86 research outputs found
Chemical evolution of the bulge of M31: predictions about abundance ratios
We aim at reproducing the chemical evolution of the bulge of M31 by means of
a detailed chemical evolution model, including radial gas flows coming from the
disk. We study the impact of the initial mass function, the star formation rate
and the time scale for bulge formation on the metallicity distribution function
of stars. We compute several models of chemical evolution using the metallicity
distribution of dwarf stars as an observational constraint for the bulge of
M31. Then, by means of the model which best reproduces the metallicity
distribution function, we predict the [X/Fe] vs. [Fe/H] relations for several
chemical elements (O, Mg, Si, Ca, C, N). Our best model for the bulge of M31 is
obtained by means of a robust statistical method and assumes a Salpeter initial
mass function, a Schmidt-Kennicutt law for star formation with an exponent
k=1.5, an efficiency of star formation of , and an
infall timescale of Gyr. Our results suggest that the bulge
of M31 formed very quickly by means of an intense star formation rate and an
initial mass function flatter than in the solar vicinity but similar to that
inferred for the Milky Way bulge. The [/Fe] ratios in the stars of the
bulge of M31 should be high for most of the [Fe/H] range, as is observed in the
Milky Way bulge. These predictions await future data to be proven.Comment: Accepted for publication by MNRA
The effect of differential galactic winds on the chemical evolution of galaxies
(Abridged) The aim of this paper is to study the basic equations of the
chemical evolution of galaxies with gas flows. We focus on models in which the
outflow is differential, namely in which the heavy elements (or some of the
heavy elements) can leave the parent galaxy more easily than other chemical
species such as H and He. We study the chemical evolution of galaxies in the
framework of simple models. This allows us to solve analytically the equations
for the evolution of gas masses and metallicities. We find new analytical
solutions for various cases in which the effects of winds and infall are taken
into account. Differential galactic winds have the effect of reducing the
global metallicity of a galaxy, with the amount of reduction increasing with
the ejection efficiency of the metals. Abundance ratios are predicted to remain
constant throughout the whole evolution of the galaxy, even in the presence of
differential winds. One way to change them is by assuming differential winds
with different ejection efficiencies for different elements. However, simple
models apply only to elements produced on short timescales, namely all by Type
II SNe, and therefore large differences in the ejection efficiencies of
different metals are unlikely. Variations in abundance ratios such as [O/Fe] in
galaxies, without including the Fe production by Type Ia supernovae, can in
principle be obtained by assuming an unlikely different efficiency in the loss
of O relative to Fe from Type II supernovae. Therefore, we conclude that it is
not realistic to ignore Type Ia supernovae and that the delayed production of
some chemical elements relative to others (time-delay model) remains the most
plausible explanation for the evolution of alpha-elements relative to Fe.Comment: 11 pages, 10 figures, A&A accepte
Is right angular gyrus involved in the metric component of the mental body representation in touch and vision? A tdcs study
Several studies have found in the sense of touch a good sensory modality by which to study body representation. Here, we address the âmetric component of body representationâ, a specific function developed to process the discrimination of tactile distances on the body. The literature suggests the involvement of the right angular gyrus (rAG) in processing the tactile metricity on the body. The question of this study is the following: is the rAG also responsible for the visual metric component of body representation? We used tDCS (anodal and sham) in 20 subjects who were administered an on-body distance discrimination task with both tactile and visual stimuli. They were also asked to perform the same task in a near-body condition. The results allow us to confirm the role of rAG in the estimation of tactile distances. Further, we also showed that rAG might be involved in the discrimination of distances on the body not only in tactile but also in visual modality. Finally, based on the significant effects of anodal stimulation even in a near-body visual discrimination task, we proposed a higher-order function of the AG in terms of a supramodal com-parator of quantities
Is the IMF in ellipticals bottom-heavy? Clues from their chemical abundances
© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.We tested the implementation of different initial mass functions (IMFs) in our model for the chemical evolution of ellipticals, with the aim of reproducing the observed relations of [Fe/H] and [Mg/Fe] abundances with galaxy mass in a sample of early-type galaxies selected from the SPIDER-SDSS catalogue. Abundances in the catalogue were derived from averaged spectra, obtained by stacking individual spectra according to central velocity dispersion, as a proxy of galaxy mass. We tested IMFs already used in a previous work, as well as two new models, based on low-mass tapered (âbimodalâ) IMFs, where the IMF becomes either (1) bottom-heavy in more massive galaxies, or (2) is time-dependent, switching from top-heavy to bottom-heavy in the course of galactic evolution. We found that observations could only be reproduced by models assuming either a constant, Salpeter IMF, or a time-dependent distribution, as other IMFs failed. We further tested the models by calculating their M/L ratios. We conclude that a constant, time-independent bottom-heavy IMF does not reproduce the data, especially the increase of the [α/Fe] ratio with galactic stellar mass, whereas a variable IMF, switching from top to bottom-heavy, can match observations. For the latter models, the IMF switch always occurs at the earliest possible considered time, i.e. tswitch = 0.1 Gyr.Peer reviewe
The thick disk rotation-metallicity correlation as a fossil of an "inverse chemical gradient" in the early Galaxy
The thick disk rotation--metallicity correlation, \partial
V_\phi/\partial[Fe/H] =40\div 50 km s^{-1}dex^{-1} represents an important
signature of the formation processes of the galactic disk. We use
nondissipative numerical simulations to follow the evolution of a Milky Way
(MW)-like disk to verify if secular dynamical processes can account for this
correlation in the old thick disk stellar population. We followed the evolution
of an ancient disk population represented by 10 million particles whose
chemical abundances were assigned by assuming a cosmologically plausible radial
metallicity gradient with lower metallicity in the inner regions, as expected
for the 10-Gyr-old MW. Essentially, inner disk stars move towards the outer
regions and populate layers located at higher |z|. A rotation--metallicity
correlation appears, which well resembles the behaviour observed in our Galaxy
at a galactocentric distance between 8 kpc and 10 kpc. In particular,we measure
a correlation of \partial V_\phi/\partial[Fe/H]\simeq 60 km s^{-1}dex^{-1} for
particles at 1.5 kpc < |z| < 2.0 kpc that persists up to 6 Gyr. Our pure N-body
models can account for the V_\phi vs. [Fe/H] correlation observed in the thick
disk of our Galaxy, suggesting that processes internal to the disk such as
heating and radial migration play a role in the formation of this old stellar
component. In this scenario, the positive rotation-metallicity correlation of
the old thick disk population would represent the relic signature of an ancient
"inverse" chemical (radial) gradient in the inner Galaxy, which resulted from
accretion of primordial gas.Comment: Accepted for publication on Astronomy and Astrophysic
Italian version of the pittsburgh rehabilitation participation scale: Psychometric analysis of validity and reliability
Patientâs active participation in therapy is a key component of successful rehabilitation. In fact, low participation has been shown to be a prognostic factor of poor outcome; however, participation is rarely assessed in clinical settings. The Pittsburgh Rehabilitation Participation Scale (PRPS) is a validated, quick, and accurate measure of participation, relying on cliniciansâ observation, and not requiring any self-report by patients. The aim of this study was to validate an Italian version of the PRPS. Following forward and back-translation of PRPS into Italian, the translated version was validated in a total of 640 therapy sessions, related to a cohort of 32 patients admitted to an Italian hospital. It was tested for concurrent validity, finding significant correlations with Barthel Index (R > 0.58, p < 0.001) and SF-36 Physical and Mental Health (R > 0.4, p < 0.02), for predictive validity, finding significant correlation with the effectiveness of rehabilitation (R = 0.358, p = 0.045), and for inter-rater and intra-rater reliability, computing an Intra-class correlation coefficient (ICC = 0.926 and 0.756, respectively). These psychometric properties results were similar to those of the original version of this scale. The proposed PRPS can be helpful for Italian clinicians in the assessment of patientâs participation during rehabilitation
Detailed abundance trends in the inner Galactic bulge
In this paper, we aim to derive high-precision alpha-element abundances using
CRIRES high-resolution IR spectra of 72 cool M giants of the inner Galactic
bulge. Silicon, magnesium, and calcium abundances were determined by fitting a
synthetic spectrum for each star. We also incorporated recent theoretical data
into our spectroscopic analysis (i.e. updated K-band line list, better
broadening parameter estimation, non-local thermodynamic equilibrium (NLTE)
corrections). We compare these inner bulge alpha abundance trends with those of
solar neighbourhood stars observed with IGRINS using the same line list and
analysis technique; we also compare our sample to APOGEE DR17 abundances for
inner bulge stars. We investigate bulge membership using spectro-photometric
distances and orbital simulations. We construct a chemical-evolution model that
fits our metallicity distribution function (MDF) and our alpha-element trends.
Among our 72 stars, we find four that are not bulge members. [Si/Fe] and
[Mg/Fe] versus [Fe/H] trends show a typical thick disc alpha-element behaviour,
except that we do not see any plateau at supersolar metallicities as seen in
other works. The NLTE analysis lowers [Mg/Fe] typically by 0.1 dex,
resulting in a noticeably lower trend of [Mg/Fe] versus [Fe/H]. The derived
[Ca/Fe] versus [Fe/H] trend has a larger scatter than those for Si and Mg, but
is in excellent agreement with local thin and thick disc trends. With our
updated analysis, we constructed one of the most detailed studies of the alpha
abundance trends of cool M giants in the inner Galactic bulge. We modelled
these abundances by adopting a two-infall chemical-evolution model with two
distinct gas-infall episodes with timescales of 0.4 Gyr and 2 Gyr,
respectively. Based on a very meticulous spectral analysis, we have constructed
detailed and precise chemical abundances of Mg, Si, and Ca for cool M giants.Comment: 19 pages, 11 figure
Beyond the two-infall model I. Indications for a recent gas infall with Gaia DR3 chemical abundances
The recent Gaia Data Release 3 (DR3) represents an unparalleled revolution in
Galactic Archaeology, providing us with numerous radial velocities chemical
abundances for millions of stars, with all-sky coverage. We present a new
chemical evolution model for the Galactic disc components (high- and low-
sequence stars) designed to reproduce the new abundance ratios
provided by the GSP-spec module for the Gaia DR3 and also constrained by the
detailed star formation histories for both the thick and thin disc stars
inferred from previous Gaia releases. Sophisticated modeling based on previous
Gaia releases has found evidence for narrow episodes of enhanced SF inferred in
recent time. Additionally, Gaia DR3 highlighted the presence of young (massive)
low- disc stars which show evidence of a recent chemical impoverishment
in several elements. Hence, in this study, we compare Gaia DR3 chemical
abundances with the predictions of a three-infall chemical evolution model for
the high- and low- components. The proposed three-infall chemical
evolution model nicely reproduces the main features of the abundance ratio
[X/Fe] versus [M/H] (X=Mg, Si, Ca, Ti, ) of Gaia DR3 stars in different
age bins for the considered elements. Moreover, the most recent gas
infall - which started 2.7 Gyr ago - allows us to predict well the Gaia
DR3 young population which has experienced a recent chemical impoverishment.Comment: Accepted for publication in Astronomy and Astrophysics (A&A), 17
pages, 16 figure
Emotional susceptibility trait modulates insula responses and functional connectivity in flavor processing
The present study aimed at investigating the relationship between Emotional Susceptibility (ES), an aspect of the personality trait Neuroticism, and individual differences in the neural responses in anterior insula to primary sensory stimuli colored by affective valence, i.e., distasting or pleasantly tasting oral stimuli. In addition, it was studied whether intrinsic functional connectivity patterns of brain regions characterized by such differential responses could be related to ES. To this purpose 25 female participants underwent functional magnetic resonance imaging scanning, while being involved in a flavor experiment. During the experiment, flavor stimuli were administered consisting of small amounts of liquid with a different affective valence: neutral, pleasant, unpleasant. The results showed that individual differences in ES trait predicted distinct neural activity patterns to the different stimulus conditions in a region of left anterior insula that a previous meta-analysis revealed to be linked with olfacto-gustatory processing. Specifically, low ES was associated with enhanced neural responses to both pleasant and unpleasant stimuli, compared to neutral stimuli. By contrast, high ES participants showed equally strong neural responses to all types of stimuli without differentiating between the neutral and affective stimuli. Finally, during a task-free state, high ES trait appeared also to be related to decreased intrinsic functional connectivity between left anterior insula and left cerebellum. Our findings show that individual differences in ES are associated with differential anterior insula responses to primary sensory (flavor) stimuli as well as to intrinsic functional cortico-cerebellar connectivity, the latter suggesting a basis in the brain intrinsic functional architecture of the regulation of emotional experiences
The cerium content of the Milky Way as revealed by Gaia DR3 GSP-Spec abundances
The recent Gaia Third Data Release contains a homogeneous analysis of
millions of high-quality Radial Velocity Spectrometer (RVS) stellar spectra by
the GSP-Spec module. This lead to the estimation of millions of individual
chemical abundances and allows us to chemically map the Milky Way. Among the
published GSP-Spec abundances, three heavy-elements produced by
neutron-captures in stellar interiors can be found: Ce, Zr and Nd. We use a
sample of about 30,000 LTE Ce abundances, selected after applying different
combinations of GSP-Spec flags. Thanks to the Gaia DR3 astrometric data and
radial velocities, we explore the cerium content in the Milky Way and, in
particular, in its halo and disc components. The high quality of the Ce
GSP-Spec abundances is quantified thanks to literature comparisons. We found a
rather flat [Ce/Fe] versus [M/H] trend. We also found a flat radial gradient in
the disc derived from field stars and, independently, from about 50 open
clusters, in agreement with previous studies. The [Ce/Fe] vertical gradient has
also been estimated. We also report an increasing [Ce/Ca] vs [Ca/H] in the
disc, illustrating the late contribution of AGB with respect to SN II. Our
cerium abundances in the disc, including the young massive population, are well
reproduced by a new three-infall chemical evolution model. Among the halo
population, the M 4 globular cluster is found to be enriched in cerium.
Moreover, eleven stars with cerium abundances belonging to the Thamnos, Helmi
Stream and Gaia-Sausage-Enceladus accreted systems were identified from
chemo-dynamical diagnostics. We found that the Helmi Stream could be slightly
underabundant in cerium, compared to the two other systems. This work
illustrates the high quality of the GSP-Spec chemical abundances, that
significantly contributes to unveil the heavy elements evolution history of the
Milky Way.Comment: 15 pages, 10 figures, submitted to A&
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