Lopsidedness in dwarf irregular galaxies
Bibliographic record
Abstract
We quantify the amplitude of the lopsidedness, the azimuthal angular asymmetry index and the concentration of star-forming regions, as represented by the distribution of the Hα emission, in a sample of 78 late-type irregular galaxies. We bin the observed galaxies into two groups representing blue compact galaxies (BCDs) and low-surface-brightness dwarf galaxies (LSBs). The light distribution is analysed with a novel algorithm, which allows detection of details in the light distribution pattern. We find that while the asymmetry of the underlying continuum light, representing the older stellar generations, is relatively small, the Hα emission is very asymmetric and is correlated in position angle with the continuum light. We show that the concentration of continuum light is correlated with the Hα concentration; this implies that the young star formation has the same spatial properties as the older stellar populations, but that these properties are more strongly expressed by the young stars. We test a model of random star formation over the extent of a galaxy by simulating H ii regions in artificial dwarf galaxies. A galaxy is traced by assuming red star clusters distributed on an underlying exponential disc of radius twice the scalelength. The disc is allowed to change in apparent magnitude, scaleradius, position angle and ellipticity. We compare the asymmetry-concentration distribution predicted by the simulations with the real observed distribution; we find that only LSBs match the distribution predicted by the model. The reason is that, independently of the number of H ii regions, LSBs show no particular location of H ii regions, whereas BCDs show current star formation activity restricted very much to the central parts of the galaxies. A consideration of the properties of the continuum light leads to the conclusion that most of LSBs can be approximated by exponential discs of radius twice their scalelength; BCDs call, however, for much more concentrated underlying systems, with smaller scalelengths than assumed in the simulations. The implication is that random star formation over the full extent of a galaxy may be generated in LSB dwarf irregular galaxies but not in BCD galaxies.
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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 | 0.004 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 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 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".