Examinando por Autor "Cunha, Katia"
Mostrando 1 - 8 de 8
Resultados por página
Opciones de ordenación
Ítem APOGEE chemical abundance patterns of the massive milky way satellites(IOP Publishing Ltd, 2021-12) Hasselquist, Sten; Hayes, Christian R; Lian, Jianhui; Weinberg, David H.; Zasowski, Gail; Horta, Danny; Beaton, Rachael; Feuillet, Diane K.; Garro, Elisa R.; Gallart, Carme; Smith, Verne V.; Holtzman, Jon A.; Minniti, Dante; Lacerna, Ivan; Shetrone, Matthew; Jönsson, Henrik; Cioni, Maria-Rosa L.; Fillingham, Sean P.; Cunha, Katia; O'Connell, Robert; Fernández-Trincado, José G.; Munoz, Ricardo R.; Schiavon, Ricardo; Almeida, Andres; Anguiano, Borja; Beers, Timothy C.; Bizyaev, Dmitry; Brownstein, Joel R.; Cohen, Roger E.; Frinchaboy, Peter; García-Hernández, D.A.; Geisler, Doug; Lane, Richard R.; Majewski, Steven R; Nidever, David L.; Nitschelm, Christian; Povick, Joshua; Price-Whelan, Adrian; Roman-Lopes, Alexandre; Rosado, Margarita; Sobeck, Jennifer; Stringfellow, Guy; Valenzuela, Octavio; Villanova, Sandro; Vincenzo, FiorenzoThe SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey has obtained high resolution spectra for thousands of red giant stars distributed among the massive satellite galaxies of the Milky Way (MW): the Large and Small Magellanic Clouds (LMC/SMC), the Sagittarius Dwarf Galaxy (Sgr), Fornax (Fnx), and the now fully disrupted Gaia Sausage/Enceladus (GSE) system. We present and analyze the APOGEE chemical abundance patterns of each galaxy to draw robust conclusions about their star formation histories, by quantifying the relative abundance trends of multiple elements (C, N, O, Mg, Al, Si, Ca, Fe, Ni, and Ce), as well as by fitting chemical evolution models to the [α/Fe]–[Fe/H] abundance plane for each galaxy. Results show that the chemical signatures of the starburst in the Magellanic Clouds (MCs) observed by Nidever et al. in the α-element abundances extend to C+N, Al, and Ni, with the major burst in the SMC occurring some 3–4 Gyr before the burst in the LMC. We find that Sgr and Fnx also exhibit chemical abundance patterns suggestive of secondary star formation epochs, but these events were weaker and earlier (∼5–7 Gyr ago) than those observed in the MCs. There is no chemical evidence of a second starburst in GSE, but this galaxy shows the strongest initial star formation as compared to the other four galaxies. All dwarf galaxies had greater relative contributions of AGB stars to their enrichment than the MW. Comparing and contrasting these chemical patterns highlight the importance of galaxy environment on its chemical evolution.Ítem Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns(Institute of Physics Publishing, 2017-09) Fernández-Trincado J.G.; Zamora O.; Garcia-Hernández D.A.; Souto, Diogo; Dell'Agli F.; Schiavon R.P.; Geisler D.; Tang B.; Villanova S.; Hasselquist, Sten; Mennickent R.E.; Cunha, Katia; Shetrone M.; Prieto, Carlos Allende; Vieira K.; Zasowski G.; Sobeck J.; Hayes C.R.; Majewski S.R.; Placco V.M.; Beers T.C.; Schleicher D.R.G.; Robin A.C.; Mészáros, Sz.; Masseron T.; Pérez, Ana E. Garcia; Anders F.; Meza A.; Alves-Brito A.; Carrera R.; Minniti D.; Lane R.R.; Fernández-Alvar E.; Moreno E.; Pichardo B.; Pérez-Villegas A.; Schultheis M.; Roman-Lopes A.; Fuentes C.E.; Nitschelm C.; Harding P.; Bizyaev D.; Pan K.; Oravetz D.; Simmons A.; Ivans, Inese; Blanco-Cuaresma S.; Hernández J.; Alonso-Garcia J.; Valenzuela O.; Chanamé J.We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe] < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] -1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution. © 2017. The American Astronomical Society. All rights reserved.Ítem Homogeneous analysis of globular clusters from the APOGEE survey with the BACCHUS code – II. The Southern clusters and overview(Oxford University Press, 2020-02) Szabolcs, Meszaros; Masseron, Thomas; García-Hernandez, D. A.; Allende Prieto, Carlos; Beers, Timothy C.; Bizyaev, Dmitry; Chojnowski, Drew; Cohen, Roger E.; Cunha, Katia; Dell’Agli, Flavia; Ebelke, Garrett; Fernandez-Trincado, Jose G.; Frinchaboy, Peter; Geisler, Doug; Hasselquist, Sten; Hearty, Fred; Holtzman, Jon; Johnson, Jennifer; Lane, Richard R; Lacerna, Ivan; Longa-Pena, Penelope; Majewski, Steven R.; Martell, Sarah L; Minniti, Dante; Nataf, David; Nidever, David L.; Pan, Kaike; Schiavon, Ricardo P.; Shetrone, Matthew; Smith, Verne V.; . Sobeck, Jennifer S; Stringfellow, Guy S.; Szigeti, Laszlo; Tang, Baitian; Wilson, John C.; Zamora, OlgaWe investigate the Fe, C, N, O, Mg, Al, Si, K, Ca, Ce, and Nd abundances of 2283 red giant stars in 31 globular clusters from high-resolution spectra observed in both the Northern and Southern hemisphere by the SDSS-IV APOGEE-2 survey. This unprecedented homogeneous data set, largest to date, allows us to discuss the intrinsic Fe spread, the shape, and statistics of Al-Mg and N-C anti-correlations as a function of cluster mass, luminosity, age, and metallicity for all 31 clusters. We find that the Fe spread does not depend on these parameters within our uncertainties including cluster metallicity, contradicting earlier observations. We do not confirm the metallicity variations previously observed in M22 and NGC 1851. Some clusters show a bimodal Al distribution, while others exhibit a continuous distribution as has been previously reported in the literature. We confirm more than two populations in ω Cen and NGC 6752, and find new ones in M79. We discuss the scatter of Al by implementing a correction to the standard chemical evolution of Al in the Milky Way. After correction, its dependence on cluster mass is increased suggesting that the extent of Al enrichment as a function of mass was suppressed before the correction. We observe a turnover in the Mg-Al anticorrelation at very low Mg in ω Cen, similar to the pattern previously reported in M15 and M92. ω Cen may also have a weak K-Mg anticorrelation, and if confirmed, it would be only the third cluster known to show such a patternÍtem How many components? Quantifying the complexity of the metallicity distribution in the Milky Way bulge with APOGEE(Oxford University Press, 2020-11-01) Rojas-Arriagada, Alvaro; Zasowski, Gail; Schultheis, Mathias; Zoccali, Manuela; Hasselquist, Sten; Chiappini, Cristina; Cohen, Roger E.; Cunha, Katia; Fernández-Trincado, José G.; Fragkoudi, Francesca; Garcia-Hernández, D. A.; Geisler, Doug; Gran, Felipe; Lian, Jianhui; Majewski, Steven; Minniti, Dante; Monachesi, Antonela; Nitschelm, Christian; Queiroz, Anna B. A.We use data of ~13 000 stars from the Sloan Digital Sky Survey/Apache Point Observatory Galactic Evolution Experiment survey to study the shape of the bulge metallicity distribution function (MDF) within the region |l| = 11° and |b| = 13°, and spatially constrained to RGC = 3.5 kpc. We apply Gaussian mixture modelling and non-negative matrix factorization decomposition techniques to identify the optimal number and the properties of MDF components. We find that the shape and spatial variations of the MDF (at [Fe/H]=-1 dex) are well represented as a smoothly varying contribution of three overlapping components located at [Fe/H] = +0.32, -0.17, and -0.66 dex. The bimodal MDF found in previous studies is in agreement with our trimodal assessment once the limitations in sample size and individual measurement errors are taken into account. The shape of the MDF and its correlations with kinematics reveal different spatial distributions and kinematical structure for the three components co-existing in the bulge region. We confirm the consensus physical interpretation of metal-rich stars as associated with the secularly evolved disc into a boxy/peanut X-shape bar. On the other hand, metal-intermediate stars could be the product of in-situ formation at high redshift in a gas-rich environment characterized by violent and fast star formation. This interpretation would help us to link a present-day structure with those observed in formation in the centre of high-redshift galaxies. Finally, metal-poor stars may correspond to the metal-rich tail of the population sampled at lower metallicity from the study of RR Lyrae stars. Conversely, they could be associated with the metal-poor tail of the early thick disc.Ítem Stellar Characterization and Radius Inflation of Hyades M-dwarf Stars from the APOGEE Survey(Institute of Physics, 2023-07-01) Wanderley, Fábio; Cunha, Katia; Souto, Diogo; Smith, Verne V.; Cao, Lyra; Pinsonneault, Marc; Allende Prieto, C.; Covey, Kevin; Masseron, Thomas; Pascucci, Ilaria; Stassun, Keivan G.; Terrien, Ryan; Bergsten, Galen J.; Bizyaev, Dmitry; Fernández-Trincado, José G.; Jönsson, Henrik; Hasselquist, Sten; Holtzman, Jon A.; Lane, Richard R.; Mahadevan, Suvrath; Majewski, Steven R.; Minniti, Dante; Pan, Kaike; Serna, Javier; Sobeck, Jennifer; Stringfellow, Guy S.We present a spectroscopic analysis of a sample of 48 M-dwarf stars (0.2 M ⊙ < M < 0.6 M ⊙) from the Hyades open cluster using high-resolution H-band spectra from the Sloan Digital Sky Survey/Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. Our methodology adopts spectrum synthesis with LTE MARCS model atmospheres, along with the APOGEE Data Release 17 line list, to determine effective temperatures, surface gravities, metallicities, and projected rotational velocities. The median metallicity obtained for the Hyades M dwarfs is [M/H] = 0.09 ± 0.03 dex, indicating a small internal uncertainty and good agreement with optical results for Hyades red giants. Overall, the median radii are larger than predicted by stellar models by 1.6% ± 2.3% and 2.4% ± 2.3%, relative to a MIST and DARTMOUTH isochrone, respectively. We emphasize, however, that these isochrones are different, and the fractional radius inflation for the fully and partially convective regimes have distinct behaviors depending on the isochrone. Using a MIST isochrone there is no evidence of radius inflation for the fully convective stars, while for the partially convective M dwarfs the radii are inflated by 2.7% ± 2.1%, which is in agreement with predictions from models that include magnetic fields. For the partially convective stars, rapid rotators present on average higher inflation levels than slow rotators. The comparison with SPOTS isochrone models indicates that the derived M-dwarf radii can be explained by accounting for stellar spots in the photosphere of the stars, with 76% of the studied M dwarfs having up to 20% spot coverage, and the most inflated stars with ∼20%-40% spot coverage.Ítem The chemical characterization of halo substructure in the Milky Way based on APOGEE(Oxford University Press, 2023-04) Horta, Danny; Schiavon, Ricardo P.; Mackereth, J. Ted; Weinberg, David H.; Hasselquist, Sten; Feuillet, Diane; O’Connell, Robert W.; Anguiano, Borja; Allende-Prieto, Carlos; Beaton, Rachael L.; Bizyaev, Dmitry; Cunha, Katia; Geisler, Doug; García-Hernández D.A.; Holtzman, Jon; Jönsson, Henrik; Lane, Richard R.; Majewski, Steve R.; Mészáros, Szabolcs; Minniti, Dante; Nitschelm, Christian; Shetrone, Matthew; Smith, Verne V.; Zasowski, GailGalactic haloes in a Λ-CDM universe are predicted to host today a swarm of debris resulting from cannibalized dwarf galaxies. The chemodynamical information recorded in their stellar populations helps elucidate their nature, constraining the assembly history of the Galaxy. Using data from APOGEE and Gaia, we examine the chemical properties of various halo substructures, considering elements that sample various nucleosynthetic pathways. The systems studied are Heracles, Gaia-Enceladus/Sausage (GES), the Helmi stream, Sequoia, Thamnos, Aleph, LMS-1, Arjuna, I’itoi, Nyx, Icarus, and Pontus. Abundance patterns of all substructures are cross-compared in a statistically robust fashion. Our main findings include: (i) the chemical properties of most substructures studied match qualitatively those of dwarf Milky Way satellites, such as the Sagittarius dSph. Exceptions are Nyx and Aleph, which are chemically similar to disc stars, implying that these substructures were likely formed in situ; (ii) Heracles differs chemically from in situ populations such as Aurora and its inner halo counterparts in a statistically significant way. The differences suggest that the star formation rate was lower in Heracles than in the early Milky Way; (iii) the chemistry of Arjuna, LMS-1, and I’itoi is indistinguishable from that of GES, suggesting a possible common origin; (iv) all three Sequoia samples studied are qualitatively similar. However, only two of those samples present chemistry that is consistent with GES in a statistically significant fashion; (v) the abundance patterns of the Helmi stream and Thamnos are different from all other halo substructures. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Ítem The Open Cluster Chemical Abundances and Mapping Survey. IV. Abundances for 128 Open Clusters Using SDSS/APOGEE DR16(Institute of Physics Publishing, 2020-05) Donor, John; Frinchaboy, Peter M.; Cunha, Katia; O'connell, Julia E.; Prieto, Carlos Allende; Almeida, Andrés; Anders, Friedrich; Beaton, Rachael; Bizyaev, Dmitry; Brownstein, Joel R.; Carrera, Ricardo; Chiappini, Cristina; Cohen, Roger; García-Hernández D. A.; Geisler, Doug; Hasselquist, Sten; Jönsson, Henrik; Lane, Richard R.; Majewski, Steven R.; Minniti, Dante; Bidin, Christian Moni; Pan, Kaike; Roman-Lopes, Alexandre; Sobeck, Jennifer S.; Zasowski, GailThe Open Cluster Chemical Abundances and Mapping (OCCAM) survey aims to constrain key Galactic dynamical and chemical evolution parameters by the construction of a large, comprehensive, uniform, infrared-based spectroscopic data set of hundreds of open clusters. This fourth contribution from the OCCAM survey presents analysis using Sloan Digital Sky Survey/APOGEE DR16 of a sample of 128 open clusters, 71 of which we designate to be "high quality" based on the appearance of their color-magnitude diagram. We find the APOGEE DR16 derived [Fe/H] abundances to be in good agreement with previous high-resolution spectroscopic open cluster abundance studies. Using the high-quality sample, we measure Galactic abundance gradients in 16 elements, and find evolution of some of the [X/Fe] gradients as a function of age. We find an overall Galactic [Fe/H] versus R GC gradient of -0.068 ± 0.001 dex kpc-1 over the range of 6 < R GC < 13.9 kpc; however, we note that this result is sensitive to the distance catalog used, varying as much as 15%. We formally derive the location of a break in the [Fe/H] abundance gradient as a free parameter in the gradient fit for the first time. We also measure significant Galactic gradients in O, Mg, S, Ca, Mn, Cr, Cu, Na, Al, and K, some of which are measured for the first time. Our large sample allows us to examine four well-populated age bins in order to explore the time evolution of gradients for a large number of elements and comment on possible implications for Galactic chemical evolution and radial migration.Ítem The Open Cluster Chemical Abundances and Mapping Survey. VI. Galactic Chemical Gradient Analysis from APOGEE DR17(American Astronomical Society, 2022-09-01) Myers, Natalie; Donor, John; Spoo, Taylor; Frinchaboy, Peter M.; Cunha, Katia; Price Whelan, Adrian M.; Majewski, Steven R.; Beaton, Rachael L.; Zasowski, Gail; O'connell, Julia; Ray, Amy E.; Bizyaev, Dmitry; Chiappini, Cristina; García Hernández, D.A.; Geisler, Doug; Jönsson, Henrik; Lane, Richard R.; Longa Peña, Penélope; Minchev, Ivan; Minniti, Dante; Nitschelm, Christian; Roman Lopes, A.The goal of the Open Cluster Chemical Abundances and Mapping (OCCAM) survey is to constrain key Galactic dynamic and chemical evolution parameters by the construction and analysis of a large, comprehensive, uniform data set of infrared spectra for stars in hundreds of open clusters. This sixth contribution from the OCCAM survey presents analysis of SDSS/APOGEE Data Release 17 (DR17) results for a sample of stars in 150 open clusters, 94 of which we designate to be "high-quality"based on the appearance of their color-magnitude diagram. We find the APOGEE DR17-derived [Fe/H] values to be in good agreement with those from previous high-resolution spectroscopic open cluster abundance studies. Using a subset of the high-quality sample, the Galactic abundance gradients were measured for 16 chemical elements, including [Fe/H], for both Galactocentric radius (R GC) and guiding center radius (R guide). We find an overall Galactic [Fe/H] versus R GC gradient of -0.073 ± 0.002 dex kpc-1 over the range of 6 > R GC < 11.5 kpc, and a similar gradient is found for [Fe/H] versus R guide. Significant Galactic abundance gradients are also noted for O, Mg, S, Ca, Mn, Na, Al, K, and Ce. Our large sample additionally allows us to explore the evolution of the gradients in four age bins for the remaining 15 elements. © 2022. The Author(s). Published by the American Astronomical Society.