Photometric survey of the polar ring galaxy NGC 6822
Bibliographic record
Abstract
Context.We have previously established, from a carbon star survey, that the Local Group dwarf irregular galaxy NGC 6822 is much larger than its central bright core. Aims. Four MegaCam fields are acquired to survey a 2$^\circ\times 2^\circ$ area centred on NGC 6822 to fully determine its extent and map its stellar populations. Methods.Photometry of over one million stars is obtained in the SDSS g', r', i' to three magnitudes below the TRGB. RGB stars, selected from their magnitudes and colours, are used to map the NGC 6822 stellar distribution up to a distance of 60 arcmin. Results.We map the reddening over the whole area. We establish that the stellar outer structure of NGC 6822 is elliptical in shape, with $\epsilon=0.36$ and a major-axis PA = 65°, contrasting with the orientation of the HI disk. The density enhancement can be seen up to a semi-major axis of $36'$ making NGC 6822 as big as the Small Magellanic Cloud. We fit two exponentials to the surface density profile of the spheroid, and identify a bulge with a scale length of $3.85'$ and an outer spheroid with a scale length of $10.0'$. We find intermediate-age C stars up to ${\sim}40'$ while demonstrating that the SDSS filters are unsuitable to identify extragalactic C stars. Conclusions.NGC 6822 is a unique Local Group galaxy with shape and structure suggesting a polar ring configuration. Radial velocities of carbon stars have indeed demonstrated that there are two kinematical systems in NGC 6822.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.003 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 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 teacher head, 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".