596 research outputs found

    Unifying static analysis of gravitational structures with a scale-dependent scalar field gravity as an alternative to dark matter

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    Aims. We investigated the gravitational effects of a scalar field within scalar-tensor gravity as an alternative to dark matter. Motivated by chameleon, symmetron and f(R)-gravity models, we studied a phenomenological scenario where the scalar field has both a mass (i.e. interaction length) and a coupling constant to the ordinary matter which scale with the local properties of the considered astrophysical system. Methods. We analysed the feasibility of this scenario using the modified gravitational potential obtained in its context and applied it to the galactic and hot gas/stellar dynamics in galaxy clusters and elliptical/spiral galaxies respectively. This is intended to be a first step in assessing the viability of this new approach in the context of "alternative gravity" models. Results. The main results are: 1. the velocity dispersion of elliptical galaxies can be fitted remarkably well by the suggested scalar field, with model significance similar to a classical Navarro-Frenk-White dark halo profile; 2. the analysis of the stellar dynamics and the gas equilibrium in elliptical galaxies has shown that the scalar field can couple with ordinary matter with different strengths (different coupling constants) producing and/or depending on the different clustering state of matter components; 3. elliptical and spiral galaxies, combined with clusters of galaxies, show evident correlations among theory parameters which suggest the general validity of our results at all scales and a way toward a possible unification of the theory for all types of gravitational systems we considered. All these results demonstrate that the proposed scalar field scenario can work fairly well as an alternative to dark matter.Comment: 23 pages, 15 figures, 5 tables, accepted for publication on Astronomy & Astrophysic

    The Grassmann Space of a Planar Space

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    AbstractIn this paper we give a characterization of the Grassmann space of a planar space

    Happy PIIGS

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    This paper investigates the causality dynamics between happiness and per capita GDP growth and the impact of the recent financial crisis using a VAR-GARCH model for 10 European EMU countries divided in peripheral and non-peripheral members. The rationale of the analysis is to look at the two different dimensions (mean and variance) of economic growth and happiness within a time-series framework.The results show that GDP growth has significant positive effects on happiness in all countries considered, particularly in the PIIGS countries; happiness volatility responds positively to economic uncertainty. The size of this effect is bigger following the most recent crisis period, especially for the PIIGS countries. Our findings confirm the important role played by economic growth in determining population happiness and, most importantly, provides new evidence on the existence of causality linkages between economic uncertainty and happiness volatility

    The central dark matter content of early-type galaxies: scaling relations and connections with star formation histories

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    We examine correlations between masses, sizes and star formation histories for a large sample of low-redshift early-type galaxies, using a simple suite of dynamical and stellar population models. We confirm an anticorrelation between the size and stellar age and go on to survey for trends with the central content of dark matter (DM). An average relation between the central DM density and galaxy size of 〈ρDM〉∝R−2eff provides the first clear indication of cuspy DM haloes in these galaxies - akin to standard Λ cold dark matter haloes that have undergone adiabatic contraction. The DM density scales with galaxy mass as expected, deviating from suggestions of a universal halo profile for dwarf and late-type galaxies. We introduce a new fundamental constraint on galaxy formation by finding that the central DM fraction decreases with stellar age. This result is only partially explained by the size-age dependencies, and the residual trend is in the opposite direction to basic DM halo expectations. Therefore, we suggest that there may be a connection between age and halo contraction and that galaxies forming earlier had stronger baryonic feedback, which expanded their haloes, or lumpier baryonic accretion, which avoided halo contraction. An alternative explanation is a lighter initial mass function for older stellar population

    An Ultra diffuse Galaxy in the NGC 5846 group from the VEGAS survey

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    Many ultra diffuse galaxies (UDGs) have now been identified in clusters of galaxies. However, the number of nearby UDGs suitable for detailed follow-up remain rare. Our aim is to begin to identify UDGs in the environments of nearby bright early-type galaxies from the VEGAS survey. Here we use a deep g band image of the NGC 5846 group, taken as part of the VEGAS survey, to search for UDGs. We found one object with properties of a UDG if it associated with the NGC 5846 group, which seems likely. The galaxy, we name NGC 5846_\_UDG1, has an absolute magnitude of Mg_g = -14.2, corresponding to a stellar mass of \sim108^8 M_{\odot}. It also reveals a system of compact sources which are likely globular clusters. Based on the number of globular clusters detected we estimate a halo mass that is greater than 8×\times1010^{10} M_{\odot} for UDG1.Comment: 5 pages, 4 figures, accepted for publication in A&

    villas on islands cost effective energy refurbishment in mediterranean coastline houses

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    Abstract This paper aims to underline the variability of constructions in Mediterranean regions, where different climates, architectural techniques and kinds of building uses determine different optimal energy refurbishments of residential buildings placed on the coastline. More in detail, by considering two different construction technologies (i.e., a lightweight house in reinforced concrete and a massive tuff-made villa), two different climates (Greek coast, climate of Athens and Italian coast, climate of Naples), two cost-optimal energy retrofits are presented. The optimized energy retrofit, performed by coupling transient energy simulations and genetic algorithm for generating improved models, have taken into account all levers of energy efficiency, and thus optimization of building envelope (thermal insulation, reflectance, windows and solar screens), active energy systems (daylight control, HVAC systems for the regulation of indoor conditions) and renewable energy sources at the building scale (namely, solar photovoltaic)

    AMICO galaxy clusters in KiDS-DR3: weak-lensing mass calibration

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    We present the mass calibration for galaxy clusters detected with the AMICO code in KiDS DR3 data. The cluster sample comprises \sim 7000 objects and covers the redshift range 0.1 < zz < 0.6. We perform a weak lensing stacked analysis by binning the clusters according to redshift and two different mass proxies provided by AMICO, namely the amplitude AA (measure of galaxy abundance through an optimal filter) and the richness λ\lambda^* (sum of membership probabilities in a consistent radial and magnitude range across redshift). For each bin, we model the data as a truncated NFW profile plus a 2-halo term, taking into account uncertainties related to concentration and miscentring. From the retrieved estimates of the mean halo masses, we construct the AA-M200M_{200} and the λ\lambda^*-M200M_{200} relations. The relations extend over more than one order of magnitude in mass, down to M2002(5)×1013M/hM_{200} \sim 2 (5) \times 10^{13} M_\odot/h at zz = 0.2 (0.5), with small evolution in redshift. The logarithmic slope is 2.0\sim 2.0 for the AA-mass relation, and 1.7\sim 1.7 for the λ\lambda^*-mass relation, consistent with previous estimations on mock catalogues and coherent with the different nature of the two observables.Comment: 19 pages, 16 figures, accepted by MNRA

    VEGAS: A VST Early-type GAlaxy Survey. III. Mapping the galaxy structure, interactions and intragroup light in the NGC 5018 group

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    Most of the galaxies in the Universe at present day are in groups, which are key to understanding the galaxy evolution. In this work we present a new deep mosaic of 1.2 x 1.0 square degrees of the group of galaxies centered on NGC 5018, acquired at the ESO VLT Survey Telescope. We use u, g, r images to analyse the structure of the group members and to estimate the intra-group light. Taking advantage of the deep and multiband photometry and of the large field of view of the VST telescope, we studied the structure of the galaxy members and the faint features into the intra-group space and we give an estimate of the intragroup diffuse light in the NGC 5018 group of galaxies. We found that ~ 41% of the total g-band luminosity of the group is in the form of intragroup light (IGL). The IGL has a (g - r) color consistent with those of other galaxies in the group, indicating that the stripping leading to the formation of IGL is ongoing. From the study of this group we can infer that there are at least two different interactions involving the group members: one between NGC 5018 and NGC 5022, which generates the tails and ring-like structures detected in the light, and another between NGC 5022 and MCG-03-34-013 that have produced the HI tail. A minor merging event also happened in the formation history of NGC 5018 that have perturbed the inner structure of this galaxy.Comment: 21 pages, 15 figures. Accepted for publication in Ap

    Combined Point of Care Tools Are Able to Improve Treatment Adherence and Health-Related Quality of Life in Patients with Severe Hemophilia: An Observational Prospective Study

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    Introduction: Ultrasound (US) assessment of joints is an evolving point of care tool for the detection of early joint arthropathy (Napolitano M, Kessler CM. Hemophilia A and B. Consultative Hemostasis and Thrombosis, Kitchens, 4th edition); population pharmacokinetic (pop-PK) studies are adopted as a useful instrument to set the prophylaxis regimen for patients with hemophilia, they may improve adherence (Nagao A.et al. Thromb Res. 2019 Jan; 173:79-84) and reduce the annual bleeding rate (ABR). Adherence to continuous intravenous administrations of factor VIII or Factor IX products is challenging, thus patients may experience breakthrough bleedings while on prophylaxis. Repeated US examinations of joint status have recently been advocated to attempt to remedy sub-optimal medication adherence (Di Minno A et al., Blood Rev. 2019 Jan;33:106-116). Aim of the current prospective analysis was to evaluate the impact of combined US assessment and pop-PK study on adherence to treatment and health related quality of life in patients with severe hemophilia A(HA) and B (HB) under regular prophylaxis. Material and methods: This prospective observational study was performed at a single tertiary center from January 2017 to June 2019. Research was conducted following the Helsinki Declaration. All patients included in the study provided a written informed consent for study participation. Patients with severe HA and HB routinely underwent, as part of regular 12-months follow-up visits, the following: US joints evaluation of elbows, knees and ankles using the HEAD-US protocol, treatment adherence evaluation by VERITAS-Pro questionnaire, health –related quality of life assessment by the standardized EQ-5D,EQ-VAS and pop-PK study (WAPPS-Hemo, McMaster University) as needed (i.e.in case of changes in life style, planned treatment switch); each patient visualised US and his estimated PK profile during medial encounters. Compliance to the prescribed treatment was also determined by analysis of patient diaries with infusion logs. Statistical analysis was performed using the SPSS software version 25.0 (SPSS Chicago, IL). Statistical tests were 2-sided, with a significance threshold of 0.05. Results: Twenty consecutive males with severe haemophilia were included in the current analysis, 13 with severe HA, 2 with HA with previous inhibitors and 5 HB, with a median age of 30 (range 14- 56) years and a median ABR of 5 (range:0-12). Nine patients were under primary prophylaxis, 8 under secondary prophylaxis and 3 under tertiary prophylaxis, they all self-infused at home. Four patients had one target joint and 3 patients had multiple target joints. For each enrolled subject, HEAD-US score, VERITAS-pro, EQ5D and EQ-VAS score were assessed at enrolment (T0) and at 12 (T12) and 24 (T24) months follow-up visits, respectively. Pop-PK was assessed in 11 patients: in 7 (5 HA,2 HB) it was assessed twice, before and after treatment switch to extended half-life (EHL) products, in 4 it was assessed once to modify prophylaxis treatment schedules for a more active life-style (N=2) or weight changes (N=2). Median ABR was 4 at T12 and 3.8 at T24. Reported breakthrough bleeds at T12 were 14, mainly trauma-related (N= 8) or affecting target joints (N=4), they were not reported at T24 in patients with PK-driven modified schedules (N=4) and in 4 patients under EHL treatments. Mean HEAD-US score at T0 resulted 8 (range:0-16), at T24 it was 6 (range:0-16). Mean Veritas-Pro score values were 42.7 at TO, 40.1 at T12 and 38.7 at T24. At T0, EQ-5D mean utility score was 0.82 (range: 0.68-1), at T24, the mean was 0.87 (range:0.72-1). In detail, at 24 months follow-up, there was a statistically significant (p&lt;0.05) improvement in adherence to treatment with particular reference to the dimensions of communication and skipped doses. A tendency toward improved HEAD-US score, higher adherence and better quality of life scores, was observed in particular in patients switched to EHL products at T24, at a mean of 10 months after switching (range: 6-22 months). Conclusion: Several combined measures of haemophilia treatment monitoring, allowing visual assessment of joints status and PK profile estimates by patients have here shown to improve treatment adherence and quality of life in patients with HA and HB, this may be not only related to new available treatments but also to an increased awareness and education of patients
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