Far‐Infrared<i>Spitzer</i>Observations of Elliptical Galaxies: Evidence for Extended Diffuse Dust
Bibliographic record
Abstract
Far-infrared Spitzer observations of elliptical galaxies are inconsistent with simple steady state models of dust creation in red giant stars and destruction by grain sputtering in the hot interstellar gas at T ~ 10 7 K. The flux at 24 μm correlates with optical fluxes, suggesting that this relatively hot dust is largely circumstellar. But fluxes at 70 and 160 μm do not correlate with optical fluxes. Elliptical galaxies with similar L B have luminosities at 70 and 160 μm ( L 70 and L 160 ) that vary over a factor of ~100, implying an additional source of dust unrelated to that produced by ongoing local stellar mass loss. Neither L 70 / L B nor L 160 / L B correlate with the stellar age or metallicity. Optical line fluxes from warm gas at T ~ 10 4 K correlate weakly with L 70 and L 160 , suggesting that the dust may be responsible for cooling this gas. Many normal elliptical galaxies have emission at 70 μm that is extended to 5-10 kpc. Extended far-infrared emission with sputtering lifetimes of ~10 8 yr is difficult to maintain by mergers with gas-rich galaxies. Instead, we propose that this cold dust is buoyantly transported from reservoirs of dust in the galactic cores, which are supplied by mass loss from stars in the core. Intermittent energy outbursts from AGNs can drive the buoyant outflow.
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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 | 0.001 |
| 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 | 0.001 |
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".