Detailed Chemical Abundances of Extragalactic Globular Clusters using High Resolution, Integrated Light Spectra.

Chemical Abundances;Globular Clusters;M31;LMC;Galaxy Formation;Astronomy;Science;Astronomy and Astrophysics

Colucci, Janet E.Oey, Marion S. ;

University of Michigan

关键词: Chemical Abundances;    Globular Clusters;    M31;    LMC;    Galaxy Formation;    Astronomy;    Science;    Astronomy and Astrophysics;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/75989/jcolucci_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Globular clusters (GCs) are luminous, observationally accessible objects that aregood tracers of the total star formation and evolutionary history of galaxies. Wepresent the first detailed chemical abundances for GCs in M31 using a new abundance analysis technique designed for high resolution, integrated light (IL) spectraof GCs. This technique has recently been developed using a training set of old GCsin the Milky Way (MW), and makes possible detailed chemical evolution studies ofdistant galaxies, where high resolution abundance analysis of individual stars are notobtainable. For the 5 M31 GCs presented here, we measure abundances of 14 elements: Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, and Ba. We find the M31 GCs have ages (>10 Gyr) and chemical properties similar to MW GCs, including anenhancement in the α-elements Ca, Ti and Si of [α/Fe]∼+0.4. In this thesis, we also further develop this IL abundance analysis method to includeGCs of ages 10 Myr-12 Gyrs using GCs in the Large Magellanic Cloud (LMC),which contains the necessary sample of clusters over this wide age range. This workdemonstrates for the first time that this IL abundance analysis method can be used on clusters of all ages, and that ages can be constrained to within 1−2 Gyr for clusters with ages of ∼2 Gyr and within a few 100 Myr for clusters with ages <1 Gyr.We find that we can measure [Fe/H] in clusters with ages <12 Gyrs with similar oronly slightly larger uncertainties (0.1-0.25 dex) than those obtained for old GCs; theslightly larger uncertainties are due to the rapid evolution in stellar populations atthese ages.Using the LMC clusters, we also investigate the effects of statistical fluctuationsin the theoretical cluster stellar populations used in our analysis. We also developstrategies to allow for statistical variations in these stellar populations, and findthat the stability of the Fe line abundance solution can provide tight constraints onthe appropriate theoretical stellar populations. Detailed chemical abundances of 22elements are reported for six LMC clusters.