Browsing by Author "Beaton, Rachael"

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    Strong chemical tagging with APOGEE: 21 candidate star clusters that have dissolved across the Milky Way disc
    (2020) Price-Jones, Natalie; Bovy, Jo; Webb, Jeremy J.; Prieto, Carlos Allende; Beaton, Rachael; Brownstein, Joel R.; Cohen, Roger E.; Cunha, Katia; Donor, John; Frinchaboy, Peter M.; Garcia-Hernandez, D. A.; Lane, Richard R.; Majewski, Steven R.; Nidever, David L.; Roman-Lopes, Alexandre
    Chemically tagging groups of stars born in the same birth cluster is a major goal of spectroscopic surveys. To investigate the feasibility of such strong chemical tagging, we perform a blind chemical tagging experiment on abundances measured from APOGEE survey spectra. We apply a density-based clustering algorithm to the 8D chemical space defined by [Mg/Fe], [Al/Fe], [Si/Fe], [K/Fe], [Ti/Fe], [Mn/Fe], [Fe/H], and [Ni/Fe], abundances ratios which together span multiple nucleosynthetic channels. In a high-quality sample of 182 538 giant stars, we detect 21 candidate clusterswith more than 15 members. Our candidate clusters are more chemically homogeneous than a population of non-member stars with similar [Mg/Fe] and [Fe/H], even in abundances not used for tagging. Group members are consistent with having the same age and fall along a single stellar-population track in log g versus T-eff space. Each group's members are distributed over multiple kpc, and the spread in their radial and azimuthal actions increases with age. We qualitatively reproduce this increase using N-body simulations of cluster dissolution in Galactic potentials that include transient winding spiral arms. Observing our candidate birth clusters with high-resolution spectroscopy in other wavebands to investigate their chemical homogeneity in other nucleosynthetic groups will be essential to confirming the efficacy of strong chemical tagging. Our initially spatially compact but now widely dispersed candidate clusters will provide novel limits on chemical evolution and orbital diffusion in the Galactic disc, and constraints on star formation in loosely bound groups.
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    The Open Cluster Chemical Abundances and Mapping Survey. IV. Abundances for 128 Open Clusters Using SDSS/APOGEE DR16
    (2020) Donor, John; Frinchaboy, Peter M.; Cunha, Katia; O'Connell, Julia E.; Prieto, Carlos Allende; Almeida, Andres; Anders, Friedrich; Beaton, Rachael; Bizyaev, Dmitry; Brownstein, Joel R.; Carrera, Ricardo; Chiappini, Cristina; Cohen, Roger; Garcia-Hernandez, D. A.; Geisler, Doug; Hasselquist, Sten; Jonsson, Henrik; Lane, Richard R.; Majewski, Steven R.; Minniti, Dante; Bidin, Christian Moni; Pan, Kaike; Roman-Lopes, Alexandre; Sobeck, Jennifer S.; Zasowski, Gail
    The 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.