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 present a comprehensive analysis of the spin temperature/covering factordegeneracy, T/f, in damped Lyman-alpha absorption systems. By normalising theupper limits and including these via a survival analysis, there is, aspreviously claimed, an apparent increase in T/f with redshift at z > 1.However, when we account for the geometry effects of an expanding Universe,neglected by the previous studies, this increase in T/f at z > 1 is preceded bya decrease at z < 1. Using high resolution radio images of the backgroundcontinuum sources, we can transform the T/f degeneracy to T/d^2, where d is theprojected linear size of the absorber. Again, there is no overall increase withredshift, although a dip at z ~ 2 persists. Furthermore, we find d^2/T tofollow a similar variation with redshift as the star formation rate. Thissuggests that, although the total hydrogen column density shows little relationto the SFR, the fraction of the cold neutral medium may. Therefore, furtherefforts to link the neutral gas with the star formation history should alsoconsider the cool component of the gas.

A possible connection between the spin temperature of damped Lyman-alpha absorption systems and star formation history