Examinando por Autor "Barbuy, Beatriz"
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Ítem An Updated Small Magellanic Cloud and Magellanic Bridge Catalog of Star Clusters, Associations, and Related Objects(Institute of Physics Publishing, 2020-03) Bica, Eduardo; Pieter, Westera; O.Kerber, Leandro; Dias, Bruno; Maia, Francisco; F.C Santos Jr., João; Barbuy, Beatriz; Oliveira, RaphaelWe present a catalog of star clusters, associations, and related extended objects in the Small Magellanic Cloud (SMC) and the Magellanic Bridge with 2741 entries, a factor 2 more than a previous version from a decade ago. Literature data up until 2018 December are included. The identification of star clusters was carried out with digital atlases in various bands currently available in the Digitized Sky Survey and the Machine Automatique à Mésurer pour l'Astronomie. imaging surveys. In particular, we cross-identified recent cluster samples from the Visible and Infrared Survey Telescope for Astronomy near-infrared YJK s survey of the Magellanic System, Optical Gravitational Lensing Experiment IV, and Survey of the MAgellanic Stellar History surveys, confirming new clusters and pointing out equivalencies. A major contribution of the present catalog consists of the accurate central positions for clusters and small associations, including a new sample of 45 clusters or candidates in the SMC and 19 in the Magellanic Bridge, as well as a compilation of the most reliable age and metallicity values from the literature. A general catalog must also deal with the recent discoveries of 27 faint and ultra-faint star clusters and galaxies projected on the far surroundings of the Clouds, most of them from the Dark Energy Survey. The information on these objects has been complemented with photometric, spectroscopic, and kinematical follow-up data from the literature. The underluminous galaxies around the Magellanic System, still very few as compared to the predictions from Λ Cold Dark Matter simulations, can bring constraints to galaxy formation and hierarchical evolution. Furthermore, we provide diagnostics, when possible, of the nature of the ultra-faint clusters, searching for borders of the Magellanic System extensions into the Milky Way gravitational potential. © 2020. The American Astronomical Society. All rights reserved..Ítem APOGEE-2S Mg-Al anti-correlation of the metal-poor globular cluster NGC 2298(EDP Sciences, 2022-06-01) Baeza, Ian; Fernández-Trincado, José G.; Villanova, Sandro; Geisler, Doug; Minniti, Dante; Garro, Elisa R.; Barbuy, Beatriz; Beers, Timothy C.; Lane, Richard R.We present detailed elemental abundances and radial velocities of stars in the metal-poor globular cluster (GC) NGC 2298, based on near-infrared high-resolution (R 22-500) spectra of 12 members obtained during the second phase of the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) at Las Campanas Observatory as part of the seventeenth Data Release (DR 17) of the Sloan Digital Sky Survey IV (SDSS-IV). We employed the Brussels Automatic Code for Characterizing High accuracy Spectra (BACCHUS) software to investigate abundances for a variety of species including α elements (Mg, Si, and Ca), the odd-Z element Al, and iron-peak elements (Fe and Ni) located in the innermost regions of NGC 2298. We find a mean and median metallicity [Fe/H 1.76 and 1.75, respectively, with a star-to-star spread of 0.14 dex, which is compatible with the internal measurement errors. Thus, we find no evidence for an intrinsic [Fe/H] abundance spread in NGC 2298. The typical α-element enrichment in NGC 2298 is overabundant relative to the Sun, and it follows the trend of other metal-poor GCs. We confirm the existence of an Al-enhanced population in this cluster, which is clearly anti-correlated with Mg, indicating the prevalence of the multiple-population phenomenon in NGC 2298. © ESO 2022Ítem CAPOS: The bulge Cluster APOgee Survey II. The intriguing “Sequoia” globular cluster FSR 1758(EDP Sciences, 2021-08-01) Romero-Colmenares, María; Fernández-Trincado, José G.; Geisler, Doug; Souza, Stefano O.; Villanova, Sandro; Longa-Peña, Penélope; Minniti, Dante; Beers, Timothy C.; Bidin, Cristian Moni; Perez-Villegas, Angeles; Moreno, Edmundo; Garro, Elisa R.; Baeza, Ian; Henao, Lady; Barbuy, Beatriz; Alonso-García, Javier; Cohen, Roger E.; Lane, Richard R.; Muñoz, CesarWe present results from a study of 15 red giant members of the intermediate-metallicity globular cluster (GC) FSR 1758 using high-resolution, near-infrared spectra collected with the Apache Point Observatory Galactic Evolution Experiment II survey (APOGEE-2) that were obtained as part of CAPOS (the bulge Cluster APOgee Survey). Since its very recent discovery as a massive GC in the bulge region, evoking the name Sequoia, this has been an intriguing object with a highly debated origin, and initially led to the suggestion of a purported progenitor dwarf galaxy of the same name. In this work, we use new spectroscopic and astrometric data to provide additional clues as to the nature of FSR 1758. Our study confirms the GC nature of FSR 1758, and as such we report the existence of the characteristic N-C anticorrelation and Al-N correlation for the first time. We thereby reveal the existence of the multiple-population phenomenon, similar to that observed in virtually all GCs. Furthermore, the presence of a population with strongly enriched aluminum makes it unlikely that FSR 1758 is the remnant nucleus of a dwarf galaxy because Al-enhanced stars are uncommon in dwarf galaxies. We find that FSR 1758 is slightly more metal rich than previously reported in the literature; this source has a mean metallicity [Fe/H] between -1.43 to -1.36, depending on the adopted atmospheric parameters and a scatter within observational error, again pointing to its GC nature. Overall, the α-enrichment ( + 0.3 dex), Fe-peak (Fe, Ni), light (C, N), and odd-Z (Al) elements follow the trend of intermediate-metallicity GCs. Isochrone fitting in the Gaia bands yields an estimated age of ∼11.6 Gyr. We used the exquisite kinematic data, including our CAPOS radial velocities and Gaia eDR3 proper motions, to constrain the N-body density profile of FSR 1758, and found that it is as massive (∼2.9 ± 0.6 × 105 Mpdbl) as NGC 6752. We confirm a retrograde and eccentric orbit for FSR 1758. A new examination of its dynamical properties with the GravPot16 model favors an association with the Gaia-Enceladus-Sausage accretion event. Thus, paradoxically, the cluster that gave rise to the name of the Sequoia dwarf galaxy does not appear to belong to this specific merging event.Ítem CAPOS: the bulge Cluster APOgee Survey IV elemental abundances of the bulge globular cluster NGC 6558(Oxford University Press, 2023-12-01) González-Díaz, Danilo; Fernández-Trincado, José G.; Villanova, Sandro; Geisler, Doug; Barbuy, Beatriz; Minniti, Dante; Beers, Timothy C.; Bidin, Christian Moni; Mauro, Francesco; Muñoz, Cesar; Tang, Baitian; Soto, Mario; Monachesi, Antonela; Lane, Richard R.; Frelijj, HeinzThis study presents the results concerning six red giant stars members of the globular cluster NGC 6558. Our analysis utilized high-resolution near-infrared spectra obtained through the CAPOS initiative (the APOgee Survey of Clusters in the Galactic Bulge), which focuses on surveying clusters within the Galactic Bulge, as a component of the Apache Point Observatory Galactic Evolution Experiment II survey (APOGEE-2). We employ the Brussels Automatic Code for Characterizing High accUracy Spectra (BACCHUS) code to provide line-by-line elemental-abundances for Fe-peak (Fe, Ni), α-(O, Mg, Si, Ca, Ti), light-(C, N), odd-Z (Al), and the s-process element (Ce) for the four stars with high-signal-to-noise ratios. This is the first reliable measure of the CNO abundances for NGC 6558. Our analysis yields a mean metallicity for NGC 6558 of 〈[Fe/H]〉 = −1.15 ± 0.08, with no evidence for a metallicity spread. We find a Solar Ni abundance, 〈[Ni/Fe]〉 ∼ +0.01, and a moderate enhancement of α-elements, ranging between +0.16 and [removed] +0.99, along with a low level of carbon, [C/Fe] < −0.12. This behaviour of Nitrogen-Carbon is a typical chemical signature for the presence of multiple stellar populations in virtually all GCs; this is the first time that it is reported in NGC 6558. We also observed a remarkable consistency in the behaviour of all the chemical species compared to the other CAPOS bulge GCs of the same metallicity. © The Author(s) 2023.Ítem FSR 1716: A New Milky Way Globular Cluster Confirmed Using VVV RR Lyrae Stars(Institute of Physics Publishing, 2017-03) Minniti, Dante; Palma, Tali; Dékány, Istvan; Hempel, Maren; Rejkuba, Marina; Pullen, Joyce; Alonso-García, Javier; Barbá, Rodolfo; Barbuy, Beatriz; Bica, Eduardo; Bonatto, Charles; Borissova, Jura; Catelan, Marcio; Carballo-Bello, Julio A.; Chene, Andre Nicolas; Clariá, Juan José; Cohen, Roger E.; Contreras Ramos, Rodrigo; Dias, Bruno; Emerson, Jim; Froebrich, Dirk; Buckner, Anne S. M.; Geisler, Douglas; Gonzalez, Oscar A.; Gran, Felipe; Hagdu, Gergely; Irwin, Mike; Ivanov, Valentin D.; Kurtev, Radostin; Lucas, Philip W.; Majaess, Daniel; Mauro, Francesco; Moni-Bidin, Christian; Navarrete, Camila; Alegría, Sebastian Ramírez; Saito, Roberto K.; Valenti, Elena; Zoccali, ManuelaWe use deep multi-epoch near-IR images of the VISTA Variables in the Vía Láctea (VVV) Survey to search for RR Lyrae stars toward the Southern Galactic plane. Here, we report the discovery of a group of RR Lyrae stars close together in VVV tile d025. Inspection of the VVV images and PSF photometry reveals that most of these stars are likely to belong to a globular cluster that matches the position of the previously known star cluster FSR 1716. The stellar density map of the field yields a >100σ detection for this candidate globular cluster that is centered at equatorial coordinates R.A.J2000 = 16:10:30.0, decl.J2000 = -53:44:56 and galactic coordinates l = 329.77812, b = -1.59227. The color-magnitude diagram of this object reveals a well-populated red giant branch, with a prominent red clump at K s = 13.35 ±0.05, and J - K s = 1.30 ±0.05. We present the cluster RR Lyrae positions, magnitudes, colors, periods, and amplitudes. The presence of RR Lyrae indicates an old globular cluster, with an age >10 Gyr. We classify this object as an Oosterhoff type I globular cluster, based on the mean period of its RR Lyrae type ab, days, and argue that this is a relatively metal-poor cluster with [Fe/H] = -1.5 ±0.4 dex. The mean extinction and reddening for this cluster are and E(J - K s) = 0.72 ±0.02 mag, respectively, as measured from the RR Lyrae colors and the near-IR color-magnitude diagram. We also measure the cluster distance using the RR Lyrae type ab stars. The cluster mean distance modulus is (m - M)0 = 14.38 ±0.03 mag, implying a distance D = 7.5 ±0.2 kpc and a Galactocentric distance R G = 4.3 kpc. © 2017. The American Astronomical Society. All rights reserved.Ítem Galactic ArchaeoLogIcaL ExcavatiOns (GALILEO): I. An updated census of APOGEE N-rich giants across the Milky Way(EDP Sciences, 2022-07-01) Fernández Trincado, José G.; Beers, Timothy C.; Barbuy, Beatriz; Minniti, Dante; Chiappini, Cristina; Garro, Elisa R.; Tang, Baitian; Alves Brito, Alan; Villanova, Sandro; Geisler, Doug; Lane, Richard R.; Diaz, Danilo G.We use the 17th data release of the second phase of the Apache Point Observatory Galactic Evolution Experiment (APOGEE-2) to provide a homogenous census of N-rich red giant stars across the Milky Way (MW). We report a total of 149 newly identified N-rich field giants toward the bulge, metal-poor disk, and halo of our Galaxy. They exhibit significant enrichment in their nitrogen abundance ratios ([N/Fe]³a+0.5), along with simultaneous depletions in their [C/Fe] abundance ratios ([C/Fe]< +0.15), and they cover a wide range of metallicities (1.8< [Fe/H]< 0.7). The final sample of candidate N-rich red giant stars with globular-cluster-like (GC-like) abundance patterns from the APOGEE survey includes a grand total of 412 unique objects. These strongly N-enhanced stars are speculated to have been stripped from GCs based on their chemical similarities with these systems. Even though we have not found any strong evidence for binary companions or signatures of pulsating variability yet, we cannot rule out the possibility that some of these objects were members of binary systems in the past and/or are currently part of a variable system. In particular, the fact that we identify such stars among the field stars in our Galaxy provides strong evidence that the nucleosynthetic process(es) producing the anomalous [N/Fe] abundance ratios occurs over a wide range of metallicities. This may provide evidence either for or against the uniqueness of the progenitor stars to GCs and/or the existence of chemical anomalies associated with likely tidally shredded clusters in massive dwarf galaxies such as Kraken/Koala, Gaia-Enceladus-Sausage, among others, before or during their accretion by the MW. A dynamical analysis reveals that the newly identified N-rich stars exhibit a wide range of dynamical characteristics throughout the MW, indicating that they were produced in a variety of Galactic environments. ©Ítem The enigmatic globular cluster UKS 1 obscured by the bulge: H -band discovery of nitrogen-enhanced stars(EDP Sciences, 2020-11-01) Fernández-Trincado, José G.; Minniti, Dante; Beers, Timothy C.; Villanova, Sandro; Geisler, Doug; Souza, Stefano O.; Smith, Leigh C.; Placco, Vinicius M.; Vieira, Katherine; Pérez-Villegas, Angeles; Barbuy, Beatriz; Alves-Brito, Alan; Moni Bidin, Christian; Alonso-García, Javier; Tang, Baitian; Palma, TaliThe presence of nitrogen-enriched stars in globular clusters provides key evidence for multiple stellar populations (MPs), as has been demonstrated with globular cluster spectroscopic data towards the bulge, disk, and halo. In this work, we employ the VVV Infrared Astrometric Catalogue (VIRAC) and the DR16 SDSS-IV release of the APOGEE survey to provide the first detailed spectroscopic study of the bulge globular cluster UKS 1. Based on these data, a sample of six selected cluster members was studied. We find the mean metallicity of UKS 1 to be [Fe/H] = -0.98 ± 0.11, considerably more metal-poor than previously reported, and a negligible metallicity scatter, typical of that observed by APOGEE in other Galactic globular clusters. In addition, we find a mean radial velocity of 66.1 ± 12.9 km s-1, which is in good agreement with literature values, within 1σ. By selecting stars in the VIRAC catalogue towards UKS 1, we also measure a mean proper motion of (μαcos(δ), μδ) = (-2.77 ± 0.23, -2.43 ± 0.16) mas yr-1. We find strong evidence for the presence of MPs in UKS 1, since four out of the six giants analysed in this work have strong enrichment in nitrogen ([N/Fe] - +0.95) accompanied by lower carbon abundances ([C/Fe] -0.2). Overall, the light- (C, N), α- (O, Mg, Si, Ca, Ti), Fe-peak (Fe, Ni), Odd-Z (Al, K), and the s-process (Ce, Nd, Yb) elemental abundances of our member candidates are consistent with those observed in globular clusters at similar metallicity. Furthermore, the overall star-to-star abundance scatter of elements exhibiting the multiple-population phenomenon in UKS 1 is typical of that found in other global clusters (GCs), and larger than the typical errors of some [X/Fe] abundances. Results from statistical isochrone fits in the VVV colour-magnitude diagrams indicate an age of 13.10-1.29+0.93 Gyr, suggesting that UKS 1 is a fossil relic in the Galactic bulge.