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

A sample of $60,410$ bona fide optical quasars with astrometric propermotions in Gaia EDR3 and spectroscopic redshifts above 0.5 in an oval 8400square degree area of the sky is constructed. Using orthogonal Zernikefunctions of polar coordinates, the proper motion fields are fitted in aweighted least-squares adjustment of the entire sample and of six equal bins ofsorted redshifts. The overall fit with 37 Zernike functions reveals astatistically significant pattern, which is likely to be of instrumentalorigin. The main feature of this pattern is a chain of peaks and dips mostly inthe R.A. component with an amplitude of 25~$\mu$as yr$^{-1}$. This field issubtracted from each of the six analogous fits for quasars grouped by redshiftscovering the range 0.5 through 7.03, with median values 0.72, 1.00, 1.25, 1.52,1.83, 2.34. The resulting residual patterns are noisier, with formaluncertainties up to 8~$\mu$as yr$^{-1}$ in the central part of the area. Wedetect a single high-confidence Zernike term for R.A. proper motion componentsof quasars with redshifts around 1.52 representing a general gradient of 30$\mu$as yr$^{-1}$ over $150\degr$ on the sky. We do not find any small- ormedium-scale systemic variations of the residual proper motion field asfunctions of redshift above the $2.5\,\sigma$ significance level.

Testing the Cosmological Principle: Astrometric Limits on Systemic Motion of Quasars at Different Cosmological Epochs