TOWARD PRECISION PHOTOMETRY FOR THE ELT ERA: THE DOUBLE SUBGIANT BRANCH OF NGC 1851 OBSERVED WITH THE GEMINI/GeMS MCAO SYSTEM
Why this work is in the frame
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Bibliographic record
Abstract
The Extremely Large Telescopes currently under construction have a collecting area that is an order of magnitude larger than the present largest optical telescopes. For seeing-limited observations the performance will scale as the collecting area but, with the successful use of adaptive optics, for many applications it will scale as $D^4$ (where $D$ is the diameter of the primary mirror). Central to the success of the ELTs, therefore, is the successful use of multi-conjugate adaptive optics (MCAO) that applies a high degree correction over a field of view larger than the few arcseconds that limits classical adaptive optics systems. In this letter, we report on the analysis of crowded field images taken on the central region of the Galactic globular cluster NGC 1851 in $K_s$ band using GeMS at the Gemini South telescope, the only science-grade MCAO system in operation. We use this cluster as a benchmark to verify the ability to achieve precise near-infrared photometry by presenting the deepest $K_s$ photometry in crowded fields ever obtained from the ground. We construct a colour-magnitude diagram in combination with the F606W band from HST/ACS. As well as detecting the "knee" in the lower main sequence at $K_s\simeq20.5$, we also detect the double subgiant branch of NGC 1851, that demonstrates the high photometric accuracy of GeMS in crowded fields.
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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 | 0.001 | 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 | 0.001 | 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