Synthetic microlensing maps of the Galactic bulge
Bibliographic record
Abstract
We present synthetic maps of the microlensing optical depth, event rate and time-scales over an area of 195 deg2 towards the Galactic bulge. The maps are computed from stellar population synthesis catalogues generated from the Besançon Galaxy Model, which comprises four stellar populations and a three-dimensional extinction map calibrated against the Two-Micron All-Sky Survey. The microlensing maps have a resolution of 15 arcmin, corresponding to the angular resolution of the extinction map. We compute optical depth and event rate maps for all resolved sources above I= 19, for unresolved ‘difference image’ (DIA) sources magnified above this limit, and for bright ‘standard candle’ sources. The resulting optical depth and rate contours are dominated by extinction effects, in contrast to previous theoretical microlensing maps, and underscore the need to include realistic extinction modelling. Comparison of optical depth measurements to the Besançon model favours a bulge mass of ∼1.3 × 1010 M⊙. The microlensing maps exhibit a systematically higher optical depth for DIA sources, in line with experimental determinations. The predicted contours of the microlensing rate show very good correspondence with the field positions of the OGLE-III survey, illustrating how they have been optimized to maximize microlensing yields. We also show how the event distribution for hypothetical J and K-band microlensing surveys, using existing ground-based facilities such as VISTA, UKIRT or CFHT, would be much less affected by extinction, especially in the K band. The near infrared provides a substantial sensitivity increase over current I-band surveys and a more faithful tracer of the underlying stellar distribution, something which upcoming variability surveys such as Vista Variables in the Via Lactea (VVV) will be able to exploit. Only a fraction of current data sets has been employed for Galactic structure studies and more detailed models will be required to fully exploit the full catalogue of current survey samples, not to mention those coming online in the near future. Synthetic population modelling offers a promising way forward towards high-precision Galactic structure studies using microlensing.
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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 | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| 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) | 0.002 | 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 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".