The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XIX. A Chemical Tagging of the Multiple Stellar Populations Over the Chromosome Maps

The HST UV Survey of Globular Clusters (GCs) has investigated GCs and their stellar populations. In previous papers of this series we have introduced a pseudo two-color diagram, "chromosome map" (ChM), that maximises the separation between the multiple populations. We have identified two main classes of GCs: Type I (~83% of the objects) and Type II, both hosting two main groups of stars, referred to in this series as first (1G) and second generation (2G). Type II clusters exhibit two or more parallel sequences of 1G and 2G stars in their ChMs. We exploit elemental abundances from literature to assign the chemical composition to the distinct populations as identified on the ChMs of 29 GCs. We find that stars in different regions of the ChM have different composition: 1G stars share the same light-element content as field stars, while 2G stars are enhanced in N, Na and depleted in O. Stars enhanced in Al and depleted in Mg populate the extreme regions of the ChM. We investigate the color spread among 1G stars observed in many GCs, and find no evidence for variations in light elements, whereas either a 0.1 dex Fe spread or a variation in He remain to be verified. In the attempt of analysing the global properties of the multiple populations, we have constructed a universal ChM, which highlights that, though variegate, the phenomenon has some common pattern. The universal ChM reveals a tight connection with Na, for which we have provided an empirical relation. The additional ChM sequences typical of Type II GCs are enhanced in metallicity and, often, in s elements. Omega Cen can be classified as an extreme Type II GC, with a ChM displaying three main streams, each with its own variations in chemical abundances. One of the most noticeable differences is between the lower and upper streams, with the latter (associated with higher He) having higher Fe and lower Li. We publicly release ChMs.Comment: 35 pages, 28 figures, 3 tables. Submitted to MNRA

Multiple stellar populations in Magellanic Cloud clusters. V. The split main sequence of the young cluster NGC1866

One of the most unexpected results in the field of stellar populations of the last few years, is the discovery that some Magellanic-Cloud globular clusters younger than ~400 Myr, exhibit bimodal main sequences (MSs) in their color-magnitude diagrams (CMDs). Moreover, these young clusters host an extended main sequence turn off (eMSTO) in close analogy with what is observed in most ~1-2 Gyr old clusters of both Magellanic Clouds. We use high-precision Hubble-Space-Telescope photometry to study the young star cluster NGC1866 in the Large Magellanic Cloud. We discover an eMSTO and a split MS. The analysis of the CMD reveals that (i) the blue MS is the less populous one, hosting about one-third of the total number of MS stars; (ii) red-MS stars are more centrally concentrated than blue-MS stars; (iii) the fraction of blue-MS stars with respect to the total number of MS stars drops by a factor of ~2 in the upper MS with F814W <~19.7. The comparison between the observed CMDs and stellar models reveals that the observations are consistent with ~200 Myr old highly-rotating stars on the red-MS, with rotation close to critical value, plus a non-rotating stellar population spanning an age interval between ~140 and 220 Myr, on the blue-MS. Noticeable, neither stellar populations with different ages only, nor coeval stellar models with different rotation rates, properly reproduce the observed split MS and eMSTO. We discuss these results in the context of the eMSTO and multiple MS phenomenon.Comment: 11 pages, 11 figures, accepted for publication in MNRA

The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XVI. The helium abundance of multiple populations

Recent work, based on data from the Hubble Space Telescope (HST) UV Legacy Survey of Galactic Globular Clusters (GCs), has revealed that all the analyzed clusters host two groups of first- (1G) and second-generation (2G) stars. In most GCs, both 1G and 2G stars host sub-stellar populations with different chemical composition. We compare multi-wavelength HST photometry with synthetic spectra to determine for the first time the average helium difference between the 2G and 1G stars in a large sample of 57 GCs and the maximum helium variation within each of them. We find that in all clusters 2G stars are consistent with being enhanced in helium with respect to 1G. The maximum helium variation ranges from less than 0.01 to more than 0.10 in helium mass fraction and correlates with both the cluster mass and the color extension of the horizontal branch (HB). These findings demonstrate that the internal helium variation is one of the main (second) parameters governing the HB morphology.Comment: 26 pages, 19 figures, accepted for publications in MNRA

Osservazioni su alcuni aspetti di carattere filosofico e giuridico nel De carne Christi, nell'Adversus Marcionem e nel De exhortatione castitatis di Tertulliano

Il punto di partenza del contributo \ue8 il De natura deorum ciceroniano, di cui si studia la presenza in diversi scritti dell\u2019Africano, raccolti per rubriche tematiche. La prima \ue8 quella della realt\ue0 della carne di Cristo (Carn 5, 8-9 ; 23, 2 ; Marc 3, 8, 2), che il Cartaginese difende come reale nella sua costituzione materiale e nelle sue funzioni (egli si avvale a questo scopo dei testi di DND 1, 92 ; 1, 48-49). In altri passaggi il nostro autore polemizza contro diverse dottrine, di origine platonica o gnostica, sostenendo la veridicit\ue0 della percezione sensoriale (Marc 4, 8, 2-3 ; ma soprattutto An 17) : in questo caso l\u2019antecedente \ue8 il testo aristotelico, che veicola le dottrine dei presocratici (De An. 3, 3, 427 a). Si giunge quindi al tema del libero arbitrio, che Tertulliano afferma a pi\uf9 riprese contro Marcione (1, 22, 8 ; 2, 6, 1) : il modello \ue8 ciceroniano (DND 3, 76-78), ma dell\u2019argomento si studia anche la ricezione, dal De Genesi ad litteram di Agostino fino a Scoto Eriugena e Girolamo Balbi. Le argomentazioni sul libero arbitrio (Cast 2, 6 ; 3, 4) tornano anche nel testo agostiniano del De libero arbitrio

Chemical Abundances along the 1G Sequence of the Chromosome Maps: The Globular Cluster NGC 3201

The Hubble Space Telescope (HST) UV Legacy Survey of Galactic Globular Clusters (GCs) has investigated multiple stellar populations by means of the “chromosome map” (ChM) diagnostic tool that maximizes the separation between stars with different chemical compositions. One of the most challenging features revealed by ChM analysis is the apparent inhomogeneity among stars belonging to the first population, a phenomenon largely attributed to He variations. However, this explanation is not supported by uniformity in the p-capture elements of these stars. The HST survey has revealed that the GC NGC 3201 shows exceptionally wide coverage in the DF275W,F814W parameter of the ChM. We present a chemical abundance analysis of 24 elements in 18 giants belonging to the first population of this GC and having a wide range in DF275W,F814W. As far as the p-capture elements are concerned, the chemical abundances are typical of first-generation (1G) stars, as expected from the location of our targets in the ChM. Based on radial velocities and chemical abundance arguments, we find that the three stars with the lowest DF275W,F814W values are binary candidates. This suggests that at least those stars could be explained with binarity. These results are consistent with evidence inferred from multiband photometry that evolved blue stragglers (BSs) populate the bluest part of the 1G sequence in the ChM. The remaining 15 spectroscopic targets show a small range in the overall metallicity by ∼0.10 dex, with stars at higher DF275W,F814W values having higher absolute abundances. We suggest that a small variation in metals and binarity governs the color spread of the 1G in the ChM and that evolved BSs contribute to the bluest tail of the 1G sequence.This work has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research innovation program (grant agreement ERC-StG 2016, No. 716082 “GALFOR,” PI: Milone) and the European Union’s Horizon 2020 research and innovation program under Marie Skłodowska-Curie grant agreement No. 797100. A.P.M. and M.T. acknowledge support from MIUR through the FARE project R164RM93XW “SEMPLICE.” H.J. acknowledges support by the Australian Research Council through the Discovery Project DP150100862

Hubble Space Telescope survey of Magellanic Cloud star clusters. Photometry and astrometry of 113 clusters and early results

In the past years, we have undertaken an extensive investigation of LMC and SMC star clusters based on HST data. We present photometry and astrometry of stars in 101 fields observed with the WFC/ACS, UVIS/WFC3 and NIR/WFC3 cameras. These fields comprise 113 star clusters. We provide differential-reddening maps and illustrate various scientific outcomes that arise from the early inspection of the photometric catalogs. In particular, we provide new insights on the extended main-sequence turn-off (eMSTO) phenomenon: i) We detected eMSTOs in two clusters, KMHK361 and NGC265, which had no previous evidence of multiple populations. This finding corroborates the conclusion that the eMSTO is a widespread phenomenon among clusters younger than ~2 Gyr. ii) The homogeneous color-magnitude diagrams (CMDs) of 19 LMC clusters reveal that the distribution of stars along the eMSTO depends on cluster age. iii) We discovered a new feature along the eMSTO of NGC1783, which consists of a distinct group of stars going on the red side of the eMSTO in CMDs composed of ultraviolet filters. Furthermore, we derived the proper motions of stars in the fields of view of clusters with multi-epoch images. Proper motions allowed us to separate the bulk of bright field stars from cluster members and investigate the internal kinematics of stellar populations in various LMC and SMC fields. As an example, we analyze the field around NGC346 to disentangle the motions of its stellar populations, including NGC364 and BS90, young and pre-MS stars in the star-forming region associated with NGC346, and young and old field stellar populations of the SMC. Based on these results and the fields around five additional clusters, we find that young SMC stars exhibit elongated proper-motion distributions that point toward the LMC, thus bringing new evidence for a kinematic connection between the LMC and SMC.Comment: 37 pages, 27 figures, accepted for publication in Astronomy & Astrophysic

Multiparametric prognostic scores in chronic heart failure with reduced ejection fraction: a long-term comparison

Aims: Risk stratification in heart failure (HF) is crucial for clinical and therapeutic management. A multiparametric approach is the best method to stratify prognosis. In 2012, the Metabolic Exercise test data combined with Cardiac and Kidney Indexes (MECKI) score was proposed to assess the risk of cardiovascular mortality and urgent heart transplantation. The aim of the present study was to compare the prognostic accuracy of MECKI score to that of HF Survival Score (HFSS) and Seattle HF Model (SHFM) in a large, multicentre cohort of HF patients with reduced ejection fraction. Methods and results: We collected data on 6112 HF patients and compared the prognostic accuracy of MECKI score, HFSS, and SHFM at 2- and 4-year follow-up for the combined endpoint of cardiovascular death, urgent cardiac transplantation, or ventricular assist device implantation. Patients were followed up for a median of 3.67 years, and 931 cardiovascular deaths, 160 urgent heart transplantations, and 12 ventricular assist device implantations were recorded. At 2-year follow-up, the prognostic accuracy of MECKI score was significantly superior [area under the curve (AUC) 0.781] to that of SHFM (AUC 0.739) and HFSS (AUC 0.723), and this relationship was also confirmed at 4 years (AUC 0.764, 0.725, and 0.720, respectively). Conclusion: In this cohort, the prognostic accuracy of the MECKI score was superior to that of HFSS and SHFM at 2- and 4-year follow-up in HF patients in stable clinical condition. The MECKI score may be useful to improve resource allocation and patient outcome, but prospective evaluation is needed

The Hubble Space Telescope UV Legacy Survey of Galactic globular clusters - XXI. Binaries among multiple stellar populations

A number of scenarios for the formation of multiple populations in globular clusters (GCs) predict that second generation (2G) stars form in a compact and dense subsystem embedded in a more extended first-generation (1G) system. If these scenarios are accurate, a consequence of the denser 2G formation environment is that 2G binaries should be more significantly affected by stellar interactions and disrupted at a larger rate than 1G binaries. The fractions and properties of binary stars can thus provide a dynamical fingerprint of the formation epoch of multiple-population GCs and their subsequent dynamical evolution. We investigate the connection between binaries and multiple populations in five GCs, NGC288, NGC6121 (M 4), NGC6352, NGC6362, and NGC6838 (M 71). To do this, we introduce a new method based on the comparison of Hubble Space Telescope observations of binaries in the F275W, F336W, F438W, F606W, and F814W filters with a large number of simulated binaries. In the inner regions probed by our data, we do not find large differences between the local 1G and the 2G binary incidences in four of the studied clusters, the only exception being M4 where the 1G binary incidence is about three times larger than the 2G incidence. The results found are in general agreement with the results of simulations predicting significant differences in the global 1G and 2G incidences and in the local values in the clusters' outer regions but similar incidences in the inner regions. The significant difference found in M4 is consistent with simulations with a larger fraction of wider binaries. Our analysis also provides the first evidence of mixed (1G-2G) binaries, a population predicted by numerical simulations to form in a cluster's inner regions as a result of stellar encounters during which one component of a binary is replaced by a star of a different population. © 2020 The Author(s)