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

The spectrum of the $z_{\rm em} = 2.63$ quasar Q1009+2956 has been observedextensively on the Keck telescope. The Lyman limit absorption system $z_{\rmabs} = 2.504$ was previously used to measure D/H by Burles & Tytler using aspectrum with signal to noise approximately 60 per pixel in the continuum nearLy {\alpha} at $z_{\rm abs} = 2.504$. The larger dataset now available combinesto form an exceptionally high signal to noise spectrum, around 147 per pixel.Several heavy element absorption lines are detected in this LLS, providingstrong constraints on the kinematic structure. We explore a suite of absorptionsystem models and find that the deuterium feature is likely to be contaminatedby weak interloping Ly {\alpha} absorption from a low column density H I cloud,reducing the expected D/H precision. We find D/H =$2.48^{+0.41}_{-0.35}\times10^{-5}$ for this system. Combining this newmeasurement with others from the literature and applying the method of LeastTrimmed Squares to a statistical sample of 15 D/H measurements results in a"reliable" sample of 13 values. This sample yields a primordial deuteriumabundance of (D/H)$_{\rm p} = (2.545 \pm 0.025)\times10^{-5}$. Thecorresponding mean baryonic density of the Universe is $\Omega_{\rm b}h^2 =0.02174\pm0.00025$. The quasar absorption data is of the same precision as, andmarginally inconsistent with, the 2015 CMB Planck (TT+lowP+lensing)measurement, $\Omega_{\rm b}h^2 = 0.02226\pm0.00023$. Further quasar and moreprecise nuclear data are required to establish whether this is a randomfluctuation.

The primordial deuterium abundance at z = 2.504 from a high signal-to-noise spectrum of Q1009+2956