FAUST
Bibliographic record
Abstract
Context. Young low-mass protostars often possess hot corinos, which are compact, hot, and dense regions that are bright in interstellar complex organic molecules (iCOMs). In addition to their prebiotic role, iCOMs can be used as a powerful tool to characterize the chemical and physical properties of hot corinos. Aims. Using ALMA/FAUST data, our aim was to explore the iCOM emission at <50 au scale around the Class 0 prototypical hot corino IRAS 4A2. Methods. We imaged IRAS 4A2 in six abundant common iCOMs (CH 3 OH, HCOOCH 3 , CH 3 CHO, CH 3 CH 2 OH, CH 2 OHCHO, and NH 2 CHO), and derived their emitting sizes. The column density and gas temperature for each species were derived at 1σ from a multiline analysis by applying a non-LTE approach for CH 3 OH, and LTE population or rotational diagram analysis for the other iCOMs. Thanks to the unique estimates of the absorption from foreground millimeter dust toward IRAS 4A2, we derived for the first time unbiased gas temperatures and column densities. Results. We resolved the IRAS 4A2 hot corino, and found evidence for a chemical spatial distribution in the inner 50 au, with the outer emitting radius increasing from ∼22–23 au for NH 2 CHO and CH 2 OHCHO, followed by CH 3 CH 2 OH (∼27 au), CH 3 CHO (∼28 au), HCOOCH 3 (∼36 au), and out to ∼40 au for CH 3 OH. Combining our estimate of the gas temperature probed by each iCOM with their beam-deconvolved emission sizes, we inferred the gas temperature profile of the hot corino on scales of 20–50 au in radius, and found a power-law index q of approximately –1. Conclusions. We observed, for the first time, a chemical segregation in iCOMs of the IRAS 4A2 hot corino, and derived the gas temperature profile of its inner envelope. The derived profile is steeper than when considering a simple spherical collapsing and optically thin envelope, hinting at a partially optically thick envelope or a gravitationally unstable disk-like structure.
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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 | 0.001 | 0.004 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.006 | 0.003 |
| Open science | 0.002 | 0.003 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.528 | 0.428 |
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".