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

Recent observations have reported that some gas-rich dwarf irregular (dIrr)galaxies appear to have spherical distributions in the outer underlying old andintermediate-age stellar populations (e.g., NGC 6822). These observations implythat some dIrr's have two distinct (or ``two-component'') structures, i.e.,inner disky and outer spherical ones, though the number fraction of dIrr's withsuch structures remains observationally unclear. We discuss how such twodistinct structures are formed during dIrr formation based on observations andsimulations. Our numerical simulations show that the remnants of mergersbetween two gas-rich dIrr's with initially extended gas disks can have bothextended spheroids composed of older stellar populations and disks composedmostly of gas and young stars. The simulated remnants with two distinctstructures can be still identified as dIrr's owing to the presence ofstar-forming regions. The structural properties of outer spherical structuresin dIrr's formed from dIrr-dIrr merging depend on initial conditions ofmerging, which suggests that outer structures in dIrr's can be diverse. We alsodiscuss other possible physical mechanisms for the formation of outer sphericalstructures composed of older stars in dIrr's.

Origin of dwarf irregular galaxies with outer early-type structures