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

Infrared Dark Clouds (IRDCs) harbor the earliest phases of massive starformation, and many of the compact cores in IRDCs, traced by millimetercontinuum or by molecular emission in high critical density lines, host massiveyoung stellar objects (YSOs). We used the Robert C. Byrd Green Bank Telescope(GBT) and the Karl G. Jansky Very Large Array (VLA) to map NH$_{3}$ and CCS innine IRDCs to reveal the temperature, density, and velocity structures andexplore chemical evolution in the dense ($>10^{22}$ cm$^{-2}$) gas. Ammonia isan excellent molecular tracer for these cold, dense environments. The internalstructure and kinematics of the IRDCs include velocity gradients, filaments,and possibly colliding clumps that elucidate the formation process of thesestructures and their YSOs. We find a wide variety of substructure includingfilaments and globules at distinct velocities, sometimes overlapping at sitesof ongoing star formation. It appears that these IRDCs are still beingassembled from molecular gas clumps even as star formation has already begun,and at least three of them appear consistent with the morphology of``hub-filament structures'' discussed in the literature. Furthermore, we findthat these clumps are typically near equipartition between gravitational andkinetic energies, so these structures may survive for multiple free-falltimes.Keywords: molecular data -- ISM: clouds -- (ISM:) dust, extinction --ISM: molecules -- Stars: formation -- radio lines: ISM

the astronomical journal

Physical Conditions of the Earliest Phases of Massive Star Formation:  Single-Dish and Interferometric Observations of Ammonia and CCS in Infrared  Dark Clouds