Dissertation submitted to the Combined Faculties of the Natural Sciences and Mathematics of the Ruperto-Carola-University of Heidelberg, Germany for the degree of Doctor of Natural Sciences Put forward by Mikhail Kovalev born in: Kursk, USSR Oral examination:11.11.2019 NLTE analysis of the Gaia-ESO spectroscopic survey. Referees: Dr. Maria Bergemann Prof. Dr. Andreas Quirrenbach 2 Abstract ZUSAMMENFASSUNG: In dieser Arbeit entwickeln wir eine Pipeline zur spektralen Analyse, die synthetischen NLTE Spektren mit the Payne (Ting et al. 2018) Spektralmodel kombiniert. Wir berechnen zwei spektrale Gitter, in einem der Gitter werden alle Elemente mit LTE behandelt und das zweite Gitter wird unter Verwendung von Eisen, Magnesium, Titan und Mangan mit NLTE modelliert, um NLTE Effekte auf die Bestimmung stellarer Parameter und Elementh¨aufigkeiten zu untersuchen. Diese Pipeline wird auf Spektren aus der dritten ¨offentlichen Datenver¨offentlichung von Gaia-ESO (Gilmore et al. 2012) angewandt. Wir pr¨ufen unsere Methodik mit einer Stichprobe von Standardsternen und Mitgliedern von Sternhaufen und finden signifikante Unterschiede zwischen NLTE und LTE im metallarmen Bereich. Die Elementhufigkeiten von Eisen und Titan sind homogen in allen Sternhaufen, aber mehrere Kugelsternhaufen zeigen eine signifikante Dispersion f¨ur[Mg/Fe]. Die Verringerung des mittleren [Mg/Fe] in einigen Kugelsternhaufen, im Vergleich zu Feldsternen mit vergleichbarer Metallizit¨at,deuten m¨oglicherweise eine ex-situ Entstehungsgeschichte an. Wir kombinieren unsere NLTE Resultate auch mit den astrometrischen Daten des Gaia DR2 (Gaia Collaboration et al. 2018), um die chemo-dynamische Entwicklung der Milchstraße zu untersuchen. Wir nutzen die Unterschiede in der chemischen Zusammensetzung, um Scheibenpopulationen mit hohem [α=Fe] und niedrigem [α=Fe] zu unterscheiden. Halo Sterne werden durch Unterschiede in der Kinematik ausgew¨ahlt. Wir best¨atigenfr¨uhereErgebnisse, wie eine h¨ohere Elementh¨aufigkeit von Mg im Vergleich zur Sonne im metallarmen Bereich und einen Abfall von [Mg/Fe] im Vergleich zur Sonne im metallreichen Bereich. Wir finden ein konstantes NLTE [Mg/Fe] ∼ 0:3 dex Verh¨altnissowohl fr die metallarme Scheibe als auch den Halo mit relativ kleiner Streuung zwischen einzelnen Sternen. Die Halo Sterne mit [Mg/Fe] vergleichbar zur Sonne wurden wahrscheinlich von anderen Galaxien eingefangen. Die beobachtete Exzentrizit¨atsverteilung f¨urhohe [α=Fe] Scheiben Populationen schließt einen gewaltsamen Formationsmechanismus f¨urdie dicke Scheibe wie direkte Akkretion und dynamische Anregung aus. Die gemessenen chemischen und kinematischen Gradienten und Geschwindigkeitsdispersionen der Populationen mit hohem [α=Fe] k¨onnenmit gasreichen Mergern erkl¨artwerden, wobei radiale Migration nicht zu vernachlssigen ist. ABSTRACT: In this work, we develop the spectral analysis pipeline that combines the NLTE synthetic spectra with the Payne spectral model (Ting et al. 2018). We compute two spectral grids, one grid with all elements treated in LTE and a second grid with iron, magnesium, titanium and manganese modelled in NLTE, to study the NLTE effects on the determination of the stellar parameters and chemical 3 abundances. This pipeline is applied to spectra from the third public data release of the Gaia-ESO (Gilmore et al. 2012). We validate the method on the subsample of standard stars and cluster's members and find significant differences between NLTE and LTE in the metal-poor regime. All clusters are homogeneous in Fe and Ti, but several globular clusters showed significant dispersion in [Mg/Fe]. The depletion of the mean [Mg/Fe] in several globular clusters, compared to field stars of the same metallicity, may indicate their ex-situ formation history. We also combine our NLTE results with Gaia DR2 (Gaia Collaboration et al. 2018) astrometric data to study Galactic chemo-dynamic evolution. We apply chemical separation to select high-[α=Fe] and low-[α=Fe] disk populations, with halo stars selected using kinematics. We confirm previous results like super-solar Mg abundance in the metal-poor regime and decrease of [Mg/Fe] to the solar abundances in the metal-rich regime. We find a constant NLTE [Mg/Fe]∼ 0:3 dex ratio for both metal-poor disk and halo with relatively small star-to-star scatter. The halo stars with solar-like [Mg/Fe] are probably accreted from the other galaxies. The observed eccentricity distribution for high-[α=Fe] disk population rules out a violent thick disk formation mechanisms like direct accretion and dynamic heating. The measured chemical and kinematic gradients and velocity dispersions of the high-[α=Fe] population can be explained by the gas-rich merger scenario with the non-negligible contribution from the radial migration. 4 Contents Abstract3 List of Figures8 List of Tables 11 Acknowledgments 14 1 Introduction1 1.1 Motivation.................................1 1.2 Theoretical basis of spectral modelling.................2 1.3 Analysis of observed spectra.......................8 1.3.1 Machine learning in spectroscopy................ 10 1.4 The Milky Way structure......................... 13 1.5 Kinematic properties of the stars.................... 15 1.5.1 Galactocentric coordinates and velocities............ 15 1.6 Probing the thick disk formation scenarios............... 17 1.7 This thesis................................. 18 2 NLTE Chemical abundances in Galactic open and globular clusters 21 2.1 Introduction................................ 21 2.2 Methods.................................. 23 5 CONTENTS 2.2.1 Observed spectra......................... 23 2.2.2 Instrumental profile........................ 23 2.2.3 Radial velocities.......................... 24 2.2.4 Model atmospheres and synthetic spectra............ 25 2.2.5 The Payne code.......................... 26 2.2.6 Internal accuracy of the method................. 28 2.3 Results................................... 31 2.3.1 Gaia-ESO benchmark stars................... 31 2.3.2 Open and globular clusters.................... 34 2.4 Discussion................................. 46 2.4.1 Comparison with the literature................. 46 2.4.2 Comparison with Milky Way field stars............. 58 2.5 Conclusions................................ 62 3 Analysis of Gaia-ESO Milky Way field stars 67 3.1 Introduction................................ 67 3.2 Spectral sample.............................. 69 3.3 Kinematic and dynamics.......................... 70 3.4 Galactic population selection....................... 73 3.5 Survey selection function and an impact of the parallax quality cut. 78 3.6 Results................................... 80 3.6.1 Eccentricity and metallicity distributions............ 80 3.6.2 Orbital properties......................... 81 3.6.3 Chemical gradients with R and jZj ............... 82 3.6.4 Velocity gradients with R, jZj and [Fe/H]............ 84 3.6.5 Velocity and velocity dispersions with [α/Fe].......... 87 3.7 Discussion................................. 88 6 CONTENTS 3.7.1 Comparison with stellar clusters................. 88 3.7.2 Formation of the thick disk................... 90 3.8 Summary and conclusions........................ 95 4 NLTE online-service 99 4.1 Introduction................................ 99 4.2 Methods.................................. 100 4.3 Functionality............................... 101 4.4 Summary and future plans........................ 102 5 Summary 105 5.1 Perspectives................................ 107 List of publications 109 References 111 7 CONTENTS 8 List of Figures 1.1 Example of simple ANN with one fully-connected hidden layer. Figure credit Bailer-Jones et al.(1997)..................... 11 1.2 Schematic description of the Payne ANN................ 13 1.3 Schematic side-view of the Galaxy. (not to scale)........... 14 1.4 Galactocentric Cartesian system definition................ 15 1.5 Eccentricity distributions as a probe of the thick disk formation sce- nario. Figure credit Sales et al.(2009)................. 18 2.1 HR10 instrumental profile......................... 24 2.3 Sensitivity of the method to the quality of the spectra......... 33 2.4 The mean NLTE-LTE difference..................... 36 2.5 NLTE results compared to isochrones.................. 37 2.6 LTE results compared to isochrones................... 38 2.7 Example of NLTE/LTE spectral fit 1.................. 39 2.8 Example of NLTE/LTE spectral fit 2.................. 40 2.9 NLTE abundances as a function of Teff .................. 42 2.10 Abundances as a function of Teff and the Teff -log(g) diagram for the open cluster NGC 2243.......................... 44 2.11 Comparison of the spectra of two M 15 stars with different [Mg/Fe].. 44 2.12 The Toomre diagram for the clusters................... 59 9 LIST OF FIGURES 2.13 Mean LTE metallicities and [Mg/Fe] and [Ti/Fe] abundance ratios for all clusters and for Milky Way field stars................. 61 2.14 Mean NLTE metallicities and [Mg/Fe] and [Ti/Fe] abundance ratios for all clusters and for Milky Way field stars.............. 61 2.15 The average abundance ratios of the clusters in comparison with the Galactic halo, thick disk, and three dSph galaxies............ 63 3.1 The Galactic coordinates for stars in our sample............ 70 3.2 The Gaia colour-magnitude diagram and The Kiel diagram for our sample of GES MW field stars...................... 71 3.3 The distribution of the distance sampling for two stars......... 72 3.4 The uncertainties for cylindrical coordinates and velocities....... 72 3.5 The spatial and kinematic distributions for