Stellar population analysis of two ellipticals

The spatial distributions of the mean luminosity-weighted stellar age, metallicity, and alpha/Fe ratio along both photometric axes of two nearby elliptical galaxies have been obtained using Lick index measurements on long slit spectra in order to reconstruct the star formation history in their kinematically distinct subsystems. Lick indexes were compared with those of single-aged stellar population (SSP) models. A population synthesis method was also applied in order to help disentangling the age-metallicity degeneracy. The stars characteristics are associated with their kinematics: they are older and alpha-enhanced in the not rotating bulge of NGC 1052 and counter rotating core of NGC 7796, while they show a strong spread of alpha/Fe and age along the rotating disk of NGC 1052 and an outwards radial decreasing of them outside the core of NGC 7796.Comment: 2 pages, to appear in the Proceedings of IAU Symposium 241 "Stellar populations as building blocks of galaxies", A. Vazdekis & R. Peletier, ed

Il Disegno per un'ipotesi: Villa Galletti Inguaggiato.

Andrea Gigante \ue8 considerato, assieme al contemporaneo Giuseppe Venanzio Marvuglia, esponente di questo particolare momento di transizione. E\u2019 in questi anni che si colloca l\u2019apertura del Gigante verso le tematiche svolte dalla cultura antibarocca che si andava progressivamente imponendo. La Villa Galletti \ue8 l\u2019opera su cui si sono dirette le osservazioni degli studiosi per un giudizio critico su Andrea Gigante architetto neoclassico, infatti si tratta di un manufatto che, inserito nella tradizione architettonica dell\u2019edilizia nobiliare siciliana, mostra nell\u2019insieme un profondo legame con le elaborazioni italiane ed europee. I tempi della redazione del progetto e della costruzione della villa da parte del Gigante possono essere individuati negli anni 1769-75; al tradizionalismo della struttura muraria della villa, un corpo a C caratterizzato dal nodo compositivo dello scalone realizzato all\u2019interno della fabbrica, si aggrega il repertorio innovativo della decorazione a trofei sul prospetto; i riferimenti culturali, che gravitano nell\u2019area francese, sono pervenuti attraverso l\u2019Accademia francese di Roma e attraverso la diffusione delle pubblicazioni del Piranesi. Andrea Gigante, nella villa Galletti, lascia traccia della sua versatilit\ue0 professionale, oscillante tra il ruolo di architetto e quello di vero e proprio decoratore. Notevoli affinit\ue0 tra villa Galletti e villa Tasca ed ancora con il progetto della villa ed il disegno di un parterre attribuito al Gigante, per il palazzo dei principi di Partanna a Palermo, probabilmente da identificare con un palazzo esistente a piazza Marina distrutto nell\u2019ultima guerra. Di impostazione chiusa e serrata, \ue8 pi\uf9 legata alla stesura del palazzo cittadino, che non all\u2019impianto aperto delle costruzioni villerecce caratteristiche dell\u2019agro palermitano. Questa villa forse \ue8 la prima del ciclo barocco che con le precedenti mostra una profonda frattura, sia come impostazione che come concezione. Alle curve fluttuanti e dinamiche, alla grandiosit\ue0 della impostazione planimetrica, alla scenografia dello scalone esterno che tanto peso ebbe nelle intenzioni formali dei prospetti, si oppone qui una composizione lineare e serena, potremmo dire forse una modesta costruzione ad un piano con una severa scala interna ed un cortile. E\u2019 probabile che Gigante abbia voluto farne, pi\uf9 che una residenza di campagna, una palazzina di caccia e che in seguito sia stata ampliata dai proprietari stessi; di sicuro traspare quel carattere di palazzotto di citt\ue0 con quegli stessi attributi riscontrabili nell\u2019ambito cittadino. Dato lo stato di forte degrado oltre che ad un ipotesi ricostruttiva del corpo basso, si \ue8 proceduto con delle visualizzazioni rendering, raggiungendo un grado notevole di possibile configurazione originaria.Andrew Gigante is considered, along with his contemporary Giuseppe Venanzio Marvuglia, exponent of this particular moment of transition. It is during these years that is the opening of the giant to the themes carried out by antibarocca culture that was progressively imposing. The Villa Galletti is the work on which they are direct observations of scholars for a critical judgment on Andrew Gigante neoclassical architect, in fact it is an artifact that, placed in the building's architectural tradition Sicilian nobleman, view the collection for a deep connection with the Italian and European processing.Closed and locked setting, is more related to the drafting of the city Palace, which did not open the villerecce construction features of Palermo. This villa is perhaps the first Baroque cycle with previous shows a deep fracture, both by that concept. To floating and dynamic curves, the grandeur of planimetric, setting the scene for the external staircase that much formal weight had intentions of prospectuses, opposes a linear composition and serene, we could say perhaps a modest one-storey building with a strict internal staircase and a courtyard. It is likely that Giant wanted to make, rather than a country house, a hunting lodge and later was enlarged by the owners themselves; certainly shows that character of city Palace with those same attributes found within the city. Given the state of degradation as well as strong a reconstructive hypothesis of the body down, we proceeded with rendering views, reaching a remarkable degree of possible configuration

A Double Main Sequence in the Globular Cluster NGC 6397

High-precision multi-band HST photometry reveals that the main sequence (MS) of the globular cluster NGC 6397 splits into two components, containing ~30% and ~70% of the stars. This double sequence is consistent with the idea that the cluster hosts two stellar populations: (i) a primordial population that has a composition similar to field stars, and containing ~30% of the stars, and (ii) a second generation with enhanced sodium and nitrogen, depleted carbon and oxygen, and a slightly enhanced helium abundance (Delta Y~0.01). We examine the color difference between the two sequences across a variety of color baselines and find that the second sequence is anomalously faint in m_F336W. Theoretical isochrones indicate that this could be due to NH depletion.Comment: 19 pages, 11 figures, accepted for pubblication in Ap

Effectiveness of a drain in surgical treatment of sacrococcygeal pilonidal disease. Results of a randomized and controlled clinical trial on 803 consecutive patients.

PURPOSE: The aim of this study was to evaluate the influence of cavity drainage in the surgical treatment of sacrococcygeal pilonidal sinuses. METHODS: The study was prospectively carried out in 803 patients randomized into two groups of respectively 401 and 402 patients. In the first group, primary excision and closure were associated with drainage of the wound; in the second group, the wound was not drained. We have analyzed time off work, time to walk without pain, time to sitting on the toilet without pain, recurrences, and wound infections. We have also evaluated the satisfaction rate and esthetic results. RESULTS: On comparing time off work, time to walk without pain, and time to sitting on toilet without pain postoperatively, there were no significant differences between the two groups. A significant difference between the two groups with regard to wound infection rates (p = 0.5) and recurrence rates (p = 0.6) was not observed. In order to prevent prolonged inpatient stay and social intolerance, this study suggests that the post-operative period is tolerated by a few when a drain was used. The visual analog scale (VAS) in the drained group was 3.2 ± 0.9, and VAS in the non-drained group was 3.5 ± 0.9 with a significant statistical difference (p = 0.0001). As regards the cosmetic appearance of the scar after surgery, we achieved a high satisfaction rate among patients in either group with 82.9% good cosmetic results. CONCLUSIONS: The use of a drain, in our experience, appears to be useless in achieving a quick healing of the sacral wound; in addition, it has a low satisfaction rate

The Near Infrared NaI Doublet Feature in M Stars

The NaI near-infrared doublet has been used to indicate the dwarf/giant population in composite systems, but its interpretation is still a contentious issue. In order to understand the behaviour of this controversial feature, we study the observed and synthetic spectra of cool stars. We conclude that the NaI infrared feature can be used as a dwarf/giant discriminator. We propose a modified definition of the NaI index by locating the red continuum at 8234 angstrons and by measuring the equivalent width in the range 8172-8197 angstrons, avoiding the region at lambda > 8197 angstrons, which contains VI, ZrI, FeI and TiO lines. We also study the dependence of this feature on stellar atmospheric parameters.Comment: 9 pages, (TeX file) + 7 Figures in Postscript format. Accepted for publication in The Astrophysical Journa

The helium spread in the Globular cluster 47 Tuc

Spectroscopy has shown the presence of the CN band dicothomy and the Na-O anticorrelations for 50--70% of the investigated samples in the cluster 47 Tuc, otherwise considered a "normal" prototype of high metallicity clusters from the photometric analysis. Very recently, the re-analysis of a large number of archival HST data of the cluster core has been able to put into evidence the presence of structures in the Sub Giant Branch: it has a brighter component with a spread in magnitude by $\sim$0.06 mag and a second one, made of about 10% of stars, a little fainter (by $\sim$0.05 mag). These data also show that the Main Sequence of the cluster has an intrinsic spread in color which, if interpreted as due to a small spread in helium abundance, suggests $\Delta$Y$\sim$0.027. In this work we examine in detail whether the Horizontal Branch morphology and the Sub Giant structure provide further independent indications that a real --although very small-helium spread is present in the cluster. We re--analyze the HST archival data for the Horizontal Branch of 47 Tuc, obtaining a sample of $\sim$500 stars with very small photometric errors, and build population synthesis based on new models to show that its particular morphology can be better explained by taking into account a spread in helium abundance of 2% in mass. The same variation in helium is able to explain the spread in luminosity of the Sub Giant Branch, while a small part of the second generation is characterized by a small C+N+O increase and provides an explanation for the fainter Sub Giant Branch. We conclude that three photometric features concur to form the paradigm that a small but real helium spread is present in a cluster that has no spectacular evidence for multiple populations like those shown by other massive clusters.Comment: Accepted for publication in the MNRAS on 2010 June 8. Received 2010 May 19; in original form 2010 February 9. 7 pages and 3 figures. No table

Four stellar populations and extreme helium variation in the massive outer-halo globular cluster NGC 2419

Recent work revealed that both the helium variation within globular clusters (GCs) and the relative numbers of first and second-generation stars (1G, 2G) depend on the mass of the host cluster. Precise determination of the internal helium variations and of the fraction of 1G stars are crucial constraints to the formation scenarios of multiple populations (MPs). We exploit multi-band Hubble Space Telescope photometry to investigate MPs in NGC 2419, which is one of the most-massive and distant GCs of the Galaxy, almost isolated from its tidal influence. We find that the 1G hosts the ~37% of the analyzed stars, and identified three populations of 2G stars, namely 2GA, 2GB, and 2GC, which comprise the ~20%, ~31% and ~12% of stars, respectively. We compare the observed colors of these four populations with the colors derived from appropriate synthetic spectra to infer the relative helium abundances. We find that 2GA, 2GB, and 2GC stars are enhanced in helium mass fraction by deltaY ~0.01, 0.06, and 0.19 with respectto 1G stars that have primordial helium (Y=0.246). The high He enrichment of 2GC stars is hardly reconcilable with most of the current scenarios for MPs. Furthermore, the relatively larger fraction of 1G stars (~37%) compared to other massive GCs is noticeable. By exploiting literature results, we find that the fractions of 1G stars of GCs with large perigalactic distance are typically higher than in the other GCs with similar masses. This suggests that NGC 2419, similarly to other distant GCs, lost a lower fraction of 1G stars.Comment: 10 pages, 8 figures, submitted to MNRAS January 22n

Near-infrared Spectral Features in Single-aged Stellar Populations

Synthetic spectra for single-aged stellar populations of metallicities [M/H] = -0.5, 0.0 and +0.5, ages = 3 to 17 Gyrs, and initial mass function exponents x = 0.1 to 2.0 were built in the wavelength range 6000-10200 Angstrons. For such we have employed the grid of synthetic spectra described in Schiavon & Barbuy (1999), computed for the stellar parameters 2500 <= Teff <= 6000 K, -0.5 <= log g <= 5.0, [M/H] = -0.5, 0.0 and +0.5, and [alpha/Fe] = 0.0, together with the isochrones by Bertelli et al. (1994) and Baraffe et al. (1998). The behavior of the features NaI8190, CaII8662, TiO6600 and FeH9900 in the integrated spectra of single stellar populations were studied in terms of metallicity, initial mass function and age variations. The main conclusions are that the NaI doublet is an IMF-sensitive feature, which is however sensitive also to metallicity and age, whereas TiO, CaII and FeH are very sensitive to metallicity and essentially insensitive to IMF and age.Comment: 13 pages + 7 figures, ApJ accepte

The extended Main Sequence Turn Off cluster NGC1856: rotational evolution in a coeval stellar ensemble

Multiple or extended turnoffs in young clusters in the Magellanic Clouds have recently received large attention. A number of studies have shown that they may be interpreted as the result of a significant age spread (several 10^8yr in clusters aged 1--2 Gyr), while others attribute them to a spread in stellar rotation. We focus on the cluster NGC 1856, showing a splitting in the upper part of the main sequence, well visible in the color m_{F336W}-m_{F555W}$, and a very wide turnoff region. Using population synthesis available from the Geneva stellar models, we show that the cluster data can be interpreted as superposition of two main populations having the same age (~350Myr), composed for 2/3 of very rapidly rotating stars, defining the upper turnoff region and the redder main sequence, and for 1/3 of slowly/non-rotating stars. Since rapid rotation is a common property of the B-A type stars, the main question raised by this model concerns the origin of the slowly/non-rotating component. Binary synchronization is a possible process behind the slowly/non-rotating population; in this case, many slowly/non-rotating stars should still be part of binary systems with orbital periods in the range from 4 to 500 days. Such periods imply that Roche lobe overflow occurs, during the evolution of the primary off the main sequence, so most primaries may not be able to ignite core helium burning, consistently why the lack of a red clump progeny of the slowly rotating population.Comment: 8 pages 4 figures, accepted for publication on Monthly Notices of the R.A.

Progress in Artificial Economics

Artificial economics aims to provide a generative approach to understanding problems in economics and social sciences. It is based on the consistent use of agent-based models and computational techniques. It encompasses a rich variety of techniques that generalize numerical analysis, mathematical programming, and micro-simulations. The peer-reviewed contributions in this volume address applications of artificial economics to markets and trading, auctions, networks, management, industry sectors, macroeconomics, and demographics and culture