Browsing by Author "Majewski, S. R."

Now showing 1 - 8 of 8
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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.
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    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.
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    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....
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    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.
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    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.
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    THE ACS SURVEY OF GLOBULAR CLUSTERS. XIII. PHOTOMETRIC CALIBRATION IN COMPARISON WITH STETSON STANDARDS
    (2014) Hempel, Maren; Sarajedini, A.; Anderson, J.; Aparicio Alonso, Andrés; Bedin, L. R.; Chaboyer, B.; Majewski, S. R.; Marín, A.; Milone, A.; Paust, N.; Piotto, G.; Reid, I.; Rosenberg, A.; Siegel, M.
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    The chemical compositions of accreted and in situ galactic globular clusters according to SDSS/APOGEE
    (2020) Horta, D.; Schiavon, R. P.; Mackereth, J. T.; Beers, T. C.; Fernández-Trincado, J. G.; Frinchaboy, P. M.; García-Hernández, D. A.; Geisler, D.; Hasselquist, S.; Jönsson, H.; Lane Richard Reade; Majewski, S. R.; Mészáros, S.; Bidin, C. M.; Nataf, D. M.; Roman-Lopes, A.; Nitschelm, C.; Vargas-González, J.; Zasowsk, G.
    Studies of the kinematics and chemical compositions of Galactic globular clusters (GCs) enable the reconstruction of the history of star formation, chemical evolution, and mass assembly of the Galaxy. Using the latest data release (DR16) of the SDSS/APOGEE survey, we identify 3090 stars associated with 46 GCs. Using a previously defined kinematic association, we break the sample down into eight separate groups and examine how the kinematics-based classification maps into chemical composition space, considering only α (mostly Si and Mg) elements and Fe. Our results show that (i) the loci of both in situ and accreted subgroups in chemical space match those of their field counterparts; (ii) GCs from different individual accreted subgroups occupy the same locus in chemical space. This could either mean that they share a similar origin or that they are associated with distinct satellites which underwent similar chemical enrichment histories; (iii) the chemical compositions of the GCs associated with the low orbital energy subgroup defined by Massari and collaborators is broadly consistent with an in situ origin. However, at the low-metallicity end, the distinction between accreted and in situ populations is blurred; (iv) regarding the status of GCs whose origin is ambiguous, we conclude the following: the position in Si–Fe plane suggests an in situ origin for Liller 1 and a likely accreted origin for NGC 5904 and NGC 6388. The case of NGC 288 is unclear, as its orbital properties suggest an accretion origin, its chemical composition suggests it may have formed in situ.
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    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.