BROADBAND SPECTRAL MODELING OF THE EXTREME GIGAHERTZ-PEAKED SPECTRUM RADIO SOURCE PKS B0008-421
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Bibliographic record
Abstract
We present broadband observations and spectral modeling of PKS B0008-421, and\nidentify it as an extreme gigahertz-peaked spectrum (GPS) source. PKS B0008-421\nis characterized by the steepest known spectral slope below the turnover, close\nto the theoretical limit of synchrotron self-absorption, and the smallest known\nspectral width of any GPS source. Spectral coverage of the source spans from\n0.118 to 22 GHz, which includes data from the Murchison Widefield Array and the\nwide bandpass receivers on the Australia Telescope Compact Array. We have\nimplemented a Bayesian inference model fitting routine to fit the data with\nvarious absorption models. We find that without the inclusion of a\nhigh-frequency exponential break the absorption models can not accurately fit\nthe data, with significant deviations above and below the peak in the radio\nspectrum. The addition of a high-frequency break provides acceptable spectral\nfits for the inhomogeneous free-free absorption and double-component\nsynchrotron self-absorption models, with the inhomogeneous free-free absorption\nmodel statistically favored. The requirement of a high-frequency spectral break\nimplies that the source has ceased injecting fresh particles. Additional\nsupport for the inhomogeneous free-free absorption model as being responsible\nfor the turnover in the spectrum is given by the consistency between the\nphysical parameters derived from the model fit and the implications of the\nexponential spectral break, such as the necessity of the source being\nsurrounded by a dense ambient medium to maintain the peak frequency near the\ngigahertz region. The discovery of PKS B0008-421 suggests that the next\ngeneration of low radio frequency surveys could reveal a large population of\nGPS sources that have ceased activity, and that a portion of the ultra-steep\nspectrum source population could be composed of these GPS sources in a relic\nphase.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 it