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

The gamma-ray burst (GRB) afterglows provide an unique opportunity to studythe interstellar medium (ISM) of star-forming galaxies at high-redshift. TheGRB-DLAs (damped Lyman-$\alpha$ absorbers) contain a large neutral hydrogencolumn density, N(H I), and are observed against the GRB afterglow. A largefraction of GRB-DLAs show presence of molecular hydrogen (H$_2$) which is anindicator of star-formation. Hence it is important to study those GRB-DLAswhich have H$_2$ lines to decipher and understand their physical conditions.The GRB-DLAs 121024A and 120815A, situated at redshift 2.30 and 2.36respectively, are two such important H$_2$-bearing GRB-DLAs. Besides H$_2$,these two GRB-DLAs also show many metal lines. In this work we have carried outa detail numerical study on the H$_2$ lines, as well as on those metal lines,in GRB-DLAs 121024A and 120815A self-consistently. We use the spectralsynthesis code CLOUDY for this study. This modeling helps us to determine theunderlying physical conditions which give rise such lines and hence tounderstand these two GRB-DLAs in much more detail than any other previousinvestigation. We find that the hydrogen densities for these two H$_2$-bearingDLAs are $\geq$ 60 cm$^{-3}$. Moreover our study infers that the linear sizesare $\leq 17.7$ pc for these two GRB-DLAs, and the mean gas temperaturesaveraged over the cloud thickness, are $\leq$ 140 K.

Physical conditions in two high-redshift H$_2$-bearing GRB-DLAs, 120815A and 121024A