a determinant role to constrain/rule out decaying Dark Energy.

scholarly journals Relieving tensions related to the lensing of the cosmic microwave background temperature power spectra

2017 ◽  
Vol 597 ◽  
pp. A126 ◽  
Author(s):  
F. Couchot ◽  
S. Henrot-Versillé ◽  
O. Perdereau ◽  
S. Plaszczynski ◽  
B. Rouillé d’Orfeuil ◽  
...  
Keyword(s):  
Cosmic Microwave Background ◽  
Power Spectra ◽  
Microwave Background ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature

scholarly journals A measurement of the cosmic microwave background temperature at 7.5 GHz

1992 ◽  
Vol 396 ◽  
pp. 3 ◽  
Author(s):  
S. Levin ◽  
M. Bensadoun ◽  
M. Bersanelli ◽  
G. de Amici ◽  
A. Kogut ◽  
...  
Keyword(s):  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature
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