Interferometric Observations of the Nuclear Region of Arp 220 at Submillimeter Wavelengths
Bibliographic record
Abstract
We report the first submillimeter interferometric observations of an ultraluminous infrared galaxy. We observed Arp 220 in the CO J = 3-2 line and 342 GHz continuum with the single-baseline CSO-JCMT interferometer consisting of the Caltech Submillimeter Observatory (CSO) and the James Clerk Maxwell Telescope (JCMT). Models were fitted to the measured visibilities to constrain the structure of the source. The morphologies of the CO J = 3-2 line and 342 GHz continuum emission are similar to those seen in published maps at 230 and 110 GHz. We clearly detect a binary source separated by ~1'' in the east-west direction in the 342 GHz continuum. The CO J = 3-2 visibility amplitudes, however, indicate a more complicated structure, with evidence for a compact binary at some velocities and rather more extended structure at others. Less than 30% of the total CO J = 3-2 emission is detected by the interferometer, which implies the presence of significant quantities of extended gas. We also obtained single-dish CO J = 2-1, CO J = 3-2, and HCN J = 4-3 spectra. The HCN J = 4-3 spectrum, unlike the CO spectra, is dominated by a single redshifted peak. The HCN J = 4-3/CO J = 3-2, HCN J = 4-3/HCN J = 1-0, and CO J = 3-2/2-1 line ratios are larger in the redshifted (eastern) source, which suggests that the two sources may have different physical conditions. This result might be explained by the presence of an intense starburst that has begun to deplete or disperse the densest gas in the western source, while the eastern source harbors undispersed high-density gas.
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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 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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 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".