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 Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Reconstruction techniques for intrinsic quasar continua are crucial for theprecision study of Lyman-$\alpha$ (Ly-$\alpha$) and Lyman-$\beta$ (Ly-$\beta$)transmission at $z>5.0$, where the $\lambda<1215 A$ emission of quasars isnearly completely absorbed. While the number and quality of spectroscopicobservations has become theoretically sufficient to quantify Ly-$\alpha$transmission at $5.0<z<6.0$ to better than $1\%$, the biases and uncertaintiesarising from predicting the unabsorbed continuum are not known to the samelevel. In this paper, we systematically evaluate eight reconstructiontechniques on a unified testing sample of $2.7<z<3.5$ quasars drawn from eBOSS.The methods include power-law extrapolation, stacking of neighbours, and sixvariants of Principal Component Analysis (PCA) using direct projection, fittingof components, or neural networks to perform weight mapping. We find thatpower-law reconstructions and the PCA with fewest components and smallesttraining sample display the largest biases in the Ly-$\alpha$ forest($-9.58\%/+8.22\%$ respectively). Power-law extrapolations have larger scattersthan previously assumed of $+13.1\%/-13.2\%$ over Ly-$\alpha$ and$+19.9\%/-20.1\%$ over Ly-$\beta$. We present two new PCAs which achieve thebest current accuracies of $9\%$ for Ly-$\alpha$ and $17\%$ for Ly-$\beta$. Weapply the eight techniques after accounting for wavelength-dependent biases andscatter to a sample $19$ quasars at $z>5.7$ with IR X-Shooter spectroscopy,obtaining well-characterised measurements for the mean flux transmission at$4.7<z<6.3$. Our results demonstrate the importance of testing and, whenrelevant, training, continuum reconstruction techniques in a systematic way.

A comparison of quasar emission reconstruction techniques for $z\geq5.0$ Lyman-$\alpha$ and Lyman-$\beta$ transmission