Determining the Absolute Luminosity of Supernovae to Measure the Expansion of the Universe
Saul Perlmutter, Professor
Physics
Closed. This professor is continuing with Fall 2024 apprentices on this project; no new apprentices needed for Spring 2025.
Our group has developed a new model for inferring the distances between Type Ia supernovae (SNe Ia) that is about twice as accurate as previous models. 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). A sample of 18 SNe have been identified as optimal for this purpose, 13 of which have been analyzed, and we are actively looking to incorporate the other 5 into our calibration of the model.
Project Description:
Compile published time-series photometry and spectroscopy of five SNe to which a Tip of the Red Giant Branch (TRGB) or Cepheid variable distance has been estimated. Evaluate the quality of the photometry in terms of photometric zero-point, and the quality of the spectroscopy in terms of tilts, warps, edge effects, second order light contamination, host-light contamination, etc. Most importantly, evaluate whether the majority of these effects can be *removed* given high enough quality photometry. That is, the primary result of this project would be the novel generation of flux-calibrated pseudo-spectrophotometry for five of the most important SNe ever to have been observed in modern history. Note "pseudo" here is only used because the spectroscopy itself wasn't spectrophotometric--or accurately flux-calibrated--but we are instead forcing it to be using concurrent photometry. The new flux-calibrated spectroscopy would then be used to calibrate our model and derive an estimate of the Hubble constant, a cosmological parameter of great importance today.
Role: The student will:
1. Familiarize themselves with relevant literature on Type Ia supernovae, recent measurements of the expansion rate based on them, and our group's model for measuring SN Ia distances.
2. It is possible for this project to result in a co-authored publication or, given sufficient time invested plus interest on the part of the student, a publication of their own. Both projects would be good fits to make up all or a part of a senior thesis.
3. The datasets available to do studies of SNe will be increasing in size by orders of magnitude in just the next few years via Rubin, Roman, in addition to their associated partner projects. The skills and knowledge developed here will set the student up to be able to contribute to these exciting projects that will take the field by storm over the course of the next decade.
Qualifications: Prerequisites for this project
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Skills: Basic Numerical and Plotting Skills (e.g., python)
Knowledge: Familiarity with Astronomical conventions (e.g., magnitudes, FITS files).
Preferred 2nd-3rd year student. Project would make for a good senior thesis.
Day-to-day supervisor for this project: Taylor Hoyt, Post-Doc
Hours: to be negotiated
Off-Campus Research Site: We will meet over zoom to discuss the project and the calculations can be run on a personal machine.
Related website: https://thoyt.lbl.gov/teachingmentoring/undergraduate-research
Engineering, Design & Technologies Mathematical and Physical Sciences