DSpace Angular :: Browsing by Author "Barbuy, B."

Browsing by Author "Barbuy, B."

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A Perspective on the Milky Way Bulge Bar as Seen from the Neutron-capture Elements Cerium and Neodymium with APOGEE
(2024) Sales-Silva, J. V.; Cunha, K.; Smith, V. V.; Daflon, S.; Souto, D.; Guerco, R.; Queiroz, A.; Chiappini, C.; Hayes, C. R.; Masseron, T.; Hasselquist, Sten; Horta, D.; Prantzos, N.; Zoccali, M.; Allende Prieto, C.; Barbuy, B.; Beaton, R.; Bizyaev, D.; Fernandez-Trincado, J. G.; Frinchaboy, P. M.; Holtzman, J. A.; Johnson, J. A.; Joensson, Henrik; Majewski, S. R.; Minniti, D.; Nidever, D. L.; Schiavon, R. P.; Schultheis, M.; Sobeck, J.; Stringfellow, G. S.; Zasowski, G.
This study probes the chemical abundances of the neutron-capture elements cerium and neodymium in the inner Milky Way from an analysis of a sample of similar to 2000 stars in the Galactic bulge bar spatially contained within divided by X-Gal divided by < 5 kpc, divided by Y-Gal divided by < 3.5 kpc, and divided by Z(Gal)divided by < 1 kpc, and spanning metallicities between -2.0 less than or similar to [Fe/H] less than or similar to +0.5. We classify the sample stars into low- or high-[Mg/Fe] populations and find that, in general, values of [Ce/Fe] and [Nd/Fe] increase as the metallicity decreases for the low- and high-[Mg/Fe] populations. Ce abundances show a more complex variation across the metallicity range of our bulge-bar sample when compared to Nd, with the r-process dominating the production of neutron-capture elements in the high-[Mg/Fe] population ([Ce/Nd] < 0.0). We find a spatial chemical dependence of Ce and Nd abundances for our sample of bulge-bar stars, with low- and high-[Mg/Fe] populations displaying a distinct abundance distribution. In the region close to the center of the MW, the low-[Mg/Fe] population is dominated by stars with low [Ce/Fe], [Ce/Mg], [Nd/Mg], [Nd/Fe], and [Ce/Nd] ratios. The low [Ce/Nd] ratio indicates a significant contribution in this central region from r-process yields for the low-[Mg/Fe] population. The chemical pattern of the most metal-poor stars in our sample suggests an early chemical enrichment of the bulge dominated by yields from core-collapse supernovae and r-process astrophysical sites, such as magnetorotational supernovae.
Abundance analysis of APOGEE spectra for 58 metal-poor stars from the bulge spheroid
(2022) Razera, R.; Barbuy, B.; Moura, T. C.; Ernandes, H.; Perez-Villegas, A.; Souza, S. O.; Chiappini, C.; Queiroz, A. B. A.; Anders, F.; Fernandez-Trincado, J. G.; Friaca, A. C. S.; Cunha, K.; Smith, V. V.; Santiago, B. X.; Schiavon, R. P.; Valentini, M.; Minniti, D.; Schultheis, M.; Geisler, D.; Sobeck, J.; Placco, V. M.; Zoccali, M.
The central part of the Galaxy hosts a multitude of stellar populations, including the spheroidal bulge stars, stars moved to the bulge through secular evolution of the bar, inner halo, inner thick disc, inner thin disc, as well as debris from past accretion events. We identified a sample of 58 candidate stars belonging to the stellar population of the spheroidal bulge, and analyse their abundances. The present calculations of Mg, Ca, and Si lines are in agreement with the ASPCAP abundances, whereas abundances of C, N, O, and Ce are re-examined. We find normal alpha-element enhancements in oxygen, similar to magnesium, Si, and Ca abundances, which are typical of other bulge stars surveyed in the optical in Baade's Window. The enhancement of [O/Fe] in these stars suggests that they do not belong to accreted debris. No spread in N abundances is found, and none of the sample stars is N-rich, indicating that these stars are not second generation stars originated in globular clusters. Ce instead is enhanced in the sample stars, which points to an s-process origin such as due to enrichment from early generations of massive fast rotating stars, the so-called spinstars.
Abundances in the Galactic bulge
(2008) Barbuy, B.; Zoccali, Manuela; Minniti, D.; Barbuy, B.; Zoccali, Manuela; Minniti, D.
Abundances of iron-peak elements in 58 bulge spheroid stars from APOGEE
(EDP SCIENCES S A, 2024) Barbuy, B.; Friaca, A. C. S.; Ernandes, H.; da Silva, P.; Souza, S. O.; Fernandez-Trincado, J. G.; Cunha, K.; Smith, V. V.; Masseron, T.; Perez-Villegas, A.; Chiappini, C.; Queiroz, A. B. A.; Santiago, B. X.; Beers, T. C.; Anders, F.; Schiavon, R. P.; Valentini, M.; Minniti, D.; Geisler, D.; Souto, D.; Placco, V. M.; Zoccali, Manuela; Feltzing, S.; Schultheis, M.; Nitschelm, C.
Context. Stars presently identified in the bulge spheroid are probably very old, and their abundances can be interpreted as due to the fast chemical enrichment of the early Galactic bulge. The abundances of the iron-peak elements are important tracers of nucleosynthesis processes, in particular oxygen burning, silicon burning, the weak s-process, and alpha-rich freeze-out. Aims. The aim of this work is to derive the abundances of V, Cr, Mn, Co, Ni, and Cu in 58 bulge spheroid stars and to compare them with the results of a previous analysis of data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE). Methods. We selected the best lines for V, Cr, Mn, Co, Ni, and Cu located within the H-band of the spectrum, identifying the most suitable ones for abundance determination, and discarding severe blends. Using the stellar physical parameters available for our sample from the DR17 release of the APOGEE project, we derived the individual abundances through spectrum synthesis. We then complemented these measurements with similar results from different bulge field and globular cluster stars, in order to define the trends of the individual elements and compare with the results of chemical-evolution models. Results. We verify that the H-band has useful lines for the derivation of the elements V, Cr, Mn, Co, Ni, and Cu in moderately metal-poor stars. The abundances, plotted together with others from high-resolution spectroscopy of bulge stars, indicate that: V, Cr, and Ni vary in lockstep with Fe; Co tends to vary in lockstep with Fe, but could be showing a slight decrease with decreasing metallicity; and Mn and Cu decrease with decreasing metallicity. These behaviours are well reproduced by chemical-evolution models that adopt literature yields, except for Cu, which appears to drop faster than the models predict for [Fe/H]<-0.8. Finally, abundance indicators combined with kinematical and dynamical criteria appear to show that our 58 sample stars are likely to have originated in situ.
CAPOS: The bulge Cluster APOgee Survey. I. Overview and initial ASPCAP results
(2021) Geisler, D.; Villanova, S.; O'Connell, J. E.; Cohen, R. E.; Moni Bidin, C.; Fernández-Trincado, J. G.; Muñoz, C.; Minniti, D.; Zoccali, M.; Rojas-Arriagada, A.; Contreras Ramos, R.; Catelan, Márcio; Mauro, F.; Cortés, C.; Ferreira Lopes, C. E.; Arentsen, A.; Starkenburg, E.; Martin, N. F.; Tang, B.; Parisi, C.; Alonso-García, J.; Gran, F.; Cunha, K.; Smith, V.; Majewski, S. R.; Jönsson, H.; García-Hernández, D. A.; Horta, D.; Mészáros, S.; Monaco, L.; Monachesi, A.; Muñoz, R. R.; Brownstein, J.; Beers, T. C.; Lane, R. R.; Barbuy, B.; Sobeck, J.; Henao, L.; González-Díaz, D.; Miranda, R. E.; Reinarz, Y.; Santander, T. A.
Context. Bulge globular clusters (BGCs) are exceptional tracers of the formation and chemodynamical evolution of this oldest Galactic component. However, until now, observational difficulties have prevented us from taking full advantage of these powerful Galactic archeological tools. Aims: CAPOS, the bulge Cluster APOgee Survey, addresses this key topic by observing a large number of BGCs, most of which have only been poorly studied previously. Even their most basic parameters, such as metallicity, [α/Fe], and radial velocity, are generally very uncertain. We aim to obtain accurate mean values for these parameters, as well as abundances for a number of other elements, and explore multiple populations. In this first paper, we describe the CAPOS project and present initial results for seven BGCs. Methods: CAPOS uses the APOGEE-2S spectrograph observing in the H band to penetrate obscuring dust toward the bulge. For this initial paper, we use abundances derived from ASPCAP, the APOGEE pipeline. Results: We derive mean [Fe/H] values of −0.85 ± 0.04 (Terzan 2), −1.40 ± 0.05 (Terzan 4), −1.20 ± 0.10 (HP 1), −1.40 ± 0.07 (Terzan 9), −1.07 ± 0.09 (Djorg 2), −1.06 ± 0.06 (NGC 6540), and −1.11 ± 0.04 (NGC 6642) from three to ten stars per cluster. We determine mean abundances for eleven other elements plus the mean [α/Fe] and radial velocity. CAPOS clusters significantly increase the sample of well-studied Main Bulge globular clusters (GCs) and also extend them to lower metallicity. We reinforce the finding that Main Bulge and Main Disk GCs, formed in situ, have [Si/Fe] abundances slightly higher than their accreted counterparts at the same metallicity. We investigate multiple populations and find our clusters generally follow the light-element (anti)correlation trends of previous studies of GCs of similar metallicity. We finally explore the abundances of the iron-peak elements Mn and Ni and compare their trends with field populations. Conclusions: CAPOS is proving to be an unprecedented resource for greatly improving our knowledge of the formation and evolution of BGCs and the bulge itself....
Cobalt and copper abundances in 56 Galactic bulge red giants
(2020) Ernandes, H.; Barbuy, B.; Friaca, A. C. S.; Hill, V.; Zoccali, Manuela; Minniti, D.; Renzini, A.; Ortolani, S.
Discovery of VVV CL001 A low-mass globular cluster next to UKS 1 in the direction of the Galactic bulge
(EDP SCIENCES S A, 2011) Minniti, D.; Hempel, M.; Toledo, I.; Ivanov, V. D.; Alonso Garcia, J.; Saito, R. K.; Catelan, M.; Geisler, D.; Jordan, A.; Borissova, J.; Zoccali, M.; Kurtev, R.; Carraro, G.; Barbuy, B.; Claria, J.; Rejkuba, M.; Emerson, J.; Moni Bidin, C.
Context. It is not known how many globular clusters may remain undetected towards the Galactic bulge.
FORS2/VLT. survey of Milky Way globular clusters II. Fe and Mg abundances of 51 Milky Way globular clusters on a homogeneous scale
(2016) Dias, B.; Barbuy, B.; Saviane, I.; Held, E.; Da Costa, G.; Ortolani, S.; Gullieuszik, M.; Vásquez Godoy, Sergio Osmán
From the bulge to the outer disc: monospace StarHorse monospace stellar parameters, distances, and extinctions for stars in APOGEE DR16 and other spectroscopic surveys
(2020) Queiroz, A. B. A.; Anders, F.; Chiappini, C.; Khalatyan, A.; Santiago, B. X.; Steinmetz, M.; Valentini, M.; Miglio, A.; Bossini, D.; Barbuy, B.; Minchev, I; Minniti, D.; Garcia Hernandez, D. A.; Schultheis, M.; Beaton, R. L.; Beers, T. C.; Bizyaev, D.; Brownstein, J. R.; Cunha, K.; Fernandez-Trincado, J. G.; Frinchaboy, P. M.; Lane, R. R.; Majewski, S. R.; Nataf, D.; Nitschelm, C.; Pan, K.; Roman-Lopes, A.; Sobeck, J. S.; Stringfellow, G.; Zamora, O.
We combine high-resolution spectroscopic data from APOGEE-2 survey Data Release 16 (DR16) with broad-band photometric data from several sources as well as parallaxes from Gaia Data Release 2 (DR2). Using the Bayesian isochrone-fitting code StarHorse, we derived the distances, extinctions, and astrophysical parameters for around 388 815 APOGEE stars. We achieve typical distance uncertainties of similar to 6% for APOGEE giants, similar to 2% for APOGEE dwarfs, and extinction uncertainties of similar to 0.07 mag, when all photometric information is available, and similar to 0.17 mag if optical photometry is missing. StarHorse uncertainties vary with the input spectroscopic catalogue, available photometry, and parallax uncertainties. To illustrate the impact of our results, we show that thanks to Gaia DR2 and the now larger sky coverage of APOGEE-2 (including APOGEE-South), we obtain an extended map of the Galactic plane. We thereby provide an unprecedented coverage of the disc close to the Galactic mid-plane (|Z(Gal)| < 1 kpc) from the Galactic centre out to R-Gal20 kpc. The improvements in statistics as well as distance and extinction uncertainties unveil the presence of the bar in stellar density and the striking chemical duality in the innermost regions of the disc, which now clearly extend to the inner bulge. We complement this paper with distances and extinctions for stars in other public released spectroscopic surveys: 324 999 in GALAH DR2, 4 928 715 in LAMOST DR5, 408 894 in RAVE DR6, and 6095 in GES DR3.
FSR 1716: A New Milky Way Globular Cluster Confirmed Using VVV RR Lyrae Stars
(2017) Hempel, Maren; Catelan, Márcio; Carballo Bello, J. A.; Ramos, R. C.; Gran, F.; Hagdu, G.; Navarrete, C.; Zoccali, Manuela; Minniti, D.; Palma, T.; Dekany, Istvan; Rejkuba, M.; Pullen, J.; Alonso Garcia, J.; Barba, R.; Barbuy, B.; Bica, E.; Borissova, J.; Chene, A. N.; Claria, J. J.; Cohen, R. E.; Dias, B.; Emerson, J.
Gemini/Phoenix H-band analysis of the globular cluster AL 3
(2021) Barbuy, B.; Ernandes, H.; Souza, S. O.; Razera, R.; Moura, T.; Melendez, J.; Perez-Villegas, A.; Zoccali, M.; Minniti, D.; Dias, B.; Ortolani, S.; Bica, E.
Context. The globular cluster AL 3 is old and located in the inner bulge. Three individual stars were observed with the Phoenix spectrograph at the Gemini South telescope. The wavelength region contains prominent lines of CN, OH, and CO, allowing the derivation of C, N, and O abundances of cool stars.Aims. We aim to derive C, N, O abundances of three stars in the bulge globular cluster AL 3, and additionally in stars of NGC 6558 and HP 1. The spectra of AL 3 allows us to derive the cluster's radial velocity.Methods. For AL 3, we applied a new code to analyse its colour-magnitude diagram. Synthetic spectra were computed and compared to observed spectra for the three clusters.Results. We present a detailed identification of lines in the spectral region centred at 15 555 angstrom, covering the wavelength range 15 525-15 590 angstrom. C, N, and O abundances are tentatively derived for the sample stars.
High-resolution abundance analysis of red giants in the globular cluster NGC 6522
(2014) Barbuy, B.; Chiappini, C.; Cantelli, E.; Depagne, E.; Pignatari, M.; Hirschi, R.; Cescutti, G.; Ortolani, S.; Hill, V.; Zoccali, Manuela; Minniti, D.; Trevisan, M.; Bica, E.; Gómez, A.
High-resolution abundance analysis of red giants in the metal-poor bulge globular cluster HP. 1
(2016) Barbuy, B.; Cantelli, E.; Vemado, A.; Ernandes, H.; Ortolani, S.; Saviane, I.; Bica, E.; Minniti, D.; Dias, B.; Zoccali, Manuela; Hill, V.; Momany, Y.; Siqueira, C.
Homogeneous metallicities and radial velocities for Galactic globular clusters II. New CaT metallicities for 28 distant and reddened globular clusters
(2018) Vasquez, S.; Saviane, I.; Held, E.V.; Da Costa, G.S.; Dias, B.; Gullieuszik, M.; Barbuy, B.; Ortolani, S.; Zoccali, Manuela
Light elements Na and Al in 58 bulge spheroid stars from APOGEE
(2023) Barbuy, B.; Friaca, A. C. S.; Ernandes, H.; Moura, T.; Masseron, T.; Cunha, K.; Smith, V. V.; Souto, D.; Perez-Villegas, A.; Souza, S. O.; Chiappini, C.; Queiroz, A. B. A.; Fernandez-Trincado, J. G.; da Silva, P.; Santiago, B. X.; Anders, F.; Schiavon, R. P.; Valentini, M.; Minniti, D.; Geisler, D.; Placco, V. M.; Zoccali, M.; Schultheis, M.; Nitschelm, C.; Beers, T. C.; Razera, R.
We identified a sample of 58 candidate stars with metallicity [Fe/H]less than or similar to-0.8 that likely belong to the old bulge spheroid stellar population, and analyse their Na and Al abundances from Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra. In a previous work, we inspected APOGEE-Stellar Parameter and Chemical Abundance Pipeline abundances of C, N, O, Mg, Al, Ca, Si, and Ce in this sample. Regarding Na lines, one of them appears very strong in about 20percent of the sample stars, but it is not confirmed by other Na lines, and can be explained by sky lines, which affect the reduced spectra of stars in a certain radial velocity range. The Na abundances for 15 more reliable cases were taken into account. Al lines in the H band instead appear to be very reliable. Na and Al exhibit a spread in abundances, whereas no spread in N abundances is found, and we found no correlation between them, indicating that these stars could not be identified as second-generation stars that originated in globular clusters. We carry out the study of the behaviour of Na and Al in our sample of bulge stars and literature data by comparing them with chemodynamical evolution model suitable for the Galactic bulge. The Na abundances show a large spread, and the chemodynamical models follow the main data, whereas for aluminum instead, the models reproduce very satisfactorily the nearly secondary-element behaviour of aluminum in the metallicity range below [Fe/H]less than or similar to-1.0. For the lower-metallicity end ([Fe/H<-2.5), hypernovae are assumed to be the main contributor to yields.
Manganese abundances in Galactic bulge red giants
(2013) Barbuy, B.; Hill, V.; Zoccali, Manuela; Minniti, D.; Renzini, A.; Ortolani, S.; Gómez, A. A.; Trevisan, M.; Dutra, N.
Milky Way demographics with the VVV survey I. The 84-million star colour-magnitude diagram of the Galactic bulge
(EDP SCIENCES S A, 2012) Saito, R. K.; Minniti, D.; Dias, B.; Hempel, M.; Rejkuba, M.; Alonso Garcia, J.; Barbuy, B.; Catelan, M.; Emerson, J. P.; Gonzalez, O. A.; Lucas, P. W.; Zoccali, M.
Context. The Milky Way (MW) bulge is a fundamental Galactic component for understanding the formation and evolution of galaxies, in particular our own. The ESO Public Survey VISTA Variables in the Via Lactea is a deep near-IR survey mapping the Galactic bulge and southern plane. Particularly for the bulge area, VVV is covering similar to 315 deg(2). Data taken during 2010 and 2011 covered the entire bulge area in the JHKs bands.
NGC 6558
(2007) Barbuy, B.; Zoccali, M.; Ortolani, S.; Minniti, D.; Hill, V.; Renzini, A.; Bica, E.; Gomez, A.
We present, for the first time, a detailed abundance analysis of five giant stars in the moderately metal-poor bulge globular cluster NGC 6558. Spectra have been obtained at the VLT with the multifiber spectrograph FLAMES in GIRAFFE mode ( R similar to 22; 000). The resulting iron abundance is [Fe/H] = -0. 97 +/- 0.15, in good agreement with the metallicity inferred from the slope of the red giant branch, but unusually high for a cluster with such a blue horizontal branch, possibly indicating an old age. A color-magnitude diagram in Vand I, based on photometry obtained with the Wide-Field Imager at ESO, is also presented. An isochrone of 14 Gyr fits the evolutionary sequences, confirming an old age. NGC 6558 is another "second-parameter'' bulge cluster. The metallicity derived is near the end of the low-metallicity tail of the bulge field-star distribution; hence, it presumably formed at the very early stages of the bulge formation. Abundance ratios show enhancements of the alpha-elements oxygen, magnesium, and silicon, with [O/Fe] = +0.38, [Mg/Fe] = +0.24, [Si/Fe] = +0.23, and solar calcium and titanium. The r-element europium is also enhanced by [Eu/Fe] = +0.36. The odd-Z elements sodium and aluminum, as well as the s-elements barium and lanthanum, show solar ratios. A heliocentric radial velocity of v(r)(hel) = -197.3 +/- 4 km s(-1) is found for NGC 6558.
NGC 6558: A blue horizontal branch moderately metal-poor globular cluster in the bulge
(2007) Barbuy, B.; Zoccali, Manuela; Minniti, D.
Oxygen abundances in the Galactic bulge
(2006) Zoccali, M.; Lecureur, A.; Barbuy, B.; Hill, V.; Renzini, A.; Minniti, D.; Momany, Y.; Gomez, A.; Ortolani, S.
Aims. We spectroscopically characterize the Galactic Bulge to infer its star formation timescale, compared to the other Galactic components, through the chemical signature on its individual stars.

Browsing by Author "Barbuy, B."

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