Space Telescope Imaging Spectrograph Long‐Slit Spectroscopy of the Narrow‐Line Region of NGC 4151. II. Physical Conditions along Position Angle 221o
Bibliographic record
Abstract
We have examined the physical conditions in the narrow-line region of the well-studied Seyfert galaxy NGC 4151, using long-slit spectra obtained with the Hubble Space Telescope Space Telescope Imaging Spectrograph. The data were taken along a position angle of 221°, centered on the optical nucleus. We have generated photoionization models for a contiguous set of radial zones, out to 2 3 in projected position to the southwest of the nucleus and 2 7 to the northeast. Given the uncertainties in the reddening correction, the calculated line ratios successfully matched nearly all the dereddened ratios. We find that the narrow-line region consists of dusty atomic gas photoionized by a power-law continuum that has been modified by transmission through a mix of low- and high-ionization gas, specifically, UV-absorbing and X-ray-absorbing components. The physical characteristics of the absorbers resemble those observed along our line of sight to the nucleus, although the column density of the X-ray absorber is a factor of 10 less than observed. The large inferred covering factor of the absorbing gas is in agreement with the results of our previous study of UV absorption in Seyfert 1 galaxies. We find evidence, specifically the suppression of Lyα, that we are observing the back end of dusty ionized clouds in the region southwest of the nucleus. Since these clouds are blueshifted, this supports the interpretation of the cloud kinematics as being due to radial outflow from the nucleus. We find that the narrow-line gas at each radial position is inhomogeneous and can be modeled as consisting of a radiation-bounded component and a more tenuous, matter-bounded component. The density of the narrow-line gas drops with increasing radial distance, which confirms our earlier results and may be a result of the expansion of radially outflowing emission-line clouds.
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 | 0.001 | 0.001 |
| 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) | 0.002 | 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".