Calibrating Spectroscopy of Type Ia supernovae to measure the Hubble constant.
Taylor Hoyt, Staff Researcher
Physics
Applications for Fall 2026 are closed for this project.
The Nearby Supernova Factory (SNfactory; Aldering+02,04) at Berkeley Lab has developed a model for inferring the distances between Type Ia supernovae (SNe Ia) that is about twice as accurate as previous ones. The model uses the spectral differences between different SNe to constrain variations in their intrinsic luminosities. The more precisely one can constrain the intrinsic luminosity of an object, the more precisely it can be used as a tool of extragalactic distance measurement and thus measure the expansion of the universe.
In order to determine the present day expansion rate, or the Hubble Constant, we need to determine a zero point calibration for the model, which is how we bring the model's relative predictions between SNe onto an absolute system. That way, the SNe can tell us how fast the universe is expanding today, which also provides the boundary condition that sets the normalization of the universe's age and size. To do this, we have to observe SNe nearby enough that we can use another means of acquiring distances to them (e.g., the Cepheid variable stars or the Tip of the Red Giant Branch; see project 1). The current calibration sample of the SNfactory spectral model is limited to just the 3-5 SNe observed as part of their main program using a specialized instrument that can provide the highly accurate spectral measurements required for the model.
This project focuses on expanding that sample by bringing in other sources of spectroscopy that are not calibrated well enough for use with the SNfactory model, and recalibrating them using contemporaneous photometry or 'light curves' which are generally better calibrated than SN spectra.
Qualifications: Skills: Basic Numerical and Plotting Skills (e.g., python). Familiarity with or interest in learning how to use agentic coding tools to accelerate scientific workflows.
Knowledge: Familiarity with Astronomical conventions (e.g., magnitudes, FITS files).
Preferred are sophomores and juniors. Project would make for a good senior thesis.
Hours: to be negotiated