Modest Methods on the Edge of Cosmic Revolution: Foundational Work to Test Outstanding Peculiarities in the ΛCDM Cosmology

Abstract

The ΛCDM cosmology has proven to be a robust model of the Universe, matching a diversity of cosmic probes. However, the ongoing ambiguity of the true nature of both dark matter (DM) and dark energy (DE) and some small but apparently robust inconsistencies between measurement and ΛCDM predictions underscore the importance of continuing to test this scientific hypothesis.

This Dissertation details the author's work to both use existing data to test the ΛCDM hypothesis in new ways, and to lay groundwork so that future scientists can make the most of the coming astronomical data revolution.

We test the consistency of the Fornax local group dwarf spheroidal galaxy (Fornax) with non-standard DM properties. We find that the DM halo of Fornax is more likely cored than cusped, more likely prolate than oblate, and shows no evidence of a dark disk that is more than 2% of the total halo mass. Our analysis provides a template methodology to search for non-standard DM signatures in the profiles of LG dSphs.

We, for the first time, apply Fourier-analysis to the existing Pantheon compendium of 1048 spectroscopically confirmed type Ia supernovae (SNe Ia) to look for small oscillations in the Universe's expansion history. We find no evidence of such cosmic oscillations, and determine that any alternate cosmological model that produces distance modulus residuals with a Fourier amplitude of >35 millimags is strongly ruled out.

We address concerns that SNe Ia compendium-based measurements of cosmological parameters might be contaminated by inter-survey photometric calibration errors. Treating such calibration errors as variable parameters in the cosmological fit, we demonstrate that SNe-Ia compendium measurements of H0 are quite robust, owing to the large number of low-redshift surveys with Cepheid-paired SNe.

Subjecting monocrystalline back-contact solar cells (SCs) to a barrage of calibration tests, we determine that such devices can serve as sub-percent accuracy, large-collecting area photometric calibrators. We expect that such cells will serve as the photocalibrator of choice for future high-precision throughput determinations of ground-based telescopes, including the Rubin Observatory.

As a solution to the known problem of airglow spectral lines producing interference fringes in Rubin Observatory detectors, we constructed and performed in situ tests of OSELOTS, a robust, self-contained spectrograph developed to monitor the emission lines of the diffuse night sky. Although the system hardware and software are still being refined, our results demonstrate that OSELOTS is fully capable of providing high S/N spectra of the NIR airglow, sampled continuously throughout the night, to the Rubin Observatory processing pipeline.

Our work, in aggregate, demonstrates that even thoroughly studied data can still provide new insight when examined with creative statistical analyses. We also provide useful experimental, theoretical, and statistical tools for future astronomers to use in acquiring, reducing, and analyzing the next generation of astronomical data. This work is not revolutionary, but does smooth the road and provide weapons for cosmological revolutionaries to come.