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

The abundance of CH+ and OH and excitation are predicted to be enhanced bythe presence of vibrationally excited H2 or hot gas (~500-1000 K) in PDRs withhigh incident FUV radiation field. The excitation may also originate in densegas (>10^5 cm-3) followed by nonreactive collisions. Previous observationssuggest that the CH+ and OH correlate with dense and warm gas, and formationpumping contributes to CH+ excitation. We examine the spatial distribution ofthe CH+ and OH emission in the Orion Bar to establish their physical origin andmain formation and excitation mechanisms. We present spatially sampled maps ofthe CH+ J=3-2 transition at 119.8 {\mu}m and the OH {\Lambda}-doublet at 84{\mu}m in the Orion Bar over an area of 110"x110" with Herschel (PACS). Wecompare the spatial distribution of these molecules with those of theirchemical precursors, C+, O and H2, and tracers of warm and dense gas. We assessthe spatial variation of CH+ J=2-1 velocity-resolved line profile observed withHerschel (HIFI). The OH and CH+ lines correlate well with the high-J COemission and delineate the warm and dense molecular region. While similar, thedifferences in the CH+ and OH morphologies indicate that CH+ formation andexcitation are related to the observed vibrationally excited H2. This indicatesthat formation pumping contributes to the excitation of CH+. Interestingly, thepeak of the rotationally excited OH 84 {\mu}m emission coincides with a brightyoung object, proplyd 244-440, which shows that OH can be an excellent tracerof UV-irradiated dense gas. The spatial distribution of CH+ and OH revealed inour maps is consistent with previous modeling studies. Both formation pumpingand nonreactive collisions in a UV-irradiated dense gas are important CH+ J=3-2excitation processes. The excitation of the OH {\Lambda}-doublet at 84 {\mu}mis mainly sensitive to the temperature and density.

Spatial distribution of FIR rotationally excited CH+ and OH emission lines in the Orion Bar PDR