MOND and IMF variations in early-type galaxies from ATLAS3D

MOdified Newtonian dynamics (MOND) represents a phenomenological alternative to dark matter (DM) for the missing mass problem in galaxies and clusters of galaxies. We analyze the central regions of a local sample of $\sim 220$ early-type galaxies from the $\rm ATLAS^{3D}$ survey, to see if the data can be reproduced without recourse to DM. We estimate dynamical masses in the MOND context through Jeans analysis, and compare to $\rm ATLAS^{3D}$ stellar masses from stellar population synthesis. We find that the observed stellar mass--velocity dispersion relation is steeper than expected assuming MOND with a fixed stellar initial mass function (IMF) and a standard value for the acceleration parameter $a_{\rm 0}$. Turning from the space of observables to model space, a) fixing the IMF, a universal value for $a_{\rm 0}$ cannot be fitted, while, b) fixing $a_{\rm 0}$ and leaving the IMF free to vary, we find that it is "lighter" (Chabrier-like) for low-dispersion galaxies, and "heavier" (Salpeter-like) for high dispersions. This MOND-based trend matches inferences from Newtonian dynamics with DM, and from detailed analysis of spectral absorption lines, adding to the converging lines of evidence for a systematically-varying IMF.Comment: 6 pages, 3 figures, accepted for publication on MNRAS Letters, typos corrected and further references adde

Dark matter scaling relations in intermediate z haloes

We investigate scaling relations between the dark matter (DM) halo model parameters for a sample of intermediate-redshift early-type galaxies (ETGs) resorting to a combined analysis of Einstein radii and aperture velocity dispersions. Modelling the dark halo with a Navarro-Frenk-White profile and assuming a Salpeter initial mass function (IMF) to estimate stellar masses, we find that the column density and the Newtonian acceleration within the halo characteristic radius rs and effective radius Reff are not universal quantities, but correlate with the luminosity LV, the stellar mass M★ and the halo mass M200, contrary to recent claims in the literature. We finally discuss a tight correlation among the DM mass MDM(Reff) within the effective radius Reff, the stellar mass M★(Reff) and Reff itself. The slopes of the scaling relations discussed here strongly depend, however, on the DM halo model and the IMF adopted so that these ingredients have to be better constrained in order to draw definitive conclusions on the DM scaling relations for ETG

Colour and stellar population gradients in galaxies

We discuss the colour, age and metallicity gradients in a wide sample of local SDSS early- and late-type galaxies. From the fitting of stellar population models we find that metallicity is the main driver of colour gradients and the age in the central regions is a dominant parameter which rules the scatter in both metallicity and age gradients. We find a consistency with independent observations and a set of simulations. From the comparison with simulations and theoretical considerations we are able to depict a general picture of a formation scenario.Comment: 4 pages, 4 figures. Proceedings of 54th Congresso Nazionale della SAIt, Napoli 4-7 May 201

Dynamical and gravitational lensing properties of a new phenomenological model of elliptical galaxies

Recent observations of the line of sight velocity profile of elliptical galaxies have furnished controversial results with some works favouring the presence of a large amount of dark matter in the outer regions and others arguing in favour of no dark matter at all. In order to shed new light on this controversy, we propose here a new phenomenological description of the total mass profile of galaxies. Under the hypothesis of spherical symmetry, we assume a double power-law expression for the global M/L ratio Upsilon(r)= Upsilon_0(r/r_0) ^{alpha}(1+r/r_0)^{beta}. In particular, Upsilon propto r^{alpha} for r/r_01 so that alpha1), Upsilon propto r^{alpha+beta} thus showing that models with alpha+beta=0 have an asymptotically constant M/L ratio. A wide range of possibilities is obtained by varying the slope parameters in the range we determine on the basis of physical considerations. Choosing a general expression for the luminosity density profile j(r), we work out an effective galaxy model that accounts for all the phenomenology observed in real elliptical galaxies. We derive the main dynamics and lensing properties of such an effective model. We analyze a general class of models, able to take into account different dynamical trends. We are able to obtain analytical expressions for the main dynamical and lensing quantities. We show that constraining the values of alpha+beta makes it possible to analyze the problem of the dark matter in elliptical galaxies. Indeed, positive values of alpha+beta would be a strong evidence for dark matter. Finally we indicate possible future approaches in order to face the observational data, in particular using velocity dispersion profiles and lensed quasar events

Cosmology and the Hubble Constant: On the Megamaser Cosmology Project (MCP)

The Hubble constant Ho describes not only the expansion of local space at redshift z ~ 0, but is also a fundamental parameter determining the evolution of the universe. Recent measurements of Ho anchored on Cepheid observations have reached a precision of several percent. However, this problem is so important that confirmation from several methods is needed to better constrain Ho and, with it, dark energy and the curvature of space. A particularly direct method involves the determination of distances to local galaxies far enough to be part of the Hubble flow through water vapor (H2O) masers orbiting nuclear supermassive black holes. The goal of this article is to describe the relevance of Ho with respect to fundamental cosmological questions and to summarize recent progress of the the `Megamaser Cosmology Project' (MCP) related to the Hubble constant.Comment: 10 pages, 7 postscript figures (8 ps files), IAU Symposium 287, uses iaus.cl

Flour from sprouted wheat as a new ingredient in bread-making

Despite the nutritional and sensory improvements associated with sprouted grains, their use in baking has been limited until recently. Indeed, severe and uncontrolled grain sprouting induces high accumulations of enzymatic activities that negatively affect dough rheology and baking performance. In this study, wheat was sprouted under controlled conditions and the effects of enrichment (i.e. 15%, 25%, 33%, 50%, 75% and 100%) of the related refined flour (SWF) on dough rheological properties, baking performances and starch digestibility were assessed. Adding SWF to flour significantly decreased dough water absorption, development time, and stability during mixing, which suggests a weakening of the gluten network. However, no significant changes in mixing properties and gluten aggregation kinetics were measured from 25 to 75% SWF. Regardless of the amount added, SWF improved dough development and gas production during leavening. Decreases in gas retention did not compromise bread-making performances. The best result – in terms of bread volume and crumb porosity – was obtained with 50% SWF instead of using SWF alone. Interestingly, in 100 % SWF bread the slowly digestible starch fraction significantly increased

Dark matter scaling relations in intermediate z haloes

We investigate scaling relations between the dark matter (DM) halo model parameters for a sample of intermediate redshift early - type galaxies (ETGs) resorting to a combined analysis of Einstein radii and aperture velocity dispersions. Modeling the dark halo with a Navarro - Frenk - White profile and assuming a Salpeter initial mass function (IMF) to estimate stellar masses, we find that the column density ${\cal{S}}$ and the Newtonian acceleration within the halo characteristic radius $r_s$ and effective radius $R_{eff}$ are not universal quantities, but correlate with the luminosity $L_V$, the stellar mass $M_{\star}$ and the halo mass $M_{200}$, contrary to recent claims in the literature. We finally discuss a tight correlation among the DM mass $M_{DM}(R_{eff})$ within the effective radius $R_{eff}$, the stellar mass $M_{\star}(R_{eff})$ and $R_{eff}$ itself. The slopes of the scaling relations discussed here strongly depend, however, on the DM halo model and the IMF adopted so that these ingredients have to be better constrained in order to draw definitive conclusions on the DM scaling relations for ETGs.Comment: 8 pages, 1 figure, 4 tables, MNRAS submitted version (including corrections after the referee report

Secondary infall model and dark matter scaling relations in intermediate-redshift early-type galaxies

Scaling relations among dark matter (DM) and stellar quantities are a valuable tool to constrain formation scenarios and the evolution of galactic structures. However, most of the DM properties are actually not directly measured, but derived through model-dependent mass-mapping procedures. It is therefore crucial to adopt theoretically and observationally well founded models. We use here an updated version of the secondary infall model (SIM) to predict the halo density profile, taking into account the effects of angular momentum, dissipative friction and baryons collapse. The resulting family of halo profiles depends only on one parameter, the virial mass, and nicely fits the projected mass and aperture velocity dispersion of a sample of intermediate redshift lens galaxies. We derive DM-related quantities (namely the column density and the Newtonian acceleration) and investigate their correlations with stellar mass, luminosity, effective radius and virial mas

Secondary infall model and dark matter scaling relations in intermediate redshift early - type galaxies

Scaling relations among dark matter (DM) and stellar quantities are a valuable tool to constrain formation scenarios and the evolution of galactic structures. However, most of the DM properties are actually not directly measured, but derived through model dependent mass mapping procedures. It is therefore crucial to adopt theoretically and observationally well founded models. We use here an updated version of the secondary infall model (SIM) to predict the halo density profile, taking into account the effects of angular momentum, dissipative friction and baryons collapse. The resulting family of halo profiles depends on one parameter only, the virial mass, and nicely fits the projected mass and aperture velocity dispersion of a sample of intermediate redshift lens galaxies. We derive DM related quantities (namely the column density and the Newtonian acceleration) and investigate their correlations with stellar mass, luminosity, effective radius and virial mass.Comment: 15 pages, 3 figures, 2 tables, accepted for publication on MNRA