Experimental radiative cooling rates of a polycyclic aromatic hydrocarbon cation

Navarrete, José E Navarro; Bull, James N.; Cederquist, H.; Indrajith, Suvasthika; Ji, MingChao; Schmidt, Henning; Zettergren, Henning; Zhu, Boxing; Stockett, Mark H.

doi:10.1039/d3fd00005b

Cited by 7 publications

(1 citation statement)

References 42 publications

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“…Theoretical studies have shown that molecules consisting of fewer carbon atoms (N c  40) are able to efficiently dissipate the absorbed UV energy via recurrent fluorescence (RF), with a relaxation timescale of ∼milliseconds as opposed to IR emission with timescales of ∼seconds (Leger et al 1988). Recently, laboratory studies have reproduced RF as a cooling mechanism for PAH molecules (e.g., Bernard et al 2017Bernard et al , 2023Navarro Navarrete et al 2023;Stockett et al 2023), indicating that RF can be a powerful mechanism to significantly enhance the survival rate of small particles under high UV radiation densities. Another potential explanation for excess shortwavelength PAH emission is the fact that larger PAHs can "act" like smaller PAHs in high radiation field environments.…”

Section: The Excess Of Pah 33mentioning

confidence: 99%

GOALS-JWST: Small Neutral Grains and Enhanced 3.3 μm PAH Emission in the Seyfert Galaxy NGC 7469

Lai 賴,

Armus,

Bianchin

et al. 2023

ApJL

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We present James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec) integral field spectroscopy of the nearby luminous infrared galaxy NGC 7469. We take advantage of the high spatial/spectral resolution and wavelength coverage of JWST/NIRSpec to study the 3.3 μm neutral polycyclic aromatic hydrocarbon (PAH) grain emission on ∼200 pc scales. A clear change in the average grain properties between the star-forming ring and the central AGN is found. Regions in the vicinity of the AGN, with [Ne iii]/[Ne ii] > 0.25, tend to have larger grain sizes and lower aliphatic-to-aromatic (3.4/3.3) ratios, indicating that smaller grains are preferentially removed by photodestruction in the vicinity of the AGN. PAH emission at the nucleus is weak and shows a low 11.3/3.3 PAH ratio. We find an overall suppression of the total PAH emission relative to the ionized gas in the central 1 kpc region of the AGN in NGC 7469 compared to what has been observed with Spitzer on 3 kpc scales. However, the fractional 3.3 μm–to–total PAH power is enhanced in the starburst ring, possibly due to a variety of physical effects on subkiloparsec scales, including recurrent fluorescence of small grains or multiple photon absorption by large grains. Finally, the IFU data show that while the 3.3 μm PAH-derived star formation rate (SFR) in the ring is 27% higher than that inferred from the [Ne ii] and [Ne iii] emission lines, the integrated SFR derived from the 3.3 μm feature would be underestimated by a factor of 2 due to the deficit of PAHs around the AGN, as might occur if a composite system like NGC 7469 were to be observed at high redshift.

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