Star Formation in Sculptor Group Dwarf Irregular Galaxies and the Nature of “Transition” Galaxies
Bibliographic record
Abstract
We present new Hα narrowband imaging of the H II regions in eight Sculptor group dwarf irregular (dI) galaxies. The Hα luminosities of the detected H II regions range from some of the faintest detected in extragalactic H II regions (∼10 35 ergs s -1 in SC 24) to some of the most luminous (∼10 40 ergs s -1 in NGC 625). The total Hα luminosities are converted into current star formation rates (SFRs). Comparing the Sculptor group dI's to the Local Group dI's, we find that the Sculptor group dI's have, on average, lower values of SFR when normalized to either galaxy luminosity or gas mass (although there is considerable overlap between the two samples). The range for both the Sculptor group and Local Group samples is large when compared with that seen for the sample of gas-rich, quiescent, low surface brightness (LSB) dI's from van Zee et al. (published in 1997) and the sample of isolated dI's from van Zee (from 2000 and 2001). This is probably best understood as a selection effect since the nearby group samples have a much larger fraction of extremely low luminosity galaxies and the smaller galaxies are much more liable to large relative variations in current SFRs. The Sculptor group and LSB samples are very similar with regard to mean values of both τ gas and τ form , and the Local Group and isolated dI samples are also similar to each other in these two quantities. Currently, the Sculptor group lacks dI galaxies with elevated normalized current SFRs as high as the Local Group dI's IC 10 and GR 8. The properties of "transition" (dSph/dIrr) galaxies in Sculptor and the Local Group are also compared and found to be similar. The transition galaxies are typically among the lowest luminosities of the gas-rich dwarf galaxies. Relative to the dwarf irregular galaxies, the transition galaxies are found preferentially nearer to spiral galaxies and are found nearer to the center of the mass distribution in the local cloud. While most of these systems are consistent with normal dI galaxies, exhibiting temporarily interrupted star formation, the observed density-morphology relationship (which is weaker than that observed for the dwarf spheroidal galaxies) indicates that environmental processes such as "tidal stirring" may play a role in causing their lower SFRs.
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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 | 0.001 | 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) | 0.001 | 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".