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 Tools annual

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 monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

We aim to study the properties of the dense molecular gas towards the innerfew 100 pc of four nearby starburst galaxies dominated both by photodissociation regions (M82) and large-scale shocks (NGC253, IC342 and Maffei2),and to relate the chemical and physical properties of the molecular clouds withthe evolutionary stage of the nuclear starbursts. We have carried outmulti-transitional observations and analyses of three dense gas moleculartracers, CS, HC3N and CH3CCH, using Boltzmann diagrams in order to determinethe rotational temperatures and column densities of the dense gas, and using aLarge Velocity Gradients model to calculate the H2 density structure in themolecular clouds. The CS and HC3N data indicate the presence of densitygradients in the molecular clouds, showing similar excitation conditions, andsuggesting that they arise from the same gas components. In M82, CH3CCH has thehighest fractional abundance determined in a extragalactic source (10^-8). Thedensity and the chemical gradients found in all galaxies can be explained inthe framework of the starburst evolution. The young shock-dominatedstarburstgalaxies, like presumably Maffei2, show a cloud structure with a rather uniformdensity and chemical composition which suggests low star formation activity.Molecular clouds in galaxies with starburst in an intermediate stage ofevolution, such as NGC253 and IC342, show clouds with a large density contrast(two orders of magnitude) between the denser regions (cores) and the less denseregions (halos) of the molecular clouds and relatively constant chemicalabundance. Finally, the galaxy with the most evolved starburst, M82, has cloudswith a rather uniform density structure, large envelopes of atomic/moleculargas subjected to UV photodissociating radiation from young star clusters, andvery different chemical abundances of HC3N and CH3CCH.

CS, HC3N and CH3CCH multi-line analyses towards starburst galaxies. The evolution of cloud structures in the central regions of galaxies