Ionized gas in NGC 4258: exploring the AGN–star formation connection
Bibliographic record
Abstract
ABSTRACT NGC 4258 is a prime target for studying feedback in low-luminosity active galactic nuclei (LLAGNs) due to its proximity and comprehensive multiwavelength coverage. Using new integral field spectroscopy (IFS) data from SITELLE at the Canada–France–Hawaii Telescope, we analysed the galaxy’s nebular emission lines. Our study focused on spatially resolved line ratios and Baldwin–Phillips–Terlevich diagrams, revealing that the ‘anomalous spiral arms’ exhibit intense interactions between the jet and interstellar medium (ISM) extending up to 6 kpc with velocity dispersions peak at 200–250 km s−1 in these regions, contrasting with star-forming areas showing lower values around of 30–50 km s−1. Analysis of covering fractions indicates heightened AGN ionization cones aligned with the radio jet, alongside evidence of shock quenching observed in the lower anomalous arc. Conversely, jet-induced compression may stimulate star formation in other areas. We derived a galaxy-wide star formation rate of $\sim 3\,{\rm M}_{\odot }\,\mathrm{yr}^{-1}$, decreasing to $0.3\,{\rm M}_{\odot }\,\mathrm{yr}^{-1}$ within the central 3.4 kpc$^2$. SITELLE’s broad field coverage elucidates the galaxy’s structural details, confirming that low-power jets significantly influence the host galaxy across parsec and kpc scales. The velocity dispersion map reveals asymmetric or double-peaked emission lines, tracing jet-disc interactions likely responsible for the formation of anomalous arm features. Small-scale ionizing clusters were detected in regions with disrupted gas flows, possibly formed through tidal interactions or shock compression. NGC 4258 thus presents a compelling case for studying LLAGN-driven feedback, illustrating how optical IFS combined with multiwavelength data clarifies the impact of outflows and shocks on nearby spiral galaxies, providing insights into how these processes shape star formation and ISM conditions.
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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 | 0.000 | 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".