Saved in:
| Main Authors: | , , , |
|---|---|
| Format: | Preprint |
| Published: |
2026
|
| Subjects: | |
| Online Access: | https://arxiv.org/abs/2602.12331 |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1866915884064309248 |
|---|---|
| author | Lee, Dennis Hensley, Brandon S. Chang, Tzu-Ching Doré, Olivier |
| author_facet | Lee, Dennis Hensley, Brandon S. Chang, Tzu-Ching Doré, Olivier |
| contents | Polycyclic aromatic hydrocarbons (PAHs) are responsible for a variety of near- and mid-infrared spectral features in Galactic and extragalactic sources. A feature at 1.05 $μ$m arising from electronic transitions in PAH cations is predicted by laboratory experiments but has never been observationally confirmed. We conduct a dedicated search for this feature in absorption on a highly-extinguished sight line toward BD+40 4223, a blue supergiant in Cyg OB2, using the TripleSpec spectrograph at Palomar Observatory. We place a $5σ$ upper limit on the feature strength of $Δτ_{1.05}/A_{V} < 5.6 \times10^{-3}$, ruling out theoretical estimates with $> 10σ$ significance. We constrain the effective temperature of BD+40 4223 to be $\log_{10}\left(T_{\rm eff}\right)=4.41\pm0.03$ and infer that it is veiled by $6.39\pm0.05$ magnitudes of visual extinction, consistent with but more constraining than previous determinations. As dust on the sight line toward BD+40 4223 appears typical of the diffuse interstellar medium, this non-detection challenges existing models of PAH material properties and/or charge distribution. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_12331 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Searching for the Shortest-wavelength Aromatic Infrared Bands: No Evidence for the Predicted 1.05 $μ$m Polycyclic Aromatic Hydrocarbon Feature Lee, Dennis Hensley, Brandon S. Chang, Tzu-Ching Doré, Olivier Astrophysics of Galaxies Polycyclic aromatic hydrocarbons (PAHs) are responsible for a variety of near- and mid-infrared spectral features in Galactic and extragalactic sources. A feature at 1.05 $μ$m arising from electronic transitions in PAH cations is predicted by laboratory experiments but has never been observationally confirmed. We conduct a dedicated search for this feature in absorption on a highly-extinguished sight line toward BD+40 4223, a blue supergiant in Cyg OB2, using the TripleSpec spectrograph at Palomar Observatory. We place a $5σ$ upper limit on the feature strength of $Δτ_{1.05}/A_{V} < 5.6 \times10^{-3}$, ruling out theoretical estimates with $> 10σ$ significance. We constrain the effective temperature of BD+40 4223 to be $\log_{10}\left(T_{\rm eff}\right)=4.41\pm0.03$ and infer that it is veiled by $6.39\pm0.05$ magnitudes of visual extinction, consistent with but more constraining than previous determinations. As dust on the sight line toward BD+40 4223 appears typical of the diffuse interstellar medium, this non-detection challenges existing models of PAH material properties and/or charge distribution. |
| title | Searching for the Shortest-wavelength Aromatic Infrared Bands: No Evidence for the Predicted 1.05 $μ$m Polycyclic Aromatic Hydrocarbon Feature |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2602.12331 |