There is an $\approx9\pm2.5$\% tension between the value of Hubble's
Constant, $H_0=67.4\pm0.5$km\,s$^{-1}$Mpc$^{-1}$, implied by the {\it Planck}
microwave background power spectrum and that given ...by the distance scale of
$H_0=73.4\pm1.7$km\,s$^{-1}$Mpc$^{-1}$. But with a plausible assumption about a
{\it Gaia} DR2 parallax systematic offset, we find that {\it Gaia} parallax
distances of Milky Way Cepheid calibrators are $\approx12-15$\% longer than
previously estimated. Similarly, {\it Gaia} also implies $\approx4.7\pm1.7$\%
longer distances for 46 Cepheids than previous distances on the scale of Riess
et al. Then we show that the existence of an $\approx150$h$^{-1}$Mpc `Local
Hole' in the galaxy distribution implies an outflow of
$\approx500$km\,s$^{-1}$. Accounting for this in the recession velocities of
SNIa standard candles out to $z\approx0.15$ reduces $H_0$ by a further
$\approx1.8$\%. Combining the above two results would reduce the distance scale
$H_0$ estimate by $\approx7$\% from $H_0\approx73.4\pm1.7$ to
$\approx68.9\pm1.6$ km\,s$^{-1}$Mpc$^{-1}$, in reasonable agreement with the
{\it Planck} value. We conclude that the discrepancy between distance scale and
{\it Planck} $H_0$ measurements remains unconfirmed due to uncertainties caused
by {\it Gaia} systematics and an unexpectedly inhomogeneous local galaxy
distribution.
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 CMB temperature map with \(\sim0.5\) 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 \(\sim2.1\) million LRGs covering \(\sim12000\) deg\(^2\) of sky. At \(\bar{z}=0.35\) and \(\bar{z}=0.55\) we detect the ISW signal at \(1.2\sigma\) and \(2.3\sigma\) (or \(2.6\sigma\) combined), in agreement with the predictions of \(\Lambda\)CDM. 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 \(z\approx0.4\) at \(\sim2\sigma\) 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 \(\Lambda\)CDM, 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.
We simulated both the matter and light (galaxy) distributions in a wedge of the Universe and calculated the gravitational lensing magnification caused by the mass along the line-of-sight of galaxies ...and galaxy groups identified in sky surveys. A large volume redshift cone containing cold dark matter particles mimics the expected cosmological matter distribution in a flat universe with low matter density and a cosmological constant. We generate a mock galaxy catalogue from the matter distribution and identify thousands of galaxy groups in the luminous sky projection. We calculate the expected magnification around galaxies and galaxy groups and then the induced quasi-stellar object (QSO)-lens angular correlation due to magnification bias. This correlation is observable and can be used both to estimate the average mass of the lens population and to make cosmological inferences. We also use analytical calculations and various analyses to compare the observational results with theoretical expectations for the cross-correlation between faint QSOs from the 2dF Survey and nearby galaxies and groups from the Automated Plate Measurement and Sloan Digital Sky Survey Early Data Release. The observed QSO-lens anticorrelations are stronger than the predictions for the cosmological model used. This suggests that there could be unknown systematic errors in the observations and data reduction, or that the model used is not adequate. If the observed signal is assumed to be solely due to gravitational lensing, then the lensing is stronger than expected, due to more massive galactic structures or more efficient lensing than simulated.
Observations in the submillimetre (submm) waveband have recently revealed a new population of luminous sources. These are proposed to lie at high redshift and to be optically faint because of their ...high intrinsic dust obscuration. The presence of dust has been previously invoked in optical galaxy count models which use the Bruzual & Charlot evolution models with an exponential τ=9 Gyr star formation rate (SFR) for spirals, and these fit the count data well from U to K. We now show that by using either a 1/λ or Calzetti absorption law for the dust and re-distributing the evolved spiral galaxy ultraviolet (UV) radiation into the far-infrared (FIR), these models can account for all of the ‘faint’ (≤1 mJy) 850-μm galaxy counts, but fail to fit ‘bright’ (≥ 2 mJy) sources, indicating that another explanation for the submm counts may apply at brighter fluxes, e.g., quasi-stellar objects (QSOs) or ultraluminous infrared galaxies (ULIRGs). We find that the main contribution to the faint, submm number counts is in the redshift range 0.5<z<3, peaking at z≈1.8. The above model, using either dust law, can also explain a significant proportion of the extragalactic background at 850 μm, as well as producing a reasonable fit to the bright 60-μm IRAS counts.
PDF
