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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Lyman Limit systems (LLSs) trace the low-density circumgalactic medium andthe most dense regions of the intergalactic medium, so their number density andevolution at high redshift, just after reionisation, are important toconstrain. We present a survey for LLSs at high redshifts, $z_{\rm LLS}=3.5$--5.4, in the homogeneous dataset of 153 optical quasar spectra at $z \sim5$ from the Giant Gemini GMOS survey. Our analysis includes detailedinvestigation of survey biases using mock spectra which provide importantcorrections to the raw measurements. We estimate the incidence of LLSs per unitredshift at $z \approx 4.4$ to be $\ell(z) = 2.6 \pm 0.4$. Combining ourresults with previous surveys at $z_{\rm LLS} <4$, the best-fit power-lawevolution is $\ell(z) = \ell_* [(1+z)/4]^\alpha$ with $\ell_* = 1.46 \pm 0.11$and $\alpha = 1.70 \pm 0.22$ (68\% confidence intervals). Despite hints inprevious $z_{\rm LLS} <4$ results, there is no indication for a deviation fromthis single power-law soon after reionization. Finally, we integrate our newresults with previous surveys of the intergalactic and circumgalactic media toconstrain the hydrogen column density distribution function, $f(N_{\rm HI},X)$,over 10 orders of magnitude. The data at $z \sim 5$ are not well described bythe $f(N_{\rm HI},X)$ model previously reported for $z \sim 2$--3 (afterre-scaling) and a 7-pivot model fitting the full $z \sim 2$--5 dataset isstatistically unacceptable. We conclude that there is significant evolution inthe shape of $f(N_{\rm HI},X)$ over this $\sim$2 billion year period.

Imprints of the first billion years: Lyman limit systems at $z \sim 5$