Graduation Year


Date of Thesis Acceptance

Spring 5-8-2017

Major Department or Program



Nathaniel Paust


We present new isochrone fits to color-magnitude diagrams from Hubble Space Telescope Wide Field Camera 3 (WFC3) and Advanced Camera for Surveys (ACS) photometry of the globular clusters M13 and M80 in five bands from the ultraviolet to near infrared. Fits from both the Dartmouth Stellar Evolution Program (DSEP) and the PAdova and TRieste Stellar Evolution Code (PARSEC) are examined. Ages, extinctions, and distances are found from the isochrone fitting, and metallicities are confirmed. We conduct careful qualitative analysis on the inconsistencies of the fits across all of the color combinations possible with the five observed bands, and find that the (F606W-F814W) color generally produces very good fits, but that there are large discrepancies when the data is fit using colors including UV bands for both models. Finally, we directly compare the two models by performing isochrone-isochrone fitting, and find that the age in PARSEC is on average 1.5 Gyr younger than DSEP for similar-appearing models at the same metallicity for globular cluster aged populations, and that the two models become less discrepant at lower metallicities.

Page Count


Subject Headings

Stars -- globular clusters -- M13, Milky Way -- M80, Stars-- Age, Astronomy -- Dartmouth Stellar Evolution Program (DSEP), Astronomy -- PAdova and Triste Stellar Evolution Code (PARSEC), Hubble Space Telescope (Spacecraft), Stars -- Evolution -- Isochrones -- Models, Whitman College 2017 -- Astrophysics and Astronomy

Document Type

Public Accessible Thesis



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