English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Context. In photo-dissociation regions (PDRs), Polycyclic AromaticHydrocarbons (PAHs) could be produced by evaporation of Very Small Grains(VSGs) by the impinging UV radiation field from a nearby star. Aims. Weinvestigate quantitatively the transition zone between evaporating Very SmallGrains (eVSGs) and PAHs in several PDRs. Methods. We study the relativecontribution of PAHs and eVSGs to the mid-IR emission in a wide range ofexcitation conditions. We fit the observed mid-IR emission of PDRs by using aset of template band emission spectra of PAHs, eVSGs and gas lines. The fittingtool PAHTAT (PAH Toulouse Astronomical Templates) is made available to thecommunity as an IDL routine. From the results of the fit, we derive thefraction of carbon f_eVSG locked in eVSGs and compare it to the intensity ofthe local UV radiation field. Results. We show a clear decrease of f_eVSG withincreasing intensity of the local UV radiation field, which supports thescenario of photo-destruction of eVSGs. Conversely, this dependence can be usedto quantify the intensity of the UV radiation field for different PDRs,including non resolved ones. Conclusions. PAHTAT can be used to trace theintensity of the local UV radiation field in regions where eVSGs evaporate,which correspond to relatively dense (nH = [100, 10^5 ] cm-3) and UV irradiatedPDRs (G0 = [100, 5x10^4]) where H2 emits in rotational lines.

Evaporating Very Small Grains as tracers of the UV radiation field in Photo-dissociation Regions