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V. Zh. Adibekyan

Bio: V. Zh. Adibekyan is an academic researcher from University of Porto. The author has contributed to research in topics: Stars & Metallicity. The author has an hindex of 22, co-authored 27 publications receiving 2788 citations.

Papers
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Journal ArticleDOI
TL;DR: In this article, a uniform and detailed analysis of 12 refractory elements (Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Co, Sc, Mn, and V) was performed for a sample of 1111 FGK dwarf stars from the HARPS GTO planet search program.
Abstract: Context. We performed a uniform and detailed abundance analysis of 12 refractory elements (Na, Mg, Al, Si, Ca, Ti, Cr, Ni, Co, Sc, Mn, and V) for a sample of 1111 FGK dwarf stars from the HARPS GTO planet search program. Of these stars, 109 are known to harbor giant planetary companions and 26 stars are exclusively hosting Neptunians and super-Earths.Aims. The two main goals of this paper are to investigate whether there are any differences between the elemental abundance trends for stars of different stellar populations and to characterize the planet host and non-host samples in terms of their [X/H]. The extensive study of this sample, focused on the abundance differences between stars with and without planets will be presented in a parallel paper.Methods. The equivalent widths of spectral lines were automatically measured from HARPS spectra with the ARES code. The abundances of the chemical elements were determined using an LTE abundance analysis relative to the Sun, with the 2010 revised version of the spectral synthesis code MOOG and a grid of Kurucz ATLAS9 atmospheres. To separate the Galactic stellar populations we applied both a purely kinematical approach and a chemical method.Results. We found that the chemically separated (based on the Mg, Si, and Ti abundances) thin- and thick disks are also chemically disjunct for Al, Sc, Co, and Ca. Some bifurcation might also exist for Na, V, Ni, and Mn, but there is no clear boundary of their [X/Fe] ratios. We confirm that an overabundance in giant-planet host stars is clear for all studied elements.We also confirm that stars hosting only Neptunian-like planets may be easier to detect around stars with similar metallicities than around non-planet hosts, although for some elements (particulary α -elements) the lower limit of [X/H] is very abrupt.

537 citations

Journal ArticleDOI
Rodolfo Smiljanic, Andreas Korn, Maria Bergemann, Antonio Frasca, Laura Magrini, Thomas Masseron, Elena Pancino, Gregory R. Ruchti, I. San Roman, Luca Sbordone, S. G. Sousa, Hugo M. Tabernero, Grazina Tautvaisiene, Marica Valentini, Marc Weber, Clare Worley, V. Zh. Adibekyan, C. Allende Prieto, G. Barisevičius, K. Biazzo, S. Blanco-Cuaresma, Piercarlo Bonifacio, Angela Bragaglia, Elisabetta Caffau, Tristan Cantat-Gaudin, Y. Chorniy, P. de Laverny, E. Delgado-Mena, P. Donati, S. Duffau, E. Franciosini, Eileen D. Friel, Douglas Geisler, J. I. González Hernández, P. Gruyters, Guillaume Guiglion, Camilla Juul Hansen, Ulrike Heiter, Vanessa Hill, Heather R. Jacobson, Paula Jofre, Henrik Jönsson, A. C. Lanzafame, Carmela Lardo, Hans-Günter Ludwig, Enrico Maiorca, Šarūnas Mikolaitis, D. Montes, Thierry Morel, Alessio Mucciarelli, C. Muñoz, Thomas Nordlander, L. Pasquini, E. Puzeras, Alejandra Recio-Blanco, Nils Ryde, G. G. Sacco, Nuno C. Santos, Aldo Serenelli, R. Sordo, Caroline Soubiran, Lorenzo Spina, Matthias Steffen, Antonella Vallenari, S. Van Eck, S. Villanova, Gerard Gilmore, Sofia Randich, Martin Asplund, James Binney, Janet E. Drew, Sofia Feltzing, Annette M. N. Ferguson, R. D. Jeffries, Giuseppina Micela, Ignacio Negueruela, T. Prusti, H. W. Rix, Emilio J. Alfaro, C. Babusiaux, Thomas Bensby, R. Blomme, Ettore Flaccomio, P. Francois, Michael G. Irwin, Sergey E. Koposov, N. A. Walton, Amelia Bayo, Giovanni Carraro, M. T. Costado, Francesco Damiani, Bengt Edvardsson, A. Hourihane, R. J. Jackson, Jack Lewis, Karin Lind, Gianni Marconi, Ch. Martayan, Lorenzo Monaco, L. Morbidelli, L. Prisinzano, Simone Zaggia 
TL;DR: In this paper, the Gaia-ESO Survey is obtaining high-quality spectroscopic data for about 10^5 stars using FLAMES at the VLT, which are analyzed in parallel by several state-of-the-art methodologies.
Abstract: The Gaia-ESO Survey is obtaining high-quality spectroscopic data for about 10^5 stars using FLAMES at the VLT. UVES high-resolution spectra are being collected for about 5000 FGK-type stars. These UVES spectra are analyzed in parallel by several state-of-the-art methodologies. Our aim is to present how these analyses were implemented, to discuss their results, and to describe how a final recommended parameter scale is defined. We also discuss the precision (method-to-method dispersion) and accuracy (biases with respect to the reference values) of the final parameters. These results are part of the Gaia-ESO 2nd internal release and will be part of its 1st public release of advanced data products. The final parameter scale is tied to the one defined by the Gaia benchmark stars, a set of stars with fundamental atmospheric parameters. A set of open and globular clusters is used to evaluate the physical soundness of the results. Each methodology is judged against the benchmark stars to define weights in three different regions of the parameter space. The final recommended results are the weighted-medians of those from the individual methods. The recommended results successfully reproduce the benchmark stars atmospheric parameters and the expected Teff-log g relation of the calibrating clusters. Atmospheric parameters and abundances have been determined for 1301 FGK-type stars observed with UVES. The median of the method-to-method dispersion of the atmospheric parameters is 55 K for Teff, 0.13 dex for log g, and 0.07 dex for [Fe/H]. Systematic biases are estimated to be between 50-100 K for Teff, 0.10-0.25 dex for log g, and 0.05-0.10 dex for [Fe/H]. Abundances for 24 elements were derived: C, N, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ba, Nd, and Eu. The typical method-to-method dispersion of the abundances varies between 0.10 and 0.20 dex.

229 citations

Journal ArticleDOI
Rodolfo Smiljanic1, Andreas Korn2, Maria Bergemann3, Antonio Frasca4, Laura Magrini4, Thomas Masseron5, Elena Pancino6, Gregory R. Ruchti7, I. San Roman8, Luca Sbordone9, Luca Sbordone10, Luca Sbordone11, S. G. Sousa12, Hugo M. Tabernero13, Gražina Tautvaišienė14, Marica Valentini15, Michael Weber15, Clare Worley16, V. Zh. Adibekyan12, C. Allende Prieto17, C. Allende Prieto18, G. Barisevičius14, K. Biazzo4, S. Blanco-Cuaresma19, Piercarlo Bonifacio20, Angela Bragaglia4, Elisabetta Caffau9, Elisabetta Caffau20, Tristan Cantat-Gaudin21, Y. Chorniy14, P. de Laverny19, E. Delgado-Mena12, P. Donati22, S. Duffau11, S. Duffau10, S. Duffau9, E. Franciosini4, Eileen D. Friel23, Douglas Geisler8, J. I. González Hernández18, Pieter Gruyters2, Guillaume Guiglion19, Camilla Juul Hansen9, Ulrike Heiter2, Vanessa Hill19, Heather R. Jacobson24, Paula Jofre16, Henrik Jönsson7, A. C. Lanzafame25, Carmela Lardo4, Hans-Günter Ludwig9, Enrico Maiorca4, S. Mikolaitis14, S. Mikolaitis19, D. Montes13, Thierry Morel26, Alessio Mucciarelli22, C. Muñoz8, Thomas Nordlander2, L. Pasquini1, E. Puzeras14, Alejandra Recio-Blanco19, Nils Ryde7, G. G. Sacco4, Nuno C. Santos12, Aldo Serenelli18, R. Sordo4, Caroline Soubiran19, Lorenzo Spina27, Lorenzo Spina4, Matthias Steffen15, Antonella Vallenari4, S. Van Eck5, S. Villanova8, Gerard Gilmore16, Sofia Randich4, Martin Asplund28, James Binney, Janet E. Drew29, Sofia Feltzing7, Annette M. N. Ferguson30, R. D. Jeffries31, Giuseppina Micela4, Ignacio Negueruela32, T. Prusti33, H. W. Rix3, Emilio J. Alfaro18, C. Babusiaux20, Thomas Bensby7, R. Blomme34, Ettore Flaccomio4, P. Francois20, Mike Irwin16, Sergey E. Koposov16, N. A. Walton16, Amelia Bayo35, Amelia Bayo3, Giovanni Carraro1, M. T. Costado18, Francesco Damiani24, Bengt Edvardsson2, A. Hourihane16, R. J. Jackson31, Jack Lewis16, Karin Lind16, Gianni Marconi1, Christophe Martayan1, Lorenzo Monaco1, L. Morbidelli4, L. Prisinzano4, Simone Zaggia4 
TL;DR: In this article, the Gaia-ESO Public Spectroscopic Survey is using FLAMES at the VLT to obtain high-quality medium-resolution Giraffe spectra for about 10(5) stars and high-resolution UVES spectra of about 5000 stars.
Abstract: Context. The ongoing Gaia-ESO Public Spectroscopic Survey is using FLAMES at the VLT to obtain high-quality medium-resolution Giraffe spectra for about 10(5) stars and high-resolution UVES spectra for about 5000 stars. With UVES, the Survey has already observed 1447 FGK-type stars. Aims. These UVES spectra are analyzed in parallel by several state-of-the-art methodologies. Our aim is to present how these analyses were implemented, to discuss their results, and to describe how a final recommended parameter scale is defined. We also discuss the precision (method-to-method dispersion) and accuracy (biases with respect to the reference values) of the final parameters. These results are part of the Gaia-ESO second internal release and will be part of its first public release of advanced data products. Methods. The final parameter scale is tied to the scale defined by the Gaia benchmark stars, a set of stars with fundamental atmospheric parameters. In addition, a set of open and globular clusters is used to evaluate the physical soundness of the results. Each of the implemented methodologies is judged against the benchmark stars to define weights in three different regions of the parameter space. The final recommended results are the weighted medians of those from the individual methods. Results. The recommended results successfully reproduce the atmospheric parameters of the benchmark stars and the expected T-eff-log g relation of the calibrating clusters. Atmospheric parameters and abundances have been determined for 1301 FGK-type stars observed with UVES. The median of the method-to-method dispersion of the atmospheric parameters is 55K for T-eff, 0.13dex for log g and 0.07 dex for [Fe/H]. Systematic biases are estimated to be between 50-100 K for T-eff, 0.10-0.25 dex for log g and 0.05-0.10 dex for [Fe/H]. Abundances for 24 elements were derived: C, N, O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Mo, Ba, Nd, and Eu. The typical method-to-method dispersion of the abundances varies between 0.10 and 0.20 dex. Conclusions. The Gaia-ESO sample of high-resolution spectra of FGK-type stars will be among the largest of its kind analyzed in a homogeneous way. The extensive list of elemental abundances derived in these stars will enable significant advances in the areas of stellar evolution and Milky Way formation and evolution.

222 citations

Journal ArticleDOI
TL;DR: In this article, a uniform and detailed analysis of 1112 high-resolution spectra of FGK-dwarfs obtained with the HARPS spectrograph at the ESO 3.6m telescope was performed.
Abstract: We performed a uniform and detailed analysis of 1112 high-resolution spectra of FGK dwarfs obtained with the HARPS spectrograph at the ESO 3.6 m telescope (La Silla, Chile). Most stars have effective temperatures 4700 K ≤ T eff ≤ 6300 K and lie in the metallicity range of −1.39 ≤ [Fe/H] ≤ 0.55. Our main goal is to investigate whether there are any differences between the elemental abundance trends (especially [α /Fe] ratio) for stars of different subpopulations. The equivalent widths of spectral lines are automatically measured from HARPS spectra with the ARES code. The abundances of three α elements are determined using a differential LTE analysis relative to the Sun, with the 2010 revised version of the spectral synthesis code MOOG and a grid of Kurucz ATLAS9 atmospheres. The stars of our sample fall into two populations, clearly separated in terms of [α /Fe] up to super-solar metallicities. In turn, high-α stars are also separated into two families with a gap in both [α /Fe] ([α /Fe] ≈ 0.17) and metallicity ([Fe/H] ≈ −0.2) distributions. The metal-poor high-α stars (thick disk) and metal-rich high-α stars are on average older than chemically defined thin disk stars (low-α stars). The two α -enhanced families have different kinematics and orbital parameters. The metal-rich α -enhanced stars, such as thin disk stars have nearly circular orbits, close to the Galactic plane. We put forward the idea that these stars may have been formed in the inner Galactic disk, but their exact nature still remains to be clarified.

175 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compare the differences in temperature between the standard spectroscopic technique based on iron lines and the infrared flux method (IRFM) and show that the differences for the cooler stars are significantly smaller and more homogeneously distributed than in previous studies.
Abstract: Context. Temperature, surface gravity, and metallicitity are basic stellar atmospheric parameters necessary to characterize a star. There are several methods to derive these parameters and a comparison of their results often shows considerable discrepancies, even in the restricted group of solar-type FGK dwarfs.Aims. We want to check the differences in temperature between the standard spectroscopic technique based on iron lines and the infrared flux method (IRFM). We aim to improve the description of the spectroscopic temperatures especially for the cooler stars where the differences between the two methods are higher, as presented in a previous work.Methods. Our spectroscopic analysis was based on the iron excitation and ionization balance, assuming Kurucz model atmospheres in LTE. The abundance analysis was determined using the code MOOG. We optimized the line list using a cool star (HD 21749) with high resolution and high signal-to-noise spectrum, as a reference in order to check for weak, isolated lines.Results. We test the quality of the new line list by re-deriving stellar parameters for 451 stars with high resolution and signal-to-noise HARPS spectra, that were analyzed in a previous work with a larger line list. The comparison in temperatures between this work and the latest IRFM for the stars in common shows that the differences for the cooler stars are significantly smaller and more homogeneously distributed than in previous studies for stars with temperatures below 5000 K. Moreover, a comparison is presented between interferometric temperatures with our results that shows good agreement, even though the sample is small and the errors of the mean differences are large. We use the new line list to re-derive parameters for some of the cooler stars that host planets. Finally, we present the impact of the new temperatures on the [Cr i/Cr ii] and [Ti i/Ti ii] abundance ratios that previously showed systematic trends with temperature. We show that the slopes of these trends for the cooler stars become drastically smaller.

170 citations


Cited by
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Journal ArticleDOI
Steven R. Majewski1, Ricardo P. Schiavon2, Peter M. Frinchaboy3, Carlos Allende Prieto4, Carlos Allende Prieto5, Robert H. Barkhouser6, Dmitry Bizyaev7, Dmitry Bizyaev8, Basil Blank, Sophia Brunner1, Adam Burton1, Ricardo Carrera4, Ricardo Carrera5, S. Drew Chojnowski1, S. Drew Chojnowski8, Katia Cunha9, Courtney R. Epstein10, Greg Fitzgerald, Ana E. García Pérez4, Ana E. García Pérez1, Fred Hearty1, Fred Hearty11, Chuck Henderson, Jon A. Holtzman8, Jennifer A. Johnson10, Charles R. Lam1, James E. Lawler12, Paul Maseman9, Szabolcs Mészáros13, Szabolcs Mészáros5, Szabolcs Mészáros4, Matthew J. Nelson1, Duy Coung Nguyen14, David L. Nidever1, David L. Nidever15, Marc H. Pinsonneault10, Matthew Shetrone16, Stephen A. Smee6, Verne V. Smith9, T. Stolberg, Michael F. Skrutskie1, E. Walker1, John C. Wilson1, Gail Zasowski6, Gail Zasowski1, Friedrich Anders17, Sarbani Basu18, Stephane Beland19, Michael R. Blanton20, Jo Bovy14, Jo Bovy21, Joel R. Brownstein22, Joleen K. Carlberg23, Joleen K. Carlberg1, William J. Chaplin24, William J. Chaplin25, Cristina Chiappini17, Daniel J. Eisenstein26, Yvonne Elsworth24, Diane Feuillet8, Scott W. Fleming27, Scott W. Fleming28, Jessica Galbraith-Frew22, Rafael A. García29, D. Anibal García-Hernández5, D. Anibal García-Hernández4, Bruce Gillespie6, Léo Girardi30, James E. Gunn21, Sten Hasselquist8, Sten Hasselquist1, Michael R. Hayden8, Saskia Hekker31, Saskia Hekker25, Inese I. Ivans22, Karen Kinemuchi8, Mark A. Klaene8, Suvrath Mahadevan11, Savita Mathur32, Benoit Mosser33, Demitri Muna10, Jeffrey A. Munn, Robert C. Nichol, Robert W. O'Connell1, John K. Parejko18, Annie C. Robin34, H. J. Rocha-Pinto35, M. Schultheis36, Aldo Serenelli4, Neville Shane1, Victor Silva Aguirre25, Jennifer Sobeck1, Benjamin A. Thompson3, Nicholas W. Troup1, David H. Weinberg10, Olga Zamora4, Olga Zamora5 
TL;DR: In this article, the Hungarian National Research, Development and Innovation Office (K-119517) and Hungarian National Science Foundation (KNFI) have proposed a method to detect the presence of asteroids in Earth's magnetic field.
Abstract: National Science Foundation [AST-1109178, AST-1616636]; Gemini Observatory; Spanish Ministry of Economy and Competitiveness [AYA-2011-27754]; NASA [NNX12AE17G]; Hungarian Academy of Sciences; Hungarian NKFI of the Hungarian National Research, Development and Innovation Office [K-119517]; Alfred P. Sloan Foundation; National Science Foundation; U.S. Department of Energy Office of Science

1,193 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review the key integrated, structural and kinematic parameters of the Galaxy, and point to uncertainties as well as directions for future progress, and show that the Galaxy is a luminous (L⋆) barred spiral with a central box/peanut bulge, a dominant disk, and a diffuse stellar halo.
Abstract: Our Galaxy, the Milky Way, is a benchmark for understanding disk galaxies. It is the only galaxy whose formation history can be studied using the full distribution of stars from faint dwarfs to supergiants. The oldest components provide us with unique insight into how galaxies form and evolve over billions of years. The Galaxy is a luminous (L⋆) barred spiral with a central box/peanut bulge, a dominant disk, and a diffuse stellar halo. Based on global properties, it falls in the sparsely populated “green valley” region of the galaxy color-magnitude diagram. Here we review the key integrated, structural and kinematic parameters of the Galaxy, and point to uncertainties as well as directions for future progress. Galactic studies will continue to play a fundamental role far into the future because there are measurements that can only be made in the near field and much of contemporary astrophysics depends on such observations.

1,084 citations

Journal ArticleDOI
TL;DR: In this paper, a high-resolution spectroscopic study of 714 F and G dwarfs and subgiant stars in the Solar neighbourhood was conducted, where the star sample has been kinematically selected to trace the Galactic thin and thick disks to their extremes, the metal-rich stellar halo, sub-structures in velocity space such as the Hercules stream and the Arcturus moving group, as well as stars that cannot be associated with either the thin disk or the thick disk.
Abstract: Aims. The aim of this paper is to explore and map the age and abundance structure of the stars in the nearby Galactic disk. Methods. We have conducted a high-resolution spectroscopic study of 714 F and G dwarf and subgiant stars in the Solar neighbourhood. The star sample has been kinematically selected to trace the Galactic thin and thick disks to their extremes, the metal-rich stellar halo, sub-structures in velocity space such as the Hercules stream and the Arcturus moving group, as well as stars that cannot (kinematically) be associated with either the thin disk or the thick disk. The determination of stellar parameters and elemental abundances is based on a standard analysis using equivalent widths and one-dimensional, plane-parallel model atmospheres calculated under the assumption of local thermodynamical equilibrium (LTE). The spectra have high resolution (R = 40 000-110 000) and high signal-to-noise)S/V = 150-300) and were obtained with the FEROS spectrograph on the ESO 1.5 in and 2.2 in telescopes, the SOFIN and PIES spectrographs on the Nordic Optical Telescope, the LIVES spectrograph on the E50 Very Large Telescope, the HARPS spectrograph on the ESO 3.6 m telescope, and the MIKE spectrograph on the Magellan Clay telescope. The abundances from individual Fe I lines were were corrected for non-LTE effects in every step of the analysis. Results. We present stellar parameters, stellar ages, kinematical parameters, orbital parameters, and detailed elemental abundances for 0, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y. and Ba for 714 nearby 12 and G dwarf stars. Our data show that there is an old and a-enhanced disk population, and a younger and less a-enhanced disk population. While they overlap greatly in metallicity between 0.7 < [Fe/HI] less than or similar to +0.1, they show a bimodal distribution in [alpha/Fe]. This bimodality becomes even clearer if stars where stellar parameters and abundances show larger uncertainties (T-eff less than or similar to 5400 K) are discarded, showing that it is important to constrain the data set to a narrow range in the stellar parameters if small differences between stellar populations are to be revealed. In addition, we find that the a-enhanced population has orbital parameters placing the stellar birthplaces in the inner Galactic disk while the loss-alpha stars mainly come from the outer Galactic disk, fully consistent with the recent claims of a short scale-length for the alpha-enhanced Galactic thick disk. We have also investigated the properties of the Hercules stream and the Arcturus moving group and find that neither of them presents chemical or age signatures that could suggest that they are disrupted clusters or extragalactic accretion remnants from ancient merger events. Instead, they are most likely dynamical features originating within the Galaxy. We have also discovered that a standard 1D. LTE analysis, utilising ionisation and excitation balance of Fe I and Fen lines produces a flat lower main sequence. As the exact cause for this effect is unclear we chose to apply an empirical correction. Turn-off stars and more evolved stars appear to be unaffected. (Less)

934 citations

Journal ArticleDOI
TL;DR: A review of the current knowledge of the occurrence of planets around other stars, their orbital distances and eccentricities, the orbital spacings and mutual inclinations in multi-planet systems, the orientation of the host star's rotation axis, and the properties of planets in binary-star systems can be found in this paper.
Abstract: The basic geometry of the Solar System—the shapes, spacings, and orientations of the planetary orbits—has long been a subject of fascination as well as inspiration for planet-formation theories. For exoplanetary systems, those same properties have only recently come into focus. Here we review our current knowledge of the occurrence of planets around other stars, their orbital distances and eccentricities, the orbital spacings and mutual inclinations in multiplanet systems, the orientation of the host star's rotation axis, and the properties of planets in binary-star systems.

824 citations

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the abundance ratios of magnesium and europium in Milky Way-like galaxies from the TNG100 simulation (stellar masses = (M_\star / {\rm M}_\odot) \sim 9.7 -11.2$).
Abstract: The distribution of elements in galaxies provides a wealth of information about their production sites and their subsequent mixing into the interstellar medium. Here we investigate the distribution of elements within stars in the IllustrisTNG simulations. In particular, we analyze the abundance ratios of magnesium and europium in Milky Way-like galaxies from the TNG100 simulation (stellar masses ${\log} (M_\star / {\rm M}_\odot) \sim 9.7 - 11.2$). As abundances of magnesium and europium for individual stars in the Milky Way are observed across a variety of spatial locations and metallicities, comparison with the stellar abundances in our more than $850$ Milky Way-like galaxies provides stringent constraints on our chemical evolutionary methods. To this end we use the magnesium to iron ratio as a proxy for the effects of our SNII and SNIa metal return prescription, and a means to compare our simulated abundances to a wide variety of galactic observations. The europium to iron ratio tracks the rare ejecta from neutron star -- neutron star mergers, the assumed primary site of europium production in our models, which in turn is a sensitive probe of the effects of metal diffusion within the gas in our simulations. We find that europium abundances in Milky Way-like galaxies show no correlation with assembly history, present day galactic properties, and average galactic stellar population age. In general, we reproduce the europium to iron spread at low metallicities observed in the Milky Way, with the level of enhancement being sensitive to gas properties during redshifts $z \approx 2-4$. We show that while the overall normalization of [Eu/Fe] is susceptible to resolution and post-processing assumptions, the relatively large spread of [Eu/Fe] at low [Fe/H] when compared to that at high [Fe/H] is very robust.

722 citations