SNLS: Overview and High-z Spectroscopy
Bibliographic record
Abstract
The Supernova Legacy Survey (SNLS) 1 will discover and obtain g ′ r ′ i ′ z ′ lightcurves for more than 700 spectroscopically confirmed SNe Ia (0.3 < z < 0.9) to differentiate between competing models for Dark Energy. We fit the multicolor lightcurves of the candidates to determine which are likely SNe Ia and send them for follow-up spectroscopy to the Keck, VLT, and Gemini telescopes. Here we show the results from Gemini, where we send most of our highest redshift (0.6 < z < 0.9) targets. 1. Lightcurves As a part of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS), the SNLS uses a rolling search strategy to discover and monitor SNe in four one degree fields over the course of five years. SNe are observed in g ′ r ′ i ′ z ′ , allowing unprecedented measurement of reddening and SN intrinsic colors. Observations are made every 2-3 rest frame days during dark and gray time. A typical run includes 10 observing blocks of 5 visits to each of two deep fields. Because we always observe the same fields, every visit brings new SN discoveries and simultaneously adds points to existing lightcurves. See the contribution of Sullivan et al. to these proceedings for an overview of the SNLS. 2. Spectroscopy For the most promising candidates, spectroscopy on 8-10m telescopes must be obtained to determined the redshift and SN type. We prescreen candidates – early data are fit with a Ia lightcurve and poor fits (core-collapse SNe or AGN) are rejected. For good fits (likely SNe Ia), the redshift and phase are estimated, allowing optimal scheduling of observations and instrument setup. Spectroscopy of candidate SNe is carried out on Gemini, Keck and VLT. The highest redshift targets are observed at Gemini N and S with GMOS (Hook et al. 2004), where we make use of the Nod and Shuffle mode to virtually eliminate the systematic errors associated with the subtraction of sky lines in the red. Gemini also observes some lower redshift targets in classical mode in the D3 (Extended Groth Strip) field, which cannot be seen by VLT. All GMOS observations use the R400 grating, 0.75 ′ ′ slit, and either the 680 or 720nm central wavelength setup. The CCD is binned 2×2.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.004 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.009 | 0.006 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.007 | 0.010 |
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 source (direct Gemma or distilled Codex), 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".