Abstract
The Kilo-Degree Survey (KiDS) has been used in several recent papers to infer constraints on the amplitude of the matter power spectrum and matter density at low redshift. Some of these ...analyses have claimed tension with the Planck Λ cold dark matter cosmology at the ∼2σ–3σ level, perhaps indicative of new physics. However, Planck is consistent with other low-redshift probes of the matter power spectrum such as redshift-space distortions and the combined galaxy-mass and galaxy–galaxy power spectra. Here, we perform consistency tests of the KiDS data, finding internal tensions for various cuts of the data at ∼2.2σ–3.5σ significance. Until these internal tensions are understood, we argue that it is premature to claim evidence for new physics from KiDS. We review the consistency between KiDS and other weak lensing measurements of S8, highlighting the importance of intrinsic alignments for precision cosmology.
To H 0 or not to H 0? Efstathiou, George
Monthly notices of the Royal Astronomical Society,
08/2021, Letnik:
505, Številka:
3
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ABSTRACT
This paper investigates whether changes to late-time physics can resolve the ‘Hubble tension’. It is argued that many of the claims in the literature favouring such solutions are caused by a ...misunderstanding of how distance ladder measurements actually work and, in particular, by the inappropriate use of a distance ladder H0 prior. A dynamics-free inverse distance ladder shows that changes to late-time physics are strongly constrained observationally and cannot resolve the discrepancy between the SH0ES data and the base ΛCDM cosmology inferred from Planck. We propose a statistically rigorous scheme to replace the use of H0 priors.
ABSTRACT
This paper explores methods for constructing low multipole temperature and polarization likelihoods from maps of the cosmic microwave background anisotropies that have complex noise ...properties and partial sky coverage. We use Planck 2018 High Frequency Instrument (HFI) and updated SRoll2 temperature and polarization maps to test our methods. We present three likelihood approximations based on quadratic cross spectrum estimators: (i) a variant of the simulation-based likelihood (SimBaL) techniques used in the Planck legacy papers to produce a low multipole EE likelihood; (ii) a semi-analytical likelihood approximation (momento) based on the principle of maximum entropy; (iii) a density-estimation ‘likelihood-free’ scheme (delfi). Approaches (ii) and (iii) can be generalized to produce low multipole joint temperature-polarization (TTTEEE) likelihoods. We present extensive tests of these methods on simulations with realistic correlated noise. We then analyse the Planck data and confirm the robustness of our method and likelihoods on multiple inter- and intra-frequency detector set combinations of SRoll2 maps. The three likelihood techniques give consistent results and support a low value of the optical depth to reoinization, τ, from the HFI. Our best estimate of τ comes from combining the low multipole SRoll2momento (TTTEEE) likelihood with the CamSpec high multipole likelihood and is $\tau = 0.0627^{+0.0050}_{-0.0058}$. This is consistent with the SRoll2 team’s determination of τ, though slightly higher by ∼0.5σ, mainly because of our joint treatment of temperature and polarization.
The evidence for a spatially flat Universe Efstathiou, George; Gratton, Steven
Monthly notices of the Royal Astronomical Society. Letters,
07/2020, Letnik:
496, Številka:
1
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ABSTRACT
We use a new and statistically powerful Planck likelihood to show that the Planck temperature and polarization spectra are consistent with a spatially flat Universe, in contrast to recent ...claims in the literature. When combined with other astrophysical data, particularly geometrical measurements of baryon acoustic oscillations, our likelihood constrains the Universe to be spatially flat to extremely high precision. We deduce a curvature density parameter ΩK = 0.0004 ± 0.0018 in good agreement with the 2018 results of the Planck team. In the context of inflationary cosmology, the observations offer strong support for models of inflation with a large number of e-foldings and disfavour models of incomplete inflation.
Abstract
We derive constraints on feedback by active galactic nuclei (AGN) by setting limits on their thermal Sunyaev–Zel'dovich (SZ) imprint on the cosmic microwave background. The amplitude of any ...SZ signature is small and degenerate with the poorly known sub-mm spectral energy distribution of the AGN host galaxy and other unresolved dusty sources along the line of sight. Here we break this degeneracy by combining microwave and sub-mm data from Planck with all-sky far-infrared maps from the AKARI satellite. We first test our measurement pipeline using the Sloan Digital Sky Survey (SDSS) redMaPPer catalogue of galaxy clusters, finding a highly significant detection (>20σ) of the SZ effect together with correlated dust emission. We then constrain the SZ signal associated with spectroscopically confirmed quasi-stellar objects (QSOs) from SDSS data release 7 (DR7) and the Baryon Oscillation Spectroscopic Survey (BOSS) DR12. We obtain a low-significance (1.6σ) hint of an SZ signal, pointing towards a mean thermal energy of ≃5 × 1060 erg, lower than reported in some previous studies. A comparison of our results with high-resolution hydrodynamical simulations including AGN feedback suggests QSO host masses of M
200c
∼ 4 × 1012 h
−1 M⊙, but with a large uncertainty. Our analysis provides no conclusive evidence for an SZ signal specifically associated with AGN feedback.
We describe high-resolution smoothed particle hydrodynamics (SPH) simulations of three approximately M* field galaxies starting from ACDM initial conditions. The simulations are made intentionally ...simple, and include photoionization, cooling of the intergalactic medium, and star formation, but not feedback from AGNs or supernovae. All of the galaxies undergo an initial burst of star formation at z -5, accompanied by the formation of a bubble of heated gas. Two out of three galaxies show early-type properties at present, whereas only one of them experienced a major merger. Heating from shocks and PdV work dominates over cooling so that for most of the gas the temperature is an increasing function of time. By z -1 a significant fraction of the final stellar system is in place and the spectral energy distribution resembles those of observed massive red galaxies. The galaxies have grown from z = 1 10 on average by 25% in mass and in size by gas-poor (dry) stellar mergers. By the present day the simulated galaxies are old (-10 Gyr), kinematically hot stellar systems surrounded by hot gaseous haloes. Stars dominate the mass of the galaxies up to -4 effective radii (-10 kpc). Kinematic and most photometric properties are in good agreement with those of observed elliptical galaxies. The galaxy with a major merger develops a counter-rotating core. Our simulations show that realistic intermediate-mass giant elliptical galaxies with plausible formation histories can be formed from ACDM initial conditions even without requiring recent major mergers or feedback from supernovae or AGNs.
A non-linear solution to the S 8 tension? Amon, Alexandra; Efstathiou, George
Monthly notices of the Royal Astronomical Society,
09/2022, Letnik:
516, Številka:
4
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ABSTRACT
Weak galaxy lensing surveys have consistently reported a lower amplitude for the matter fluctuation spectrum, as measured by the S8 parameter, than expected in the ΛCDM cosmology favoured by ...Planck. However, the expansion history follows the predictions of the Planck ΛCDM cosmology to high accuracy, as do measurements of lensing of the cosmic microwave background anisotropies. Redshift space distortion measurements also appear to be consistent with Planck ΛCDM. In this paper, we argue that these observations can be reconciled with the Planck ΛCDM cosmology if the matter power spectrum is suppressed more strongly on non-linear scales than assumed in analyses of weak galaxy lensing. We demonstrate this point by fitting a one-parameter model, characterizing a suppression of the non-linear power spectrum, to the KiDS-1000 weak lensing measurements. Such a suppression could be attributed to new properties of the dark matter that affect non-linear scales, or to a response of the matter fluctuations to baryonic feedback processes that are stronger than expected from recent cosmological simulations. Our proposed explanation can be tested using measurements of the amplitude of the matter fluctuation spectrum on linear scales, in particular via high precision redshift space distortion measurements from forthcoming galaxy and quasar redshift surveys.
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