MaGICC thick disc – I. Comparing a simulated disc formed with stellar feedback to the Milky Way
Bibliographic record
Abstract
We analyse the structure and chemical enrichment of a Milky Way-like galaxy with a stellar mass of 2 × 1010 M⊙, formed in a cosmological hydrodynamical simulation. It is disc dominated with a flat rotation curve, and has a disc scalelength similar to the Milky Way's, but a velocity dispersion that is ∼50 per cent higher. Examining stars in narrow [Fe/H] and [α/Fe] abundance ranges, we find remarkable qualitative agreement between this simulation and observations. (a) The old stars lie in a thickened distribution with a short scalelength, while the young stars form a thinner disc, with scalelengths decreasing, as [Fe/H] increases. (b) Consequently, there is a distinct outward metallicity gradient. (c) Mono-abundance populations exist with a continuous distribution of scaleheights (from thin to thick). However, the simulated galaxy has a distinct and substantive very thick disc (hz ∼ 1.5 kpc), not seen in the Milky Way. The broad agreement between simulations and observations allows us to test the validity of observational proxies used in the literature: we find in the simulation that mono-abundance populations are good proxies for single age populations (<1 Gyr) for most abundances.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| 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 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".