Uncovering the formation of the counter-rotating stellar discs in SDSS J074834.64+444117.8
Bibliographic record
Abstract
ABSTRACT Using the integral field spectroscopic data from Mapping Nearby Galaxies at Apache Point Observatory survey, we study the kinematics and stellar population properties of the two counter-rotating stellar discs in a nearby galaxy SDSS J074834.64+444117.8. We disentangle the two stellar discs by three methods, including Ca ii λ8542 double Gaussian fit, penalized pixel fitting (pPXF) spectral decomposition, and orbit-based dynamical model. These three different methods give consistent stellar kinematics. The pPXF spectral decomposition provides the spectra of two stellar discs, with one being more luminous across the whole galaxy named primary disc, and the other named secondary disc. The primary disc is counter-rotating with ionized gas, while the secondary disc is co-rotating with ionized gas. The secondary disc has younger stellar population and poorer stellar metallicity than the primary disc. We estimate the stellar mass ratio between the primary and secondary discs to be ∼5.2. The DESI g, r, z colour image does not show any merger remnant feature in this galaxy. These findings support a scenario that the counter-rotating stellar discs in SDSS J074834.64+444117.8 formed through gas accretion from the cosmic web or a gas-rich companion.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.002 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".