Spectroscopy

Portion of a simulated DESI observation constructed by HARP on the fly and used as input to the extraction tools.

Application to Cosmology

Several types of spectrographs are used in astrophysical observations. In cosmology, the large scale structure of the universe (clusters of galaxies, filaments, and voids) gives us insight into many global properties of the universe. These structures began as Baryon-Acoustic Oscillations in the plasma of the early universe. These oscillations were driven by the counteracting forces of gravity (from clumps of dark matter) and radiation pressure. As the universe expanded and cooled, eventually electrons and protons combined to form neutral Hydrogen. This decoupled the photons from the matter by removing the source of scattering (the electrons). The radiation streamed away to become what we now observe as the Cosmic Microwave Background. Without the radiation pressure, the baryons were free to coalesce into the first galaxies. As the universe continued to expand, these structures have grown and evolved. The statistical properties of this matter distribution across the expansion history of the universe can allow us to constrain several key parameters, including the rate of that expansion and how it varies. In order to map out the matter distribution, we measure spectra of selected galaxies, and then determine their redshift, for example by fitting to model spectra.

Software

My spectroscopy work is currently implemented within a set of tools called High performance Astrophysical Reconstruction and Processing (HARP).