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 3-Point Correlation Function (3PCF), which measures correlations betweentriplets of galaxies encodes information about peculiar velocities, whichdistort the observed positions of galaxies along the line of sight away fromtheir true positions. To access this information, we must track the 3PCF'sdependence not only on each triangle's shape, but also on its orientation withrespect to the line of sight. Consequently, different choices for the line ofsight will affect the measured 3PCF. Up to now, the line of sight has beentaken as the direction to a single triplet member (STM), but which tripletmember is used impacts the 3PCF by ~20% of the statistical error for aBOSS-like survey. For DESI (2019-24), which is 5X more precise, this wouldtranslate to 100% of the statistical error, increasing the total error bar by40%. We here propose a new method that is fully symmetric between the tripletmembers, and uses either the average of the three galaxy position vectors(which we show points to the triangle centroid), or the average of their unit(direction) vectors. Naively, these approaches would seem to require tripletcounting, scaling as $N^3$, with $N$ the number of objects in the survey. Byharnessing the solid harmonic shift theorem, we here show how these methods canbe evaluated scaling as $N^2$. We expect that they can be used to make arobust, systematics-free measurement of the anisotropic 3PCF of upcomingredshift surveys such as DESI. So doing will in turn open an additional channelto constrain the growth rate of structure and thereby learn the matter densityas well as test the theory of gravity.

Improving the Line of Sight for the Anisotropic 3-Point Correlation  Function of Galaxies: Centroid and Unit-Vector-Average Methods Scaling as  $\mathcal{O}(N^2)$