Narrow Results

We report an instantaneous heating scheme at z=2 that can produce bound objects obeying the observed mass-temperature and luminosity-temperature relations. Such heating reduces the Sunyaev–Zeldovich (SZ) flux by a factor 3–2 on scale of 4–6 arcminutes. It exacerbates the need for the matter-fluctuation normalization to σ₈ to assume an exceedingly high value (~1.2), if the several-arcminute excess anisotropy detected by the CBI experiment is entirely caused by the SZ effect of inter-galactic hot gas. By contrast, we find that the several-arcminute excess detected by ACBAR can be consistent with the preheated SZ signals of σ₈=1.

The combination of the first-year Wilkinson Microwave Anisotropy Probe (WMAP) data with other finer scale cosmic microwave background (CMB) experiments (CBI and ACBAR) and two structure formation measurements (2dFGRS and Lyman α forest) suggest a ΛCDM cosmological model with a running spectral power index of primordial density fluctuations. Motivated by this new result on the index of primordial power spectrum, we present the first study on the predicted lensing probabilities of image separation in a spatially flat ΛCDM model with a running spectral index (RSI-ΛCDM model). It is shown that the RSI-ΛCDM model suppresses the predicted lensing probabilities on small splitting angles of less than about 4″ compared with that of standard power-law ΛCDM (PL-ΛCDM) model.

In this paper, we try to detect the SZ effect in the 2MASS DWT clusters and less bound objects in order to constrain the warm-hot intergalactic medium distribution on large scales by cross-correlation analysis. The results of both observed WMAP and mock SZ effect map indicate that the hot gas distributes from inside as well as outside of the high density regions of galaxy clusters, which is consistent with the results of both observation and hydro simulation. Therefore, the DWT measurement of the cross-correlation would be a powerful tool to probe the missing of baryons in the universe.

We study how galaxy morphology changes the relation among the inner slope $\alpha$ of galactic density profiles and the stellar mass, and rotation velocity.

We find that the slope $\alpha$ flattens monotonically from $\alpha \simeq -1$ to $\alpha \simeq 0$ going from giant galaxies (ellipticals, spirals) to dwarf galaxies ($\simeq 10^8{M}_{*}$). At masses smaller than $\simeq 10^8{M}_{*}$, in the mass range dominated by nonrotational supported galaxies (e.g. dSphs), the slope steepens due to the offset in angular momentum of rotational dominated, and nonrotational dominated galaxies.

A comparison with SPH simulations finds our result in qualitative agreement with them, but the inner slope $\alpha$ at small stellar masses is flatter than that in their simulations. Density profiles become cuspy for $M_{*}$ in the range $10^4$–$10^5{M}_{\odot }$, similarly to Õnorbe.

An overview is given on properties of the Large Scale Structure (LSS) using recent sky surveys (SDSS Main sample). LSS evolves very slowly, thus it contains imprints of physical conditions in the early Universe, as well as processes during its evolution. Present physical experiments are still unable to reproduce conditions in the very early Universe, thus the study of the properties of the LSS yields valuable information for fundamental physics.

Calculations of the flux power spectrum of the Lyman α forest are performed as a means to quantify the possible effects of time-dependent dark energy. We use a parameterized version of the time-dependent dark energy equation of state consistent with the Planck analysis. We have run high-resolution, large-scale cosmological simulation with a modified version of the publicly available SPH code GADGET-2. These simulations were used to extract synthetic Lyman α forest spectra. These were then used to simulate the flux power spectrum at various observed quasar redshifts. We conclude that the effect of time-dependent dark energy on the flux power spectrum is of marginal statistical significance compared to the intrinsic cosmic variance.

Cosmological data still allow for the presence of a non-negligible amount of dark energy at very high redshifts, namely during the matter- and radiation-dominated epochs. This is the so-called early dark energy (EDE), which could help to mitigate the tensions that affect the standard model of cosmology since (i) it reduces the sound horizon at the baryon-drag epoch, hence giving room to higher values of H₀ than those found in the ΛCDM; and (ii) it could potentially decrease the number of large-scale structures in the Universe due its negative pressure and its inability to cluster efficiently for large enough values of its sound speed. Here we put constraints on the fraction of EDE using two methods: first, we use a perfect fluid parameterization that produces plateaux in Ω_ede(z) during the relativistic and non-relativistic matter-dominated eras. Second, we apply a tomographic approach to constrain the EDE density in redshift bins, which allows us to reconstruct the evolution of the EDE fraction before and after the decoupling of the Cosmic Microwave Background (CMB) photons. We have employed Planck data 2018, the Pantheon compilation of supernovae of Type Ia (SNIa), data on galaxy clustering, the prior on the absolute magnitude of SNIa by SH0ES, and weak lensing data from KiDS+VIKING-450 and DES-Y1. Using our minimal parameterization we find that EDE is not able to loosen the cosmological tensions, and show that the constraints on the EDE fraction weaken considerably when its sound speed takes lower values. Thanks to our binned analysis we are able to put tight constraints on the EDE fraction around the CMB decoupling time, ≲ 0.4% at 2σ c.l. We confirm previous results that a significant EDE fraction in the radiation-dominated epoch loosens the H₀ tension, but tends to worsen the tension for σ₈. A subsequent presence of EDE in the matter-dominated era helps to alleviate this problem. When both the SH0ES prior and weak lensing data are considered in the fitting analysis in combination with data from CMB, SNIa and baryon acoustic oscillations, the EDE fractions are constrained to be ≲ 2.6% in the radiation-dominated epoch and ≲ 1.5% in the redshift range z ∈ (100, 1000) at 2σ c.l. The two tensions remain with a statistical significance of ∽ 2 − 3σ c.l. This contribution to the proceedings of the CM3 parallel session of the MG16 Marcel Grossmann virtual Conference: “Status of the H₀ and σ8 tensions: theoretical models and model-independent constraints” is based on the paper arXiv:2107.11065, which appeared in the arXiv shortly after my talk of July 6th 2021.

We provide constraints on coupled dark energy (CDE) cosmology with Peebles-Ratra (PR) potential, V (ϕ) = V₀ϕ^−α, and constant coupling strength β. This modified gravity scenario introduces a fifth force between dark matter particles, mediated by a scalar field that plays the role of dark energy. The mass of the dark matter particles does not remain constant, but changes with time as a function of the scalar field. Here we assess the ability of the model to describe updated cosmological data sets that include the Planck 2018 cosmic microwave background (CMB) temperature, polarization and lensing, baryon acoustic oscillations, the Pantheon compilation of supernovae of Type Ia, data on H(z) from cosmic chronometers, and redshift-space distortions. We also study the impact of the local measurement of H0 from SH0ES and the strong-lensing time delay data from the H0LICOW collaboration on β. We find a peak corresponding to a coupling β > 0 and to a potential parameter α > 0, more or less evident depending on the data set combination. We show separately the impact of each data set and remark that it is especially CMB lensing the one data set that shifts the peak the most towards ΛCDM. When a model selection criterion based on the full Bayesian evidence is applied, however, ΛCDM is still preferred in all cases, due to the additional parameters introduced in the CDE model. The model is not able to loosen significantly the H₀ tension. This contribution to the proceedings of the DM1 parallel session of the 16th Marcel Grossmann virtual Conference: “Interacting dark matter” is based on the paper 2004.00610.

A complete census of baryons in the late universe is a long-standing challenge due to the intermediate temperate and rarefied character of the majority of cosmic gas. To gain insight into this problem, we extract measurements of the kinematic Sunyaev-Zel’dovich (kSZ) effect from the cross-correlation of angular redshift fluctuations maps, which contain precise information about the cosmic density and velocity fields, and CMB maps high-pass filtered using aperture photometry; we refer to this technique as ARF-kSZ tomography. Remarkably, we detect significant cross-correlation for a wide range of redshifts and filter apertures using 6dF galaxies, BOSS galaxies, and SDSS quasars as tracers, yielding a 11 sigma detection of the kSZ effect. We then leverage these measurements to set constraints on the location, density, and abundance of gas inducing the kSZ effect, finding that this gas resides outside dark matter haloes, presents densities ranging from 10 to 250 times the cosmic average, and comprises half of cosmic baryons. Taken together, these findings indicate that ARF-kSZ tomography provides a nearly complete census of intergalactic gas from z = 0 to 5. This contribution is a summary of the work already published in Ref. 1.

We performed a set of cosmological N-body simulations of scale-free models (i.e. P(k) ∝ kⁿ) and investigated the central logarithmic slope of relaxed dark matter halo density profiles α and its dependence on the spectral index n of the linear matter power spectrum P(k). The simulations are started and stopped according to a set of clear, reproducible and physically motivated criteria, allowing to compare haloes across models with different spectral indices. In each simulation we identify samples of well resolved haloes in dynamical equilibrium and we analyse their mass profiles. Using a "generalized" Navarro, Frenk & White profile in which the central logarithmic slope α is allowed to vary while the r^-3 asymptotic form at large radii is preserved, we obtain best-fit central slopes for haloes in the different models. We find a strong correlation between α and n, such that α becomes shallower as n becomes steeper. When normalising the mass profiles by r_-2, the radius at which the logarithmic slope of the density profile is -2, we find that the differences between the models are no longer present. This becomes clearly visible when plotting the maximum slope as a function of r/r_-2: We observe a similar behaviour for haloes forming in different n models. This traces back to the concentration of the haloes, in steep-n cosmologies we find smaller concentration than in shallow-n cosmologies. Also, we do not find evidence for a convergence to a unique central asymptotic slope on the scale we can resolve.

Using two complementary X-ray galaxy cluster studies we present new constraints on dark energy and modified gravity. Using Chandra measurements of the X-ray gas mass fraction, f_gas, in 42 hot, X-ray luminous, dynamically relaxed clusters spanning the redshift range 0.05 < z < 1.1, we obtain a tight constraint on the mean matter density and a detection of the effects of dark energy on the distances to the clusters comparable in significance to recent type Ia supernovae (SNIa) studies. Using measurements of the growth of cosmic structure, as inferred from the observed evolution of the X-ray luminosity function (XLF) of clusters, we obtain the first precise determination of the dark energy equation of state and constrain departures from General Relativity (GR) on cosmological scales. For the latter, we employ the growth rate parameterization, Ω_m(z)^γ, for which GR predicts a growth index γ ~ 0.55. Combining the XLF with observations of the cosmic microwave background, SNIa, and f_gas, to simultaneously constrain a flat cosmological constant (ΛCDM) background model, we obtain , which is consistent with GR. Both the f_gas and XLF analyses provide strong, independent support to the GR+ΛCDM paradigm.

The scalar field cosmology model proposed by Huang et al.^{1, 2} predicts that the early pre-inflationary universe was a superfluid. This superfluid is likely to have contained quantized vortices, and it is postulated that remnants of these vortices persist in the present-day moderate-redshift galaxy distribution. We attempt to search for remnants of these primordial vortices in the SDSS BOSS galaxy catalogue. We manage to observe hints of a few vortex tubes, which might lend weight to the credibility of the theory.

We perform a counts-in-cells analysis of galaxies in the COSMOS mag 25 dataset at redshifts up to z = 1.8. Our results suggest that even at 2 square degrees, the COSMOS footprint is not sufficient for adequate statistics, but is an improvement over earlier results by Rahmani et al. (2009) using the GOODS surveys. We confirm that at high redshift, the counts-in-cells distribution agrees with the gravitational quasi-equilibrium distribution.