Suchergebnisse

A Li-rich red giant (RG) star (2M19411367+4003382) recently discovered in the direction of NGC 6819 belongs to the rare subset of Li-rich stars that have not yet evolved to the luminosity bump, an evolutionary stage where models predict Li can be replenished. The currently favored model to explain Li enhancement in first-ascent RGs like 2M19411367+4003382 requires deep mixing into the stellar interior. Testing this model requires a measurement of C-12/C-13, which is possible to obtain from Apache Point Observatory Galactic Evolution Experiment (APOGEE) spectra. However, the Li-rich star also has abnormal asteroseismic properties that call into question its membership in the cluster, even though its radial velocity and location on color-magnitude diagrams are consistent with membership. To address these puzzles, we have measured a wide array of abundances in the Li-rich star and three comparison stars using spectra taken as part of the APOGEE survey to determine the degree of stellar mixing, address the question of membership, and measure the surface gravity. We confirm that the Li-rich star is a RG with the same overall chemistry as the other cluster giants. However, its log g is significantly lower, consistent with the asteroseismology results and suggestive of a very low mass if the star is indeed a cluster member. Regardless of the cluster membership, the C-12/C-13 and C/N ratios of the Li-rich star are consistent with standard first dredge-up, indicating that Li dilution has already occurred, and inconsistent with internal Li enrichment scenarios that require deep mixing. ; National Science Foundation AST1109888 ; NSF AST-1358862, AST 1109718, AST 1312863 ; Alfred P. Sloan Foundation ; National Science Foundation ; U.S. Department of Energy Office of Science ; University of Arizona ; Brazilian Participation Group ; Brookhaven National Laboratory ; Carnegie Mellon University ; University of Florida ; French Participation Group ; German Participation Group ; Harvard University ; Instituto de Astrofisica de Canarias ; Michigan State/NotreDame/JINA Participation Group ; Johns Hopkins University ; Lawrence Berkeley National Laboratory ; Max Planck Institute for Astrophysics ; Max Planck Institute for Extraterrestrial Physics ; New Mexico State University ; New York University ; Ohio State University ; Pennsylvania State University ; University of Portsmouth ; Princeton University ; Spanish Participation Group ; University of Tokyo ; University of Utah ; Vanderbilt University ; University of Virginia ; University of Washington ; Yale University ; National Aeronautics and Space Administration ; Two Micron All Sky Survey ; University of Massachusetts ; Infrared Processing and Analysis Center/California Institute of Technology ; U.S. Government NAG W-2166 ; Astronomy

We present a map of the total intrinsic reddening across similar or equal to 34 deg(2) of the Small Magellanic Cloud (SMC) derived using optical (ugriz) and near-infrared (IR; YJK(s)) spectral energy distributions (SEDs) of background galaxies. The reddening map is created using a subsample of 29 274 galaxies with low levels of intrinsic reddening based on the LEPHARE chi(2) minimization SED-fitting routine. We find statistically significant enhanced levels of reddening associated with the main body of the SMC compared with regions in the outskirts [Delta E(B - V) similar or equal to 0.3 mag]. A comparison with literature reddening maps of the SMC shows that, after correcting for differences in the volume of the SMC sampled, there is good agreement between our results and maps created using young stars. In contrast, we find significant discrepancies between our results and maps created using old stars or based on longer wavelength far-IR dust emission that could stem from biased samples in the former and uncertainties in the far-IR emissivity and the optical properties of the dust grains in the latter. This study represents one of the first large-scale categorizations of extragalactic sources behind the SMC and as such we provide the LEPHARE outputs for our full sample of similar to 500 000 sources. ; European Research Council (ERC) 682115 ERC consolidator grant project STARKEY 615604 National Science Foundation (NSF) AST 1655677 Spanish Ministry for Science, Innovation and Universities AYA2016-81065-C2-2 European Commission AYA2016-81065-C2-2 State Agency for Research of the Spanish MCIU through the 'Centre of Excellence Severo Ochoa' award SEV-2017-0709 PGC2018-095049B-C21 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT PIA/BASAL AFB-170002 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1170364 Science and Engineering Research Board, India through a Ramanujan Fellowship UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) VISTA at the La Silla Paranal Observatory 179.B-2003 United States Department of Energy (DOE) National Science Foundation (NSF) Spanish Government UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) Higher Education Funding Council for England National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign Kavli Institute of Cosmological Physics at the University of Chicago Ohio State University Ciencia Tecnologia e Inovacao (FINEP) Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro (FAPERJ) Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) Ministerio da Ciencia, Tecnologia e Inovacao German Research Foundation (DFG) Mitchell Institute for Fundamental Physics and Astronomy at Texas AM University United States Department of Energy (DOE) University of Chicago University of California at Santa Cruz University of Cambridge Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid University of Chicago University College London DES-Brazil Consortium University of Edinburgh ETH Zurich United States Department of Energy (DOE) University of Chicago University of Illinois atUrbanaChampaign Institut de Ciencies de l'Espai (IEEC/CSIC) Institut de Fisica d'Altes Energies United States Department of Energy (DOE) Ludwig-Maximilians Universitat Munchen associated Excellence Cluster Universe University of Michigan System National Science Foundation (NSF) NSF - Directorate for Mathematical & Physical Sciences (MPS) University of Nottingham Ohio State University University of Pennsylvania University of Portsmouth Stanford University United States Department of Energy (DOE) Stanford University University of Sussex Texas AM University

The periphery of the Small Magellanic Cloud (SMC) can unlock important information regarding galaxy formation and evolution in interacting systems. Here, we present a detailed study of the extended stellar structure of the SMC using deep colour-magnitude diagrams, obtained as part of the Survey of the MAgellanic Stellar History (SMASH). Special care was taken in the decontamination of our data from Milky Way (MW) foreground stars, including from foreground globular clusters NGC 362 and 47 Tuc. We derived the SMC surface brightness using a `conservative' approach from which we calculated the general parameters of the SMC, finding a staggered surface brightness profile. We also traced the fainter outskirts by constructing a stellar density profile. This approach, based on stellar counts of the oldest main-sequence turn-off stars, uncovered a tidally disrupted stellar feature that reaches as far out as 12 deg from the SMC centre. We also serendipitously found a faint feature of unknown origin located at similar to 14 deg from the centre of the SMC and that we tentatively associated with a more distant structure. We compared our results to in-house simulations of a 1 x 10(9) M-circle dot SMC, finding that its elliptical shape can be explained by its tidal disruption under the combined presence of the MW and the Large Magellanic Cloud. Finally, we found that the older stellar populations show a smooth profile while the younger component presents a jump in the density followed by a flat profile, confirming the heavily disturbed nature of the SMC. ; National Science Foundation (NSF) AST-1909497 Fondo Nacional de Desarrollo Cientifico y Tecnologico (FONDECYT) Regular grant 1181797 Max Planck Society Foundation CELLEX French National Research Agency (ANR) ANR-18-CE31-0017 INSU,CNRS through the Programme National Galaxies et Cosmologie European Research Council (ERC) 682115 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT PIA/BASAL AFB-170002 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1170364 AEI/FEDER, UE AYA2017-89076-P AYA2015-63810-P Ministerio de Ciencia, Innovacion y Universidades (MCIU) Consejeria de Economia, Industria, Comercio y Conocimiento of the Canary Islands Autonomous Community, through the Regional Budget (IAC project, TRACES) RAVET project AYA2016-77237-C3-1-P MCIU Juan de la Cierva - Formacion grant FJCI-2016-30342 State Agency for Research of the Spanish MCIU through the 'Centre of Excellence Severo Ochoa' award SEV-2017-0709 United States Department of Energy (DOE) National Science Foundation (NSF) Spanish Government UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) Higher Education Funding Council for England National Center for Supercomputing Applications Kavli Institute for Cosmological Physics Ciencia Tecnologia e Inovacao (FINEP) Fundacao Carlos Chagas Filho de Amparo a Pesquisa Ministerio da Ciencia e Tecnologia (Brazil) German Research Foundation (DFG) National Council for Scientific and Technological Development (CNPq)

We present a map of the total intrinsic reddening across similar or equal to 34 deg(2) of the Small Magellanic Cloud (SMC) derived using optical (ugriz) and near-infrared (IR; YJK(s)) spectral energy distributions (SEDs) of background galaxies. The reddening map is created using a subsample of 29 274 galaxies with low levels of intrinsic reddening based on the LEPHARE chi(2) minimization SED-fitting routine. We find statistically significant enhanced levels of reddening associated with the main body of the SMC compared with regions in the outskirts [Delta E(B - V) similar or equal to 0.3 mag]. A comparison with literature reddening maps of the SMC shows that, after correcting for differences in the volume of the SMC sampled, there is good agreement between our results and maps created using young stars. In contrast, we find significant discrepancies between our results and maps created using old stars or based on longer wavelength far-IR dust emission that could stem from biased samples in the former and uncertainties in the far-IR emissivity and the optical properties of the dust grains in the latter. This study represents one of the first large-scale categorizations of extragalactic sources behind the SMC and as such we provide the LEPHARE outputs for our full sample of similar to 500 000 sources. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society ; This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 682115). SR acknowledges support from the ERC consolidator grant project STARKEY(grant agreement no. 615604). YC acknowledges support from NSF grant AST 1655677. DMDacknowledges financial support from the Spanish Ministry for Science, Innovation and Universities and FEDER funds through grant AYA2016-81065-C2-2, the State Agency for Research of the Spanish MCIU through the 'Centre of Excellence Severo Ochoa' award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709) and from grant PGC2018-095049B-C21. RRM acknowledges partial support from project BASAL AFB-170002 as well as FONDECYT project no. 1170364. SS acknowledges support from the Science and Engineering Research Board, India through a Ramanujan Fellowship. The authors would like to thank the Cambridge Astronomy Survey Unit (CASU) and theWide Field Astronomy Unit (WFAU) in Edinburgh for providing the necessary data products under the support of the Science and Technology Facilities Council (STFC) in theU.K. The authorswould also like to thank K. Gordon and J. Roman-Duval for discussions related to the use of the HERITAGE dust maps. The authors would like to extend their gratitude to the referee, Geoff Clayton, who provided several comments that improved the manuscript. This study was based on observations made with VISTA at the La Silla Paranal Observatory under programme ID 179.B-2003. This project used data obtained with the Dark Energy Camera (DECam), which was constructed by the Dark Energy Survey (DES) collaboration. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the STFC, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundacao Carlos Chagas Filho de Amparo 'a Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and the Ministerio da Ciencia, Tecnologia e Inovacao, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. The Collaborating Institutions are Argonne National Laboratory, the University of California at Santa Cruz, the University of Cambridge, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid, the University of Chicago, University College London, the DES-Brazil Consortium, the University of Edinburgh, the Eidgenossische Technische Hochschule (ETH) Zurich, Fermi NationalAccelerator Laboratory, the University of Illinois atUrbanaChampaign, the Institut de Ciencies de l'Espai (IEEC/CSIC), the Institut de Fisica d'Altes Energies, Lawrence Berkeley National Laboratory, the Ludwig-Maximilians Universitat Munchen and the associated Excellence Cluster Universe, the University of Michigan, the National Optical Astronomy Observatory, the University of Nottingham, the Ohio State University, the University of Pennsylvania, the University of Portsmouth, SLAC National Accelerator Laboratory, Stanford University, the University of Sussex, and Texas A&M University. Based on observations at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory (NOAO Prop. ID: 2013A-0411 and 2013B-0440; PI: Nidever), which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. Finally, this project has made extensive use of the Tool for OPerations on Catalogues And Tables (TOPCAT) software package (Taylor 2005) as well as the following open-source PYTHON packages: Astropy (The Astropy Collaboration 2018), MATPLOTLIB (Hunter 2007), NUMPY (Oliphant 2015), PANDAS (McKinney 2010), and SCIPY (Virtanen et al. 2020). ; Peer reviewed

The periphery of the Small Magellanic Cloud (SMC) can unlock important information regarding galaxy formation and evolution in interacting systems. Here, we present a detailed study of the extended stellar structure of the SMC using deep colour-magnitude diagrams, obtained as part of the Survey of the MAgellanic Stellar History (SMASH). Special care was taken in the decontamination of our data from Milky Way (MW) foreground stars, including from foreground globular clusters NGC 362 and 47 Tuc. We derived the SMC surface brightness using a `conservative' approach from which we calculated the general parameters of the SMC, finding a staggered surface brightness profile. We also traced the fainter outskirts by constructing a stellar density profile. This approach, based on stellar counts of the oldest main-sequence turn-off stars, uncovered a tidally disrupted stellar feature that reaches as far out as 12 deg from the SMC centre. We also serendipitously found a faint feature of unknown origin located at similar to 14 deg from the centre of the SMC and that we tentatively associated with a more distant structure. We compared our results to in-house simulations of a 1 x 10(9) M-circle dot SMC, finding that its elliptical shape can be explained by its tidal disruption under the combined presence of the MW and the Large Magellanic Cloud. Finally, we found that the older stellar populations show a smooth profile while the younger component presents a jump in the density followed by a flat profile, confirming the heavily disturbed nature of the SMC. © 2020 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society ; SRM acknowledges funding from grant AST-1909497 from the National Science Foundation. AM acknowledges support from Fondo Nacional de Desarrollo Cientifico y Tecnologico (FONDECYT) Regular grant 1181797 and funding from the Max Planck Society through a Partner Group grant. NFM gratefully acknowledge support from the French National Research Agency (ANR) funded project 'Pristine' (ANR-18-CE31-0017) along with funding from INSU,CNRS through the Programme National Galaxies et Cosmologie. M-RC and CPMB acknowledge support from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement no. 682115). RRM acknowledges partial support from project BASAL AFB-170002 as well as FONDECYT project N. 1170364. CG, TRL, and MMacknowledge financial support through the grants (AEI/FEDER, UE) AYA2017-89076-P and AYA2015-63810-P, as well as by the Ministerio de Ciencia, Innovacion y Universidades (MCIU), through the State Budget and by the Consejeria de Economia, Industria, Comercio y Conocimiento of the Canary Islands Autonomous Community, through the Regional Budget (including IAC project, TRACES). TRL is also supported by grant AYA2016-77237-C3-1-P (RAVET project) and a MCIU Juan de la Cierva - Formacion grant (FJCI-2016-30342). DMDacknowledges financial support from the State Agency for Research of the Spanish MCIU through the 'Centre of Excellence Severo Ochoa' award for the Instituto de Astrof ' isica de Andalucia (SEV-2017-0709). Based on observations at Cerro Tololo Inter-American Observatory, NSF's National Optical-Infrared Astronomy Research Laboratory (NOIRLab Prop. ID: 2013A-0411 and 2013B-0440; PI: Nidever), which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. This project used data obtained with the Dark Energy Camera (DECam), which was constructed by the Dark Energy Survey (DES) collaborating institutions: Argonne National Lab, University of California Santa Cruz, University of Cambridge, Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas-Madrid, University of Chicago, University College London, DES-Brazil consortium, University of Edinburgh, ETH-Zurich, University of Illinois at Urbana-Champaign, Institut de Ci`encies de l'Espai, Institut de F ' isica d'Altes Energies, Lawrence Berkeley National Lab, Ludwig-Maximilians Universitat, University of Michigan, National Optical Astronomy Observatory, University of Nottingham, Ohio State University, University of Pennsylvania, University of Portsmouth, SLAC National Lab, Stanford University, University of Sussex, and Texas A&M University. Funding for DES, including DECam, has been provided by the U.S. Department of Energy, National Science Foundation, Ministry of Education and Science (Spain), Science and Technology Facilities Council (UK), Higher Education Funding Council for England (England), National Center for Supercomputing Applications, Kavli Institute for Cosmological Physics, Financiadora de Estudos e Projetos, Fundacao Carlos Chagas Filho de Amparo a Pesquisa, Conselho Nacional de Desenvolvimento Cientifico e Tecnologico and the Ministerio da Ciencia e Tecnologia (Brazil), the German Research Foundation-sponsored cluster of excellence `Origin and Structure of the Universe' and the DES collaborating institutions. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. ; Peer reviewed

We report the first APOGEE metallicities and alpha-element abundances measured for 3600 red giant stars spanning a large radial range of both the Large (LMC) and Small Magellanic Clouds, the largest Milky Way (MW) dwarf galaxies. Our sample is an order of magnitude larger than that of previous studies and extends to much larger radial distances. These are the first results presented that make use of the newly installed southern APOGEE instrument on the du Pont telescope at Las Campanas Observatory. Our unbiased sample of the LMC spans a large range in metallicity, from [Fe/H] = -0.2 to very metal-poor stars with [Fe/H] -2.5, the most metal-poor Magellanic Cloud (MC) stars detected to date. The LMC [alpha/Fe]-[Fe/H] distribution is very flat over a large metallicity range but rises by similar to 0.1 dex at -1.0 < [Fe/H] less than or similar to -0.5. We interpret this as a sign of the known recent increase in MC star formation activity and are able to reproduce the pattern with a chemical evolution model that includes a recent "starburst." At the metal-poor end, we capture the increase of [alpha/Fe] with decreasing [Fe/H] and constrain the "alpha-knee" to [Fe/H] less than or similar to -2.2 in both MCs, implying a low star formation efficiency of similar to 0.01 Gyr(-1). The MC knees are more metal-poor than those of less massive MW dwarf galaxies such as Fornax, Sculptor, or Sagittarius. One possible interpretation is that the MCs formed in a lower-density environment than the MW, a hypothesis that is consistent with the paradigm that the MCs fell into the MW's gravitational potential only recently. ; State Research Agency (AEI) of the Spanish Ministry of Science, Innovation and Universities (MCIU) European Union (EU) AYA2017-88254-P National Science Foundation (NSF) AST-1801940 Crafoord Foundation Swedish Research Council Ruth och Nils-Erik Stenbacks stiftelse Physics Frontier Center/JINA Center for the Evolution of the Elements (JINA-CEE) - US National Science Foundation PHY 14-30152 Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT FONDECYT 3180210 1170364 Becas Iberoamerica Investigador 2019, Banco Santander Chile Comisión Nacional de Investigación Científica y Tecnológica (CONICYT) CONICYT PIA/BASAL AFB-170002 Programa de Apoyo a Proyectos de Investigación e Innovación Tecnológica (PAPIIT) Universidad Nacional Autónoma de México IN109919 Alfred P. Sloan Foundation United States Department of Energy (DOE) Center for High-Performance Computing at the University of Utah

The Sloan Digital Sky Survey III's Apache Point Observatory Galactic Evolution Experiment (APOGEE) is a high-resolution near-infrared spectroscopic survey covering all of the major components of the Galaxy, including the dust-obscured regions of the inner Milky Way disk and bulge. Here we present a sample of 10,341 likely red-clump stars (RC) from the first two years of APOGEE operations, selected based on their position in color-metallicity-surface-gravity-effective-temperature space using a new method calibrated using stellar evolution models and high-quality asteroseismology data. The narrowness of the RC locus in color-metallicity-luminosity space allows us to assign distances to the stars with an accuracy of 5%-10%. The sample extends to typical distances of about 3 kpc from the Sun, with some stars out to 8 kpc, and spans a volume of approximately 100 kpc(3) over 5 kpc less than or similar to R less than or similar to 14 kpc, vertical bar Z vertical bar less than or similar to 2 kpc, and -15 degrees less than or similar to Galactocentric azimuth less than or similar to 30 degrees. The APOGEE red-clump (APOGEE-RC) catalog contains photometry from the Two Micron All Sky Survey, reddening estimates, distances, line-of-sight velocities, stellar parameters and elemental abundances determined from the high-resolution APOGEE spectra, and matches to major proper motion catalogs. We determine the survey selection function for this data set and discuss how the RC selection samples the underlying stellar populations. We use this sample to limit any azimuthal variations in the median metallicity within the approximate to 45 degrees azimuthal region covered by the current sample to be <= 0.02 dex, which is more than an order of magnitude smaller than the radial metallicity gradient. This result constrains coherent non-axisymmetric flows within a few kiloparsecs from the Sun. ; NASA through Space Telescope Science Institute HST-HF-51285.01 ; NASA NAS5-26555, NNX13AE70G ; McLaughlin Fellowship at the University of Michigan ; European Research Council under the European Union 321035 ; NSF AST-1105930, AST-1311835 ; CNPq-Brazil ; Physics Frontier Center/Joint Institute for Nuclear Astrophysics (JINA) - U.S. National Science Foundation PHY 08-22648 ; Danish National Research Foundation DNRF106 ; Spanish Ministry of Economy and Competitiveness AYA-2011-27754 ; European Research Council under the European Community 338251 ; Deutsche Forschungsgemeinschaft (DFG) SFB 963/1 ; ASTERISK project (ASTERoseismic Investigations with SONG and Kepler) - European Research Council 267864 ; MICINN AYA2011-24704 ; Alfred P. Sloan Foundation ; U.S. Department of Energy Office of Science ; University of Arizona ; Brookhaven National Laboratory ; Carnegie Mellon University ; University of Florida ; Harvard University ; Instituto de Astrofisica de Canarias ; Johns Hopkins University ; Lawrence Berkeley National Laboratory ; Max Planck Institute for Astrophysics ; Max Planck Institute for Extraterrestrial Physics ; New Mexico State University ; New York University ; Ohio State University ; Pennsylvania State University ; University of Portsmouth ; Princeton University ; University of Tokyo ; University of Utah ; Vanderbilt University ; University of Virginia ; University of Washington ; Yale University ; McDonald Observatory