Linking compact dwarf starburst galaxies in the RESOLVE survey to downsized blue nuggets
Bibliographic record
Abstract
ABSTRACT We identify and characterize compact dwarf starburst (CDS) galaxies in the REsolved Spectroscopy Of a Local VolumE (RESOLVE) survey, a volume-limited census of galaxies in the local Universe, to probe whether this population contains any residual ‘blue nuggets,’ a class of intensely star-forming compact galaxies first identified at high redshift z. Our 50 low-z CDS galaxies are defined by dwarf masses (stellar mass M* < 109.5 M⊙), compact bulged-disc or spheroid-dominated morphologies (using a quantitative criterion, $\mu _\Delta \gt 8.6$), and specific star formation rates (SSFRs) above the defining threshold for high-z blue nuggets (log SSFR [Gyr−1] > −0.5). Across redshifts, blue nuggets exhibit three defining properties: compactness relative to contemporaneous galaxies, abundant cold gas, and formation via compaction in mergers or colliding streams. Those with halo mass below Mhalo ∼ 1011.5 M⊙ may in theory evade permanent quenching and cyclically refuel until the present day. Selected only for compactness and starburst activity, our CDS galaxies generally have Mhalo ≲ 1011.5 M⊙ and gas-to-stellar mass ratio ≳1. Moreover, analysis of archival DECaLS photometry and new 3D spectroscopic observations for CDS galaxies reveals a high rate of photometric and kinematic disturbances suggestive of dwarf mergers. The SSFRs, surface mass densities, and number counts of CDS galaxies are compatible with theoretical and observational expectations for redshift evolution in blue nuggets. We argue that CDS galaxies represent a maximally starbursting subset of traditional compact dwarf classes such as blue compact dwarfs and blue E/S0s. We conclude that CDS galaxies represent a low-z tail of the blue nugget phenomenon formed via a moderated compaction channel that leaves open the possibility of disc regrowth and evolution into normal disc 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 | 0.002 |
| 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".