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

We measure IRAC colors of extended emission in several fields covering arange of Galactic latitudes and longitudes outside of star forming regions. Wedetermine the nature of the Galactic diffuse emission in Spitzer/IRAC images bycombining them with spectroscopic data. We show that PAH features make theemission in the IRAC 5.8 and 8.0 $\mu$m channels, whereas the 3.3 $\mu$mfeature represents only 20 to 50% of the IRAC 3.6 $\mu$m channel. A NIRcontinuum is necessary to account for IRAC 4.5 $\mu$m emission and theremaining fraction of the IRAC 3.6 $\mu$m emission. This continuum cannot beaccounted by scattered light. It represents 9% of the total power absorbed byPAHs and 120% of the interstellar UV photon flux. The 3.3 $\mu$m feature isobserved to vary from field-to-field with respect to the IRAC 8.0 $\mu$mchannel. The continuum and 3.3 $\mu$m feature intensities are not correlated.We present model calculations which relate our measurements of the PAHsspectral energy distribution to the particles size and ionization state. Cationand neutral PAHs emission properties are inferred empirically from\object{NGC7023} observations. PAHs caracteristics are best constrained in aline of sight towards the inner Galaxy, dominated by the Cold Neutral Mediumphase : we find that the PAH cation fraction is about 50% and that their meansize is about 60 carbon atoms. A significant field-to-field dispersion in thePAH mean size, from 40 to 80 carbon atoms, is necessary to account for theobserved variations in the 3.3 $\mu$m feature intensity relative to the IRAC8.0 $\mu$m flux. However, one cannot be secure about the feature interpretationas long as the continuum origin remains unclear.Comment: 11 pages, 11 figures accepted by A&

Spitzer/IRAC and ISOCAM/CVF insights on the origin of the near to mid-IR Galactic diffuse emission