Examinando por Autor "Pan, Kaike"
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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 Is Terzan 5 the remnant of a building block of the Galactic bulge? Evidence from APOGEE(Oxford University Press, 2022-07-01) Taylor, Dominic J.; Mason, Andrew C.; Schiavon, Ricardo P.; Horta, Danny; Nataf, David M.; Geisler, Doug; Kisku, Shobhit; Phillips, Siân G.; Cohen, Roger E.; Fernández Trincado, José G.; Beers, Timothy C.; Bizyaev, Dmitry; García Hernández, Domingo Aníbal; Lane, Richard R.; Longa Peña, Penélope; Minniti, Dante; Muñoz, Cesar; Pan, Kaike; Villanova, SandroIt has been proposed that the globular cluster-like system Terzan 5 is the surviving remnant of a primordial building block of the Milky Way bulge, mainly due to the age/metallicity spread and the distribution of its stars in the α-Fe plane. We employ Sloan Digital Sky Survey data from the Apache Point Observatory Galactic Evolution Experiment to test this hypothesis. Adopting a random sampling technique, we contrast the abundances of 10 elements in Terzan 5 stars with those of their bulge field counterparts with comparable atmospheric parameters, finding that they differ at statistically significant levels. Abundances between the two groups differ by more than 1σ in Ca, Mn, C, O, and Al, and more than 2σ in Si and Mg. Terzan 5 stars have lower [α/Fe] and higher [Mn/Fe] than their bulge counterparts. Given those differences, we conclude that Terzan 5 is not the remnant of a major building block of the bulge. We also estimate the stellar mass of the Terzan 5 progenitor based on predictions by the Evolution and Assembly of GaLaxies and their Environments suite of cosmological numerical simulations, concluding that it may have been as low as ∼3 × 108 M⊙ so that it was likely unable to significantly influence the mean chemistry of the bulge/inner disc, which is significantly more massive (∼1010 M⊙). We briefly discuss existing scenarios for the nature of Terzan 5 and propose an observational test that may help elucidate its origin. © 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.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 Stellar Properties for a Comprehensive Collection of Star-forming Regions in the SDSS APOGEE-2 Survey* Based on SDSS Data Releases 16 and 17.(American Astronomical Society, 2023-02) Román-Zúñiga, Carlos G.; Kounkel, Marina; Hernández, Jesús; Peña Ramírez, Karla; López-Valdivia, Ricardo; Covey, Kevin R.; Stutz, Amelia M.; Roman-Lopes, Alexandre; Campbell, Hunter; Khilfeh, Elliott; Tapia, Mauricio; Stringfellow, Guy S.; Downes, Juan José; Stassun, Keivan G.; Minniti, Dante; Bayo, Amelia; Kim, Jinyoung Serena; Suárez, Genaro; Ybarra, Jason E.; Fernández-Trincado, José G.; Longa-Peña, Penélope; Ramírez-Preciado, Valeria; Serna, Javier; Lane, Richard R.; García-Hernández D.A.; Beaton, Rachael L.; Bizyaev, Dmitry; Pan, KaikeThe Sloan Digital Sky Survey IV APOGEE-2 primary science goal was to observe red giant stars throughout the Galaxy to study its dynamics, morphology, and chemical evolution. The APOGEE instrument, a high-resolution 300-fiber H-band (1.55-1.71 μm) spectrograph, is also ideal to study other stellar populations in the Galaxy, among which are a number of star-forming regions and young open clusters. We present the results of the determination of six stellar properties (T eff, log g , [Fe/H], L/L ⊙, M/M ⊙, and age) for a sample that is composed of 3360 young stars, of subsolar to supersolar types, in 16 Galactic star formation and young open cluster regions. Those sources were selected by using a clustering method that removes most of the field contamination. Samples were also refined by removing targets affected by various systematic effects of the parameter determination. The final samples are presented in a comprehensive catalog that includes all six estimated parameters. This overview study also includes parameter spatial distribution maps for all regions and Hertzsprung-Russell ( log L / L ⊙ vs. T eff) diagrams. This study serves as a guide for detailed studies on individual regions and paves the way for the future studies on the global properties of stars in the pre-main-sequence phase of stellar evolution using more robust samples. © 2023. The Author(s). Published by the American Astronomical Society.Ítem The age–chemical abundance structure of the Galaxy I: evidence for a late-accretion event in the outer disc at z ∼ 0.6(Oxford University Press, 2020-05) Lian, Jianhui; Thomas, Daniel; Claudia, Maraston; Zamora, Olga; Tayar, Jamie; Pan, Kaike; Tissera, Patricia; Fernandez-Trincado, Jose G.; Garcia-Hernandez, D. A.We investigate the age-chemical abundance structure of the outer Galactic disc at a galactocentric distance of r > 10 kpc as recently revealed by the SDSS/APOGEE survey. Two sequences are present in the [α/Fe]-[Fe/H] plane with systematically different stellar ages. Surprisingly, the young sequence is less metal rich, suggesting a recent dilution process by additional gas accretion. As the stars with the lowest iron abundance in the younger sequence also show an enhancement in α-element abundance, the gas accretion event must have involved a burst of star formation. In order to explain these observations, we construct a chemical evolution model. In this model, we include a relatively short episode of gas accretion at late times on top of an underlying secular accretion over long time-scales. Our model is successful at reproducing the observed distribution of stars in the three-dimensional space of [α/Fe]-[Fe/H]-age in the outer disc. We find that a late-time accretion with a delay of 8.2 Gyr and a time-scale of 0.7 Gyr best fits the observed data, in particular the presence of the young, metal-poor sequence. Our best-fitting model further implies that the amount of accreted gas in the late-time accretion event needs to be about three times the local gas reservoir in the outer disc at the time of accretion in order to sufficiently dilute the metal abundance. Given this large fraction, we interpret the late-time accretion event as a minor merger presumably with a gas-rich dwarf galaxy with a mass M∗ < 109 M☉ and a gas fraction of ∼75 per cent. © 2020 The Author(s)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 SDSS-IV extended baryon oscillation spectroscopic survey: Overview and early data(Institute of Physics Publishing, 2016-02) Dawson, Kyle S.; Kneib, Jean-Paul; Percival, Will J.; Alam, Shadab; Albareti, Franco D.; Anderson, Scott F.; Armengaud, Eric; Aubourg, Éric; Bailey, Stephen; Bautista, Julian E.; Berlind, Andreas A.; Bershady, Matthew A.; Beutler, Florian; Bizyaev, Dmitry; Blanton, Michael R.; Blomqvist, Michael; Bolton, Adam S.; Bovy, Jo; Brandt, W.N.; Brinkmann, Jon; Brownstein, Joel R.; Burtin, Etienne; Busca, N.G.; Cai, Zheng; Chuang, Chia-Hsun; Clerc, Nicolas; Comparat, Johan; Cope, Frances; Croft, Rupert A. C.; Cruz-Gonzalez, Irene; Da Costa, Luiz N; Cousinou, Marie-Claude; Darling, Jeremy; De La MacOrra, Axel; De La Torre, Sylvain; Delubac, Timothée; Du Mas Des Bourboux, Hélion; Dwelly, Tom; Ealet, Anne; Eisenstein, Daniel J.; Eracleous, Michael; Escoffier, S.; Fan, Xiaohui; Finoguenov, Alexis; Font-Ribera, Andreu; Frinchaboy, Peter; Gaulme, Patrick; Georgakakis, Antonis; Green, Paul; Guo, Hong; Guy, Julien; Ho, Shirley; Holder, Diana; Huehnerhoff, Joe; Hutchinson, Timothy; Jing, Yipeng; Jullo, Eric; Kamble, Vikrant; Kinemuchi, Karen; Kirkby, David; Kitaura, Francisco-Shu; Klaene, Mark A.; Laher, Russ R.; Lang, Dustin; Laurent, Pierre; Goff, Jean-Marc Le; Li, Cheng; Liang, Yu; Lima, Marcos; Lin, Qiufan; Lin, Weipeng; Lin, Yen-Ting; Long, Daniel C.; Lundgren, Britt; MacDonald, Nicholas; Maia, Marcio Antonio Geimba; Malanushenko, Elena; Malanushenko, Viktor; Mariappan, Vivek; McBride, Cameron K.; McGreer, Ian D.; Ménard, Brice; Merloni, Andrea; Meza, Andres; Montero-Dorta, Antonio D.; Muna, Demitri; Myers, Adam D.; Nandra, Kirpal; Naugle, Tracy; Newman, Jeffrey A.; Noterdaeme, Pasquier; Nugent, Peter; Ogando, Ricardo; Olmstead, Matthew D.; Oravetz, Audrey; Oravetz, Daniel J.; Padmanabhan, Nikhil; Palanque-Delabrouille, Nathalie; Pan, Kaike; Parejko, John K.; Pâris, Isabelle; Peacock, John A.; Petitjean, Patrick; Pieri, Matthew M.; Pisani, Alice; Prada, Francisco; Prakash, Abhishek; Raichoor, Anand; Reid, Beth; Rich, James; Ridl, Jethro; Rodriguez-Torres, Sergio; Rosell, Aurelio Carnero; Ross, Ashley J.; Rossi, Graziano; Ruan, John; Salvato, Mara; Sayres, Conor; Schneider, Donald P.; Schlegel, David J.; Seljak, Uros; Seo, Hee-Jong; Sesar, Branimir; Shandera, Sarah; Shu, Yiping; Slosar, Anže; Sobreira, Flavia; Streblyanska, Alina; Suzuki, Nao; Taylor, Donna; Tao, Charling; Tinker, Jeremy L.; Tojeiro, Rita; Vargas-Magaña, Mariana; Wang, Yuting; Weaver, Benjamin A.; Weinberg, David H.; White, Martin; Wood-Vasey, W.M.; Yeche, Christophe; Zhai, Zhongxu; Zhao, Cheng; Zhao, Gong-Bo; Zheng, Zheng; Zhu, Guangtun Ben; Zou, HuIn a six-year program started in 2014 July, the Extended Baryon Oscillation Spectroscopic Survey (eBOSS) will conduct novel cosmological observations using the BOSS spectrograph at Apache Point Observatory. These observations will be conducted simultaneously with the Time Domain Spectroscopic Survey (TDSS) designed for variability studies and the Spectroscopic Identification of eROSITA Sources (SPIDERS) program designed for studies of X-ray sources. In particular, eBOSS will measure with percent-level precision the distance-redshift relation with baryon acoustic oscillations (BAO) in the clustering of matter. eBOSS will use four different tracers of the underlying matter density field to vastly expand the volume covered by BOSS and map the large-scale structures over the relatively unconstrained redshift range 0.6 < z < 2.2. Using more than 250,000 new, spectroscopically confirmed luminous red galaxies at a median redshift z = 0.72, we project that eBOSS will yield measurements of the angular diameter distance dA(z) to an accuracy of 1.2% and measurements of H(z) to 2.1% when combined with the z > 0.6 sample of BOSS galaxies. With ∼195,000 new emission line galaxy redshifts, we expect BAO measurements of dA(z) to an accuracy of 3.1% and H(z) to 4.7% at an effective redshift of z = 0.87. A sample of more than 500,000 spectroscopically confirmed quasars will provide the first BAO distance measurements over the redshift range 0.9 < z < 2.2, with expected precision of 2.8% and 4.2% on dA(z) and H(z), respectively. Finally, with 60,000 new quasars and re-observation of 60,000 BOSS quasars, we will obtain new Lyα forest measurements at redshifts z > 2.1; these new data will enhance the precision of dA(z) and H(z) at z > 2.1 by a factor of 1.44 relative to BOSS. Furthermore, eBOSS will provide improved tests of General Relativity on cosmological scales through redshift-space distortion measurements, improved tests for non Gaussianity in the primordial density field, and new constraints on the summed mass of all neutrino species. Here, we provide an overview of the cosmological goals, spectroscopic target sample, demonstration of spectral quality from early data, and projected cosmological constraints from eBOSS.