178 research outputs found
Spectral properties of the narrow-line region in Seyfert galaxies selected from the SDSS-DR7
Although the properties of the narrow-line region (NLR) of active galactic
nuclei(AGN) have been deeply studied by many authors in the past three decades,
many questions are still open. The main goal of this work is to explore the NLR
of Seyfert galaxies by collecting a large statistical spectroscopic sample of
Seyfert 2 and Intermediate-type Seyfert galaxies having a high signal-to-noise
ratio in order to take advantage of a high number of emission-lines to be
accurately measured. 2153 Seyfert 2 and 521 Intermediate-type Seyfert spectra
were selected from Sloan Digital Sky Survey - Data Release 7 (SDSS-DR7) with a
diagnostic diagram based on the oxygen emission-line ratios. All the
emission-lines, broad components included, were measured by means of a
self-developed code, after the subtraction of the stellar component. Physical
parameters, such as internal reddening, ionization parameter, temperature,
density, gas and stellar velocity dispersion were determined for each object.
Furthermore, we estimated mass and radius of the NLR, kinetic energy of the
ionized gas, and black-hole accretion rate. From the emission-line analysis and
the estimated physical properties, it appears that the NLR is similar in
Seyfert 2 and Intermediate-Seyfert galaxies. The only differences, lower
extinction, gas kinematics in general not dominated by the host galaxy
gravitational potential and higher percentage of [O III]5007 blue asymmetries
in Intermediate-Seyfert can be ascribed to an effect of inclination of our line
of sight with respect to the torus axis.Comment: Accepted for publication in MNRA
The Relation between Nuclear Activity and Stellar Mass in Galaxies
The existence of correlations between nuclear properties of galaxies, such as
the mass of their central black holes, and larger scale features, like the
bulge mass and luminosity, represent a fundamental constraint on galaxy
evolution. Although the actual reasons for these relations have not yet been
identified, it is widely believed that they could stem from a connection
between the processes that lead to black hole growth and stellar mass assembly.
The problem of understanding how the processes of nuclear activity and star
formation can affect each other became known to the literature as the
Starburst-AGN connection. Despite years of investigation, the physical
mechanisms which lie at the basis of this relation are known only in part. In
this work, we analyze the problem of star formation and nuclear activity in a
large sample of galaxies. We study the relations between the properties of the
nuclear environments and of their host galaxies. We find that the mass of the
stellar component within the galaxies of our sample is a critical parameter,
that we have to consider in an evolutionary sequence, which provides further
insight in the connection between AGN and star formation processes.Comment: 13 pages, 10 figures, accepted for publication on MNRAS. Reference to
the mass derivation procedure correcte
Patient safety culture in Italian out-ofhours primary care service: a national cross-sectional survey study
Background: Out-of-hours (OOH) services in Italy provide >10 million consultations every year. To the authors' knowledge, no data on patient safety culture (PSC) have been reported. Aim: To assess PSC in the Italian OOH setting. Design & setting: National cross-sectional survey using the Safety Attitudes Questionnaire â Ambulatory Version (SAQ-AV). Method: The SAQ-AV was translated into Italian and distributed in a convenience sample of OOH doctors in 2015. Answers were collected anonymously by Qualtrics. Stata (version 14) was used to estimate Cronbach's alpha, perform exploratory and confirmatory factor analysis, correlate items to doctors' characteristics, and to do item descriptive analysis. Results: Overall, 692 OOH doctors were contacted, with a 71% response rate. In the exploratory factor analysis (EFA), four factors were identified: Communication and Safety Climate (14 items); Perceptions of Management (eight items); Workload and Clinical Risk (six items); and Burnout Risk (four items). These four factors accounted for 68% of the total variance (Kaiser-Meyer-Olkin [KMO] statistic = 0.843). Cronbach's alpha ranged from 0.710-0.917. OOH doctors were often dissatisfied with their job; there is insufficient staff to provide optimal care and there is no training or supervision for new personnel and family medicine trainees. Service managers are perceived as distant, with particular issues concerning the communication between managers and OOH doctors. A large proportion of OOH doctors (56.8%) state that they do not receive adequate support. Conclusion: These findings could be useful for informing policies on how to improve PSC in Italian OOH service
Nuclear activity and stellar mass in galaxies
It is widely believed that the correlations between Supermassive Black Holes and host galaxies descend from a connection between black hole growth and stellar mass assembly. Here we present the results of our investigation on star formation a nd nuclear activity, studying the relations between the circum-nuclear environments of both active and quiescent galaxies. We find that the mass of the stellar component is a critical paramete r that we have to consider to gain further insight into the connection between AGN and star formation processes
The origin of gas in the Extended Narrow Line Region of nearby Seyfert galaxies.I. NGC 7212
The Extended Narrow Line Region (ENLR) of Active Galactic Nuclei (AGN) is a
region of highly ionized gas with a size of few up to 15-20 kpc. When it shows
a conical or bi-conical shape with the apexes pointing towards the active
nucleus, this region is also called ionization cones. The ionization cones are
an evidence of the Unified Model that predicts an anisotropic escape of
ionizing photons from the nucleus confined to a cone by a dusty torus. Many
details about the complex structure of the ENLR still remain unveiled, as for
example the origin of the ionized gas. Here we present new results of a study
of the physical and kinematical properties of the circumnuclear gas in the
nearby Seyfert 2 galaxy NGC 7212. Medium and high resolution integral field
spectra and broad-band photometric data were collected and analysed in the
frame of an observational campaign of nearby Seyfert galaxies, aiming to handle
the complicated issue of the origin of the gas in the ENLR. This work is based
on: (i) analysis of gas physical properties (density, temperature and
metallicity), (ii) analysis of emission line ratios, and (iii) study of
kinematics of gas and stars. By reconstructing the [O III]/Hbeta ionization
map, we pointed out for the first time the presence of an ionization cone
extended up to about 6 kpc, made by a large amount of low metallicity gas,
kinematically disturbed and decoupled from stars, whose highly ionized
component shows radial motions at multiple velocities proved by the complex
profiles of the specral lines. Since NGC 7212 is a strongly interacting triple
galaxy system, the gravitational effects are likely to be at the origin of the
ENLR in this Seyfert galaxy.Comment: 13 pages, 21 figures, accepte
Stellar population properties for a sample of hard X-ray AGNs
The aim of this paper is to study the stellar population of galaxies hosting
an active galactic nucleus (AGN). We studied a sub-sample of hard X-ray
emitting AGNs from the INTEGRAL and Swift catalogs which were previously
identified and characterized through optical spectroscopy. Our analysis
provides complementary information, namely age and metallicity, which is
necessary to complete the panoramic view of such interesting objects.
We selected hard X-ray emitting objects identified as AGNs by checking their
optical spectra in search for absorption lines suitable for the stellar
population analysis. We obtained a final sample consisting of 20 objects with
redshift lower than 0.3. We used the full-spectrum fitting method and, in
particular, the penalized pixel one applying the PPXF code. After masking all
the regions affected by emission lines, we fitted the spectra with the MILES
single stellar population templates and we derived mass-weighted ages and
metallicities.
Most of the objects in our sample show an old stellar population, but three
of them are characterized by a bimodal distribution with a non negligible
contribution from young stars. The values of the mass-weighted metallicity span
a large range of metallicity with most of them slightly above the solar value.
No relations between the stellar population properties and the morphological
ones have been found.Comment: 10 pages, 8 postscript figures and 3 tables. A&A in pres
Online patient simulation training to improve clinical reasoning: a feasibility randomised controlled trial
Background Online patient simulations (OPS) are a novel method for teaching clinical reasoning skills to students and could contribute to reducing diagnostic errors. However, little is known about how best to implement and evaluate OPS in medical curricula. The aim of this study was to assess the feasibility, acceptability and potential effects of eCREST â the electronic Clinical Reasoning Educational Simulation Tool. Methods A feasibility randomised controlled trial was conducted with final year undergraduate students from three UK medical schools in academic year 2016/2017 (cohort one) and 2017/2018 (cohort two). Student volunteers were recruited in cohort one via email and on teaching days, and in cohort two eCREST was also integrated into a relevant module in the curriculum. The intervention group received three patient cases and the control group received teaching as usual; allocation ratio was 1:1. Researchers were blind to allocation. Clinical reasoning skills were measured using a survey after 1 week and a patient case after 1 month. Results Across schools, 264 students participated (18.2% of all eligible). Cohort two had greater uptake (183/833, 22%) than cohort one (81/621, 13%). After 1 week, 99/137 (72%) of the intervention and 86/127 (68%) of the control group remained in the study. eCREST improved studentsâ ability to gather essential information from patients over controls (ORâ=â1.4; 95% CI 1.1â1.7, nâ=â148). Of the intervention group, most (80/98, 82%) agreed eCREST helped them to learn clinical reasoning skills. Conclusions eCREST was highly acceptable and improved data gathering skills that could reduce diagnostic errors. Uptake was low but improved when integrated into course delivery. A summative trial is needed to estimate effectiveness
La dimensione d\u2019impresa nell\u2019analisi economica
Il contributo passa in rassegna gli studi principali sulla dimensione di impresa
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