Sharpless 170 and the surrounding interstellar medium
Bibliographic record
Abstract
Sharpless 170 is a diffuse Hii region ionized by a single main sequence O-star located near the periphery of a small dense molecular cloud at a distance of ~2 kpc. We describe wide-field observations of the region in the radio continuum, in Hi and CO-lines, and in the far-infrared which delineate the major ionized, atomic, molecular and dust components of the gas affected by the exciting star. From the thermal continuum emission we estimate the mass of ionized gas at ~350 within a radius of ~7 pc. The Hi (λ21 cm) and far-infrared observations show an extended low-density atomic component, of ~1000 , within an irregular boundary surrounding the ionized gas of mean radius ~10 pc. Mean densities in the Hi and Hii are similar, in the range 9–16 nucleons cm-3. CO emission shows a molecular cloud of ~1150 within an area 6 pc 4 pc with densities ~2000 nucleons cm-3. A compact infrared component coincides with the cloud. The exciting star is located on the near side of the cloud, just inside the southern periphery. Sh170 is an example of a young Hii region with the ionized gas, seen in Hα emission, streaming outward in the manner of a “champagne flow”. Although the observed velocities of the Hi are close to the mean velocity of the CO cloud, the morphology of the associated atomic hydrogen closely resembles that seen in the surrounds of other young Hii regions which show clear evidence of expansion of their Hi. We propose that much of the Hi is a diffuse dissociation zone beyond the ionization front, in directions from the star within a wide annulus, approximately transverse to the line-of-sight, between the dense photon-bounded region on the far side of the star and the density-bounded ionized flow region on the near side. In this view, much of the associated atomic gas, like the ionized gas, has been eroded from the molecular cloud in a small fraction (≤10%) of the star's main sequence lifetime.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.005 | 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".