Cold Dark Matter Research Articles

Measuring the reionization optical depth without large-scale CMB polarization

We study the possibility of measuring the optical depth at reionization τ without relying on large-scale cosmic microwave background (CMB) polarization. Our analysis is driven by the need to obtain competitive measurements that can validate the state-of-the-art constraints on this parameter, widely based on E-mode polarization measurements at ℓ≤30. This need is partially motivated by the typical concerns regarding anomalies observed in the Planck large-scale CMB data as well as by the remarkable fact that, excluding these latter, τ consistently exhibits correlations with anomalous parameters, such as Alens and Ωk, suggesting that slightly higher values of the optical depth at reionization could significantly alleviate or even eliminate anomalies. Within the Λ cold dark matter model, our most constraining result is τ=0.080±0.012, obtained by combining Planck temperature and polarization data at ℓ>30, the Atacama Cosmology Telescope (ACT) and Planck measurements of the lensing potential, baryon acoustic oscillations (BAOs), and type-Ia supernova data from the Pantheon+catalog. Notably, using only ACT temperature, polarization, and lensing data in combination with BAOs and supernovae, we obtain τ=0.076±0.015, which is entirely independent of Planck. The relative precision of these results is approaching the constraints based on large-scale CMB polarization (τ=0.054±0.008). Despite the overall agreement, we report a slight 1.8σ shift toward larger values of τ. We also test how these results change by extending the cosmological model. While in many extensions they remain robust, in general, obtaining precise measurements of τ may become significantly more challenging. Published by the American Physical Society 2024

Satellite group infall into the Milky Way: Exploring the Crater-Leo case with new HST proper motions

Within Lambda cold dark matter (Lambda CDM) simulations, Milky Way-like galaxies accrete some of their satellite galaxies in groups of 3-5 members rather than individually, and this has been suggested as a possible mechanism driving the formation of satellite planes. Objects accreted in groups are expected to share similar specific total energy and angular momentum, and to also have identical orbital planes and directions. Looking at observations of Milky Way satellites, the dwarf galaxies Leo II, IV, V, and Crater II, and the star cluster Crater 1 were proposed to be a vestige of group infall. The suggested `Crater-Leo group' shows a coherent distance gradient and all these objects align along a great circle on the sky. We used proper motion data to investigate whether the phase-space distribution of the members of the proposed group are indeed consistent with group infall. To further investigate this possibility, we used Gaia Data Release 3 (DR3) and new Hubble Space Telescope (HST) proper motions -- namely, $( alpha* 0.0523)$ mas $ for Leo IV and $( alpha* 0.1704)$ mas $ for Leo V -- to derive accurate orbital properties for the proposed group objects. In addition, we explored other possible members of this putative association. par Leo II, Leo IV, and Crater 1 show orbital properties consistent with those we predict from assuming group infall. However, our results suggest that Crater II was not accreted with the rest of the objects. If confirmed with increasingly accurate proper motions in the future, the Crater-Leo objects would appear to constitute the first identified case of a cosmologically expected, typical group infall event, as opposed to the highly hierarchical Magellanic Cloud system.

Quantum model of galactic halos with an Navarro-Frenk-White dark matter profile

A quantum model of a cold dark matter galactic halo is developed. The model requires specifying the mass and radius of the halo as well as its density profile. The structure of the halo resulting from the theory is predicted and its physical properties are determined. Verification of these theoretical predictions by observations is proposed and discussed. The model is constructed by analytically solving the governing equation and using its time-independent solutions to determine the internal structure of a galactic halo with an Navarro-Frenk-White cold dark matter density profile. The governing equation that is the basis of the developed theory is derived from the irreducible representations of the extended Galilean group. The method of finding the solutions is analytical, even though an Navarro-Frenk-White density profile is used in the calculations. The theory predicts a halo with a core composed of free dark matter particles that move randomly with frequent collisions. It also predicts an envelope in which the particles are confined to their orbits, which are quantized. Except in the close vicinity of the core, the population of the orbits remains fixed, and physical reasons for the nonexistence of quantum jumps between these orbits are presented. A quantum model of a galactic cold dark matter halo with a given Navarro-Frenk-White density profile is constructed. It predicts a quantum structure of the halo that is significantly different than any previously known dark matter model. The quantum model naturally accounts for dark matter being collisionless, and it predicts that dark matter can only emit radiation of one fixed frequency. The values of this frequency are computed for dark matter particles of different masses. A potential observational verification of the theory is also discussed.

Axion dark matter

Axions have a double motivation: they solve the ‘strong CP problem’ of the Standard Model of elementary particles and they are a candidate for the dark matter of the Universe. Dark matter axions can be detected on Earth by converting them to photons in an electromagnetic cavity permeated by a strong magnetic field. A signal in such a detector, called an axion haloscope, would immediately reveal the velocity spectrum of dark matter axions on Earth in great detail. This prospect motivated the study of the special properties that axions have in large scale structure formation. It is shown that cold dark matter axions thermalize through their gravitational self-interactions, and form a Bose-Einstein condensate. As a result, axion dark matter behaves differently from the other proposed forms of dark matter. The differences are observable.

Constraining hot dark matter sub-species with weak lensing and the cosmic microwave background radiation

Although it is well known that the bulk of dark matter (DM) has to be cold, the existence of an additional sub-dominant, hot species remains a valid possibility. In this paper we investigate the potential of the cosmic shear power spectrum to constrain such a mixed (hot plus cold) DM scenario with two additional free parameters, the hot-to-total DM fraction ($f_ hdm $) and the thermal mass of the hot component ($m_ hdm $). Running a Bayesian inference analysis for both the Kilo-Degree Survey cosmic shear data ( as well as the cosmic microwave background (CMB) temperature and polarisation data from Planck we derive new constraints for the mixed DM scenario. We find a 95 per cent confidence limit of $f_ hdm <0.08$ for a very hot species of $m_ hdm eV. This constraint is weakened to hdm <0.25$ for $m_ hdm eV. Scenarios with masses above hdm eV remain unconstrained by the data. Next to providing limits, we investigate the potential of mixed DM to address the clustering (or $S_8$) tension between lensing and the CMB. We find a reduction of the 2D ($ - S_8$) tension from 2.9sigma to 1.6sigma when going from a pure cold DM to a mixed DM scenario. When computing the 1D Gaussian tension on $S_8$ the improvement is milder, from 2.4sigma to 2.0sigma

Constraining on the non-standard cosmological models combining the observations of high-redshift quasars and BAO

In this work, we studied four types of cosmological models with different mechanisms driving the accelerated expansion of the universe, include Braneworld models, Chaplygin Gas models, Emergent Dark Energy models, and cosmological torsion models. Considering that the dynamics of these models at low redshifts are very similar and difficult to distinguish, we used the latest and largest UV and X-ray measurements of quasars (QSOs) observations covering the range of redshift 0.009<z<7.5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0.009<z<7.5$$\\end{document}. However, the high intrinsic dispersion of this sample and the degeneracy between cosmological model parameters, we added 2D-BAO and 3D-BAO datasets to help us constrain the parameters of these cosmological models. Our results suggest that standard cold dark matter scenario may not be the best cosmological model preferred by the high-redshift observations. The Generalized Chaplygin Gas (GCG) and cosmological constant plus torsion (named Case II) models perform best by Akaike Information Criterion (AIC), but the Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}CDM is the best cosmological model preferred by Bayesian Information Criterion (BIC). Our work also supports that the Phenomenologically Emergent Dark Energy and cosmological torsion models may alleviate the Hubble tension, the reported value of the Hubble constant obtained from QSO+BAO datasets combination lies between Planck 2018 observations and local measurements from the SH0ES collaboration, while other cosmological models all support that the Hubble constant tends to be closer to recent Planck 2018 results, but these model are penalized by information criterion.

The missing quasar image in the gravitationally lensed quasar HE0230−2130: Implications for the cored lens mass distribution and dark satellites

Strongly lensed systems with peculiar configurations allow us to probe the local properties of the deflecting lens mass while simultaneously testing general profile assumptions. The quasar HE0230−2130 is lensed by two galaxies at similar redshifts (Δz ∼ 0.003) into four observed images. Using modeled quasar positions from fitting the brightness of the quasar images in ground-based imaging data from the Magellan telescope, we find that lens-mass models where each of these two galaxies is parametrized with a singular power-law (PL) profile predict five quasar images. One of the predicted images is unobserved despite it being distinctively offset from the lensing galaxies and likely bright enough to be observable. This missing image gives rise to new opportunities to study the mass distribution of these galaxies. To interpret the quad configuration of the system, we tested 12 different profile assumptions with the aim of obtaining lens-mass models that correctly predict only four observed images. We tested the effects of adopting: cored profiles for the lensing galaxies; external shear; and additional profiles to represent a dark matter clump. We find that half of our model classes can produce the correct image multiplicity. By comparing the Bayesian evidence of different model parametrizations, we favor two model classes: (i) one that incorporates two singular PL profiles for the lensing galaxies and a cored isothermal sphere in the region of the previously predicted fifth image (rNIS profile), and (ii) one with a bigger lensing galaxy parametrized by a singular PL profile and the smaller galaxy by a cored PL profile with external shear. We estimated the mass of the rNIS clump for each candidate model of our final Markov chain Monte Carlo sample, and find that only 2% are in the range of 106 M⊙ ≤ MrNIS ≤ 109 M⊙, which is the predicted mass range of dark matter subhalos in cold dark matter simulations, or the mass of dark-matter-dominated and low-surface-brightness galaxies. We therefore favor the models with a cored mass distribution for the lens galaxy close to the predicted fifth image. Our study further demonstrates that lensed quasar images are sensitive to the dark matter structure in the gravitational lens. We are able to describe this exotic lensing configuration with relatively simple models, which demonstrates the power of strong lensing for studying galaxies and lens substructure.

GRB 221009A: Spectral Signatures Based on ALPs Candidates

GRB 221009A has posed a significant challenge to our current understanding of the mechanisms that produce TeV photons in gamma-ray bursts (GRBs). On one hand, the Klein–Nishina (KN) effect of the inverse Compton scattering leads to less efficient energy losses of high-energy electrons. On the other hand, at a redshift of 0.151, the TeV spectrum of GRB 221009A undergoes significant absorption by the extragalactic background light (EBL). Therefore, the observation of a 13 TeV photon in this event implies the presence of enormous photon fluxes at the source, which the synchrotron self-Compton mechanism in external shocks cannot easily generate. As an alternative, some authors have suggested the possibility of converting the TeV photons into axion-like particles (ALPs) at the host galaxy, in order to avoid the effects of EBL absorption, and then reconverting them into photons within the Milky Way. While this solution relaxes the requirement of very high photon fluxes, the KN effect still poses a challenge. Previously, we have shown that the injections of ALPs could explain the observation of 13 TeV photons. Here, we include the energy dependence of the probability of survival and the amount of energy carried to determine the ALP candidates, which could potentially explain the TeV photons observed by the Large High Altitude Air Shower Observatory and their hard spectrum. We found that the allowed candidates are generally clustered around masses of 10−7 eV. We also considered different EBL models, for the one predicting larger attenuation tends to reject ALP candidates with the lowest coupling factor. For some hypotheses of the EBL model, these candidates are found below a region of the parameter space in which, if detected, ALPs could account for all of the cold dark matter in the Universe.

Multiple Beads on a String: Dark-matter-deficient Galaxy Formation in a Mini-Bullet Satellite–Satellite Galaxy Collision

Dark-matter-deficient galaxies (DMDGs) discovered in the survey of ultra-diffuse galaxies (UDGs), in apparent conflict with standard cold dark matter, may be produced by high-velocity galaxy–galaxy collisions, the so-called Mini-Bullet scenario. Recent observations of an aligned trail of 7–11 UDGs near NGC 1052, including DMDGs DF2 and DF4, suggesting a common formation event, ∼8.9 ± 1.5 Gyr ago, provide a test.Hydro/N-body simulations, supplemented by galaxy orbit integrations, demonstrate that satellite–satellite collisions outside the host-galaxy virial radius can reproduce the observed UDGs in the NGC 1052 group. A trail of ∼10 DMDGs is shown to form, including 2 massive ones that replicate the observed motions of DF2 and DF4. The linear relation, v = A x + v 0, conjectured previously to relate positions ( x ) and velocities ( v ) of the aligned DMDGs as a signature of the collision event, is approximately obeyed, but individual DMDGs can deviate significantly from it. The progenitors whose collision spawned the trail of DMDGs survive the collision without themselves becoming DMDGs. We predict that one progenitor is located at the end of the trail, which can be tested by observing the difference between its stars, formed pre-collision, from those of the DMDGs, formed post-collision. By contrast, stellar ages and metallicities of the DMDGs are nearly identical. We further offer a hint that the tidal field of host NGC 1052 may contribute to making DMDGs diffuse. ΛCDM simulation in a 100 cMpc box finds our required initial conditions ∼10 times at z < 3. These results indicate current observations are consistent with the Mini-Bullet scenario.

Inverse Cosmos

The Big Bang Model is the most widely accepted cosmological model regarding the origin of the universe, resting on two fundamental assumptions: one is Einstein's theory of general relativity, describing the gravitational interaction of matter with space-time, and the other is the cosmological principle, stating that an observer viewing the universe will be faced with homogeneity and isotropy, meaning that the universe has no edge. According to this model, one cannot seek a specific point of origin of the big bang, as this explosion occurred simultaneously throughout the whole universe. Through the evolution of various cosmological models, the Standard Cosmological Model (Lambda-CDM) also assumes that the universe consists of three main components: 1. A cosmological constant associated with dark energy, 2. Cold dark matter, and 3. Ordinary matter. From the perspective of cosmologists, this model provides a general explanation for a wide range of observed phenomena, including the abundance of light elements, cosmic microwave background radiation, and large-scale structures in the universe. However, there still exist aspects of the observed universe that currently pose challenges not explained by the big bang model. In response to these challenges, "T-Consciousness Cosmology" proposes multiple hypotheses, offering not only a new interpretative angle on the behavior and function of the components of the cosmos, but also stating that the latest cosmological models have paradoxes relative to the observations made. T-Consciousness Cosmology asserts that if we accept the prevalent models of cosmology, we are then faced with illogical manifestations of an expanding universe. In this discussion, several reasons are presented under the concept of an "Inverse Cosmos," challenging certain interpretations of the standard cosmological model or the latest big bang model regarding the origin of the cosmos, its geometric shape, and the stages accepted by most cosmologists for cosmic expansion. These challenges include issues such as the Density Obscurity Horizon for Matter and Energy, the Thermal Obscurity Horizon, the Timelessness Horizon, and others.

ΛCDM not dead yet: massive high-z Balmer break galaxies are less common than previously reported

ABSTRACT Early JWST observations that targeted so-called double-break sources (attributed to Lyman and Balmer breaks at z &amp;gt; 7), reported a previously unknown population of very massive, evolved high-redshift galaxies. This surprising discovery led to a flurry of attempts to explain these objects’ unexpected existence including invoking alternatives to the standard Λ cold dark matter (ΛCDM) cosmological paradigm. To test these early results, we adopted the same double-break candidate galaxy selection criteria to search for such objects in the JWST images of the CAnadian Near Infrared Imager and Slitless Spectrograph (NIRISS) Unbiased Cluster Survey (CANUCS), and found a sample of 19 sources over five independent CANUCS fields that cover a total effective area of ∼60 arcmin2 at z ∼ 8. However, (1) our spectral energy distribution fits do not yield exceptionally high-stellar masses for our candidates, while (2) spectroscopy of five of the candidates shows that while all five are at high redshifts, their red colours are due to high-equivalent width emission lines in star-forming galaxies rather than Balmer breaks in massive, evolved systems. Additionally, (3) field-to-field variance leads to differences of ∼1.5 dex in the maximum stellar masses measured in the different fields, suggesting that the early single-field JWST observations may have suffered from cosmic variance and/or sample bias. Finally, (4) we show that the presence of even a single massive outlier can dominate conclusions from small samples such as those in early JWST observations. In conclusion, we find that the double-break sources in CANUCS are not sufficiently massive or numerous to warrant questioning the standard ΛCDM paradigm.

Restoring cosmological concordance with axion-like early dark energy and dark matter characterized by a constant equation of state?

Abstract The Hubble tension persists as a challenge in cosmology. Even early dark energy (EDE) models, initially considered the most promising for alleviating the Hubble tension, fall short of addressing the issue without exacerbating other tensions, such as the S8 tension. Considering that a negative dark matter (DM) equation of state (EoS) parameter is conducive to reduce the value of σ8 parameter, we extend the axion-like EDE model in this paper by replacing the cold dark matter (CDM) with DM characterized by a constant EoS wdm (referred as WDM hereafter). We then impose constraints on this axion-like EDE extension model, along with three other models: the axion-like EDE model, ΛWDM, and ΛCDM. These constraints are derived from a comprehensive analysis incorporating data from the Planck 2018 cosmic microwave background (CMB), baryon acoustic oscillations (BAO), the Pantheon compilation, as well as a prior on H0 (i.e., H0=73.04±1.04, based on the latest local measurement by Riess et al.) and a Gaussianized prior on S8 (i.e., S8=0.766±0.017, determined through the joint analysis of KID1000+BOSS+2dLenS). We find that although the new model maintains the ability to alleviate the Hubble tension to ∼1.4σ, it still exacerbate the S8 tension to a level similar to that of the axion-like EDE model.

Dark Radiation Constraints on Heavy QCD Axions

The naturalness problem of PQ symmetry motivates study of the heavy QCD axion, with masses ma> 1 MeV generated at scales above the QCD scale, and low values of the PQ symmetry breaking scale, fa. We compute the abundance of such axions in a model-independent way, assuming only that they freeze-out after reheating from inflation, and are not subsequently diluted by new physics. If these axions decay between neutrino decoupling and the last scatter era of the Cosmic Microwave Background (CMB), they dilute the neutrinos and their abundance is constrained by CMB measurements of the energy density in dark radiation, Neff. We accurately compute this bound using a numerical code to evolve the axion momentum distribution, including many key processes and effects previously ignored. We assume that the only relevant axion decays are to final states involving Standard Model particles. We determine regions of (ma, fa) that will give a signal in Neff at CMB Stage 4 experiments. We similarly compute the Neff bound and CMB Stage 4 signal for heavy axions that can decay to light mirror photons. Finally, we compute the bounds on heavy axions with mass below 1 MeV that decay after the era of CMB last scatter, from their contribution to cold or hot dark matter or Neff at this era.

Dynamical stability of new wormhole solutions via cold dark matter and solitonic quantum wave halos in [formula omitted] gravity

This current analysis offers novel wormhole solutions in the background of newly developed extended f(R,Lm) gravity. We use an anisotropic matter source and a particular type of energy density demonstrating cold dark matter halo and quantum wave dark matter halo to calculate two different wormhole solutions. The properties of the exotic matter within the wormhole geometry and the matter contents via energy conditions are studied in detail, both analytically and graphically, by showing valid and invalid regions. The calculated shape functions of wormhole geometry satisfy the required conditions in both cases. Further, we investigate the stability of the shell around wormhole structures by considering black hole solutions in the framework of cold dark matter halo and quantum wave dark matter by assuming matter contents located at the shell follow the phantom-like equations of state. Then, for quintessence and phantom energy type equations of state, the choice of cold dark matter halo has maximum stability at lower equilibrium shell radii and declines as the radius rises. More petite wormhole throats have an unstable configuration for the dark energy matter content, while higher wormhole throat radius has the lowest stability. For the choice of quantum wave dark matter, the shell around the wormhole structure is unstable for both quintessence and phantom energy, while dark energy shows a stable configuration for smaller values of wormhole throat.

Structure formation with primordial black holes to alleviate early star formation tension revealed by JWST

This Letter explores the potential role of primordial black holes (PBHs) to address cosmological tensions as the presence of more massive than expected galaxies at high redshifts, as indicated by recent James Webb Space Telescope observations. Motivated by inflation models that enhance the power at scales beyond the observable range that produce PBHs with Schechter-like mass functions, we aim to explain the excess of high redshift galaxies via a modification of the Lambda cold dark matter power spectrum that consists in adding (i) a blue spectral index $n_b$ at $k_ piv =10/$Mpc and (ii) Poisson and isocurvature contributions from massive PBHs that only make up $0.5&lt;!PCT!&gt;$ of the dark matter. We simulated these models using the SWIFT code and find an increased abundance of high redshift galaxies in simulations that include PBHs. We compared these models to estimates from James Webb Space Telescope observations. Unlike the Lambda cold dark matter model, the inclusion of PBHs allowed us to reproduce the the observations with reasonable values for the star formation efficiency. Furthermore, the power spectra we adopted potentially produce PBHs that can serve as seeds for supermassive black holes with masses $7.57 odot

F(R) gravity dark energy model of an interaction between dark radiation and dark matter

In this work, we will study the late-time dynamic evolution of the F(R) gravity dark energy model of an interaction between dark radiation and dark matter. We explore the possibility of the apparent extra dark radiation being linked directly to the physics of cold dark matter (CDM). In particular, we consider a generic scenario where dark radiation, as a result of an interaction, is produced directly by a fraction of the dark matter density effectively decaying into dark radiation. The decay process is controlled by its rate Q=αHρdm\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Q=\\alpha H\\rho _{dm}$$\\end{document}, where α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha $$\\end{document} is the (constant) dimensionless parameter quantifying the strength of the decay mechanism, for the weak coupling between dark matter and dark radiation α≪1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha \\ll 1$$\\end{document}. We will solve the field equations numerically by using the statefinder function yH\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$y_{H}$$\\end{document} to appropriately represent the field equation. The F(R) gravity model we consider is described by a nearly R2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R^{2}$$\\end{document}-model at early epochs and at late-time the model mimic the Λ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda $$\\end{document}-Cold-Dark-Matter model (ΛCDM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda CDM$$\\end{document}), and we fine tune the parameters to achieve viability and compatibility with the latest Planck constraints at late-time. Furthermore, we consider the behavior of several well-known statefinder quantities, we find that statefinder diagnostic and Om diagnostic can not only break the degeneracy of different parameter values in the F(R) gravity dark energy model, but also effectively distinguish the difference between the F(R) gravity model and the ΛCDM\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda CDM$$\\end{document} model. At last, we compared the theoretical results with the SNIa data.

Cosmological parameters estimated from peculiar velocity – density comparisons: calibrating 2M++

Abstract Cosmological parameters can be measured by comparing peculiar velocities with those predicted from a galaxy density field. Previous work has tested the accuracy of this approach with N-body simulations, but generally on idealised mock galaxy surveys. However, systematic biases may arise solely due to survey selection effects such as flux-limited samples, edge-effects and complications due to the obscuration of the Galactic plane. In this work, we explore the impact of each of these effects individually as well as collectively using the semi-analytic models from numerical simulations to generate mock catalogues that mimic the 2M++ density field. We find the reconstruction and analysis methods used for our 2M++ mocks produce a value of fσ8 that is biased high by a factor 1.04 ± 0.01 compared to the true value. Moreover, a cosmic volume matching that of 2M++ has a cosmic variance uncertainty in fσ8 of $\sim 5~{{\%}}$. The systematic bias is a function of distance: it is unbiased close to the origin but is biased slightly high for distances in the range 100–180 h−1Mpc. Correcting for this small bias, we find that recent peculiar velocity samples yield $f\sigma _8^{\textrm {lin}} = 0.362\pm 0.023$, a value that is in tension with the extrapolations from cosmic microwave background measurements. The predicted peculiar velocities from 2M++ have an error of 170 km s−1 that slowly increases with distance, exceeding 200 km s−1 only at distances of 180-200 h−1Mpc. Finally, the residual bulk flow speeds found in previous work are shown to be not in conflict with those expected in the Λ cold dark matter model.

Shapes of dark matter haloes with discrete globular cluster dynamics: The example of NGC 5128 (Centaurus A)

Within the Lambda cold dark matter (Lambda CDM) cosmology, dark matter haloes are expected to deviate from spherical symmetry. The particular shape of a galactic halo reflects the environment and mass assembly history of its host, as well as the nature of dark matter. Constraining halo shapes at large galactocentric distances is challenging because of the low density of luminous tracers. The well-studied massive early-type galaxy NGC 5128, also known as Centaurus A (CenA), has a large number of radial velocity measurements for globular clusters (GCs) and planetary nebulae (PNe) extending over a vast area of its extended low-surface-brightness stellar halo. In this work, we aim to determine the deviation from spherical symmetry of the dark matter halo of CenA at 5 using its GCs as kinematic tracers of the gravitational potential. We investigated the largest photometric catalogue of GC candidates in order to accurately characterise the spatial distribution of the relaxed population of GCs. To investigate the presence of non-relaxed structures in the kinematic catalogue of GCs, we used the relaxed point-symmetric velocity field as determined by the host's PNe population. We used anisotropic Jeans modelling under axisymmetric assumptions together with the Gaussian likelihood and GCs as discrete tracers. The gravitational potential is generated by flattened stellar and dark matter distributions. We leveraged the different orbital properties of the blue and red GCs ---such as rotation and velocity anisotropy--- to model both populations separately. By minimising $ we iteratively find the best-fit parameters. We find that the discrete kinematics of the GCs are consistent with being drawn from an underlying relaxed velocity field determined from PNe. The best-fit parameters of the gravitational potential recovered from the blue and red GCs separately agree well and we use them to compute the final results: $M_ $, and the flattening $q_ DM $. Both GC populations show mild rotation, with red having a slightly stronger rotational signature and radially biased orbits, and blue GCs preferring negative velocity anisotropy. An oblate or a spherical dark matter halo of NGC 5128 is strongly disfavoured by our modelling.

Hooks &amp; Bends in the radial acceleration relation: discriminatory tests for dark matter and MOND

ABSTRACT The radial acceleration relation (RAR) connects the total gravitational acceleration of a galaxy at a given radius, atot(r), with that accounted for by baryons at the same radius, abar(r). The shape and tightness of the RAR for rotationally-supported galaxies have characteristics in line with MOdified Newtonian Dynamics (MOND) and can also arise within the cosmological constant + cold dark matter (ΛCDM) paradigm. We use zoom simulations of 20 galaxies with stellar masses of M⋆ ≃ 107–11 M⊙ to study the RAR in the FIRE-2 simulations. We highlight the existence of simulated galaxies with non-monotonic RAR tracks that ‘hook’ down from the average relation. These hooks are challenging to explain in Modified Inertia theories of MOND, but naturally arise in all of our ΛCDM-simulated galaxies that are dark-matter dominated at small radii and have feedback-induced cores in their dark matter haloes. We show, analytically and numerically, that downward hooks are expected in such cored haloes because they have non-monotonic acceleration profiles. We also extend the relation to accelerations below those traced by disc galaxy rotation curves. In this regime, our simulations exhibit ‘bends’ off of the MOND-inspired extrapolation of the RAR, which, at large radii, approach atot ≈ abar/fb, where fb is the cosmic baryon fraction. Future efforts to search for these hooks and bends in real galaxies will provide interesting tests for MOND and ΛCDM.

Role of future SNIa data from Rubin LSST in reinvestigating cosmological models

ABSTRACT We study how future Type Ia supernovae (SNIa) standard candles detected by the Vera C. Rubin Observatory (LSST) can constrain some cosmological models. We use a realistic 3-yr SNIa simulated data set generated by the LSST Dark Energy Science Collaboration time domain pipeline, which includes a mix of spectroscopic and photometrically identified candidates. We combine these data with cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) measurements to estimate the dark energy model parameters for two models – the baseline Lambda cold dark matter (ΛCDM) and Chevallier–Polarski–Linder (CPL) dark energy parametrization. We compare them with the current constraints obtained from the joint analysis of the latest real data from the Pantheon SNIa compilation, CMB from Planck 2018 and BAO. Our analysis finds tighter constraints on the model parameters along with a significant reduction of correlation between H0 and σ8,0. We find that LSST is expected to significantly improve upon the existing SNIa data in the critical analysis of cosmological models.