arXiv subjects

Antonino Del Popolo

Publications and source records attributed to Antonino Del Popolo.

At least 37 records · Page 2Linked to original sources

arXiv2023

Solution to the hyperon puzzle using dark matter

In this paper, we studied the ``hyperon puzzle", a problem that nevertheless the large number of studies is still an open problem. The solution of this issue requires one or more mechanisms that could eventually provide the additional repulsion needed to make the EoS stiffer and, therefore, the value of $M_{\rm{max}, T}$ compatible with the current observational limits. In this paper we proposed that including dark matter (DM) admixed with ordinary matter in neutron stars (NSs), change the hydrostatic equilibrium and may explain the observed discrepancies, regardless to hyperon multi-body interactions, which seem to be unavoidable. We have studied how non-self-annihilating, and self-interacting, DM admixed with ordinary matter in NSs changes their inner structure, and discussed the mass-radius relations of such NSs. We considered DM particle masses of 1, 10, and 100 GeV, while taking into account a rich list of the DM interacting strengths, $y$. By analyzing the multidimensional parameter space, including several quantities like: a. the DM interacting strength, b. the DM particle mass as well as the quantity of DM in its interior, and c. the DM fraction, ${\rm f}_{DM}$, we put constraints in the parameter space ${\rm f}_{DM} - p^{\prime}_{\rm DM}/p^{\prime}_{\rm OM}$. Our bounds are sensitive to the recently observed NSs total masses.

gr-qc↗

arXiv2023

Effect of a High-Precision Semi-Analytical Mass Function on the Merger Rate of Primordial Black Holes in Dark Matter Halos

In this work, we study the effect of a high-precision semianalytical mass function on the merger rate of primordial black holes (PBHs) in dark matter halos. For this purpose, we first explain a theoretical framework for dark matter halo models and introduce relevant quantities such as halo density profile, concentration parameter, and a high-precision semianalytical function namely Del Popolo (DP) mass function. In the following, we calculate the merger rate of PBHs in the framework of ellipsoidal-collapse dark matter halo models while considering the DP mass function, and compare it with our previous study for the Sheth-Tormen (ST) mass function. The results show that by taking the mass of PBHs as $M_{\rm PBH} = 30M_{\odot}$, the DP mass function can potentially amplify the merger rate of PBHs. Moreover, we calculate the merger rate of PBHs for the DP mass function as a function of their mass and fraction and compare it with the black hole mergers recorded by the LIGO-Virgo detectors during the latest observing run. Our findings show that the merger rate of PBHs will fall within the LIGO-Virgo band if $f_{\rm PBH} \gtrsim \mathcal{O}(10^{-1})$. This implies that the DP mass function can be used to strengthen constraints on the fraction of PBHs.

astro-ph.CO↗

arXiv2022

Non self-similar Luminosity-temperature relation and dynamical friction

Extending the results of a previous paper \citep{DelPopolo2005}, by taking into account the role of dynamical friction, we recovered the luminosity-temperature relation (LTR). While by assuming self-similarity, a scaling law in which $L\propto T^2$ is obtained, observations show that the relation between luminosity and temperature is steeper, ${L \propto T^ {\simeq 3}}$. This difference can be explained in terms of energy input by non-gravitational processes, like pre-heating, supernovae feedback, and heating from AGN. In this paper, we studied the LTR by means of a modified version of the punctuated equilibria model \citep{Cavaliere1999}, taking into account in addition dynamical friction, thus extending the approach found in \citep{DelPopolo2005}. The result is a non-self-similar LTR with a bend at $\simeq 2$ keV, with a slope $2.76 \pm 0.18$ at larger energies and $3.4 \pm 0.18$ at energies smaller than 2 keV. This result is in agreement with the XXL survey \citep{Giles2016}. Moreover the steeper slopes at smaller energies is in agreement with some studies claiming a further steepening of the LTR at the low mass end. We also compared the results of our model with the 400d groups sample, finding that in groups the slope is slightly steeper than in clusters, %and namely $3.35 \pm 0.3$, in agreement with the \citep{Zou2016} study for the 400d groups sample, that gives a slope $3.29 \pm 0.33$.

astro-ph.CO↗

arXiv2022

Splashback radius in a spherical collapse model

It has been shown some years ago that dark matter haloes outskirts are characterized by very steep density profiles in a very small radial range. This feature has been interpreted as a pile up of at a similar location of different particle orbits, namely splashback material at half an orbit after collapse. Adhikari et al. (2014), obtained the location of the splashback radius through a very simple model, namely calculating a dark matter shell trajectory in the secondary infall model while it crosses a growing, NFW profile shaped, dark matter halo. Since they imposed a halo profile instead of calculating it from the trajectories of the shells of dark matter, they were not able to find the dark matter profile around the splashback radius. In the present paper, we use an improved spherical infall model taking into shell crossing, and several physical effects like ordered, and random angular momentum, dynamical friction, adiabatic contraction, etc. This allow us to determine the density profile from the inner to outer region, and study the behavior of the outer density profile. We will compare the density profiles, and the logarithmic slope of the density profile with the results of Diemer \& Kravtsov (2014) simulations, finding a good agreement between the prediction of the model and the simulations.

astro-ph.CO↗

arXiv2022

Review of solutions to the Cusp-core problem of the $Λ$CDM Model

This review aims at proposing to the field an overview of the Cusp-core problem, including a discussion of its advocated solutions, assessing how each can satisfactorily provide a description of central densities. Whether the Cusp-core problem reflects our insufficient grasp on the nature of dark matter, of gravity, on the impact of baryonic interactions with dark matter at those scales, as included in semi-analytical models or fully numerical codes, the solutions to it can point either to the need for a paradigm change in cosmology, or to to our lack of success in ironing out the finer details of the $Λ$CDM paradigm.

astro-ph.CO↗

arXiv2022

The effect of magnetic field on the inner Galactic rotation curve

In the past few decades, some studies pointed out that magnetic field might affect the rotation curves in galaxies. However, the impact is relatively small compared with the effects of dark matter and the baryonic components. In this letter, we revisit the impact of magnetic field on the rotation curve of our Galaxy. We show that the inner Galactic rotation curve could be affected significantly by the magnetic field. The addition of the inner bulge component, which has been proposed previously to account for the inner rotation curve data, is not necessary. The magnetic field contribution can fully account for the excess of the inner rotation velocity between 5 pc to 50 pc from the Galactic Centre. Our analysis can also constrain the azimuthal component of the central regular magnetic field strength to $B_0 \sim 50-60$ $μ$G, which is consistent with the observed range.

astro-ph.GA↗

arXiv2022

A Mass Dependent Density Profile from Dwarfs to Clusters

In this paper, we extend the work of Freundlich et al. 2020 who showed how to obtain a Dekel-Zhao density profile with mass dependent shape parameters in the case of galaxies. In the case of Freundlich et al. 2020, the baryonic dependence was obtained using the NIHAO set of simulations. In our case, we used simulations based on a model of ours. Following Freundlich et al. 2020, we obtained the dependence from baryon physics of the two shape parameters, obtaining in this way a mass dependent Dekel-Zhao profile describing the dark matter profiles from galaxies to clusters of galaxies. The extension to the Dekel-Zhao mass dependent profile to clusters of galaxies is the main result of the paper. In the paper, we show how the Dekel-Zhao mass dependent profile gives a good description of the density profiles of galaxies, already shown by Freundlich et al. 2020, but also to a set of clusters of galaxies.

astro-ph.CO↗

arXiv2022

There is no universal acceleration scale in galaxies

Recently, many studies seem to reveal the existence of some correlations between dark matter and baryonic matter. In particular, the unexpected tight Radial Acceleration Relation (RAR) discovered in rotating galaxies has caught much attention. The RAR suggests the existence of a universal and fundamental acceleration scale in galaxies, which seems to challenge the $Λ$CDM model and favour some modified gravity theories. A large debate about whether RAR is compatible with the $Λ$CDM model has arisen. Here, by analysing the high quality velocity dispersion profiles of 13 E0-type elliptical galaxies in the SDSS-IV MaNGA sample and assuming a power-law function of radius $r$ for the 3-dimensional velocity dispersion in each galaxy, we report the RAR for E0-type elliptical galaxies and we show that the resultant RAR has more than $5σ$ deviations from the RAR in late-type galaxies. This new RAR provides an independent probe to falsify the existence of any universal acceleration scale in galaxies. Our result significantly challenges those modified gravity theories which suggest the existence of any universal acceleration scale.

astro-ph.GA↗

arXiv2021

Cluster density slopes from Dark Matter-Baryons Energy Transfer

In this paper, we extend previous works on the relation between mass and the inner slope in dark matter density profiles. We calculate that relation in the mass range going from dwarf galaxies to cluster of galaxies. This was done thanks to a modeling of energy transfer via SN and AGN feedback, as well as via dynamical friction of baryon clumps. We show that, in the mass range above galaxy masses (Groups and clusters), the inner slope-mass relation changes its trend. It flattens (towards less cuspy profile) around masses corresponding to groups of galaxies and steepens again for large galaxy cluster masses. The flattening is produced by the AGN outflows (AGN feedback). The one-$ σ$ scatter on $α$ is approximately constant in all the mass range ($Δα\simeq 0.3$). This is the first paper extending the inner density profile slope-mass relationship to clusters of galaxies, accounting for the role of baryons. The result can be used to obtain a complete density profile, also taking baryons into account. Such kind of density profile was previously only available for galaxies.

astro-ph.GA↗

arXiv2021

Turnaround radius in $Λ$CDM, and dark matter cosmologies with shear and vorticity

We determine the relationship between the turnaround radius, $R_{\rm t}$, and mass, $M_{\rm t}$, in $Λ$CDM, and in dark energy scenarios, using an extended spherical collapse model taking into account the effects of shear and vorticity. We find a more general formula than that usually described in literature, showing a dependence of $R_{\rm t}$ from shear, and vorticity. The $R_{\rm t}-M_{\rm t}$ relation differs from that obtained not taking into account shear, and rotation, especially at galactic scales, differing $\simeq 30\%$ from the result given in literature. This has effects on the constraint of the $w$ parameter of the equation of state. We compare the $R_{\rm t}-M_{\rm t}$ relationship obtained for the $Λ$CDM, and different dark energy models to that obtained in the $f(R)$ modified gravity (MG) scenario. The $R_{\rm t}-M_{\rm t}$ relationship in $Λ$CDM, and dark energy scenarios are tantamount to the prediction of the $f(R)$ theories. Then, the $R_{\rm t}-M_{\rm t}$ relationship is not a good probe to test gravity theories beyond Einstein's general relativity.

astro-ph.CO↗

arXiv2021

Turnaround radius in $Λ$CDM, and dark matter cosmologies II: the role of dynamical friction

This paper is an extension of the paper by Del Popolo, Chan, and Mota (2020) to take account the effect of dynamical friction. We show how dynamical friction changes the threshold of collapse, $δ_c$, and the turn-around radius, $R_t$. We find numerically the relationship between the turnaround radius, $R_{\rm t}$, and mass, $M_{\rm t}$, in $Λ$CDM, in dark energy scenarios, and in a $f(R)$ modified gravity model. Dynamical friction gives rise to a $R_{\rm t}-M_{\rm t}$ relation differing from that of the standard spherical collapse. In particular, dynamical friction amplifies the effect of shear, and vorticity already studied in Del Popolo, Chan, and Mota (2020). A comparison of the $R_{\rm t}-M_{\rm t}$ relationship for the $Λ$CDM, and those for the dark energy, and modified gravity models shows, that the $R_{\rm t}-M_{\rm t}$ relationship of the $Λ$CDM is similar to that of the dark energy models, and small differences are seen when comparing with the $f(R)$ models. The effect of shear, rotation, and dynamical friction is particularly evident at galactic scales, giving rise to a difference between the $R_{\rm t}-M_{\rm t}$ relation of the standard spherical collapse of the order of $\simeq 60\%$. Finally, we show how the new values of the $R_{\rm t}-M_{\rm t}$ influence the constraints to the $w$ parameter of the equation of state.

astro-ph.CO↗

arXiv2021

Improved Lemaitre-Tolman model and the mass and turn-around radius in group of galaxies

We extended the modified Lemaitre-Tolman model taking into account the effect of angular momentum and dynamical friction. The inclusion of these quantities in the equation of motion modifies the evolution of a perturbation, initially moving with the Hubble flow. Solving the equation of motions we got the relationships between mass, $M$, and the turn-around radius, $R_0$. Knowing $R_0$, the quoted relation allows the determination of the mass of the object studied. The relationships for the case in which also the angular momentum is taken into account gives a mass $\simeq 90$ \% larger than the standard Lemaitre-Tolman model, and two times the value of the standard Lemaitre-Tolman model, in the case also dynamical friction is taken into account. As a second step, we found relationships between the velocity, $v$, and radius, $R$, and fitted them to data of the Local Group, M81, NGC 253, IC342, CenA/M83, and to the Virgo clusters obtained by Ref.[New Astronomy 11(4):325, A&A 488(3):845]. This allowed us to find optimized values of the mass and Hubble constant of the objects studied. The fit gives values of the masses smaller with respect to the $M-R_0$ relationship method, but in any case 30-40\% larger than the $v-R$ relationship obtained from the standard Lemaitre-Tolman model. Differently from mass, the Hubble parameter becomes smaller with respect to the standard Lemaitre-Tolman model, when angular momentum, and dynamical friction are introduced. This is in agreement with Ref.[New Astronomy 11(4):325, A&A 488(3):845], who improved the standard Lemaitre-Tolman model taking into account the cosmological constant. Finally, we used the mass, $M$, and $R_0$ of the studied objects to put constraints to the dark energy equation of state parameter, $w$. Comparison with previous studies show different constraints on $w$.

astro-ph.CO↗

arXiv2020

Can Pulsars in the inner parsecs from Galactic Centre probe the existence of Dark Matter?

We discuss the formation of dark compact objects in a dark matter environment in view of the possible mass dependence of pulsars on the distribution of dark matter in the Galaxy. Our results indicate that the pulsar masses should decrease going towards the center of the Milky Way due to dark matter capture, thus becoming a probe for the existence and nature of dark matter. We thus propose that the evolution of the pulsar mass in a dark matter rich environment can be used to put constraints, when combined with future experiments, on the characteristics of our Galaxy halo dark matter profile, on the dark matter particle mass and on the dark matter self-interaction strength.

astro-ph.HE↗

arXiv2020

On the change of old neutron star masses with galactocentric distance

We show that the pulsar mass depends on the environment, and that it decreases going towards the center of the Milky Way. This is due to two combined effects, the capture and accumulation of self-interacting, non-annihilating dark matter by pulsars, and the increase of the dark matter density going towards the galactic center. We show that mass decrease depends both on the density profile of dark matter, steeper profiles producing a faster and larger decrease of the pulsar mass, and on the strength of self-interaction. Once future observations will provide the pulsar mass in a dark matter rich environment, close to the galactic center, the present result will be able to put constraints on the characteristics of our Galaxy halo dark matter profile, on the nature of dark matter, namely on its annihilating or non-annihilating nature, on its strength of self-interaction, and on the particle mass.

gr-qc↗

arXiv2020

Reply to: Overconfidence in Bayesian analyses of galaxy rotation curves

Cameron {\it et al.}~2019 (hereafter C19) recommends a more cautious and rigorous approach to statistical analysis in astronomy. We welcome this particular side of their communication as it helps stimulating the effort towards the adoption of better statistical methods in galaxy rotation curves, an effort to which we contributed with Rodrigues {\it et al.}~2018 (hereafter R18). Indeed, R18 was the first work that, in order to conclude on the universality of the acceleration scale $a_0$, studied the posterior distributions on $a_0$ of a large set of galaxies. As C19 agrees, the credible intervals were found within the Bayesian framework, that is, the marginalized posteriors on $a_0$ were found using Bayes' theorem to update the priors in light of the observational data; this process was done without introducing any approximation. Considering R18, C19 also remarks that: i) better methods to select the nuisance parameters and the corresponding priors could be used; ii) a quality cut based on $χ^2$ values should not be used, and iii) the compatibility of the posteriors should be assessed in a more robust way. In the following, after first clarifying the context of our work, we address these criticisms.

astro-ph.GA↗

arXiv2020

The radial acceleration relation in galaxy clusters

Recently, the discovery of the radial acceleration relation (RAR) in galaxies has been regarded as an indirect support of alternative theories of gravity such as Modified Newtonian Dynamics (MOND) and modified gravity. This relation indicates a tight correlation between dynamical mass and baryonic mass in galaxies with different sizes and morphology. However, if the RAR relation is scale-independent and could be explained by alternative theories of gravity, this relation should be universal and true for galaxy clusters as well. In this article, by using the x-ray data of a sample of galaxy clusters, we investigate if there exists any tight correlation between dynamical mass and baryonic mass in galaxy clusters, assuming hot gas mass distribution almost representing baryonic distribution and that the galaxy clusters are virialized. We show that the resulting RAR of 52 non-cool-core galaxy clusters scatters in a large parameter space, possibly due to our simplifying assumptions and unclear matter content in galaxy clusters. This might indicate that the RAR is unlikely to be universal and scale-independent.

astro-ph.GA↗

arXiv2019

Halo collapse: virialization by shear and rotation in dynamical dark-energy models. Effects on weak-lensing peaks

The evolution of the virial overdensity $Δ_{\rm vir}$ for $Λ$CDM and seven dynamical dark-energy models is investigated in the extended spherical collapse model (SCM). Here the virialization process is naturally achieved by introducing shear and rotation instead of using the virial theorem. We generalise two approaches proposed in the literature and show that, regardless of the dark-energy model, the new virialization term can be calibrated on the peculiar velocity of the shell as measured from Einstein-de Sitter simulations. The two virialization recipes qualitatively reproduce the features of the ordinary SCM, i.e., a constant $Δ_{\rm vir}$ for the EdS model and time-variation for dark-energy models, but without any mass dependence. Depending on the actual description of virialization and on the dark-energy model, the value of $Δ_{\rm vir}$ varies between 10 and 40 percent. We use the new recipes to predict the surface-mass-density profile of dark matter haloes and the number of convergence density peaks for LSST- and Euclid-like weak lensing surveys.

astro-ph.CO↗

arXiv2019

Mass-Temperature relation in $Λ$CDM and modified gravity

We derive the mass-temperature relation using an improved top-hat model and a continuous formation model which takes into account the effects of the ordered angular momentum acquired through tidal-torque interaction between clusters, random angular momentum, dynamical friction, and modifications of the virial theorem to include an external pressure term usually neglected. We show that the mass-temperature relation differs from the classical self-similar behavior, $M \propto T^{3/2}$, and shows a break at $3--4$ keV, and a steepening with a decreasing cluster temperature. We then compare our mass-temperature relation with those obtained in the literature with $N$-body simulations for $f(R)$ and symmetron models. We find that the mass-temperature relation is not a good probe to test gravity theories beyond Einstein's general relativity, because the mass-temperature relation of the $Λ$CDM model is similar to that of the modified gravity theories.

astro-ph.CO↗