Date of Award

6-2022

Document Type

Open Access

Degree Name

Bachelor of Science

Department

Physics and Astronomy

First Advisor

Jonathan Marr

Keywords

MW satellite galaxies and globular clusters, galaxy formation, DEIMOS spectrograph, synthetic templates, PHOENIX atmosphere-modeling code

Abstract

High-precision kinematics of individual stars in Milky Way satellite galaxies and globular clusters is crucial for studies of galaxy formation, cosmology, alternative gravity models, and dark matter. We tested a rigorous method that matches model DEIMOS observations of such targets with synthetic template spectra that deduces radial velocities and [Fe/H] abundances. We added noise to create a model spectrum with SNR = 30, fitted templates with different parameters to it, and calculated the
best-match velocity and the goodness of the fit. The best fits occur for templates that are close in parameter space to the model spectrum, and the fits get worse the further away the templates are from the model spectrum. Within a window of ∼ ±1500 K from the model spectrum, the bias in inferred velocity increases at a rate of roughly ≲ 0.5 km s−1/1000 K , but stays below the DEIMOS resolution. We conclude that the method does not introduce a bias to the inferred velocity larger than ∼ 30% of the instrumental resolution and that the uncertainty is dominated by the resolution, suggesting that the step size in our parameter space was well chosen.

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Rights Statement

In Copyright - Educational Use Permitted.