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The formation and growth of black holes can strongly influence the distribution of dark matter around them. I discuss here the different types of dark matter overdensities around black holes, including dark matter cusps, spikes, mounds, crests, and gravitational atoms. I then review recent results on the evolution of a black holes binary in presence of dark matter, focusing on the energy transfer between binary and dark matter induced by dynamical friction. Finally, I present the prospects for studying dark matter with gravitational wave observations, and argue that future interferometers might be able to detect and characterise dark matter overdensities around black holes., Comment: 12 pages, 3 figures. Review article, to appear in the proceedings of the 182nd Nobel Symposium

We forecast constraints on minimal model-independent parametrisations of several Modified Gravity theories using mock Stage-IV cosmic shear data. We include nonlinear effects and screening, which ensures recovery of General Relativity on small scales. We introduce a power spectrum emulator to accelerate our analysis and evaluate the robustness of the growth index parametrisation with respect to two cosmologies: $\Lambda$CDM and the normal branch of the DGP model. We forecast the uncertainties on the growth index $\gamma$ to be of the order $\sim 10\%$. We find that our halo-model based screening approach demonstrates excellent performance, meeting the precision requirements of Stage-IV surveys. However, neglecting the screening transition results in biased predictions for cosmological parameters. We find that the screening transition shows significant degeneracy with baryonic feedback, requiring a much better understanding of baryonic physics for its detection. Massive neutrinos effects are less prominent and challenging to detect solely with cosmic shear data., Comment: 22 pages, 16 figures, 2 tables plus Appendices. Our power spectrum boost emulators for extended cosmologies are publicly available at https://github.com/nebblu/ReACT-emus/tree/main/emulators

The distribution of masses of neutron stars, particularly the maximum mass value, is considered a probe of their formation, evolution and internal physics (i.e., equation of state). This mass distribution could in principle be inferred from the detection of gravitational waves from binary neutron star mergers. Using mock catalogues of $10^5$ dark sirens events, expected to be detected by Einstein Telescope over an operational period of $\sim1\, \rm year$ , we show how the biased luminosity distance measurement induced by gravitational lensing affects the inferred redshift and mass of the merger. This results in higher observed masses than expected. Up to $2\%$ of the events are predicted to fall above the maximum allowed neutron star mass depending on the intrinsic mass distribution and signal-to-noise ratio threshold adopted. The underlying true mass distribution and maximum mass could still be approximately recovered in the case of bright standard sirens., Comment: 9 pages, 5 figures, 1 table

To fully exploit the data from next generation surveys, we need an accurate modelling of the matter power spectrum up to non-linear scales. Therefore in this work we present the halo model reaction framework for the Generalized Cubic Covariant Galileon (GCCG) model, a modified gravity model within the Horndeski class of theories which extends the cubic covariant Galileon (G3) by including power laws of the derivatives of the scalar field in the K-essence and cubic terms. We modify the publicly available software ReACT for the GCCG in order to obtain an accurate prediction of the non-linear power spectrum. In the limit of the G3 model we compare the modified ReACT code to $N$-body simulations and we find agreement within 5\% for a wide range of scales and redshifts. We then study the relevant effects of the modifications introduced by the GCCG on the non-linear matter power spectrum. Finally, we provide forecasts from spectroscopic and photometric primary probes by next generation surveys using a Fisher matrix method. We show that future data will be able to constrain at 1$\sigma$ the two additional parameters of the model at the percent level and that considering non-linear corrections to the matter power spectrum beyond the linear regime is crucial to obtain this result., Comment: 17 pages, 7 figures, code available at https://github.com/nebblu/ACTio-ReACTio

We examine the thin accretion disk behaviors surrounding black holes embedded in cold dark matter halos and scalar field dark matter halos. We first calculate the event horizons and derive the equations of motion and effective potential in black hole geometries with different dark matter halos. We then compute the specific energy, specific angular momentum, and angular velocity of particles moving along circular orbits. We also derive the effective potentials to find the locations of the innermost stable circular orbit (ISCO) and compare them to the Schwarzschild and Kerr black holes without the dark matter haloes. We also use the observed ISCO of the supermassive black hole at the Galactic Center of the Milky Way, Sagittarius A*, to constrain the dark matter halos and discuss the astrophysical Gamma-ray bursts (GRBs) generation from systems.

Gravitational clustering in our cosmic vicinity is expected to lead to an enhancement of the local density of relic neutrinos. We derive expressions for the neutrino density, using a perturbative approach to kinetic field theory and perturbative solutions of the Vlasov equation up to second order. Our work reveals that both formalisms give exactly the same results and can thus be considered equivalent. Numerical evaluation of the local relic neutrino density at first and second order provides some fundamental insights into the frequently applied approach of linear response to neutrino clustering (also known as the Gilbert equation). Against the naive expectation, including the second-order contribution does not lead to an improvement of the prediction for the local relic neutrino density but to a dramatic overestimation. This is because perturbation theory breaks down in a momentum-dependent fashion and in particular for densities well below unity., Comment: 34 pages, 7 figures

We use continuous wavelet transform techniques to construct the global and environment-dependent wavelet statistics, such as energy spectrum and kurtosis, to study the fluctuation and intermittency of the turbulent motion in the cosmic fluid velocity field with the IllustrisTNG simulation data. We find that the peak scales of the energy spectrum and the spectral ratio define two characteristic scales, which can be regarded as the integral scale and the dissipation scale of turbulence, respectively, so that the energy spectrum can be divided into the energy-containing range, the inertial range and the dissipation range of turbulence. The wavelet kurtosis is an increasing function of the wavenumber $k$, first grows rapidly then slowly with $k$, indicating that the cosmic fluid becomes increasingly intermittent with $k$. In the energy-containing range, the energy spectrum increases significantly from $z = 2$ to $1$, but remains almost unchanged from $z = 1$ to $0$. We find that both the environment-dependent spectrum and kurtosis are similar to the global ones, and the magnitude of the spectrum is smallest in the lowest-density and largest in the highest-density environment, suggesting that the cosmic fluid is more turbulent in a high-density than in a low-density environment. In the inertial range, the exponent of the energy spectrum is steeper than not only the Kolmogorov but also the Burgers exponent, suggesting that there may be more complex mechanisms for energy transfer than Kolmogorov and Burgers turbulence., Comment: 15 pages, 9 figures, 1 table, comments welcome

Density profiles are important tools in galaxy cluster research, offering insights into clusters dynamical states and their relationship with the broader Universe. While these profiles provide valuable information about the matter content of the Universe, their utility in understanding its dark energy component has remained limited due a lack of tools allowing us to study the transition from cluster portions that are relaxed and infalling, to those that are merging with the Hubble flow. In this work we investigate signatures of this transition in stacked density profiles of simulated cluster-sized halos at different redshifts. To highlight the Hubble flow around clusters we use their turnaround radius to normalize stacked simulated density profiles and calculate their logarithmic slope. Then, we complement our analysis by modeling the outer portions of these profiles assuming Gaussian early Universe statistics and spherical collapse without shell-crossing. We find the logarithmic slope of median cluster density profiles beyond the turnaround radius - where the Hubble flow dominates - to be Universal and well described by our model. Importantly, we find the slope of the profiles to diverge from the SCM prediction from within the turnaround radius where the actual profiles exhibit caustics which give rise to the splashback feature. We suggest utilizing this divergence from the spherical collapse model as a method to identify the turnaround radius in stacked cluster density profiles, offering a new perspective on understanding cluster dynamics and their cosmological implications., Comment: 8 pages, 5 figures, submitted to A&A

We present model-marginalized limits on the six standard $\Lambda$CDM cosmological parameters ($\Omega_{\rm c} h^2$, $\Omega_{\rm b} h^2$, $\theta_{\rm MC}$, $\tau_{\rm reio}$, $n_s$ and $A_s$), as well as on selected derived quantities ($H_0$, $\Omega_{\rm m}$, $\sigma_8$, $S_8$ and $r_{\rm drag}$), obtained by considering three independent Cosmic Microwave Background (CMB) experiments: the Planck satellite, the Atacama Cosmology Telescope, and South Pole Telescope. We also consider low redshift observations in the form of Baryon Acoustic Oscillation (BAO) data from the SDSS-IV eBOSS survey and Supernovae (SN) distance moduli measurements from the Pantheon-Plus catalog. The marginalized errors are stable against the different fiducial cosmologies explored in this study. The largest impact on the parameter accuracy is produced by varying the effective number of relativistic degrees of freedom ($N_{\rm eff}$) or the lensing amplitude ($A_{\rm lens}$). Nevertheless the marginalized errors on some derived parameters such as $H_0$ or $\Omega_{\rm m}$ can be up to two orders of magnitude larger than in the canonical $\Lambda$CDM scenario when considering only CMB data. In these cases, low redshift measurements are crucial for restoring the stability of the marginalized cosmological errors computed here. Overall, our results underscore remarkable stability in the mean values and precision of the main cosmological parameters, making irrelevant the choice of different possible cosmological scenarios once both high and low redshift probes are fully accounted for. The very same results should be understood as a tool to test exotic cosmological scenarios, as the marginalized values should be used in numerical analyses due to their robustness and slightly larger errors, providing a more realistic and conservative approach., Comment: 18 pages, 11 figures, 12 tables. Prepared for submission to PRD

We calculate the abundance of UV-bright galaxies in the presence of ultralight axion (ULA) dark matter (DM), finding that axions suppress their formation with a non-trivial dependence on redshift and luminosity. We set limits on axion DM using both Planck cosmic microwave background (CMB) and UV luminosity function (UVLF) data. We exclude a single axion as all the DM for $m_{ax} < 10^{-21.6}$ eV and limit axions with $-26 < \log( m_{ax}/{eV}) < -23$ to be less than $22\%$ of the DM (both limits at $95\%$ credibility). These limits use UVLF measurements from 24,000 sources from the Hubble Space Telescope (HST) that probe small-scale structure at redshifts $4 < z < 10$. We marginalize over a parametric model that connects halo mass and UV luminosity that has been shown to match hydrodynamical simulations. Our results bridge a window in axion mass and DM fraction previously unconstrained by cosmological data, between large-scale CMB and galaxy clustering and the small-scale Lyman-$\alpha$ forest. These high-$z$ measurements provide a powerful consistency check of low-$z$ tests of axion DM, which include the recent hint for a sub-dominant ULA DM fraction in Lyman-$\alpha$ forest data. We also consider a sample of 25 spectroscopically-confirmed high-$z$ galaxies from the James Webb Space Telescope (JWST). We find that these data are consistent with the HST UVLF assuming $\Lambda$CDM and our flexible parametric model of UV luminosity. Combining HST and JWST UVLF data does not improve our constraints beyond HST alone, but future JWST measurements have the potential to improve these results significantly. We also find an excess of low-mass halos ($< 10^9 M_\odot$) at $z < 3$, which could be probed by sub-galactic structure probes (e.g., stellar streams, satellite galaxies and strong lensing)., Comment: 23 pages, 20 figures. Minor changes to match version submitted to journal, references added

We study the prospects for measuring the cosmological distribution and abundance of ionized electrons in the intergalactic medium using galaxy surveys. Optical light from distant galaxies is subject to Thomson screening by intervening electrons which distorts the observed galaxy number density, similar to the effect of weak gravitational lensing magnification. We construct an estimator for the optical-depth fluctuations from the statistical anisotropies of galaxy number counts induced by the spatially-varying optical-depth field. We find near-future galaxy surveys can detect this signal at signal-to-noise above $\sim10$ depending on galaxy survey specifications. We highlight various science cases for the measurement of optical-depth fluctuations., Comment: 8+9 pages, 11 figures, comments welcome

Deep JWST imaging of the giant galaxy cluster Abell 2744, at redshift $z=0.308$, is used to explore the features of its rich population of globular clusters (GCs), building on our initial survey of the system (Harris & Reina-Campos 2023). We use the photometry of more than $10,000$ GCs over a three-magnitude range to construct the GC luminosity function (GCLF) and color distribution (CDF). These results now specifically account for photometric incompleteness as a function of location relative to the five giant galaxies that dominate the gravitational potential of A2744. The total GC population in A2744 is estimated at $N_{\rm GC} \geq 1.1 \times 10^5$, consistent with its high total mass. We also directly compare the observed distributions with theoretical predictions for GC populations drawn from the recent EMP-Pathfinder simulations (Reina-Campos et al. 2022), viewed at the same 3.5 Gyr lookback time as the cluster. The simulations match the observations well, with the only notable disagreement being that the simulations predict larger numbers of GCs at high metallicity formed after $z\simeq2$ than are seen in the data., Comment: 15 pages, 9 figures; submitted to ApJ

The James Webb Space Telescope (JWST) is revolutionizing our understanding of black holes formation and growth in the early Universe. However, JWST has also revealed that some of the classical diagnostics, such as the BPT diagrams and X-ray emission, often fail to identify narrow line TypeII active galactic nuclei (AGN) at high redshift. Here we present three new rest-frame optical diagnostic diagrams leveraging the [OIII]$\lambda4363$ auroral line, which has been detected in several JWST spectra. Specifically, we show that high values of the [OIII]$\lambda4363/$H$\gamma$ ratio provide a sufficient (but not necessary) condition to identify the presence of an AGN, both based on empirical calibrations (using local and high-redshift sources) and a broad range of photoionization models. These diagnostics are able to separate much of the AGN population from Star Forming Galaxies (SFGs). This is because the average energy of AGN's ionizing photons is higher than that of young stars in SFGs, hence AGN can more efficiently heat the gas, therefore boosting the [OIII]$\lambda4363$ line. We also found independent indications of AGN activity in some high-redshift sources that were not previously identified as AGN with the traditional diagnostics diagrams, but that are placed in the AGN region of the diagnostics presented in this work. We note that, conversely, low values of [OIII]$\lambda4363/$H$\gamma$ can be associated either with SFGs or AGN excitation. We note that the fact that strong auroral lines are often associated with AGN does not imply that they cannot be used for direct metallicity measurements (provided that proper ionization corrections are applied), but it does affect the calibration of strong line metallicity diagnostics., Comment: Submitted to A&A. 16 pages, 7 figures. Comments are welcome

We explore the impact of corrections to the propagation on the waveforms of gravitationally lensed gravitational waves under the geometrical optics approximation, focusing on both uniform cosmological modifications and local modifications localized around lensing objects. By adopting a model-independent phenomenological approach, we systematically investigate the effects of these modifications in strong lensing scenarios, where detection of multiple images is expected. Our analysis reveals that cosmological modifications can yield corrections to the time delay that remain to be minor compared with the effects that accumulate over the whole propagation process, which are present also in the unlensed waveform. By contrast, local modifications around lensing objects can alter the image position and also the magnification factor, which is potentially polarization-selective and frequency-dependent. In some case we can have image disappearance as well as signal amplification. Furthermore, we demonstrate that such modifications can cause degradation of waveform match with the templates based on general relativity. This study highlights the importance of considering waveform modifications to search for the signature of modified propagation or the existence of extra polarization modes, and proposes potential observational targets., Comment: 18 pages, 11 figures

Almost 50% of galaxies in the local Universe are in clusters or groups coexisting with both hot and cold gas components. In the present study, we observationally probed the cold-gas content of X-ray-selected massive galaxy clusters with spectroscopic redshift measured from the SDSS/SPIDERS survey. This paper focuses on the most massive structures: galaxy clusters with a mean mass of M$_{500c}$ = 2.7$\times 10^{14}$ M$_{\odot}$. We used a large number of background quasar optical spectra from SDSS DR16 to probe the diffuse T$=$10$^4$K gas in their intracluster medium. We first analysed a sample of spectra with known MgII absorbers, and then blindly stacked about 16,000 archival spectra at the redshifts of the foreground galaxy clusters. We tentatively ($3.7 \sigma$ significance) detect MgII in the clusters with an equivalent width EW(MgII $\lambda$2796) of 0.056$\pm$0.015 \r{A}, corresponding to a column density of log [N(MgII)/cm$^{-2}$]=12.12$\pm0.1$. We tested our methodology by generating 22,000 mock SDSS spectra with MgII absorbers from TNG50 cosmological magnetohydrodynamical simulations, combining photo-ionisation modelling and ray tracing. We also performed bootstrapping stacking at different cluster redshifts and stacked quasar spectra with no intervening clusters in the line of sight to measure the significance of our detection. These results are in line with the findings of recent, similar observational studies but challenge predictions from TNG simulations. Together, our findings indicate that large amounts of cold gas may be found in the most massive structures of the Universe.

The capability of Cosmic Inflation to explain the latest Cosmic Microwave Background and Baryonic Acoustic Oscillation data is assessed by performing Bayesian model comparison within the landscape of nearly three-hundred models of single-field slow-roll inflation. We present the first Bayesian data analysis based on the third-order slow-roll primordial power spectra. In particular, the fourth Hubble-flow function $\epsilon_4$ remains unbounded while the third function verifies, at two-sigma, $\epsilon_{3}\in[-0.4,0.5]$, which is perfectly compatible with the slow-roll predictions for the running of the spectral index. We also observe some residual excess of $B$-modes within the BICEP/Keck data favoring, at a non-statistically significant level, non-vanishing primordial tensor modes: $\log(\epsilon_{1}) > -3.9$, at $68\%$ confidence level. Then, for 283 models of single-field inflation, we compute the Bayesian evidence, the Bayesian dimensionality and the marginalized posteriors of all the models' parameters, including the ones associated with the reheating era. The average information gain on the reheating parameter $R_\mathrm{reh}$ reaches $1.3 \pm 0.18$ bits, which is more than a factor two improvement compared to the first Planck data release. As such, inflationary model predictions cannot meet data accuracy without specifying, or marginalizing over, the reheating kinematics. We also find that more than $40\%$ of the scenarios are now strongly disfavored, which shows that the constraining power of cosmological data is winning against the increase of the number of proposed models. In addition, about $20\%$ of all models have evidences within the most probable region and are all favored according to the Jeffreys' scale of Bayesian evidences., Comment: 77 pages, 37 figures, uses jcappub

We propose a new model of scalar field dark matter interacting with dark energy. Adopting a fluid description of the dark matter field in the regime of rapid oscillations, we find that the equation of state for dark matter is non-zero and even becomes increasingly negative at late times during dark energy domination. Furthermore, the speed of sound of dark matter is non-vanishing at all length scales, and a non-adiabatic pressure contribution arises. The results indicate that there are still unexplored possible interactions within the dark sector that lead to novel background effects and can impact structure formation processes., Comment: 20 pages, 3 figures

We study the dynamical evolution of superradiant instabilities of rotating black holes for multiple axion fields with comparable masses, motivated by string theory constructions, which typically exhibit a large number of light axions, with a broad range of masses. We show, in particular, that even though superradiant clouds for the heavier axion species grow faster, they are eventually reabsorbed by the black hole as the latter amplifies the lighter axion field(s), analogously to the dynamics of different species competing for the same resources in an ecosystem. We also incorporate in our study the effects of accretion and gravitational wave emission. We further demonstrate that the existence of multiple axion species with comparable masses may have a substantial impact on the stochastic gravitational wave background produced by axion clouds around black hole binary merger remnants, which could be probed with planned detectors., Comment: 14 pages, 11 figures

We present novel findings concerning the parameter space of axion stars, extended object forming in dense dark matter environments through gravitational condensation. We emphasize their formation within the dense minihalos that potentially surround primordial black holes and in axion miniclusters. Our study investigates the relation between the radius and mass of an axion star in these dense surroundings, revealing distinct morphological characteristics compared to isolated scenarios. We explore the implications of these results when applied to gravitational microlensing from extended objects and gravitational wave detection from compact binaries, leading to insights on the observational constraints from such ``halo'' axion stars. We provide a constraint on the fraction of the galactic population of axion stars from their contribution to the microlensing events from the EROS-2 survey, using the numerical resolution of the Schr\"odinger-Poisson equation., Comment: 19 pages + references, 8 figures. Part of COST actions CA21106 and CA21136

This study undertakes a reconsideration of the potential for a first-order electroweak phase transition, focusing on the next-to-minimal two Higgs doublet model (N2HDM). Our exploration spans diverse parameter spaces associated with the phase transition, with a particular emphasis on examining the generation of stochastic Gravitational Waves (GW) resulting from this transition. The obtained results are meticulously compared against data from prominent gravitational wave observatories, and the possibility of their detection in the future GW observations have been established. In passing by we analyse the strength of the phase transition through the production of entropy during the electroweak phase transition., Comment: 15 pages, 7 figures

We propose a novel leptogenesis scenario in the gauged $U(1)_{L_{\mu}-L_{\tau}}$ model. Achieving successful leptogenesis in the $U(1)_{L_{\mu}-L_{\tau}}$ symmetric phase is challenging due to the absence of a CP phase, caused by restriction from the gauge symmetry. To overcome this issue, we introduce an additional global symmetry, $U(1)_{B-L}$, and a scalar field $\Phi$ responsible for breaking this symmetry. Through the kinetic misalignment mechanism, the majoron field associated with $U(1)_{B-L}$ symmetry breaking has a kinetic motion in the early universe. Subsequently, time-dependent majoron field background induces the background CP phase dynamically, leading to successful leptogenesis in the $U(1)_{L_{\mu}-L_{\tau}}$ symmetric phase. Furthermore, majoron itself serves as a dark matter candidate in this scenario. As one of the phenomenological applications, we consider the model that can also explain the muon $g-2$ anomaly., Comment: 27 pages, 9 figures

Gravitational lensing effect is one of most significant observational probes to investigate compact dark matter/objects over a wide mass range. In this work, we first propose to derive the population information and the abundance of supermassive compact dark matter in the mass range $\sim10^5-10^7~M_{\odot}$ from 6 millilensed gamma-ray burst (GRB) candidates in 3000 Fermi GRB events using the hierarchical Bayesian inference method. We obtain that, for the mass range $\sim10^5-10^7~M_{\odot}$, the abundance of supermassive compact dark matter is $f_{\rm CO}=10^{-1.60}$ in the log-normal mass distribution scenario. This result is in obvious tension with some other observational constraints, e.g. ultra-faint dwarfs and dynamical friction. However, it also was argued that there is only one system in these 6 candidates has been identified as lensed GRB event with fairly high confidence. In this case, the tension would be significantly alleviated. Therefore, it would be an interesting clue for both the millilensed GRB identification and the formation mechanism of supermassive compact dark matter., Comment: 7 pages, 4 figures, accepted by PRD Letter

Using 3D dust maps and Planck polarized dust emission data, we investigate the influence of the 3D geometry of the nearby interstellar medium (ISM) on the statistics of the dust polarization on large ($80'$) scales. We test the idea that the magnetic field in the nearby dust is preferentially tangential to the Local Bubble wall, but we do not find an imprint of the Local Bubble geometry on the dust polarization fraction. We also test the hypothesis that the complexity of the 3D dust distribution drives some of the measured variation of the dust polarization fraction. We compare sightlines with similar total column densities and find evidence that, on average, the dust polarization fraction decreases when the dust column is substantially distributed among multiple components at different distances. Conversely, the polarization fraction is higher for sightlines where the dust is more concentrated in 3D space. This finding is statistically significant for the dust within 1.25 kpc, but the effect disappears if we only consider dust within 270 pc. The extended 3D dust distribution, rather than solely the dust associated with the Local Bubble, plays a role in determining the observed dust polarization fraction on these scales. This conclusion is consistent with a simple analytical prediction and remains robust under various modifications to the analysis. These results illuminate the relationship between the 3D geometry of the ISM and tracers of the interstellar magnetic field. We also discuss implications for our understanding of the polarized dust foreground to the cosmic microwave background., Comment: 18 pages, 9 figures

Space-based missions studying the cosmic microwave background (CMB) have progressively refined the parameter space in conventional models of inflation shortly ($\sim 10^{-37}$ seconds) after the big bang. While most inflationary scenarios proposed thus far in the context of GR have since been ruled out, the basic idea of inflation may still be tenable, albeit with several unresolved conundrums, such as conflicting initial conditions and inconsistencies with the measured CMB power spectrum. In the new slow-roll inflationary picture, inflation arising in plateau-like potentials requires an initiation beyond the Planck time. This delay may be consistent with the cutoff, $k_{\rm min}$, measured recently in the primordial power spectrum. However, the actual value of $k_{\rm min}$ would imply an initiation time too far beyond the big bang for inflation to solve the horizon problem. In this paper, we also describe several other undesirable consequences of this delay, including an absence of well motivated initial conditions and a significant difficulty providing a viable mechanism for properly quantizing the primordial fluctuations. Nevertheless, many of these inconsistencies may still be avoided if one introduces non-conventional modifications to inflation, such as a brief departure from slow-roll dynamics, possibly due to a dramatic change in the inflationary potential, inflation driven by multiple fields, or a non-minimal coupling to gravity. In addition, some of these difficulties could be mitigated via the use of alternative cosmologies based, e.g., on loop quantum gravity, which replaces the initial big-bang singularity with finite conditions at a bounce-like beginning., Comment: 10 pages, 2 figures. Accepted for publication in ApJ

Precise lens modeling is a critical step in time delay studies of multiply imaged quasars, which are key for measuring some important cosmological parameters (specially $H_0$). However, lens models (in particular those semi-automatically generated) often show discrepancies with the observed flux-ratios between the different quasar images. These flux-ratio anomalies are usually explained through differential effects between images (mainly microlensing) that alter the intrinsic magnification ratios predicted by the models. To check this hypothesis, we collect direct measurements of microlensing to obtain the histogram of microlensing magnifications. We compare this histogram with recently published model flux-ratio anomalies and conclude that they cannot be statistically explained by microlensing. The average value of the model anomalies ($0.74\,$magnitudes) significantly exceeds the mean impact of microlensing ($0.33\,$magnitudes). Moreover, the histogram of model anomalies presents a significant tail with high anomalies ($|\Delta m| \ge 0.7$ magnitudes) which is completely unexpected from the statistics of microlensing observations. Microlensing simulations neither predict the high mean nor the fat tail of the histogram of model anomalies. We perform several statistical tests which exclude that microlensing can explain the observed flux-ratio anomalies (although Kolmogorov-Smirnov, which is less sensitive to the tail of the distributions, is not always conclusive). Thus, microlensing cannot statistically explain the bulk of flux-ratio anomalies, and models may explore different alternatives to try to reduce them. In particular, we propose to complement photometric observations with accurate flux ratios of the broad emission lines obtained from integral field spectroscopy to check and, ideally, constrain lens models.

The continuously expanding sample of gravitational-wave observations is revealing the formation and evolutionary mechanism of merging compact binaries. Two primary channels, namely, isolated field binary evolution and dynamical capture, are widely accepted as potential producers of merging binary black holes (BBHs), which are distinguishable with the spin-orientation distributions of the BBHs. We investigate the two formation channels in GWTC-3, with a dedicated semi-parametric population model, i.e., a mixture of two sub-populations with different spin-orientation distributions (one is nearly-aligned and the other is nearly-isotropic). It turns out that the two sub-populations have different mass and mass-ratio distributions. The nearly-aligned sub-population, which is consistent with the isolated field formation channels, has a less preference for symmetric systems, and likely dominate the 10-solar-mass peak in the primary-mass function. While the isotropic sub-population shows a stronger preference for symmetric systems, and mainly contribute to the 35-solar-mass peak in the primary-mass function, consistent with the dynamical channels. Moreover, our results show that the purely isotropic-spin and the single well-aligned (i.e., the width of $\cos\theta$ distribution $\sigma_{\rm t}<0.5$) scenario are ruled out (by a Bayes factor of $\ln\mathcal{B}=5.2$ and $\ln\mathcal{B}=9.8$)., Comment: 26 pages, 16 figures

Using the recently developed cosmological bootstrap method, we compute the exact analytical solution for the seed integral appearing in cosmological correlators with double massive scalar exchanges. The result is explicit, valid in any kinematic configuration, and free from spurious divergences. It is applicable to any number of fields' species with any masses. With an appropriate choice of variables, the results contain only single-layer summations. We also propose simple approximate formulas valid in different limits, enabling direct and instantaneous evaluation.Supported by exact numerical results using CosmoFlow, we explore the phenomenology of double massive exchange diagrams. Contrary to single-exchange diagrams with ubiquitous Lorentz-covariant interactions, the size of the cubic coupling constant can be large while respecting perturbativity bounds. Because of this property, the primordial bispectrum from double-exchange diagrams can be as large as, coincidentally, current observational constraints. In addition to being sizable on equilateral configurations, we show that the primordial bispectrum exhibits a large cosmological collider signal in the squeezed limit, making the double massive exchanges interesting channels for the detection of massive primordial fields. We propose to decisively disentangle double-exchange channels from single-exchange ones with cosmological observations by exploiting the phase information of the cosmological collider signal, the inflationary flavor oscillations from multiple fields' species exchanges and the double soft limit in the primordial trispectrum., Comment: 66 pages, 13 figures

We present the discovery of large radio shells around a massive pair of interacting galaxies and extended diffuse X-ray emission within the shells. The radio data were obtained with the Australian Square Kilometer Array Pathfinder (ASKAP) in two frequency bands centred at 944 MHz and 1.4 GHz, respectively, while the X-ray data are from the XMM-Newton observatory. The host galaxy pair, which consists of the early-type galaxies ESO 184-G042 and LEDA 418116, is part of a loose group at a distance of only 75 Mpc (redshift z = 0.017). The observed outer radio shells (diameter ~ 145 kpc) and ridge-like central emission of the system, ASKAP J1914-5433 (Physalis), are likely associated with merger shocks during the formation of the central galaxy (ESO 184-G042) and resemble the new class of odd radio circles (ORCs). This is supported by the brightest X-ray emission found offset from the centre of the Physalis system, instead centered at the less massive galaxy, LEDA 418116. The host galaxy pair is embedded in an irregular envelope of diffuse light, highlighting on-going interactions. We complement our combined radio and X-ray study with high-resolution simulations of the circumgalactic medium (CGM) around galaxy mergers from the Magneticum project to analyse the evolutionary state of the Physalis system. We argue that ORCs / radio shells could be produced by a combination of energy release from the central AGN and subsequent lightening up in radio emission by merger shocks traveling through the CGM of these systems., Comment: 12 pages, 8 figures, submitted to MNRAS

We propose a lightweight deep convolutional neural network (lCNN) to estimate cosmological parameters from simulated three-dimensional DM halo distributions and associated statistics. The training dataset comprises 2000 realizations of a cubic box with a side length of 1000 $h^{-1}{\rm Mpc}$, and interpolated over a cubic grid of $300^3$ voxels, with each simulation produced using $512^3$ DM particles and $512^3$ neutrinos . Under the flat $\Lambda$CDM model, simulations vary standard six cosmological parameters including $\Omega_m$, $\Omega_b$, $h$, $n_s$, $\sigma_8$, $w$, along with the neutrino mass sum, $M_\nu$. We find that: 1) within the framework of lCNN, extracting large-scale structure information is more efficient from the halo density field compared to relying on the statistical quantities including the power spectrum, the two-point correlation function, and the coefficients from wavelet scattering transform; 2) combining the halo density field with its Fourier transformed counterpart enhances predictions, while augmenting the training dataset with measured statistics further improves performance; 3) achieving high accuracy in inferring $\Omega_m$, $h$, $n_s$, and $\sigma_8$ by the neural network model, while being inefficient in predicting $\Omega_b$,$M_\nu$ and $w$; 4) compared to the simple random forest network trained with three statistical quantities, lCNN yields unbiased estimations with reduced statistical errors: approximately 33.3\% for $\Omega_m$, 20.0\% for $h$, 8.3\% for $n_s$, and 40.0\% for $\sigma_8$. Our study emphasizes this lCNN-based novel approach in extracting large-scale structure information and estimating cosmological parameters., Comment: 10 pages,9 figures

We perform in this work an analysis of the background dynamics for $\alpha$-attractor models in the context of loop quantum cosmology. Particular attention is given to the determination of the duration of the inflationary phase that is preceded by the quantum bounce in these models. From an analysis of the general predictions for these models, it is shown that we can be able to put constraints in the parameter $\alpha$ of the potentials and also on the quantum model itself, in special the Barbero-Immirzi parameter., Comment: 10 pages, 5 figures

We consider the scattering of low-mass halo dark-matter particles in the hot plasma of the Sun, focusing on dark matter that interact with ordinary matter through a dark-photon mediator. The resulting ``solar-reflected'' dark matter (SRDM) component contains high-velocity particles, which significantly extend the sensitivity of terrestrial direct-detection experiments to sub-MeV dark-matter masses. We use a detailed Monte-Carlo simulation to model the propagation and scattering of dark-matter particles in the Sun, including thermal effects, with special emphasis on ultralight dark-photon mediators. We study the properties of the SRDM flux, obtain exclusion limits from various direct-detection experiments, and provide projections for future experiments, focusing especially on those with silicon and xenon targets. We find that proposed future experiments with xenon and silicon targets can probe the entire ``freeze-in benchmark,'' in which dark matter is coupled to an ultralight dark photon, including dark-matter masses as low as $\mathcal{O}$(keV). Our simulations and SRDM fluxes are publicly available., Comment: 40 pages, 23 figures including appendices and references

The increasingly neutral intergalactic gas at $z>6$ impacts the Lyman-$\alpha$ flux observed from galaxies. One luminous galaxy, COLA1, stands out because of its unique double-peaked Ly$\alpha$ line at $z=6.6$, unseen in any simulation of reionization. Here we present JWST/NIRCam wide-field slitless spectroscopy in a 21 arcmin$^2$ field centered on COLA1. We find 141 galaxies spectroscopically-selected through the [OIII]($\lambda4969,5008$) doublet at $5.35M_{\rm UV}>-19.5$)., Comment: 15 pages, 13 figures. Submitted to A&A. Main figs. 1, 2, 10 (SFR surface density), 11 (spectra and positions of galaxies in the bubble)

Radio observations of strongly lensed objects are valuable as cosmological probes. Lensed radio sources have proven difficult to identify in large part due to the limited depth and angular resolution of the previous generation of radio sky surveys, and as such, only a few dozen lensed radio sources are known. In this work we present the results of a pilot study using the Very Large Array Sky Survey (VLASS) in combination with optical data to more efficiently identify lensed radio sources. We obtain high-resolution (0.2") VLA follow-up observations for 11 targets that we identify using three different techniques: i) a search for compact radio sources offset from galaxies with high lensing potential, ii) VLASS detections of known lensed galaxies, iii) VLASS detections of known lensed quasars. 5 of our targets show radio emission from the lensed images, including 100% of the lensed optical quasar systems. This work demonstrates the efficacy of combining deep and high-resolution wide-area radio and optical survey data to efficiently find lensed radio sources, and we discuss the potential impact of such an approach using next-generation surveys with the Vera C. Rubin Observatory, Euclid, and Nancy Grace Roman Space Telescope., Comment: 29 pages, 9 figures, 3 tables, submitted to AAS Journals

The advent of massive broad-band photometric surveys enabled photometric redshift estimates for unprecedented numbers of galaxies and quasars. These estimates can be improved using better algorithms or by obtaining complementary data such as narrow-band photometry, and broad-band photometry over an extended wavelength range. We investigate the impact of both approaches on photometric redshifts for quasars using data from S-PLUS DR4, GALEX DR6/7, and unWISE in three machine learning methods: Random Forest (RF), FlexCoDE, and Bayesian Mixture Density Network (BMDN). Including narrow-band photometry improves the root-mean-square error by 11% in comparison to a model trained with only broad-band photometry. Narrow-band information only provided an improvement of 3.8% when GALEX and WISE colours were included. Thus narrow bands play a more important role for objects that do not have GALEX or WISE counterparts, which respectively makes 92% and 25% of S-PLUS data considered here. Nevertheless, the inclusion of narrow-band information provided better estimates of the probability density functions obtained with FlexCoDE and BMDN. We publicly release a value-added catalogue of photometrically-selected quasars with the photo-z predictions from all methods studied here. The catalogue provided with this work covers the S-PLUS DR4 area (~3000deg$^2$), containing 645 980, 244 912, 144 991 sources with the probability of being a quasar higher than, 80%, 90%, 95% up to r < 21.3 and good photometry quality in the detection image. More quasar candidates can be retrieved from the S-PLUS database by considering less restrictive selection criteria., Comment: Accepted to MNRAS

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

The Dark Energy Spectroscopic Instrument (DESI) survey will measure spectroscopic redshifts for millions of galaxies across roughly $14,000 \, \mathrm{deg}^2$ of the sky. Cross-correlating targets in the DESI survey with complementary imaging surveys allows us to measure and analyze shear distortions caused by gravitational lensing in unprecedented detail. In this work, we analyze a series of mock catalogs with ray-traced gravitational lensing and increasing sophistication to estimate systematic effects on galaxy-galaxy lensing estimators such as the tangential shear $\gamma_{\mathrm{t}}$ and the excess surface density $\Delta\Sigma$. We employ mock catalogs tailored to the specific imaging surveys overlapping with the DESI survey: the Dark Energy Survey (DES), the Hyper Suprime-Cam (HSC) survey, and the Kilo-Degree Survey (KiDS). Among others, we find that fiber incompleteness can have significant effects on galaxy-galaxy lensing estimators but can be corrected effectively by up-weighting DESI targets with fibers by the inverse of the fiber assignment probability. Similarly, we show that intrinsic alignment and lens magnification are expected to be statistically significant given the precision forecasted for the DESI year-1 data set. Our study informs several analysis choices for upcoming cross-correlation studies of DESI with DES, HSC, and KiDS., Comment: 18 pages, 13 figures

The standard approach to test for deviations from General Relativity on cosmological scales is to combine measurements of the growth rate of structure with gravitational lensing. In this study, we show that this method suffers from an important limitation with regard to these two probes: models of dark matter with additional interactions can lead to the very same observational signatures found in modified gravity (and viceversa). Using synthetic data of redshift-space distortions, weak lensing, and cosmic microwave background, we demonstrate that this degeneracy is inevitable between modifications of gravity and a dark fifth force. We then show that the coming generation of surveys, in particular the Square Kilometer Array, will allow us to break the degeneracy between such models through measurements of gravitational redshift. Performing a Markov Chain Monte Carlo analysis of the synthetic data set, we quantify the extent to which gravitational redshift can distinguish between two representative classes of models, Generalized Brans-Dicke (modified gravity) and Coupled Quintessence (fifth force)., Comment: 10 pages, 3 figures

We analyze the volume-limited subsamples extracted from the sixteenth data release of the SDSS-IV eBOSS quasar survey spanning a redshift interval of $0.8 < z < 2.2$, to estimate the scale of transition to homogeneity in the Universe. The multi-fractal analysis used for this purpose considers the scaling behavior of different moments of quasar distribution in different density environments. This analysis gives the spectrum of generalized dimension $D_q$, where positive values of $q$ characterize the scaling behavior in over-dense regions and the negative ones in under-dense regions. We expect fractal correlation dimension $D_q(r) = 3$, for a homogeneous, random point distribution in 3-Dimensions. The fractal correlation dimension $D_q(r)$, corresponding to $q=2$ obtained in our study stabilizes in the range (2.8-2.9) for scales $r>80$ $h^{-1}$ Mpc. The observed quasar distribution shows consistency with the simulated mock data and the random distribution of quasars within one sigma. Further, the generalized dimension spectrum $D_q(r)$ also reveals transition to homogeneity beyond $>110$ $h^{-1}$ Mpc, and the dominance of clustering at small scales $r<80$ $h^{-1}$ Mpc. Consequently, our study provides strong evidence for the homogeneity in SDSS quasar distribution, offering insights into large-scale structure properties and, thus can play a pivotal role in scrutinizing the clustering properties of quasars and its evolution in various upcoming surveys such as Dark Energy Spectroscopic Instrument (DESI) and Extremely Large Telescope (ELT)., Comment: 11 pages, 8 figures, 1 table, Accepted for publication in MNRAS

The Lunar Gravitational-wave Antenna (LGWA) is a proposed array of next-generation inertial sensors to monitor the response of the Moon to gravitational waves (GWs). Given the size of the Moon and the expected noise produced by the lunar seismic background, the LGWA would be able to observe GWs from about 1 mHz to 1 Hz. This would make the LGWA the missing link between space-borne detectors like LISA with peak sensitivities around a few millihertz and proposed future terrestrial detectors like Einstein Telescope or Cosmic Explorer. In this article, we provide a first comprehensive analysis of the LGWA science case including its multi-messenger aspects and lunar science with LGWA data. We also describe the scientific analyses of the Moon required to plan the LGWA mission.

Quantum gravity has been baffling the theoretical physicist for decades now: both for its mathematical obscurity and phenomenological testing. Nevertheless, the new era of precision cosmology presents a promising avenue to test the effects of quantum gravity. In this study, we consider a bottom-up approach. Without resorting to any candidate quantum gravity, we invoke a generalized uncertainty principle (GUP) directly into the cosmological Hamiltonian for a universe sourced by a phantom scalar field with potential to study the early epoch of the evolution. This is followed by a systematic analysis of the dynamics, both qualitatively and quantitatively. Our qualitative analysis shows that the introduction of GUP significantly alters the existence of fixed points for the potential considered in this contribution. In addition, we confirm the existence of an inflationary epoch and analyze the behavior of relevant cosmological parameters with respect to the strength of GUP distortion.

Large-scale cosmic filaments may have played an important role in shaping the properties of galaxies. Meanwhile, cosmic filaments are believed to harbor a substantial portion of the missing baryons at redshift z < 2. To inspect the role of filaments in these issues, many properties of filaments need to be examined, including their lengths, thicknesses, and density profiles. However, measuring some of these properties poses challenges. This study concentrates on estimating filament width/thickness, investigating potential correlations between the local width of filaments and the properties of dark matter halos within filaments. We find that the local width of filaments generally increases with the mass of dark matter halos embedded in filaments per unit length, roughly following a secondorder polynomial, although with notable scatter. We probe and discuss means that may refine our findings. After further verification and improvements, this relation could be applied to filament samples constructed from the observed galaxy distribution, aiding in understanding the roles of cosmic filaments in galaxy evolution and uncovering the missing baryons., Comment: 11 pages, 7 figures, accepted to ApJ

To describe the dark side of the Universe, we adopt a novel approach where dark energy is explained as an electrically charged majority of dark matter. Dark energy, as such, does not exist. The Friedmann equation at the present time coincides with that in a conventional approach, although the cosmological "constant" in the Electromagnetic Accelerating Universe (EAU) Model shares a time dependence with the matter component. Its equation of state is $\omega \equiv P/\rho \equiv -1$ within observational accuracy., Comment: 26 pages LaTeX Submitted to {\it Particle Theory and Theoretical Cosmology}, Festschrift for 80th anniversary of P.H. Frampton. To appear in {\it Entropy} journal, and Special Edition, MDPI Books (2024). arXiv admin note: substantial text overlap with arXiv:1511.08801, arXiv:2304.10370

Intrinsic Conformal Symmetries have emerged as a tool for developing viable and physically coherent models, particularly in scenarios incorporating a negative cosmological constant. This study demonstrates that when the bulk geometry accommodates a set of $10$ Intrinsic Conformal Symmetries, which operate on three-dimensional hypersurfaces (be they spacelike or timelike), it leads to the existence of two distinct families of five-dimensional spacetimes. These spacetimes represent the general solutions to the bulk field equations. An aspect of these models is the composition of their energy-momentum tensor, which includes two key components: a negative cosmological constant and a parallel pressure $p_{\parallel}$ aligned with the extra spatial dimension. This framework can be perceived as a $5D$ extension of the recently identified Spatially Inhomogeneous and Irrotational spacetimes. Significantly, these models offer a novel perspective for investigating the impacts of spatial inhomogeneity on the cosmological evolution of the Universe, particularly within the context of the Randall-Sundrum theory. This exploration is essential for deepening our understanding of the role of higher dimensions in cosmological models., Comment: 16 pages, no figures, Latex2e source file, one Appendix

We explore the asymptotic future evolution of holographic dark energy (HDE) models, in which the density of the dark energy is a function of a cutoff scale $L$. We develop a general methodology to determine which models correspond to future big rip, little rip, and pseudo-rip (de Sitter) evolution, and we apply this methodology to a variety of well-studied HDE models. None of these HDE models display little rip evolution, and we are able to show, under very general assumptions, that HDE models with a Granda-Oliveros cutoff almost never evolve toward a future little rip. We extend these results to HDE models with nonstandard Friedman equations and show that a similar conclusion applies: little rip evolution is a very special case that is almost never realized in such models., Comment: v2, new citations added and minor typos corrected, 8 pages with no figures

Dark matter overdensities around black holes can be searched for by looking at the characteristic imprint they leave on the gravitational waveform of binary black hole mergers. Current theoretical predictions of the density profile of dark matter overdensities are based on highly idealised formation scenarios, in which black holes are assumed to grow adiabatically from an infinitesimal seed to their final mass, compressing dark matter cusps at the center of galactic halos into very dense `spikes'. These scenarios were suitable for dark matter indirect detection studies, since annihilating dark matter cannot reach very high densities, but they fail to capture the dark matter distribution in the innermost regions where the gravitational wave signal is produced. We present here a more realistic formation scenario where black holes form from the collapse of supermassive stars, and follow the evolution of the dark matter density as the supermassive star grows and collapses to a black hole. We show that in this case dark matter forms shallower `mounds', instead of `spikes', on scales comparable with the size of the supermassive stars originating them. We discuss the implications for the detectability of these systems., Comment: 8 pages, 4 figures

The Hubble tension has proven to be stubbornly persistent, despite widespread efforts to relax it. As a possible resolution of this problem we propose a radical alternative to the way in which cosmological models are viewed. Specifically, we consider building cosmological models from spaces that exhibit intrinsic symmetries, rather than as space-times with explicit symmetry. This change in perspective allows statistical homogeneity and isotropy to be maintained, while relaxing some strong mathematical constraints that the standard approach imposes. We show that a Hubble tension arises naturally in our new approach, and that (as a corollary) a prediction can be made for the radial component of the Baryon Acoustic Oscillations. Our prediction appears to be consistent with the DESI first-year data release, which has otherwise been interpreted as evidence for dynamical dark energy., Comment: 15 pages, 3 figures

Gravitational waves induce correlated perturbations to the arrival times of pulses from an array of galactic millisecond pulsars. The expected correlations, obtained by averaging over many pairs of pulsars having the same angular separation (pulsar averaging) and over an ensemble of model universes (ensemble averaging), are described by the Hellings and Downs curve. As shown by Allen [1], the pulsar-averaged correlation will not agree exactly with the expected Hellings and Downs prediction if the gravitational-wave sources interfere with one another, differing instead by a "cosmic variance" contribution. The precise shape and size of the cosmic variance depends on the statistical properties of the ensemble of universes used to model the background. Here, we extend the calculations of the cosmic variance for the standard Gaussian ensemble to an ensemble of model universes which collectively has rotationally-invariant correlations in the GW power on different angular scales (described by an angular power spectrum, $C_\ell$ for $\ell=0,1,\cdots$.). We obtain an analytic form for the cosmic variance in terms of the $C_\ell$'s and show that for realistic values $C_{\ell}/C_0\lesssim 10^{-3}$, there is virtually no difference in the cosmic variance compared to that for the standard Gaussian ensemble (which has zero angular power spectra)., Comment: 13 pages, 2 figures

We study the nature of transient events detected in the "Dragon Arc", a star-forming galaxy at a redshift of $0.7251$ that is gravitationally lensed by the galaxy cluster Abell 370. In particular, we focus on a subset of ten transients that are identified as unresolved young star clusters in the deep broadband, F200LP, taken as part of the "Flashlights" Hubble Space Telescope program, showing flux variations of $\sim 10-20\%$ over a period of about a year. Here we develop several methods to address whether stellar microlensing alone is capable of explaining the transients, or whether intrinsic stellar outbursts or variability are required to explain them. We first present a lens model that has new constraints in the Dragon Arc itself to understand the properties of the lensed young star clusters. Using our improved galaxy-cluster lens model, we simulate the effect of microlensing on the flux variation for unresolved stars within lensed young star clusters. We find good agreement between the observed and the expected detection rates of microlensing events by intracluster stars of young star clusters within $1\sigma$. However, we cannot fully exclude the possibility that a minority of these transients are caused by intrinsic stellar variability such as outbursts of Luminous Blue Variables (LBVs). With JWST observations taken recently or coming in the near future, the color information will be able to break the degeneracy and definitively test whether or not these lensed young star cluster transients are caused by stellar microlensing., Comment: 28 pages, 14 figures. To be submitted, comments welcomed

The relativistic Sunyaev-Zel'dovich (SZ) effect can be used to measure intracluster gas temperatures independently of X-ray spectroscopy. Here, we use the large-volume FLAMINGO simulation suite to determine whether SZ $y$-weighted temperatures lead to more accurate hydrostatic mass estimates in massive ($M_{\rm 500c} > 7.5\times 10^{14}\,{\rm M}_{\odot}$) clusters than when using X-ray spectroscopic-like temperatures. We find this to be the case, on average. The median bias in the SZ mass at redshift zero is $\left< b \right> \equiv 1-\left< M_{\rm 500c,hse}/M_{\rm 500c,true} \right> = -0.05 \pm 0.01$, over 4 times smaller in magnitude than the X-ray spectroscopic-like case, $\left< b \right> = 0.22 \pm 0.01$. However, the scatter in the SZ bias, $\sigma_{b} \approx 0.2$, is around 40 per cent larger than for the X-ray case. We show that this difference is strongly affected by clusters with large pressure fluctuations, as expected from shocks in ongoing mergers. Selecting the clusters with the best-fitting generalized NFW pressure profiles, the median SZ bias almost vanishes, $\left< b \right> = -0.009 \pm 0.005$, and the scatter is halved to $\sigma_{b} \approx 0.1$. We study the origin of the SZ/X-ray difference and find that, at $R_{\rm 500c}$ and in the outskirts, SZ weighted gas better reflects the hot, hydrostatic atmosphere than the X-ray weighted gas. The SZ/X-ray temperature ratio increases with radius, a result we find to be insensitive to variations in baryonic physics, cosmology and numerical resolution., Comment: 19 pages, 22 figures, submitted to MNRAS. Comments welcome

It has been recently proposed that the boosted dark matter (BDM) by supernova neutrinos (SN$\nu$) from SN1987a or from the next galactic SN can serve as a novel component to probe nonvanishing interaction between DM and the Standard Model leptons. In this work, we extend this concept and evaluate the present-day diffuse flux of SN$\nu$ BDM originated from all galaxies at higher redshifts. We show that by considering this diffuse BDM (DBDM) component, the best model-independent sensitivity on the product of the DM-$\nu$ and DM-electron cross sections, $\sqrt{\sigma_{\chi\nu}\sigma_{\chi e}}\simeq \mathcal{O}(10^{-37})$~cm$^2$ for sub-MeV DM, can be obtained with large-size neutrino experiments such as Super-Kamiokande or Hyper-Kamiokande, surpassing the estimated SN$\nu$ BDM bound from SN1987a. We also examine the impact due to the presence of DM spikes around the supermassive black holes in galaxies on SN$\nu$ BDM and DBDM. Our results suggest that both the DBDM and the SN$\nu$ BDM probes are insensitive to the uncertain properties of DM spikes, unless the next galactic SN happens to occur at a location extremely close to or right behind the galactic center along the SN line of sight., Comment: 9 pages, 6 figures and 99 references