DSpace Angular :: Browsing by Author "Cunha, K."

Browsing by Author "Cunha, K."

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A Chemical and Kinematical Analysis of the Intermediate-age Open Cluster IC 166 from APOGEE and Gaia DR2
(2018) Schiappacasse-Ulloa, J.; Tang, B.; Fernandez-Trincado, J. G.; Zamora, O.; Geisler, D.; Frinchaboy, P.; Schultheis, M.; Dell'Agli, F.; Villanova, S.; Masseron, T.; Meszaros, Sz; Souto, D.; Hasselquist, S.; Cunha, K.; Smith, V. V.; Garcia-Hernandez, D. A.; Vieira, K.; Robin, A. C.; Minniti, D.; Zasowski, G.; Moreno, E.; Perez-Villegas, A.; Lane, R. R.; Ivans, I. I.; Pan, K.; Nitschelm, C.; Santana, F. A.; Carrera, R.; Roman-Lopes, A.
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 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.
APOGEE DR14/DR15 abundances in the Inner Milky Way
(2019) Zasowski, G.; Schultheis, M.; Hasselquist, S.; Cunha, K.; Sobeck, J.; Johnson, J.A.; Rojas Arriagada, Alvaro; Majewski, S.R.; Andrew, B.H.; Minniti, D.
Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns
(2017) Fernández Trincado J.; Zamora, O.; García Hernández, D.; Souto, D.; Dell'Agli, F.; Schiavon, R.; Geisler, D.; Tang, B.; Villanova, S.; Chanamé, Julio; Hasselquist, S.; Mennickent, R.; Cunha, K.; Shetrone, M.; Prieto, C.; Vieira, K.; Zasowski, G.; Sobeck, J.; Hayes, C.; Majewski, S.; Placco, V.; Beers, T.; Schleicher, D.; Robin, A.; Mészáros, S.; Masseron, T.; Pérez, A.; Anders, F.; Meza, A.; Alves-Brito A.; Carrera, R.; Minniti, D.; Lane, R.; Fernández-Alvar E.; Moreno, E.; Pichardo, B.; Pérez-Villegas, A.; Schultheis, M.; Roman-Lopes, A.; Fuentes, C.; Nitschelm, C.; Harding, P.; Bizyaev, D.; Pan, K.; Oravetz, D.; Simmons, A.; Ivans, I.; Blanco-Cuaresma, S.; Hernández J.; Alonso-García, J.; Valenzuela, O.
Baade's window and APOGEE Metallicities, ages, and chemical abundances
(2017) Schultheis, M.; Rojas Arriagada, Alvaro; Pérez, A. E. García; Jönsson, H.; Hayden, M.; Nandakumar, G.; Cunha, K.; Prieto, C. Allende; Holtzman, J. A.; Beers, T. C.; Bizyaev, D.; Brinkmann, J.; Carrera, R.; Cohen, R. E.; Geisler, D.; Hearty, F. R.; Fernández-Trincado, J. G.; Maraston, C.; Minniti, D.; Nitschelm, C.; Roman-Lopes, A.; Schneider, D. P.; Tang, B.; Villanova, S.; Zasowski, G.; Majewski, S. R.
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....
Chemical evolution of fluorine in the bulge High-resolution K-band spectra of giants in three fields
(2014) Jonsson, H.; Ryde, N.; Harper, G.; Cunha, K.; Schultheis, M.; Eriksson, K.; Kobayashi, C.; Smith, V.; Zoccali, Manuela
Cool stars in the Galactic center as seen by APOGEE : M giants, AGB stars, and supergiant stars and candidates
(2020) Schultheis, M.; Rojas Arriagada, Alvaro; Cunha, K.; Zoccali, Manuela; Chiappini, C.; Zasowski, G.; Queiroz, A. B. A.; Minniti, D.; Fritz, T.; Garcia Hernandez, D. A.; Nitschelm, C.; Zamora, O.; Hasselquist, S.; Fernandez Trincado, J. G.; Munoz, R. .R
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.
H-band discovery of additional second-generation stars in the Galactic bulge globular cluster NGC 6522 as observed by APOGEE and Gaia
(2019) Fernandez-Trincado, J. G.; Zamora, O.; Souto, Diogo; Cohen, R. E.; Agli, F. Dell; Garcia-Hernandez, D. A.; Masseron, T.; Schiavon, R. P.; Meszaros, Sz; Cunha, K.; Hasselquist, S.; Shetrone, M.; Schiappacasse Ulloa, J.; Tang, B.; Geisler, D.; Schleicher, D. R. G.; Villanova, S.; Mennickent, R. E.; Minniti, D.; Alonso-Garcia, J.; Manchado, A.; Beers, T. C.; Sobeck, J.; Zasowski, G.; Schultheis, M.; Majewski, S. R.; Rojas-Arriagada, A.; Almeida, A.; Santana, F.; Oelkers, R. J.; Longa-Pena, P.; Carrera, R.; Burgasser, A. J.; Lane, R. R.; Roman-Lopes, A.; Ivans, I. I.; Hearty, F. R.
We present an elemental abundance analysis of high-resolution spectra for five giant stars spatially located within the innermost regions of the bulge globular cluster NGC 6522 and derive Fe, Mg, Al, C, N, O, Si, and Ce abundances based on H-band spectra taken with the multi-object APOGEE-north spectrograph from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. Of the five cluster candidates, two previously unremarked stars are confirmed to have second-generation (SG) abundance patterns, with the basic pattern of depletion in C and Mg simultaneous with enrichment in N and Al as seen in other SG globular cluster populations at similar metallicity. In agreement with the most recent optical studies, the NGC 6522 stars analyzed exhibit (when available) only mild overabundances of the s-process element Ce, contradicting the idea that NGC 6522 stars are formed from gas enriched by spinstars and indicating that other stellar sources such as massive AGB stars could be the primary polluters of intra-cluster medium. The peculiar abundance signatures of SG stars have been observed in our data, confirming the presence of multiple generations of stars in NGC 6522.
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.
The K2 Galactic Caps Project - going beyond the Kepler field and ageing the Galactic disc
(2019) Rendle, B. M.; Miglio, A.; Chiappini, C.; Valentini, M.; Davies, G. R.; Mosser, B.; Elsworth, Y.; Garcia, R. A.; Mathur, S.; Jofre, P.; Worley, C. C.; Casagrande, L.; Girardi, L.; Lund, M. N.; Feuillet, D. K.; Gavel, A.; Magrini, L.; Khan, S.; Rodrigues, T. S.; Johnson, J. A.; Cunha, K.; Lane, R. L.; Nitschelm, C.; Chaplin, W. J.
Analyses of data from spectroscopic and astrometric surveys have led to conflicting results concerning the vertical characteristics of the Milky Way. Ages are often used to provide clarity, but typical uncertainties of >40 per cent from photometry restrict the validity of the inferences made. Using the Kepler APOKASC sample for context, we explore the global population trends of two K2 campaign fields (3 and 6), which extend further vertically out of the Galactic plane than APOKASC. We analyse the properties of red giant stars utilizing three asteroseismic data analysis methods to cross-check and validate detections. The Bayesian inference tool PARAM is used to determine the stellar masses, radii, and ages. Evidence of a pronounced red giant branch bump and an [a/Fe] dependence on the position of the red clump is observed from the K2 fields radius distribution. Two peaks in the age distribution centred at similar to 5 and similar to 12 Gyr are found using a sample with sigma(age) < 35 per cent. In comparison with Kepler, we find the older peak to be more prominent for K2. This age bimodality is also observed based on a chemical selection of low-[alpha/Fe] (<= 0.1) and high-[alpha/Fe] (>0.1) stars. As a function of vertical distance from the Galactic mid-plane (|Z|), the age distribution shows a transition from a young to old stellar population with increasing |Z| for the K2 fields. Further coverage of campaign targets with high-resolution spectroscopy is required to increase the yield of precise ages achievable with asteroseismology.
The Milky Way bar and bulge revealed by APOGEE and Gaia EDR3
(2021) Queiroz, A. B. A.; Chiappini, C.; Perez-Villegas, A.; Khalatyan, A.; Anders, F.; Barbuy, B.; Santiago, B. X.; Steinmetz, M.; Cunha, K.; Schultheis, M.; Majewski, S. R.; Minchev, I; Minniti, D.; Beaton, R. L.; Cohen, R. E.; da Costa, L. N.; Fernandez-Trincado, J. G.; Garcia-Hernandez, D. A.; Geisler, D.; Hasselquist, S.; Lane, R. R.; Nitschelm, C.; Rojas-Arriagada, A.; Roman-Lopes, A.; Smith, V; Zasowski, G.
We investigate the inner regions of the Milky Way using data from APOGEE and Gaia EDR3. Our inner Galactic sample has more than 26 500 stars within |X-Gal|< 5 kpc, |Y-Gal|< 3.5 kpc, |Z(Gal)|< 1 kpc, and we also carry out the analysis for a foreground-cleaned subsample of 8000 stars that is more representative of the bulge-bar populations. These samples allow us to build chemo-dynamical maps of the stellar populations with vastly improved detail. The inner Galaxy shows an apparent chemical bimodality in key abundance ratios [alpha/Fe], [C/N], and [Mn/O], which probe different enrichment timescales, suggesting a star formation gap (quenching) between the high- and low-alpha populations. Using a joint analysis of the distributions of kinematics, metallicities, mean orbital radius, and chemical abundances, we can characterize the different populations coexisting in the innermost regions of the Galaxy for the first time. The chemo-kinematic data dissected on an eccentricity-|Z|(max) plane reveal the chemical and kinematic signatures of the bar, the thin inner disc, and an inner thick disc, and a broad metallicity population with large velocity dispersion indicative of a pressure-supported component. The interplay between these different populations is mapped onto the different metallicity distributions seen in the eccentricity-|Z|(max) diagram consistently with the mean orbital radius and V-phi distributions. A clear metallicity gradient as a function of |Z|(max) is also found, which is consistent with the spatial overlapping of different populations. Additionally, we find and chemically and kinematically characterize a group of counter-rotating stars that could be the result of a gas-rich merger event or just the result of clumpy star formation during the earliest phases of the early disc that migrated into the bulge. Finally, based on 6D information, we assign stars a probability value of being on a bar orbit and find that most of the stars with large bar orbit probabilities come from the innermost 3 kpc, with a broad dispersion of metallicity. Even stars with a high probability of belonging to the bar show chemical bimodality in the [alpha/Fe] versus [Fe/H] diagram. This suggests bar trapping to be an efficient mechanism, explaining why stars on bar orbits do not show a significant, distinct chemical abundance ratio signature.

Browsing by Author "Cunha, K."

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