Pavo: Discovery of a star-forming dwarf galaxy just outside the Local Group
Bibliographic record
Abstract
We report the discovery of Pavo, a faint ($M_V = -10.0$), star-forming, irregular, and extremely isolated dwarf galaxy at $D\approx2$ Mpc. Pavo was identified in Dark Energy Camera Legacy Survey imaging via a novel approach that combines low surface brightness galaxy search algorithms and machine learning candidate classifications. Follow-up imaging with the Inamori-Magellan Areal Camera & Spectrograph on the 6.5 m Magellan Baade telescope revealed a color--magnitude diagram (CMD) with an old stellar population, in addition to the young population that dominates the integrated light, and a tip-of-the-red-giant-branch distance estimate of $1.99^{+0.20}_{-0.22}$ Mpc. The blue population of stars in the CMD is consistent with the youngest stars having formed no later than 150 Myr ago. We also detected no H$α$ emission with SOAR telescope imaging, suggesting we may be witnessing a temporary low in Pavo's star formation. We estimate the total stellar mass of Pavo to be $\log M_\ast/\mathrm{M_\odot} = 5.6 \pm 0.2$ and measure an upper limit on its HI gas mass of $1.0 \times 10^6\,\mathrm{M_\odot}$ based on the HIPASS survey. Given these properties, Pavo's closest analog is Leo P ($D=1.6$ Mpc), previously the only known isolated, star-forming, Local Volume dwarf galaxy in this mass range. However, Pavo appears to be even more isolated, with no other known galaxy residing within over 600 kpc. As surveys and search techniques continue to improve, we anticipate an entire population of analogous objects being detected just outside the Local Group.
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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 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".