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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The chemical changes of high-mass star-forming regions provide a potentialmethod for classifying their evolutionary stages and, ultimately, ages. In thisstudy, we search for correlations between molecular abundances and theevolutionary stages of dense molecular clumps associated with high-mass starformation. We use the molecular line maps from Year 1 of the MillimetreAstronomy Legacy Team 90 GHz (MALT90) Survey. The survey mapped several hundredindividual star-forming clumps chosen from the ATLASGAL survey to span thecomplete range of evolution, from prestellar to protostellar to H II regions.The evolutionary stage of each clump is classified using the SpitzerGLIMPSE/MIPSGAL mid-IR surveys. Where possible, we determine the dusttemperatures and H2 column densities for each clump from Herschel Hi-GALcontinuum data. From MALT90 data, we measure the integrated intensities of theN2H+, HCO+, HCN and HNC (1-0) lines, and derive the column densities andabundances of N2H+ and HCO+. The Herschel dust temperatures increase as afunction of the IR-based Spitzer evolutionary classification scheme, with theyoungest clumps being the coldest, which gives confidence that thisclassification method provides a reliable way to assign evolutionary stages toclumps. Both N2H+ and HCO+ abundances increase as a function of evolutionarystage, whereas the N2H+ (1-0) to HCO+ (1-0) integrated intensity ratios show nodiscernable trend. The HCN (1-0) to HNC(1-0) integrated intensity ratios showmarginal evidence of an increase as the clumps evolve.

Chemical Evolution in High-Mass Star-Forming Regions: Results from the MALT90 Survey