Search

For a precise determination of cosmological parameters we need to understand the effects of the local large-scale structure of the Universe on the measurements. They include modifications of the cosmic microwave background, distortions of sky images by large-scale gravitational lensing, and the influence of large-scale streaming motions on measurements of the Hubble constant. The streaming motions, for example, originate from mass concentrations with distances up to 250 Mpc. In this paper we provide the first all-sky assessment of the largest structures at distances between 130 and 250 Mpc and discuss their observational consequences, using X-ray galaxy clusters to map the matter density distribution. Among the five most prominent superstructures found, the largest has a length longer than 400 Mpc with an estimated mass of about 2 10e17 Msun. This entity, which we named Quipu, is the largest cosmic structure discovered to date. These superstructures contain about 45% of the galaxy clusters, 30% of the galaxies, 25% of the matter, and occupy a volume fraction of 13%, thus constituting a major part of the Universe. The galaxy density is enhanced in the environment of superstructures out to larger distances from the nearest member clusters compared to the outskirts of clusters in the field. We find superstructures with similar properties in simulations based on Lambda-CDM cosmology models. We show that the superstructures should produce a modification on the cosmic microwave background through the integrated Sachs-Wolf effect. Searching for this effect in the Planck data we found a signal of the expected strength, however, with low significance. Characterising these superstructures is also important for astrophysical research, for example the study of the environmental dependence of galaxy evolution as well as for precision tests of cosmological models., Comment: accepted for publication in Astronomy and Astrophysis, 13 pages, 20 figures

There has been recent interest in the cosmological consequences of energy-momentum-powered gravity models, in which the matter side of Einstein's equations includes a term proportional to some power, $n$, of the energy-momentum tensor, in addition to the canonical linear term. Previous works have suggested that these models can lead to a recent accelerating universe without a cosmological constant, but they can also be seen as phenomenological extensions of the standard $\Lambda$CDM, which are observationally constrained to be close to the $\Lambda$CDM limit. Here we show that these models violate the temperature-redshift relation, and are therefore further constrained by astrophysical measurements of the cosmic microwave background temperature. We provide joint constraints on these models from the combination of astrophysical and background cosmological data, showing that this power is constrained to be about $|n|<0.01$ and $|n|<0.1$, respectively in models without and with a cosmological constant, and improving previous constraints on this parameter by more than a factor of three. By breaking degeneracies between this parameter and the matter density, constraints on the latter are also improved by a factor of about two., Comment: 10 pages, 4 figures; Phys. Rev. D (in press)

The weak gravitational lensing magnification of Type Ia supernovae (SNe Ia) is sensitive to the matter power spectrum on scales $k>1 h$ Mpc$^{-1}$, making it unwise to interpret SNe Ia lensing in terms of power on linear scales. We compute the probability density function of SNe Ia magnification as a function of standard cosmological parameters, plus an empirical parameter $A_{\rm mod}$ which describes the suppression or enhancement of matter power on non-linear scales compared to a cold dark matter only model. While baryons are expected to enhance power on the scales relevant to SN Ia lensing, other physics such as neutrino masses or non-standard dark matter may suppress power. Using the Dark Energy Survey Year-5 sample, we find $A_{\rm mod} = 0.77^{+0.69}_{-0.40}$ (68\% credible interval around the median). Although the median is consistent with unity there are hints of power suppression, with $A_{\rm mod} < 1.09$ at 68\% credibility., Comment: 12 pages, submitted to MNRAS. arXiv admin note: text overlap with arXiv:2410.07956

Several processes in the Universe convert a fraction of gas kinetic energy into the acceleration of relativistic electrons, making them observable at radio wavelengths, or contributing to a dormant reservoir of low-energy cosmic rays in cosmic structures. We present a new suite of cosmological simulations, with simple galaxy formation models calibrated to work at a specific spatial resolution, tailored to study all most important processes of injection of relativistic electrons in evolving large-sale structures: accretion and merger shocks, feedback from active galactic nuclei and winds from star forming regions. We also follow the injection of magnetic fields by active galactic nuclei and star formation, and compute the observational signatures of these mechanisms. We find that the injection of cosmic ray electrons by shocks is the most volume filling process, and that it also dominates the energy density of fossil relativistic electrons in halos. The combination of the seeding mechanisms studied in this work, regardless of the uncertainties related to physical or numerical uncertainties, is more than enough to fuel large-scale radio emissions with a large amount of seed fossil electrons. We derive an approximated formula to predict the number of fossil cosmic ray electrons injected by z=0 by the total activity of shocks, AGN and star formation in the volume of halos. By looking at the maximum possible contribution to the magnetisation of the cosmic web by all our simulated sources, we conclude that galaxy formation-related processes, alone, cannot explain the values of Faraday Rotation of background polarised sources recently detected using LOFAR., Comment: 31 pages, 30 figures, Astronomy & Astrophysics

Massive states produce higher derivative corrections to Einstein gravity in the infrared, which are encoded into operators of the Effective Field Theory (EFT) of gravity. These EFT operators modify the geometry and affect the tidal properties of black holes, either neutral or charged. A thorough analysis of the perturbative tidal deformation problem leads us to introduce a tidal Green function, which we use to derive two universal formulae that efficiently provide the constant and running Love numbers induced by the EFT. We apply these formulae to determine the tidal response of EFT-corrected non-spinning black holes induced by vector and tensor fields, reproducing existing results where available and deriving new ones. We find that neutral black hole Love numbers run classically for $l\geq 3$ while charged ones run for $l\geq2$. Insights from the Frobenius method and from EFT principles confirm that the Love number renormalization flow is a well-defined physical effect. We find that extremal black holes can have Love numbers much larger than neutral ones, up to ${\cal O}(1)$ within the EFT validity regime, and that the EFT cutoff corresponds to the exponential suppression of the Schwinger effect. We discuss the possibility of probing an Abelian dark sector through gravitational waves, considering a scenario in which dark-charged extremal black holes exist in the present-day Universe., Comment: 59 pages, 2 figures

Redshift-space distortions (RSD), caused by the peculiar velocities of galaxies, are a key modelling challenge in galaxy clustering analyses, limiting the scales from which cosmological information can be reliably extracted. Unlike dynamical or galaxy bias effects, RSD imprint features that are sensitive to non-linearities across all scales. Yet, no distinction between these effects is made by the state-of-the-art analytical approach - the effective field theory (EFT) - which applies the same perturbative expansion to each of them. This paper explores an alternative approach, where the non-perturbative nature of RSD is partially preserved, and compares its effectiveness against the EFT in analysing power spectrum and bispectrum multipoles from synthetic samples of luminous red galaxies, using the projected sensitivity of a Stage-IV galaxy survey. Our results demonstrate that this distinct treatment of RSD improves the robustness of model predictions for both statistics, extending the validity range of the EFT from approximately $0.2\,h\,\mathrm{Mpc}^{-1}$ to $0.35\,h\,\mathrm{Mpc}^{-1}$ for the one-loop power spectrum and from $0.1\,h\,\mathrm{Mpc}^{-1}$ to $0.14\,h\,\mathrm{Mpc}^{-1}$ for the tree-level bispectrum. This leads to a significant enhancement in the precision of cosmological parameter constraints, with uncertainties on the Hubble rate, matter density, and scalar amplitude of fluctuations reduced by $20$-$40\,\%$ for the power spectrum multipoles alone compared to the EFT, and by $25$-$50\,\%$ for joint analyses with the bispectrum. The RSD treatment proposed here may thus play a crucial role in maximising the scientific return of current and future galaxy surveys. To support this advancement, all models for the power spectrum and bispectrum used in this work are made available through an extended version of the Python package COMET., Comment: 28+6 pages, 17 figures

We investigate the realization of a nonsingular bounce within the framework of Myrzakulov \( F(R,T) \) gravity. This modified gravitational theory uses a non-special connection that combines both curvature and torsion, giving rise to an effective sector that can easily satisfy the violation of the null energy condition. We suitably choose the functions that parametrize the connection in order to be able to produce simple and matter bounce scale factors at the background level. Finally, we examine the evolution of scalar perturbations through the bounce using the Mukhanov-Sasaki formalism, and we calculate the power spectrum., Comment: 9 pages

We study vorticity production in isothermal, subsonic, acoustic (nonvortical), decaying turbulence due to the presence of magnetic fields. Using three-dimensional numerical simulations, we always find that the resulting turbulent kinetic energy cascade follows the ordinary Kolmogorov phenomenology involving a constant spectral energy flux. For acoustic turbulence, the corresponding nondimensional prefactor is larger than the standard Kolmogorov constant due to an inefficiency in dissipating kinetic energy. We find that the Lorentz force can not only drive the direct production of vortical motions, but it can also facilitate the conversion of acoustic energy into vortical energy. This conversion is shown to be quadratic in the magnetic field strength and linear in the acoustic flow speed. By contrast, the direct production of vortical motions by the magnetic field is linear in the field strength. Our results suggest that magnetic fields play a crucial role in vorticity production in cosmological flows, particularly in scenarios where significant acoustic turbulence is prevalent. We also discuss the implications of our findings for the early universe, where magnetic fields may convert acoustic turbulence generated during cosmological phase transitions into vortical turbulence., Comment: 11 pages, 12 figures, 1 table, comments welcome

Recent observations by pulsar timing arrays (PTAs) such as NANOGrav, EPTA, PPTA, and CPTA suggest the presence of nanohertz stochastic gravitational wave background (GWB). While such signals could be explained by gravitational waves from a network of metastable cosmic strings (CSs), standard scenarios involving the Kibble-Zurek mechanism triggered by a thermal potential face significant challenges. Specifically, these scenarios predict a GWB spectrum inconsistent with the non-detection at higher frequencies by LIGO-Virgo-KAGRA (LVK) for CSs with relatively large string tension. It is also difficult to prevent the monopole forming phase transition just before the CS forming symmetry breaking, which spoils the CS network formation. In contrast, a delayed scaling scenario, where the CSs start to emit GWs at a later time due to the dilution during inflation, alleviates these issues. This scenario allows for a larger string tension while monopoles are sufficiently diluted such that the CS network safely forms. In this study, we clarify the spectrum of stochastic GWB from metastable CSs in the delayed scaling scenario, consistent with the PTA observations while satisfying the LVK constraints. Furthermore, we explore its potential signatures at frequencies accessible to other detectors such as LVK as well as LISA, Taiji, and TianQin or DECIGO and BBO. We also discuss the implications on inflation and underlying UV theories, such as the grand unified theories., Comment: 21 pages, 3 figures

In this article we use the latest cosmological observations, including SNe, BAO, CC and RSD, to reconstruct the cosmological evolution via the Gaussian process. At the background level, we find consistency with the quintom dynamics for different data combinations and divide the characteristics of dark energy into three different categories, which are negative-energy dark energy, late-dominated dark energy and oscillating dark energy, respectively. Considering the effect of modified gravity on the growth of matter perturbations, the reconstruction results at the perturbative level show that we only need minor corrections to general relativity. Furthermore, we provide theoretical interpretation for the three different types of dynamical dark-energy behavior, in the framework of modified gravity, scalar fields, and dark-energy equation-of-state parametrizations. Finally, we show that all of these models can be unified in the framework of effective field theory., Comment: 19 pages, 6 figures

Deep learning and convolutional neural networks in particular are powerful and promising tools for cosmological analysis of large-scale structure surveys. They are already providing similar performance to classical analysis methods using fixed summary statistics, are showing potential to break key degeneracies by better probe combination and will likely improve rapidly in the coming years as progress is made in the physical modelling through both software and hardware improvement. One key issue remains: unlike classical analysis, a convolutional neural network's decision process is hidden from the user as the network optimises millions of parameters with no direct physical meaning. This prevents a clear understanding of the potential limitations and biases of the analysis, making it hard to rely on as a main analysis method. In this work, we explore the behaviour of such a convolutional neural network through a novel method. Instead of trying to analyse a network a posteriori, i.e. after training has been completed, we study the impact on the constraining power of training the network and predicting parameters with degraded data where we removed part of the information. This allows us to gain an understanding of which parts and features of a large-scale structure survey are most important in the network's prediction process. We find that the network's prediction process relies on a mix of both Gaussian and non-Gaussian information, and seems to put an emphasis on structures whose scales are at the limit between linear and non-linear regimes., Comment: 11 pages, 13 figures, submitted to A&A

We explore the implications of incorporating an Anti-de Sitter (AdS) vacua in the Dark Energy (DE) sector using the recent DESI BAO measurements in combination with Planck-2018 CMB, Pantheon-Plus(+SH0ES) supernovae and KiDS weak lensing data. We show that the presence of a {\it Negative Cosmological Constant} ($\Lambda < 0$, nCC) together with an evolving part (modelled by the CPL parametrisation) in DE sector allows a {\it non-phantom} region for the DE in the constrained parameter space consistent with different observational data. This essentially solves the problem of {\it phantom} behaviour in the DE sector which is difficult to obtain through reasonable field theory. The implications nCC in the DE sector for different cosmological tensions are also studied. Our findings highlight the importance of the presence of AdS in the DE sector for theoretical model building, especially in the context of quantum gravity theories, e.g. string theory., Comment: 5 pages, 4 sets of figures. Comments are welcome

Combining an effective theory description of spin-1/2 dark matter (DM)-electron interactions in materials with linear response theory provides a powerful framework to model the scattering of DM, including in-medium effects, in detectors used for direct searches. Within this framework, we show that the rate of DM-induced electronic transitions in detector materials admits a theoretical upper bound under general assumptions on the underlying DM-electron coupling. In particular, our theoretical upper bound applies to models where DM couples to the electron density as well as the spin, paramagnetic and Rashba currents in materials, and arises from the Kramers-Kronig relations that constrain the analytic properties of the scattering rate. We evaluate our maximum rate formula numerically for Ar, Xe, Ge, and Si targets and find that Ge and Si detectors are closer to saturate this theoretical upper bound, but still far from saturation when DM couples to densities or currents which are different from the electron density. This motivates the exploration of a different class of materials to effectively probe such coupling forms., Comment: 26 pages, 3 figures

Through numerical experiments, we have predicted that if dark matter (DM) contains even a small fraction, $f_0\sim10^{-4}$, of primordial black holes (PBHs), during the formation of the gravitationally bound halo of a dwarf galaxy, these PBHs will concentrate in a region with a radius of about 10 pc, so that their local fraction will exceed 1%. Unlike previous studies of PBH migration to the centers of galaxies, the numerical experiments conducted here take into account the early formation of a massive "dress" of DM around the PBHs and the non-stationarity of the halo during its formation. Applying our results to models of heating stellar clusters in the Eridanus II and Segue I galaxies due to dynamical friction between stars and PBHs allows us to impose constraints on the abundance of PBHs that are two orders of magnitude stricter than previously thought., Comment: 9 pages, 6 figures, accepted in JETPL

We present constraints on the baryonic matter density parameter, $\Omega_b$, within the framework of the $\Lambda$CDM model. Our analysis utilizes observational data on the effective optical depth from high-redshift quasars. To parameterize the photoionization rate $\Gamma_{-12}$, we employ a B\'{e}zier polynomial. Additionally, we approximate the Hubble parameter at high redshifts as $H(z)\approx 100h\Omega_m^{1/2} (1+z)^{3/2}$ km s$^{-1}$ Mpc$^{-1}$. Confidence regions are obtained with $h=0.701\pm0.013$ and $\Omega_m = 0.315$, optimized by the Planck mission. The best-fit values are $\Omega_b =0.043^{+0.005}_{-0.006}$ and $\Omega_b = 0.045^{+0.004}_{-0.006}$, corresponding to an old data set and a new data set, respectively. And we test the non-parametric form of $\Gamma_{-12}$, obtaining $\Omega_b = 0.048^{+0.001}_{-0.003}$. These results are consistent with the findings of Planck at the 1 $\sigma$ confidence level. Our findings underscore the effectiveness of quasar datasets in constraining $\Omega_b$, eliminating the need for independent photoionization rate data. This approach provides detailed cosmic information about baryon density and the photoionization history of the intergalactic medium., Comment: 14 pages, 10 figures, accepted by Research in Astronomy and Astrophysics (RAA)

Observations have argued that Milky Way (MW), Andromeda, and lower-mass galaxies exhibit extended soft X-ray diffuse halos to radii $R\gtrsim100\,$kpc in the circumgalactic medium (CGM). If interpreted as thermal emission, the shallow surface brightness profiles $S_{X}\propto R^{-1}$ are difficult to explain and contradict other observations. We show that such halos instead arise from inverse Compton (IC) scattering of CMB photons with GeV cosmic ray (CR) electrons. GeV electrons have ~Gyr lifetimes and escape the galaxy, forming a shallow extended profile out to $\gtrsim100\,$kpc, where IC off the CMB should produce soft, thermal-like X-ray spectra peaked at ~keV. The observed keV halo luminosities and brightness profiles agree well with those expected for CRs observed in the local interstellar medium (LISM) escaping the galaxy, with energetics consistent with known CRs from SNe and/or AGN, around galaxies with stellar masses $M_{\ast}\lesssim2\times 10^{11}\,M_{\odot}$. At higher masses observed X-ray luminosities are larger than predicted from IC and should be dominated by hot gas. In the MW+M31, the same models of escaping CRs reproduce gamma-ray observations if we assume an LISM-like proton-to-electron ratio and CR-pressure-dominated halo. In all other halos, the radio and $\gamma$-ray brightness is below detectable limits. If true, the observations provide qualitatively new constraints on CGM and CR physics: X-ray brightness directly traces the CR lepton energy density in the CGM. This agrees with LISM values within 10 kpc, which following the profile expected for escaping CRs in the CGM. The inferred CR pressure is a major part of the MW CGM pressure budget. X-ray surface brightness and luminosity allows one to further determine the CGM diffusivity at radii $\sim10-1000\,$kpc. These also agree with LISM values at small radii but increase in the CGM., Comment: Submitted to the Open Journal of Astrophysics. 13 pages, 7 figures, comments welcome

We present the first results of the HI intensity mapping power spectrum analysis with the MeerKAT International GigaHertz Tiered Extragalactic Exploration (MIGHTEE) survey. We use data covering $\sim$ 4 square degrees in the COSMOS field using a frequency range 962.5 MHz to 1008.42 MHz, equivalent to HI emission in $0.4

We develop a new semi-analytic framework of Population (Pop) III and subsequent galaxy formation designed to run on dark matter halo merger trees. In our framework, we consider the effect of the Lyman-Werner flux from Pop III and II stars and the dark matter baryon streaming velocity on the critical minihalo mass for the Pop III formation. Our model incorporates the Lyman-Werner feedback in a self-consistent way, therefore, the spatial variation of Lyman-Werner feedback naturally emerges. The Pop III mass depends on the properties of a minihalo as reproducing radiative hydrodynamical simulation results. We perform statistical studies of Pop III stars by applying this framework to high-resolution cosmological N-body simulations with a maximum box size of 16 Mpc/h and enough mass resolution to resolve Pop III-forming minihalos. A top-heavy initial mass function emerges and two peaks corresponding to the H$_2$ ($20 \lesssim z \lesssim 25$) and atomic cooling halos ($z \lesssim 15$) exist in the distribution. Supermassive stars can be formed in the atomic cooling halos, and the fractions of such supermassive stars increase with the value of streaming velocity. At least an 8 Mpc/h simulation box and the self-consistent model for the Lyman-Werner feedback are necessary to correctly model the Pop III formation in the atomic cooling halos. Our model predicts one supermassive star per halo with several $10^9$ Msun at z=7.5, which is enough to reproduce a high redshift quasar., Comment: 18 pages, 10 figures, submitted to ApJ

It has been suggested that star-forming galaxies may host a substantial, dark reservoir of gas in the form of planetary-mass molecular clouds that are so cold that $\text{H}_{2}$ can condense. Here we investigate the process of tidal disruption of such "snow clouds" by close passage of field stars. We construct a suite of simulations using the hydrodynamic formalism introduced by Carter and Luminet, and use it to explore the properties of the resulting tidal debris. The debris streams are tiny structures that are highly over-pressured relative to the ambient ISM. They are also unusual in their composition -- initially consisting of cold, gaseous He together with $\text{H}_{2}$ "snowballs" that may be as much as a metre in size. Each stream expands and cools and is subsequently shocked as it ploughs through the ISM; the snowballs are gradually eroded by the shocked gas. Snowballs streaming through the shocked ISM create microstructured plasma that is somewhat reminiscent of the "scattering screens" revealed by radio-wave scintillation studies. However, the tidal disruption rate is too low to account for the observed number of scattering screens if, as we assume here, the stars and clouds have no prior physical association so that disruptions occur as a result of chance encounters between stars and clouds., Comment: 24 pages, 12 figures. Accepted for publication in ApJ

The concept of a rapidly sign-switching cosmological constant, interpreted as a mirror AdS-dS transition in the late universe and known as the $\Lambda_{\rm s}$CDM, has significantly improved the fit to observational data, offering a promising framework for alleviating major cosmological tensions such as the $H_0$ and $S_8$ tensions. However, when considered within general relativity, this scenario does not predict any effects on the evolution of the matter density contrast beyond modifications to the background functions. In this work, we propose a new gravitational model in which the background dynamics predicted by the $\Lambda_{\rm s}$CDM framework are mapped into $f(T)$ gravity, dubbed $f(T)-\Lambda_{\rm s}$CDM, rendering the models indistinguishable at the background level. However, in this new scenario, the sign-switching cosmological constant dynamics modify the evolution of linear matter perturbations through an effective gravitational constant, $G_{\rm eff}$. We investigate the evolution of the growth rate and derive new observational constraints for this scenario using RSD measurements. We also present new constraints in the standard $\Lambda_{\rm s}$CDM case, incorporating the latest Type Ia supernovae data samples available in the literature, along with BAO data from DESI. Our findings indicate that the new corrections expected at the linear perturbative level, as revealed through RSD samples, can provide significant evidence in favor of this new scenario. Additionally, this model may be an excellent candidate for resolving the current $S_8$ tension., Comment: 12 pages, 4 figures, 3 tables. Matches the version published in Universe

We investigate the Deser-Woodard model of nonlocal gravity involving four auxiliary scalar fields, introduced to explain the standard cosmological background expansion history without fine-tuning issues. In particular, we propose a novel approach to simplify the complex field equations within the proper tetrad frame, thereby recasting the original system into a more tractable equivalent differential problem. We show that, by only assuming the form of the $tt$ metric component, it is possible to reconstruct the distortion function of the gravitational model through a step-by-step procedure involving the use of either analytical, perturbative, or numerical methods. We then outline a potential strategy for solving the vacuum field equations in the case of a static and spherically symmetric spacetime. Specifically, we applied our technique to find three traversable wormholes supported purely by gravity, discussing then their main geometric properties. The obtained results provide a possible pathway for determining new compact object solutions while offering a deeper understanding of nonlocal theories of gravity., Comment: 9 pages, 2 figures, 1 table

In this paper we consider a new approach to unify inflation and the late universe with dark energy and dark matter formulated in a model that includes a non-Riemannian metric independent measure and a scalar field with spontaneously broken scale symmetry. Here first of all inflation is possible, which is then followed by a reheating oscillating period and this leads to the formation of all kind of particles, including fermions, which as the universe expands can contribute to the dark energy and the to the dark matter of the universe. During the inflationary epoch, we find different constraints on the parameter space associated to the effective potential of the scalar field from the observational data. After reheating the scalar field retraces its trajectory in field space but now the scalar field potential can be drastically modified by the effect of the fermions. In this sense, the present dark energy with its very small value in comparison to the inflationary phase which can be adjusted by choosing appropriately the parameter space of couplings of the Riemannian and non Riemannian measures to the fermions., Comment: 11 pages and one figure

Most gravitational wave searches to date have included only the quadrupole mode in their search templates. Here, we demonstrate that incorporating higher harmonics improves the search sensitive volume for detecting binary black hole mergers, challenging the conclusion of previous studies. Using the $\tt{IAS-HM}$ detection pipeline, and the simulated (injection) signals from the LIGO-Virgo-Kagra (LVK) collaboration, we quantify the improvement in sensitivity due to the inclusion of higher harmonics. This improvement is significant for systems with higher mass ratios and larger total masses, with gains in sensitivity even exceeding $100\%$ at certain high masses. We also show that, due to using a marginalized detection statistic, the $\tt{IAS-HM}$ pipeline performs roughly as well as its quadrupole-mode-only counterpart even for equal mass-ratio mergers, and its sensitive volume is either better than or comparable to that of the individual LVK pipelines., Comment: 8 pages, 3 figures

Rare events of large-scale spatially-correlated exponential random fields are studied. The influence of spatial correlations on clustering and non-sphericity is investigated. The size of the performed simulations permits to study beyond-$7.5$-sigma events ($1$ in $10^{13}$). As an application, this allows to resolve individual Hubble patches which fulfill the condition for primordial black hole formation. It is argued that their mass spectrum is drastically altered due to co-collapse of clustered overdensities as well as the mutual threshold-lowering through the latter. Furthermore, the corresponding non-sphericities imply possibly large changes in the initial black hole spin distribution., Comment: 7 pages, 6 figures

Precise, unbiased measurements of extragalactic background anisotropies require careful treatment of systematic effects in fluctuation-based, broad-band intensity mapping measurements. In this paper we detail improvements in methodology for the Cosmic Infrared Background ExpeRiment (CIBER), concentrating on flat field errors and source masking errors. In order to bypass the use of field differences, which mitigate flat field errors but reduce sensitivity, we characterize and correct for the flat field on pseudo-power spectra, which includes both additive and multiplicative biases. To more effectively mask point sources at 1.1 $\mu$m and 1.8 $\mu$m, we develop a technique for predicting masking catalogs that utilizes optical and NIR photometry through random forest regression. This allows us to mask over two Vega magnitudes deeper than the completeness limits of 2MASS alone, with errors in the shot noise power remaining below $<10\%$ at all masking depths considered. Through detailed simulations of CIBER observations, we validate our formalism and demonstrate unbiased recovery of the sky fluctuations on realistic mocks. We demonstrate that residual flat field errors comprise $<20\%$ of the final CIBER power spectrum uncertainty with this methodology., Comment: 29 pages, 17 figures. Submitted to ApJ

A promising solution to the Hubble tension is a local void that is roughly 20% underdense out to 300 Mpc, as suggested by galaxy number counts in the near-infrared. Gravitationally driven outflows from this KBC void might inflate redshifts enough to solve the Hubble tension, a scenario explored in detail by Haslbauer et al. We obtain predictions for the baryon acoustic oscillation (BAO) observables in their best-fitting void models and a control model that assumes the homogeneous $Planck$ cosmology. We compare these models against our compilation of available BAO measurements from the past twenty years. We find that the quality and quantity of available measurements are best using the isotropically averaged distance $D_V$. Taking its ratio with the expected value in the control model yields good agreement with unity at high redshift, but a discrepancy appears that systematically grows with decreasing redshift. Assuming independent uncertainties, the 41 considered $D_V$ observations give a total $\chi^2$ of 70.5 for the control void-free model, while the void models give only $44.8 - 46.7$ depending on the density profile. This represents a reduction in overall tension from $3.0\sigma$ without a void to $1.0\sigma - 1.2\sigma$ in the void models. The $\chi^2$ differences are smaller when considering measurements of the angular BAO scale or its redshift depth, but the void-free model provides the worst fit in all cases. Overall, our results suggest that recent hints of BAO observables deviating from expectations in the homogeneous $Planck$ cosmology could indicate a local void, which was motivated by considerations unrelated to BAO data or the Hubble tension., Comment: 14 pages, 4 figures, 2 tables. Submitted to MNRAS in this form

We present new anisotropy measurements in the near-infrared (NIR) for angular multipoles $300<\ell<10^5$ using imaging data at 1.1 $\mu$m and 1.8 $\mu$m from the fourth flight of the Cosmic Infrared Background ExpeRiment (CIBER). Using improved analysis methods and higher quality fourth flight data, we detect surface brightness fluctuations on scales $\ell<2000$ with CIBER auto-power spectra at $\sim14\sigma$ and 18$\sigma$ for 1.1 and 1.8 $\mu$m, respectively, and at $\sim10\sigma$ in cross-power spectra. The CIBER measurements pass internal consistency tests and represent a $5-10\times$ improvement in power spectrum sensitivity on several-arcminute scales relative to that of existing studies. Through cross-correlations with tracers of diffuse galactic light (DGL), we determine that scattered DGL contributes $<10\%$ to the observed fluctuation power at high confidence. On scales $\theta > 5'$, the CIBER auto- and cross-power spectra exceed predictions for integrated galactic light (IGL) and integrated stellar light (ISL) by over an order of magnitude, and are inconsistent with our baseline IGL+ISL+DGL model at high significance. We cross-correlate two of the CIBER fields with 3.6 $\mu$m and 4.5 $\mu$m mosaics from the Spitzer Deep Wide-Field Survey and find similar evidence for departures from Poisson noise in Spitzer-internal power spectra and CIBER $\times$ Spitzer cross-power spectra. A multi-wavelength analysis indicates that the auto-power of the fluctuations at low-$\ell$ is bluer than the Poisson noise from IGL and ISL; however, for $1' <\theta < 10'$, the cross-correlation coefficient $r_{\ell}$ of nearly all band combinations decreases with increasing $\theta$, disfavoring astrophysical explanations that invoke a single correlated sky component., Comment: 41 pages, 32 figures. Submitted to ApJ

In the age of large-scale galaxy and lensing surveys, such as DESI, Euclid, Roman and Rubin, we stand poised to usher in a transformative new phase of data-driven cosmology. To fully harness the capabilities of these surveys, it is critical to constrain the poorly understood influence of baryon feedback physics on the matter power spectrum. We investigate the use of a powerful and novel cosmological probe - fast radio bursts (FRBs) - to capture baryonic effects on the matter power spectrum, leveraging simulations from the CAMELS projects, including IllustrisTNG, SIMBA, and Astrid. We find that FRB statistics exhibit a strong correlation, independet of the subgrid model and cosmology, with quantities known to encapsulate baryonic impacts on the matter power spectrum, such as baryon spread and the halo baryon fraction. We propose an innovative method utilizing FRB observations to quantify the effects of feedback physics and enhance weak lensing measurements of $S_{8}$. We outline the necessary steps to prepare for the imminent detection of large FRB populations in the coming years, focusing on understanding the redshift evolution of FRB observables and mitigating the effects of cosmic variance., Comment: 13 pages, 6 figures, submitted to ApJL

In this work, we investigate the properties of string effective theories with scalar field(s) and a scalar potential. We first claim that in most examples known, such theories are multifield, with at least 2 non-compact field directions; the few counter-examples appear to be very specific and isolated. Such a systematic multifield situation has important implications for cosmology. Characterising properties of the scalar potential $V$ is also more delicate in a multifield setting. We provide several examples of string effective theories with $V>0$, where the latter admits an asymptotically flat direction along an off-shell field trajectory: in other words, there exists a limit $\varphi \rightarrow \infty$ for which $\frac{|\partial_{\varphi} V|}{V} \rightarrow 0$. It is thus meaningless to look for a lower bound to this single field quantity in a multifield setting; the complete gradient $\nabla V$ is then better suited. Restricting to on-shell trajectories, this question remains open, especially when following the steepest descent or more generally a gradient flow evolution. Interestingly, single field statements in multifield theories seem less problematic for $V<0$., Comment: Details of the group manifold example can be found in the notebook given as ancillary file

We use Spitzer/IRAC deep exposure data covering two significantly larger than before sky areas to construct maps suitable for evaluating source-subtracted fluctuations in the cosmic infrared background (CIB). The maps are constructed using the self-calibration methodology eliminating artifacts to sufficient accuracy and subset maps are selected in each area containing approximately uniform exposures. These maps are clipped and removed of known sources and then Fourier transformed to probe the CIB anisotropies to new larger scales. The power spectrum of the resultant CIB anisotropies is measured from the data to >1 degree revealing the component well above that from remaining known galaxies on scales >1 arcmin. The fluctuations are demonstrated to be free of Galactic and Solar System foreground contributions out to the largest scales measured. We discuss the proposed theories for the origin of the excess CIB anisotropies in light of the new data. Out of these, the model where the CIB fluctuation excess originates from the granulation power due to LIGO-observed primordial black holes as dark matter appears most successful in accounting for all observations related to the measured CIB power amplitude and spatial structure, including the measured coherence between the CIB and unresolved cosmic X-ray background (CXB). Finally we point out the use of the data to probe the CIB-CXB cross-power to new scales and higher accuracy. We also discuss the synergy of these data with future CIB programs at shorter near-IR wavelengths with deep wide surveys and sub-arcsecond angular resolution as provided by Euclid and Roman space missions., Comment: Astrophysical Journal Letters, to be published

Cosmological gravitational-wave backgrounds are an exciting science target for next-generation ground-based detectors, as they encode invaluable information about the primordial Universe. However, any such background is expected to be obscured by the astrophysical foreground from compact-binary coalescences. We propose a novel framework to detect a cosmological gravitational-wave background in the presence of binary black holes and binary neutron star signals with next-generation ground-based detectors, including Cosmic Explorer and the Einstein Telescope. Our procedure involves first removing all the individually resolved binary black hole signals by notching them out in the time-frequency domain. Then, we perform joint Bayesian inference on the individually resolved binary neutron star signals, the unresolved binary neutron star foreground, and the cosmological background. For a flat cosmological background, we find that we can claim detection at $5\,\sigma$ level when $\Omega_\mathrm{ref}\geqslant 2.7\times 10^{-12}/\sqrt{T_\mathrm{obs}/\mathrm{yr}}$, where $T_\mathrm{obs}$ is the observation time (in years), which is within a factor of $\lesssim2$ from the sensitivity reached in absence of these astrophysical foregrounds., Comment: Main text: 7 pages, 3 figures, 1 table. Supplemental material: 12 pages, 9 figures, 1 table

This paper presents results for the innermost stable circular orbit in a Kerr-like spacetime. The metric employed is an approximation that combines the Kerr metric with the Erez-Rosen metric, expanded in a Taylor series. Consequently, this spacetime incorporates three relativistic multipole moments: mass, spin, and quadrupole moment. Our derivation builds upon the analysis conducted by Chandrasekhar for the Kerr metric. Utilizing the Euler-Lagrange method and Hamiltonian dynamics, we define an effective potential for the radial coordinate. This equation can be used to measure the mass quadrupole through observational methods, as it yields a quadratic polynomial for the quadrupole moment. As anticipated, the limiting cases of this equation correspond to the established cases of Kerr and Schwarzschild spacetimes.

Cosmological moduli generically come to dominate the energy density of the early universe, and thereby trigger an early matter dominated era. Such non-standard cosmological histories are expected to have profound effects on the evolution and production of axion cold dark matter and dark radiation, as well as their prospects for detection. We consider moduli-axion couplings and investigate the early history of the coupled system, considering closely the evolution of the homogeneous modulus field, the back-reaction from the axion, and the energy densities of the two fields. A particular point of interest is the enhancement of axion production from modulus decay, due to tachyonic and parametric resonant instabilities, and the implications of such production on the cosmological moduli problem, axion dark radiation, and the available parameter space for axion dark matter. Using an effective field theory approach, WKB-based semi-analytical analysis, and detailed numerical estimates of the co-evolution of the system, we evaluate the expected decay efficiency of the modulus to axions. The effects of higher-order operators are studied and implications for UV-complete frameworks such as the Large Volume Scenarios in Type IIB string theory are considered in detail., Comment: 40 pages, 15 figures

We show that primordial adiabatic curvature fluctuations generate an instability of the scalar field sourcing a kination era. We demonstrate that the generated higher Fourier modes constitute a radiation-like component dominating over the kination background after about $11$ e-folds of cosmic expansion. Current constraints on the extra number of neutrino flavors $\Delta N_{\rm eff}$ thus imply the observational bound of approximately 10 e-folds, representing the most stringent bound to date on the stiffness of the equation of state of the pre-Big-Bang-Nucleosynthesis universe., Comment: 5 pages, 2 figures + appendix (10 pages)

Weak gravitational lensing perturbations have a non-negligible impact on strong lensing observables, and several degeneracies exist between the properties of the main lens, line of sight, and cosmology. In this work, we consider the impact of the line of sight on double-source-plane lenses (DSPLs), a rare class of lens systems in which two sources at different redshifts are lensed by the same foreground galaxy, and which enable competitive constraints on the dark energy equation of state. Generating and sampling statistically representative lines of sight from N-body simulations, we show that line-of-sight perturbations add a $\sim1\%$ uncertainty to measurements of the cosmological scaling factor $\eta$ (a ratio of angular diameter distance ratios), which is subdominant but non-negligible compared to the measurement error. We also show that the line-of-sight shear experienced by images of the two sources can differ significantly in both magnitude and direction. Including a line-of-sight error budget, we measure $w=-1.17^{+0.19}_{-0.21}$ from the Jackpot DSPL in combination with Planck. We show that the line of sight is expected to introduce an additional scatter in the constraints possible with a larger sample of DSPLs from Euclid, but that this scatter is subdominant compared to other sources of error., Comment: 13 + 7 pages, 6 figures

While the $\Lambda$CDM model succeeds on large scales, its validity on smaller scales remains uncertain. Recent works suggest that non-halo dark matter structures, such as filaments and walls, could significantly influence gravitational lensing and that the importance of these effects depends on the dark matter model: in warm dark matter scenarios, fewer low-mass objects form and thus their mass is redistributed into the cosmic-web. We investigate these effects on galaxy-galaxy lensing using fragmentation-free Warm Dark Matter (WDM) simulations with particle masses of m$_{\chi}$ = 1 keV and m$_{\chi}$ = 3 keV. Although these cosmological scenarios are already observationally excluded, the fraction of mass falling outside of haloes grows with the thermal velocity of the dark matter particles, which allows for the search for first-order effects. We create mock datasets, based on gravitationally-lensed systems from the BELLS-Gallery, incorporating non-halo contributions from these simulations to study their impact in comparison to mocks where the lens has a smooth mass distribution. Using Bayesian modelling, we find that perturbations from WDM non-halo structures produce an effect on the inferred parameters of the main lens and shift the reconstructed source position. However, these variations are subtle and are effectively absorbed by standard elliptical power-law lens models, making them challenging to distinguish from intrinsic lensing features. Most importantly, non-halo perturbation does not appear as a strong external shear term, which is commonly used in gravitational lensing analyses to represent large-scale perturbations. Our results demonstrate that while non-halo structures can affect the lensing analysis, the overall impact remains indistinguishable from variations of the main lens in colder WDM and CDM scenarios, where non-halo contributions are smaller., Comment: 13+4 pages, submitted to A&A, comments welcome

This chapter presents Modified Newtonian Dynamics (MOND), the proposal that, below a certain acceleration scale $a_0$, dynamics departs from the Newtonian expectation. In that context, the determining factor for the emergence of apparent missing matter in galactic systems is predicted to be the acceleration, and not the mass or size of the system. MOND enables, for example, the prediction of rotation curves from only the baryonic distribution of galaxies. The simple rule is that the acceleration observed in the low-acceleration regime is the square root of the Newtonian expectation times $a_0$. Immediately, the flatness of rotation curves follows, as well as the proportionality of the fourth power of the asymptotic circular speed to only the baryonic mass of the galaxy. While the asymptotic circular speed is predicted not to depend on the baryonic surface density of galaxies of fixed baryonic mass, the inner shape of rotation curves is predicted to strongly depend on it. More generally, MOND implies an algebraic relation between the acceleration expected from Newtonian gravity and the total observed acceleration, at any radius in a galaxy. This is known, observationally, as the Radial Acceleration Relation. For galaxy clusters, it is commonly accepted that MOND fails, needing a stronger gravitational force (or more baryonic mass than observed) to account for the thermodynamic state of galaxy clusters, their lensing and kinematics. MOND, however, is not a complete theory, but a phenomenological non-relativistic paradigm in the limit of low accelerations, in need of embedding in a more fundamental theory. While various non-relativistic field theories of MOND exist, the search for a relativistic theory that recovers general relativity for high accelerations and MOND for low accelerations in the quasi-static limit, as well as a cosmology compatible with observations, is still on-going., Comment: 20 pages, 5 figures, pre-print of a chapter for the Encyclopedia of Astrophysics (edited by I. Mandel, section editor C. Howlett) to be published by Elsevier as a Reference Module

While cosmological simulations of galaxy formation have reached maturity, able to reproduce many fundamental galaxy and halo properties, no consensus has yet been reached on the impact of `baryonic feedback' on the non-linear matter power spectrum. This severely limits the precision of (and potentially biases) small-scale cosmological constraints obtained from weak lensing and galaxy surveys. Recent observational evidence indicates that `baryonic feedback' may be more extreme than commonly assumed in current cosmological hydrodynamical simulations. In this paper, we therefore explore a range of empirical AGN feedback models, within the FABLE simulation suite, with different parameterizations as a function of cosmic time, host halo properties, and/or spatial location where feedback energy is thermalized. We demonstrate that an AGN radio-mode feedback acting in a larger population of black holes, with jets thermalizing at relatively large cluster-centric distances, as exemplified by our XFABLE model, is in good agreement with the latest weak lensing + kSZ constraints across all k-scales. Furthermore, XFABLE maintains good agreement with the galaxy stellar mass function, gas fraction measurements, and all key galaxy group and cluster properties, including scaling relations and ICM radial profiles. Our work highlights the pressing need to model black hole accretion and feedback physics with a greater level of realism, including relativistic, magnetized jets in full cosmological simulations. Finally, we discuss how a range of complementary observational probes in the near future will enable us to constrain AGN feedback models, and therefore reduce `baryonic feedback' modelling uncertainty for the upcoming era of large cosmological surveys.

Sterile neutrinos with masses on the $\mathrm{eV}$ scale are promising candidates to account for the origin of neutrino mass and the reactor neutrino anomalies. The mixing between sterile and active neutrinos in the early universe could result in a large abundance of relic sterile neutrinos, which depends on not only their physical mass $m_{\rm phy}$ but also their degree of thermalization, characterized by the extra effective number of relativistic degrees of freedom $\Delta N_{\rm eff}$. Using neutrino-involved N-body simulations, we investigate the effects of sterile neutrinos on the matter power spectrum, halo pairwise velocity, and halo mass and velocity functions. We find that the presence of sterile neutrinos suppress the matter power spectrum and halo mass and velocity functions, but enhance the halo pairwise velocity. We also provide fitting formulae to quantify these effects., Comment: 22 pages, 9 main + 2 appendix figures. Second update only corrects the abstract on arXiv page

The sound horizon-independent $H_0$ extracted by using galaxy clustering surveys data through, e.g., EFTofLSS or ShapeFit analyses, is considered to have the potential to constrain the early new physics responsible for solving the Hubble tension. Recent observations, e.g. DESI, have shown that the sound horizon-independent measurement of $H_0$ is consistent with $\Lambda$CDM. In this work, we clarify some potential misuses and misinterpretations in these analyses. On the one hand, imposing some prior from other cosmological probes is often used to strengthen the constraints on the results, however, these priors are usually derived using the assumption of $\Lambda$CDM, it is not suitable to apply these so-called $\Lambda$CDM priors (e.g., the $n_s$ prior from CMB), which would bias the results, to early new physics because these early new physics are usually accompanied by shifts of the $\Lambda$CDM parameters. On the other hand, the constraints on $H_0$ in the sound horizon-independent EFTofLSS analysis arise from not only the shape of the power spectrum ($k_\text{eq}$-based $H_0$), but also the overall amplitude (when combined with CMB lensing observations) and the relative amplitudes of the BAO wiggles, thus besides $k_\text{eq}$ other information may also play a role in constraining $H_0$. We also make forecasts for an Euclid-like survey, which suggest that ongoing observations will also have difficulty ruling out early new physics., Comment: 34 pages, 9 figures

Measuring the growth rate of large-scale structures ($f$) as a function of redshift has the potential to break degeneracies between modified gravity and dark energy models, when combined with expansion-rate probes. Direct estimates of peculiar velocities of galaxies have gained interest to estimate $f\sigma_8$. In particular, field-level methods can be used to fit the field nuisance parameter along with cosmological parameters simultaneously. This article aims to provide the community with an unified framework for the theoretical modeling of the likelihood-based field-level inference by performing fast field covariance calculations for velocity and density fields. Our purpose is to lay the foundations for non-linear extension of the likelihood-based method at the field level. We develop a generalized framework, implemented in the dedicated software flip to perform a likelihood-based inference of $f\sigma_8$. We derive a new field covariance model, which includes wide-angle corrections. We also include the models previously described in the literature inside our framework. We compare their performance against ours, we validate our model by comparing it with the two-point statistics of a recent N-body simulation. The tests we perform allow us to validate our software and determine the appropriate wavenumber range to integrate our covariance model and its validity in terms of separation. Our framework allows for a wider wavenumber coverage used in our calculations than previous works, which is particularly interesting for non-linear model extensions. Finally, our generalized framework allows us to efficiently perform a survey geometry-dependent Fisher forecast of the $f\sigma_8$ parameter. We show that the Fisher forecast method we developed gives an error bar that is 30 % closer to a full likelihood-based estimation than a standard volume Fisher forecast., Comment: 20 pages, 11 figures

The probability distribution, $p(\mathrm{DM})$ of cosmic dispersion measures (DM) measured in fast radio bursts (FRBs) encodes information about both cosmology and galaxy feedback. In this work, we study the effect of feedback parameters in the $p(\mathrm{DM})$ calculated from the full Latin Hypercube of parameters sampled by the CAMELS hydrodynamical simulation suite, building a neural network (NN) model that performs well in emulating the effect of feedback on $p(\mathrm{DM})$ at arbitrary redshifts at $z\leq1$. Using this NN model, we further study the parameter $F\equiv \sigma_{\rm DM} \, z^{1/2}$, which is commonly used to summarize the scatter on $p(\mathrm{DM})$. We find that $F$ does not depend monotonically on every feedback parameter; instead each feedback mechanism jointly influences the final feedback strength in non-trivial ways. Even the largest values of $F$ that we find in our entire parameter space are small compared to the current constraints from observed FRB DMs by Baptista et al. 2024, pointing at the limitations of the CAMELS suite due to the small simulation box sizes. In the future, with larger box-sizes from CAMELS-like suites, similar models can be used to constrain the parameters governing galaxy feedback in the increasing observational samples of FRBs., Comment: 9 pages, 4 figures

The concentration of dark matter haloes is closely linked to their mass accretion history. We utilize the halo mass accretion histories from large cosmological N-body simulations as inputs for our neural networks, which we train to predict the concentration of individual haloes at a given redshift. The trained model performs effectively in other cosmological simulations, achieving the root mean square error between the actual and predicted concentrations that significantly lower than that of the model by Zhao et al. and Giocoli et al. at any redshift. This model serves as a valuable tool for rapidly predicting halo concentrations at specified redshifts in large cosmological simulations., Comment: 12 pages, 6 figures, version published by Universe

We investigate the central density structure of dark matter halos in cold dark matter (CDM) and self-interacting dark matter (SIDM) models using simulations that are part of the Feedback In Realistic Environments (FIRE) project. For simulated halos of dwarf galaxy scale ($M_{\rm halo}(z=0)\approx 10^{10}\,M_\odot$), we study the central structure in both dissipationless simulations and simulations with full FIRE-2 galaxy formation physics. As has been demonstrated extensively in recent years, both baryonic feedback and self-interactions can convert central cusps into cores, with the former process doing so in a manner that depends sensitively on stellar mass at fixed $M_{\rm halo}$. Whether the two processes (baryonic feedback and self-interactions) are distinguishable, however, remains an open question. Here we demonstrate that, compared to feedback-induced cores, SIDM-induced cores transition more quickly from the central region of constant density to the falling density at larger radial scales. This result holds true even when including identical galaxy formation modeling in SIDM simulations as is used in CDM simulations, since self-interactions dominate over galaxy formation physics in establishing the central structure of SIDM halos in this mass regime. The change in density profile slope as a function of radius therefore holds the potential to discriminate between self-interactions and galaxy formation physics as the driver of core formation in dwarf galaxies., Comment: 11 pages, 7 figures

The 2-point correlation function of the galaxy spatial distribution is a major cosmological observable that enables constraints on the dynamics and geometry of the Universe. The Euclid mission aims at performing an extensive spectroscopic survey of approximately 20--30 million H$\alpha$-emitting galaxies up to about redshift two. This ambitious project seeks to elucidate the nature of dark energy by mapping the 3-dimensional clustering of galaxies over a significant portion of the sky. This paper presents the methodology and software developed for estimating the 3-dimensional 2-point correlation function within the Euclid Science Ground Segment. The software is designed to overcome the significant challenges posed by the large and complex Euclid data set, which involves millions of galaxies. Key challenges include efficient pair counting, managing computational resources, and ensuring the accuracy of the correlation function estimation. The software leverages advanced algorithms, including kd-tree, octree, and linked-list data partitioning strategies, to optimise the pair-counting process. The implementation also includes parallel processing capabilities using shared-memory open multi-processing to further enhance performance and reduce computation times. Extensive validation and performance testing of the software are presented. The results indicate that the software is robust and can reliably estimate the 2-point correlation function, which is essential for deriving cosmological parameters with high precision. Furthermore, the paper discusses the expected performance of the software during different stages of the Euclid Wide Survey observations and forecasts how the precision of the correlation function measurements will improve over the mission's timeline, highlighting the software's capability to handle large data sets efficiently., Comment: 17 pages, 13 figures, submitted to A&A

Modern time-domain astronomical surveys produce high throughput data streams which require tools for processing and analysis. This will be critical for programs making full use of the alert stream from the Vera Rubin Observatory (VRO), where spectroscopic labels will only be available for a small subset of all transients. In this context, the AMPEL toolset can work as a code-to-data platform for the development of efficient, reproducible and flexible workflows for real-time astronomical application. We here introduce three different AMPEL channels constructed to highlight different uses of alert streams: to rapidly find infant transients (SNGuess), to provide unbiased transient samples for follow-up (FollowMe) and to deliver final transient classifications (FinalBet). These pipelines already contain placeholders for mechanisms which will be essential for the optimal usage of VRO alerts: combining different classifiers, including host galaxy information, population priors and sampling non-gaussian photometric redshift distributions. Based on the ELAsTiCC simulation, all three channels are already working at a high level: SNGuess correctly tags 99% of all young supernovae, FollowMe illustrates how an unbiased subset of alerts can be selected for spectroscopic follow-up in the context of cosmological probes and FinalBet includes priors to achieve successful classifications for >~80% of all extragalactic transients. The fully functional workflows presented here are all public and can be used as starting points for any group wishing to optimize pipelines for their specific VRO science programs. AMPEL is designed to allow this to be done in accordance with FAIR principles: both software and results can be easily shared and results reproduced. The code-to-data environment ensures that models developed this way can be directly applied to the real-time LSST stream parsed by AMPEL., Comment: Submitted to Astronomy & Astrophysics

In this study, we explore the characteristics of bulk flow across various redshift ranges within the frameworks of $f(R)$ gravity, perturbed $f(R)$ gravity, and perturbed $f(R)$ gravity coupled with neutrinos. Our investigation reveals profound insights into large-scale cosmic flows and their interactions with major cosmic structures, such as the Sloan Great Wall (SGW) and the King Ghidorah Supercluster (KGSc). We find that incorporating neutrinos into the perturbed $f(R)$ gravity model results in a substantial increase in bulk flow velocities across all redshifts, with notable enhancements in the higher redshift ranges, where velocities can exceed $3000 \, \mathrm{km/s}$ in the $0.8 < z < 1.4$ range. Moreover, the direction of the bulk flow in this model closely aligns with the dark energy dipole, especially at redshifts $z > 0.4$, showing near-perfect congruence with cosmic superclusters. This suggests a significant interaction between neutrinos and cosmic structures, influencing cosmic acceleration. At lower redshifts, such as $0.1 < z < 0.2$, the bulk flow aligns with the SGW, while in the $0.4 < z < 0.6$ range, it aligns with the KGSc. In the low redshift range $0.001 < z < 0.016$, although velocities are lower, neutrinos still subtly increase the bulk flow velocity and maintain alignment with nearby cosmic structures, like the Local Supercluster. Our results underscore the critical role of neutrinos in shaping cosmic flows and offer new insights into the interplay between dark energy, neutrinos, and modified gravity models., Comment: 11 figures, 27 pages. arXiv admin note: substantial text overlap with arXiv:2402.18841

Cosmic voids, the nearly empty regions nestled between walls and filaments, are recognized for their extensive applications in the field of cosmology and astrophysics. However, a consensus on the definition of voids remains elusive, as various void-finding methods identify different types of voids, each differing in shape and density based on the method that were used. In this paper, we introduce an innovative void identification method that utilizes Genetic Algorithm analysis. VEGA employs the Voronoi tessellation technique and the Convex Hull algorithm to partition the dataset plane into distinct regions and calculate the volume of each region. For the first time, VEGA integrates Genetic Algorithm analysis with the luminosity density contrast function to identify and locate the possible void region candidates. This method utilizes a set of grid points, which enhances the implementation of Voronoi tessellation and enables VEGA to more effectively access the dataset space for the identification of void regions candidates, finding the center and the ultimate structure of voids. Finally, we applied the VEGA and Aikio-M\"ah\"onen (AM) methods to the same test dataset and compared the cosmic voids identified by VEGA with those identified by the AM method. This comparison demonstrated that the VEGA void-finding method yields reliable results and can be effectively applied to various particle distributions., Comment: 10 pages, 4 figures, 1 table, for submission to Physical Review X

Next-generation ground-based gravitational wave observatories will observe mergers of intermediate-mass black holes (IMBHs) out to high redshift. Such IMBHs can form through runaway tidal encounters in the cores of dense stellar clusters. In this paper, we ask if the gravitational wave observation of a single merger event between two IMBHs, occurring in the aftermath of the coalescence of the clusters in which they formed, can be used to infer the properties of their host clusters, such as mass, redshift, and half-mass radius. We implement an astrophysically motivated analytic model for cluster evolution and IMBH growth, and we perform IMBH binary parameter estimation using a network of three next-generation detectors. We find that inferring the structural properties of clusters in this way is challenging due to model degeneracy. However, the posteriors on the cluster formation redshifts have relatively narrow peaks, and it may still be possible to infer the cluster formation history by measuring a whole population of IMBH binary merger events., Comment: 29 pages, 16 figures

The detection of galaxy clusters, the most massive bounded structures in the universe, is crucial for cosmological analysis. Weak lensing signals allow us to track the distribution of all (dark and baryonic) matter regardless of its observable electromagnetic properties. Upcoming wide-field surveys like Euclid and LSST-Rubin will provide enhanced shape measurements of billions of background galaxies, presenting an unparalleled opportunity to detect galaxy clusters on a vast cosmic scale. The immense data volume generated by these surveys will require efficient and accurate analysis techniques. In this work, we introduce AMICO-WL, an extension of the optimal filtering algorithm implemented in AMICO, a well-tested code developed for optical cluster detection. AMICO-WL implements a specific linear optimal matched filter for weak lensing data in the AMICO infrastructure, using parallelisation and adding an efficient signal-to-noise ratio thresholding approach to set a desired sample purity and a cleaning procedure to deal with blended detections. The algorithm has been tested on a 25 deg$^2$ field of Euclid-like mock galaxy catalogue with the simulated shear signal produced using DUSTGRAIN-$pathfinder$ past-light-cones. We implemented a foreground removal procedure based on different cuts of low redshift galaxies from the input catalogue. To evaluate the performance of the method, we used an efficient matching procedure based on the 'blinking' of the simulation's individual redshift lensing planes. Cross-matching the AMICO-WL detections with the dark matter halo sample in the simulation having $M_{200} > 5 \times 10^{13}$ $M_{\odot}/h$ and considering a purity level of $\sim70\%$, the application of the foreground removal doubles the completeness from $6.5\%$ to $13.0\%$ and at the same time produces a significant decrease of spurious detections.