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 have studied 14 southern infrared dark clouds (IRDCs) using the data takenfrom the Millimetre Astronomy Legacy Team 90 GHz (MALT90) survey and theGLIMPSE and MIPSGAL mid-infrared survey of the inner Galaxy. The physical andchemical characteristics of the 14 IRDCs are investigated using N2H+(1-0),HNC(1-0), HCO+(1-0), and HCN(1-0) molecular lines. We find that the 14 IRDCsare in different evolutionary stages from the "starless" to the sources with anUCHII region. Three IRDCs are detected to have the star forming activities. Theintegrated intensity ratios I(HCO+)/I(HCN), I(N2H+)/I(HCN), and I(HNC)/I(HCN)are all about 1.5, which is different from the previous measurements,suggesting that the integrated intensity ratios may be affected by the cloudenvironments. The integrated intensities of HNC, HCO+ and HCN show a tightcorrelation for the 14 IRDCs, implying a close link to the chemical evolutionof these three species in the IRDCs. The derived excitation temperature foreach IRDC is less than 25 K. We estimate the abundances of the four moleculesfrom 10^(-11) to 10^(-9), and the average abundance ratios N(HNC)/N(HCN) = 1.4+-0.50, N(HNC)/N(HCO+) = 1.74 + - 0.22, N(HCN)/N(HCO+)= 1.21 + - 0.41.

A Systemic Study of 14 Southern Infrared Dark Clouds with the N2H+, HNC, HCO+, and HCN Lines