Dark Matter Halos: The Dynamical Basis of Effective Empirical Models

We investigate the dynamical basis of the classic empirical models (specifically, Sersic-Einasto and generalized NFW) that are widely used to describe the distributions of collisionless matter in galaxies. We submit that such a basis is provided by our \alpha-profiles, shown to constitute solutions of the Jeans dynamical equilibrium with physical boundary conditions. We show how to set the parameters of the empirical in terms of the dynamical models; we find the empirical models, and specifically Sersic-Einasto, to constitute a simple and close approximation to the dynamical models. Finally, we discuss how these provide an useful baseline for assessing the impact of the small-scale dynamics that may modulate the density slope in the central galaxy regions.Comment: 11 pages, 2 figures, Accepted by Advances in Astronom

Two phase galaxy formation: The Evolutionary Properties of Galaxies

We use our model for the formation and evolution of galaxies within a two-phase galaxy formation scenario, showing that the high-redshift domain typically supports the growth of spheroidal systems, whereas at low redshifts the predominant baryonic growth mechanism is quiescent and may therefore support the growth of a disc structure. Under this framework we investigate the evolving galaxy population by comparing key observations at both low and high-redshifts, finding generally good agreement. By analysing the evolutionary properties of this model, we are able to recreate several features of the evolving galaxy population with redshift, naturally reproducing number counts of massive star-forming galaxies at high redshifts, along with the galaxy scaling relations, star formation rate density and evolution of the stellar mass function. Building upon these encouraging agreements, we make model predictions that can be tested by future observations. In particular, we present the expected evolution to z=2 of the super-massive black hole mass function, and we show that the gas fraction in galaxies should decrease with increasing redshift in a mass, with more and more evolution going to higher and higher masses. Also, the characteristic transition mass from disc to bulge dominated system should decrease with increasing redshift.Comment: 15 pages, 11 figures. Version polished for publication in MNRA

Probing the Astrophysics of Cluster Outskirts

In galaxy clusters the entropy distribution of the IntraCluster Plasma modulates the latter's equilibrium within the Dark Matter gravitational wells, as rendered by our Supermodel. We argue the entropy production at the boundary shocks to be reduced or terminated as the accretion rates of DM and intergalactic gas peter out; this behavior is enforced by the slowdown in the outskirt development at late times, when the Dark Energy dominates the cosmology while the outer wings of the initial perturbation drive the growth. In such conditions, we predict the ICP temperature profiles to steepen into the cluster outskirts. The detailed expectations from our simple formalism agree with the X-ray data concerning five clusters whose temperature profiles have been recently measured out to the virial radius. We predict steep temperature declines to prevail in clusters at low redshift, tempered only by rich environs including adjacent filamentary structures.Comment: 4 pages, 3 figures, uses aa.cls. Typos corrected. Accepted by A&A

Probing the evolution of galaxy clusters with the SZ effect

In galaxy clusters the thermal Sunyaev-Zel'dovich (SZ) effect from the hot intracluster medium (ICM) provides a direct, self-contained measure of the pressure integrated over crossing lines of sight, that is intrinsically independent of redshift and well suited for evolutionary studies. We show in detail how the size of the effect and its pattern on the sky plane are directly related to the entropy levels in the ICM, and how they characterize the cluster cores and outskirts independently. We find that at redshifts z 72 0.3 the signals to be expected in the cores considerably exceed those detected at 10' resolution with the Planck satellite. We propose that at 1' resolutions as implemented on recent ground instrumentation for mapping features in individual clusters, the average patterns of the SZ signals can provide a direct and effective way to find and count cool, low-entropy cores and hot, high-entropy outskirts out to z ~ 2. Such counts will tell the timing and the mode of the processes that drive the evolution of the ICM from the distant to the local cluster population

The Universal Rotation Curve of Spiral Galaxies. II The Dark Matter Distribution out to the Virial Radius

In the current LambdaCDM cosmological scenario, N-body simulations provide us with a Universal mass profile, and consequently a Universal equilibrium circular velocity of the virialized objects, as galaxies. In this paper we obtain, by combining kinematical data of their inner regions with global observational properties, the Universal Rotation Curve (URC) of disk galaxies and the corresponding mass distribution out to their virial radius. This curve extends the results of Paper I, concerning the inner luminous regions of Sb-Im spirals, out to the edge of the galaxy halos.Comment: In press on MNRAS. 10 pages, 8 figures. The Mathematica code for the figures is available at: http://www.novicosmo.org/salucci.asp Corrected typo

Biodistribution and PET Imaging of pharmacokinetics of manganese in mice using Manganese-52

<div><p>Manganese is essential to life, and humans typically absorb sufficient quantities of this element from a normal healthy diet; however, chronic, elevated ingestion or inhalation of manganese can be neurotoxic, potentially leading to <i>manganism</i>. Although imaging of large amounts of accumulated Mn(II) is possible by MRI, quantitative measurement of the biodistribution of manganese, particularly at the trace level, can be challenging. In this study, we produced the positron-emitting radionuclide ⁵²Mn (<i>t</i>_<i>1/2</i> = 5.6 d) by proton bombardment (<i>E</i>_<i>p</i><15 MeV) of chromium metal, followed by solid-phase isolation by cation-exchange chromatography. An aqueous solution of [⁵²Mn]MnCl₂ was nebulized into a closed chamber with openings through which mice inhaled the aerosol, and a separate cohort of mice received intravenous (IV) injections of [⁵²Mn]MnCl₂. <i>Ex vivo</i> biodistribution was performed at 1 h and 1 d post-injection/inhalation (p.i.). In both trials, we observed uptake in lungs and thyroid at 1 d p.i. Manganese is known to cross the blood-brain barrier, as confirmed in our studies following IV injection (0.86%ID/g, 1 d p.i.) and following inhalation of aerosol, (0.31%ID/g, 1 d p.i.). Uptake in salivary gland and pancreas were observed at 1 d p.i. (0.5 and 0.8%ID/g), but to a much greater degree from IV injection (6.8 and 10%ID/g). In a separate study, mice received IV injection of an imaging dose of [⁵²Mn]MnCl₂, followed by <i>in vivo</i> imaging by positron emission tomography (PET) and <i>ex vivo</i> biodistribution. The results from this study supported many of the results from the biodistribution-only studies. In this work, we have confirmed results in the literature and contributed new results for the biodistribution of inhaled radiomanganese for several organs. Our results could serve as supporting information for environmental and occupational regulations, for designing PET studies utilizing ⁵²Mn, and/or for predicting the biodistribution of manganese-based MR contrast agents.</p></div

SuperModel Analysis of A1246 and J255: On the Evolution of Galaxy Clusters from High to Low Entropy States

We present an analysis of high-quality X-ray data out to the virial radius for the two galaxy clusters A1246 and GMBCG J255.34805+64.23661 (J255) by means of our entropy-based SuperModel. For A1246 we find that the spherically averaged entropy profile of the intracluster medium (ICM) progressively flattens outward, and that a nonthermal pressure component amounting to 4820% of the total is required to support hydrostatic equilibrium in the outskirts; there we also estimate a modest value C 48 1.6 of the ICM clumping factor. These findings agree with previous analyses on other cool-core, relaxed clusters, and lend further support to the picture by Lapi et al. that relates the entropy flattening, the development of the nonthermal pressure component, and the azimuthal variation of ICM properties to weakening boundary shocks. In this scenario clusters are born in a high-entropy state throughout, and are expected to develop on similar timescales a low-entropy state both at the center due to cooling, and in the outskirts due to weakening shocks. However, the analysis of J255 testifies how such a typical evolutionary course can be interrupted or even reversed by merging especially at intermediate redshift, as predicted by Cavaliere et al. In fact, a merger has rejuvenated the ICM of this cluster at z 48 0.45 by reestablishing a high-entropy state in the outskirts, while leaving intact or erasing only partially the low-entropy, cool core at the center

A Grand Design for Galaxy Clusters: Connections and Predictions

We take up from a library of 12 galaxy clusters featuring extended X-ray observations of their Intra Cluster Plasma (ICP), analyzed with our entropy-based Supermodel. Its few intrinsic parameters - basically, the central level and the outer slope of the entropy profile - enable us to uniformly derive not only robust snapshots of the ICP thermal state, but also the 'concentration' parameter marking the age of the host dark matter halo. We test these profiles for consistency with numerical simulations and observations. We find the central and the outer entropy to correlate, so that these clusters split into two main classes defined on the basis of low (LE) or high (HE) entropy conditions prevailing throughout the ICP. We also find inverse correlations between the central/outer entropy and the halo concentration. We interpret these in terms of mapping the ICP progress on timescales around 5 Gyr toward higher concentrations, under the drive of the dark matter halo development. The progress proceeds from HEs to LEs, toward states of deeper entropy erosion by radiative cooling in the inner regions, and of decreasing outer entropy production as the accretion peters out. We propose these radial and time features to constitute a cluster Grand Design, that we use here to derive a number of predictions. For HE clusters we predict sustained outer temperature profiles. For LEs we expect the outer entropy ramp to bend over, hence the temperature decline to steepen at low z; this feature goes together with an increasing turbulent support, a condition that can be directly probed with the SZ effect.Comment: 23 pages, 8 figures, 1 table. Typos corrected. Accepted by Ap

Self-Similar Dynamical Relaxation of Dark Matter Halos in an Expanding Universe

We investigate the structure of cold dark matter halos using advanced models of spherical collapse and accretion in an expanding Universe. These base on solving time-dependent equations for the moments of the phase-space distribution function in the fluid approximation; our approach includes non-radial random motions, and most importantly, an advanced treatment of both dynamical relaxation effects that takes place in the infalling matter: phase-mixing associated to shell crossing, and collective collisions related to physical clumpiness. We find self-similar solutions for the spherically-averaged profiles of mass density rho(r), pseudo phase-space density Q(r) and anisotropy parameter beta(r). These profiles agree with the outcomes of state-of-the-art N-body simulations in the radial range currently probed by the latter; at smaller radii, we provide specific predictions. In the perspective provided by our self-similar solutions we link the halo structure to its two-stage growth history, and propose the following picture. During the early fast collapse of the inner region dominated by a few merging clumps, efficient dynamical relaxation plays a key role in producing a closely universal mass density and pseudo phase-space density profiles; in particular, these are found to depend only weakly on the detailed shape of the initial perturbation and the related collapse times. The subsequent inside-out growth of the outer regions feeds on the slow accretion of many small clumps and diffuse matter; thus the outskirts are only mildly affected by dynamical relaxation but are more sensitive to asymmetries and cosmological variance.Comment: 31 pages, 16 figures. Typos corrected. Accepted by Ap

Nonthermal Support for the Outer Intracluster Medium

We submit that nonthermalized support for the outer intracluster medium in relaxed galaxy clusters is provided by turbulence, which is driven by inflows of intergalactic gas across the virial accretion shocks. We expect this component to increase briskly during the cluster development for z \u2a89 1/2, owing to three factors. First, the accretion rates of gas and dark matter subside when they feed on the outer wings of the initial perturbations in the accelerating Universe. Second, the infall speeds decrease across the progressively shallower gravitational potential at the shock position. Third, the shocks eventually weaken and leave less thermal energy to feed the intracluster entropy, but relatively more bulk energy to drive turbulence into the outskirts. The overall outcome from these factors is physically modeled and analytically computed; thus we ascertain how these concur in setting the equilibrium of the outer intracluster medium, and predict how the observables in X-rays and \u3bcwaves are affected, so as to probe the development of outer turbulence over wide cluster samples. By the same token, we quantify the resulting negative bias to be expected in the total mass evaluated from X-ray measurements