Spectropolarimetry of Fast Radio Bursts, Radio Galaxies, and the Milky Way
Bibliographic record
Abstract
Fast radio bursts (FRBs) are microsecond to millisecond extragalactic radio transients. Despite a published sample of over 600 FRB observations, the nature of their progenitor/s, the mechanism for their emission and their domain of applicability as probes remain open problems. Here, information on their polarized signals may offer illuminating clues, however, only a small fraction of the current FRB sample report polarization information. This modest sample exhibits a rich phenomenology in its polarized properties and has provided some important discoveries that have refined our under- standing of the FRB population. The FRB survey operating between 400-800 MHz on the Canadian Hydrogen Intensity Mapping Experiment (CHIME/FRB) should detect several thousand FRBs over the next few years. A significant fraction of these events will be recorded in a mode that enables po- larization analysis. Such a large sample requires an automated pipeline in order to reduce recorded data into useful summary statistics for different FRB properties.\nThis thesis reviews the polarization analysis pipeline developed for CHIME/FRB, along with the various science enabled with polarized data. The analysis tools developed specifically for CHIME/FRB observations are illustrated using a combination of simulated and real FRBs. These tools include a parametric method that robustly characterizes dominant sources of instrumental polarization affecting the CHIME telescope. A novel method for circumventing bandwidth depolar- ization is outlined and validated with a real CHIME-detected FRB whose Faraday rotation measure (RM) is the second largest from any FRB observed to date. Time dependence in the polarization properties of two prolific repeating CHIME/FRB sources is studied where significant changes in RM are observed, strongly suggesting a dynamic local environment. Joint analysis of dispersion and rotation measures are used to constrain the field strength in the local environment and are compared to equivalent measurements from other repeating FRBs and pulsars. Finally, this thesis explores new methods for refining the Faraday rotating Galactic foreground, a major contaminant in the interpretation of FRB RMs, through joint analysis of RMs obtained from extragalactic sources and foreground emission from the interstellar medium.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.034 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".