On the basis of a fermionic dark matter model we fit rotation curves of The HI Nearby Galaxy Survey THINGS sample and compare our 3-parametric model to other models widely used in the literature: 2-parametric Navarro--Frenk--White, pseudoisothermal sphere, Burkhert models, and 3-parametric Einasto model, suggested as the new "standard dark matter profile" model in the paper by Chemin et. al., AJ 142 (2011) 109. The results from the fitting procedure provides evidence for an underlying fermionic nature of the dark matter candidate, with rest mass above the keV regime.
Context: The Einasto model has become one of the most popular models for describing the density profile of dark matter haloes. There have been relatively few comprehensive studies on the dynamical structure of the Einasto model, mainly because only a limited number of properties can be calculated analytically. Aims: We want to systematically investigate the photometric and dynamical structure of the family of Einasto models over the entire model parameter space. Methods: We used the SpheCow code to explore the properties of the Einasto model. We systematically investigated how the most importa…
N-body simulations predict that dark matter haloes are described by specific density profiles on both galactic- and cluster-sized scales. Weak gravitational lensing through the measurements of their first and second order properties, shear and flexion, is a powerful observational tool for investigating the true shape of these profiles. One of the three-parameter density profiles recently favoured in the description of dark matter haloes is the Einasto profile. We present exact expressions for the shear and the first and second flexions of Einasto dark matter haloes derived using a Mellin-trans…
We analyse the density profiles of the stellar halo populations in eight Milky-Way mass galaxies, simulated within the $Λ$-Cold Dark Matter scenario. We find that accreted stars can be well-fitted by an Einasto profile, as well as any subsample defined according to metallicity. We detect a clear correlation between the Einasto fitting parameters of the low-metallicity stellar populations and those of the dark matter haloes. The correlations for stars with [Fe/H]$<-3$ allow us to predict the shape of the dark matter profiles within residuals of $\sim 10 $ per cent, in case the contribution from…
We use high resolution N-Body simulations to study the concentration and spin parameters of dark matter haloes in the mass range $10^8\, {\rm M}_{\odot}\, h^{-1} < {\rm M} < 10^{11}\, {\rm M}_{\odot}\, h^{-1}$ and redshifts $5{<}z{<}10$, corresponding to the haloes of galaxies thought to be responsible for reionization. We build a sub-sample of equilibrium haloes and contrast their properties to the full population that also includes unrelaxed systems. Concentrations are calculated by fitting both NFW and Einasto profiles to the spherically-averaged density profiles of individual haloes. After…
The density profiles of dark matter haloes are commonly described by fitting functions such as the NFW or Einasto models, but these approximations break down in the transition region where halos become dominated by newly accreting matter. Here we present a simple, accurate new fitting function that is inspired by the asymptotic shapes of the separate orbiting and infalling halo components. The orbiting term is described as a truncated Einasto profile, $ρ_{\rm orb} \propto \exp \left[-2/α (r / r_{\rm s})^α- 1/β (r / r_{\rm t})^β\right]$, with a five-parameter space of normalization, physically …
A family of spherical halo models with flat circular velocity curves is presented. This includes models in which the rotation curve has a finite central value but declines outwards (like the Jaffe model). It includes models in which the rotation curve is rising in the inner parts, but flattens asymptotically (like the Binney model). The family encompasses models with both finite and singular (cuspy) density profiles. The self-consistent distribution function depending on binding energy $E$ and angular momentum $L$ is derived and the kinematical properties of the models discussed. These really …
The Einasto profile has been successful in describing the density profiles of dark matter haloes in $Λ$CDM N-body simulations. It has also been able to describe multiple components in the surface brightness profiles of galaxies. However, analytically projecting it to calculate quantities under projection is challenging. In this paper, we will see the development of a highly accurate analytical approximation for the mass (or counts) enclosed in an infinitely long cylindrical column for Einasto profiles--also known as the projected mass (or counts)--using a novel methodology. We will then develo…
Cold dark matter haloes consist of a relatively smooth dark matter component as well as a system of bound subhaloes. It is the prevailing practice to include all halo mass, including mass in subhaloes, in studies of halo density profiles. However, often in observational studies satellites are treated as having their own distinct dark matter density profiles in addition to the profile of the host. This difference makes comparisons between theoretical and observed results difficult. In this work we investigate density profiles of the smooth components of host haloes by excluding mass contained w…
We study the scaling relations between dark matter (DM) haloes and galaxy discs using 175 galaxies from the SPARC database. We explore two cosmologically motivated DM halo profiles: the Einasto profile from DM-only simulations and the DC14 profile from hydrodynamic simulations. We fit the observed rotation curves using a Markov Chain Monte Carlo method and break the disc-halo degeneracy using near-infrared photometry and $Λ$CDM-motivated priors. We find that the characteristic volume density $ρ_{\rm s}$ of DM haloes is nearly constant over $\sim$5 decades in galaxy luminosity. The scale radius…
We analyze the cold dark matter density profiles of 54 galaxy halos simulated with FIRE-2 galaxy formation physics, each resolved within $0.5\%$ of the halo virial radius. These halos contain galaxies with masses that range from ultra-faint dwarfs ($M_\star \simeq 10^{4.5} M_{\odot}$) to the largest spirals ($M_\star \simeq 10^{11} M_{\odot}$) and have density profiles that are both cored and cuspy. We characterize our results using a new analytic density profile that extends the standard Einasto form to allow for a pronounced constant-density core in the resolved innermost radius. With one ad…
Simple but flexible dynamical models are useful for many purposes, including serving as the starting point for more complex models or numerical simulations of galaxies, clusters, or dark matter haloes. We present SpheCow, a new light-weight and flexible code that allows one to easily explore the structure and dynamics of any spherical model. Assuming an isotropic or Osipkov-Merritt anisotropic orbital structure, the code can automatically calculate the dynamical properties of any model with either an analytical density profile or an analytical surface density profile as starting point. We have…
We use dark matter only and full hydrodynamical Constrained Local UniversE Simulations (CLUES) of the formation of the Local Group to study the density profile of subhaloes of the simulated Milky Way and Andromeda galaxies. We show that the Einasto model provides the best description of the subhaloes' density profile, as opposed to the more commonly used NFW profile or any generalisation of it. We further find that the Einasto shape parameter \nEin\ is strongly correlated with the total subhalo mass, pointing towards the notion of a non-universality of the subhaloes' density profile. We observ…
Discoveries of extended rotation curves have suggested the presence of dark matter in spiral galaxy haloes. It has led to many studies that estimated the galaxy total mass, mostly by using the Navarro Frenk and White (NFW) density profile. We aim at verifying how the choice of the dark-matter profile may affect the predicted values of extrapolated total masses. We have considered the recent Milky Way (MW) rotation curve, firstly because of its unprecedented accuracy, and secondly because the Galactic disk is amongst the least affected by past major mergers having fully reshaped the initial dis…
By means of high resolution 2D hydrodynamical simulations, we study the evolution of the hot ISM for a large set of early-type galaxy models, characterized by various degrees of flattening and internal rotation. The galaxies are described by state-of-the-art axisymmetric two-component models, tailored to reproduce real systems; the dark matter haloes follow the Navarro-Frenk-White or the Einasto profile. The gas is produced by the evolving stars, and heated by Type Ia SNe. We find that, in general, the rotation field of the ISM in rotating galaxies is very similar to that of the stars, with a …
While N-body simulations testify for a cuspy profile of the central region of the dark matter haloes, observations favor a shallow, cored density profile of the central region of, at least, some spiral galaxies and dwarf spheroidals. We show that a central profile, very close to the observed one, inevitably forms in the center of dark matter haloes if we make a supposition about a moderate energy relaxation of the system during the halo formation. If we assume the energy exchange between dark matter particles during the halo collapse to be not too intensive, the profile is universal: it depend…
A large body of work based on collisionless cosmological N-body simulations going back over two decades has advanced the idea that collapsed dark matter haloes have simple and approximately universal forms for their mass density and pseudo-phase space density (PPSD) distributions. However, a general consensus on the physical origin of these results has not yet been reached. In the present study, we explore to what extent the apparent universality of these forms holds when we vary the initial conditions (i.e., the primordial power spectrum of density fluctuations) away from the standard CMB-nor…
Several lines of evidence suggest that as dark matter haloes grow their scale radius increases, and that the density in their central region drops. Major mergers seem an obvious mechanism to explain both these phenomena, and the resulting patterns in the concentration--mass--redshift relation. To test this possibility, we have simulated equal-mass mergers between haloes with a variety of cosmological density profiles, placed on various different orbits. The remnants typically have higher densities than the initial conditions, but differ only slightly from self-similar scaling predictions. They…
The disparity between the density profiles of galactic dark matter haloes predicted by dark matter only cosmological simulations and those inferred from rotation curve decomposition, the so-called cusp-core problem, suggests that baryonic physics has an impact on dark matter density in the central regions of galaxies. Feedback from black holes, supernovae and massive stars may each play a role by removing matter from the centre of the galaxy on shorter timescales than the dynamical time of the dark matter halo. Our goal in this paper is to determine constraints on such feedback scenarios based…
The Andromeda galaxy (M31) contains a box/peanut bulge (BPB) entangled with a classical bulge (CB) requiring a triaxial modelling to determine the dynamics, stellar and dark matter mass. We construct made-to-measure models fitting new VIRUS-W IFU bulge stellar kinematic observations, the IRAC-3.6$μ$m photometry, and the disc's HI rotation curve. We explore the parameter space for the 3.6$μ$m mass-to-light ratio $(Υ_{3.6})$, the bar pattern speed ($Ω_p$), and the dark matter mass in the composite bulge ($M^B_{DM}$) within 3.2kpc. Considering Einasto dark matter profiles, we find the best models…
Well-motivated elementary particle candidates for the dark matter, such as the sterile neutrino, behave as warm dark matter (WDM).For particle masses of order a keV, free streaming produces a cutoff in the linear fluctuation power spectrum at a scale corresponding to dwarf galaxies. We investigate the abundance and structure of WDM haloes and subhaloes on these scales using high resolution cosmological N-body simulations of galactic haloes of mass similar to the Milky Way's. On scales larger than the free-streaming cutoff, the initial conditions have the same power spectrum and phases as one o…
We introduce a very simple model of a dark halo. It is a close relative of Hernquist's model, being generated by the same transformation but this time applied to the logarithmic potential rather than the point mass. The density is proportional to (distance)$^{-1}$ at small radii, whilst the rotation curve is flat at large radii. Isotropic and radially anisotropic distributions functions are readily found, and the intrinsic and line of sight kinematical quantities are available as simple formulae. We also provide an analytical approximation to the Hamiltonian as a function of the actions. As an…
We have performed a series of numerical experiments to investigate how the primordial thermal velocities of fermionic dark matter particles affect the physical and phase space density profiles of the dark matter haloes into which they collect. The initial particle velocities induce central cores in both profiles, which can be understood in the framework of phase space density theory. We find that the maximum coarse-grained phase space density of the simulated haloes (computed in 6 dimensional phase space using the EnBid code) is very close to the theoretical fine-grained upper bound, while the…
Galaxies show different halo scaling relations such as the Radial Acceleration Relation, the Mass Discrepancy Acceleration Relation (MDAR) or the dark matter Surface Density Relation (SDR). At difference with traditional studies using phenomenological $Λ$CDM halos, we analyze the above relations assuming that dark matter (DM) halos are formed through a Maximum Entropy Principle (MEP) in which the fermionic (quantum) nature of the DM particles is dully accounted for. For the first time a competitive DM model based on first physical principles, such as (quantum) statistical-mechanics and thermod…
The AIDA-TNG project: dark matter profiles and concentrations in alternative dark matter models
Alma Mater Studiorum Università di Bologna（博洛尼亚大学）；INAF-Osservatorio di Astrofisica e Scienza dello Spazio di Bologna（博洛尼亚天文物理与空间科学研究所）；INFN-Sezione di Bologna（博洛尼亚意大利国家核物理研究所）；Max-Planck-Institut für Astronomie（马克斯·普朗克天文学研究所）；Massachusetts Institute of Technology（麻省理工学院）
In the first part of this article we expand three fundamental aspects of the methodology connected to the determination of a relation among the spatial density and the gravitational potential that can be specialised to distinct mass density agglomerations. As a consequence, we obtain general relations for the diagonal entries of a square symmetric matrix without zeros, we provide an expression of the gravitational potential, suitable, to represent several different mass density configurations, and we determine relations for the semi-axes of a triaxial spheroidal mass distribution, as a functio…
We explore a function with two shape parameters for the dark-matter halo density profile subject to baryonic effects, which is a special case of the general Zhao family of models applied to simulated dark matter haloes by Dekel et al. This profile has variable inner slope and concentration parameter, and analytic expressions for the gravitational potential, velocity dispersion, and lensing properties. Using the NIHAO cosmological simulations, we find that it provides better fits than the Einasto profile and the generalized NFW profile with variable inner slope, in particular towards the halo c…
The cosmological simulations indicates that the dark matter haloes have specific self similar properties. However the halo similarity is affected by the baryonic feedback, the momentum injected by the supernovae re-shape the dark matter core and transform it to a flat density core, with a scale length imposed by the baryonic feedback. Additionally the baryon feedback impose also an equilibrium condition, which when coupled with the imposed baryonic scale length induce a new type of similarity. The new self similar solution implies that the acceleration generated by dark matter is scale free, w…
We calculate the most stringent constraints up to date on the parameter space for sterile neutrino warm dark matter models possessing a radiative decay channel into X-rays. These constraints arise from the X-ray flux observations from the Galactic center (central parsec), taken by the XMM and NuSTAR missions. We compare the results obtained from using different dark matter density profiles for the Milky Way, such as NFW, Burkert or Einasto, to that produced by the Ruffini-Argüelles-Rueda (RAR) fermionic model, which has the distinct feature of depending on the particle mass. We show that due t…
Triaxiality of the Milky Way dark matter halo and the microlensing optical depth towards the Large Magellanic Cloud
Institute for Astronomy, University of Edinburgh（爱丁堡大学天体物理研究所）；Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK（英国爱丁堡黑福德山皇家天文台）；Instituto de Física Teórica UAM/CSIC, Universidad Autónoma de Madrid（马德里自治大学理论物理研究所）
