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

We present the first constraints on the cross-correlation power spectrum ofHeII ($^{+}{\rm He}^3$) signal strength using the redshifted 8.67GHz hyperfinetransition between $z=2.9$ and $z=4.1$ and with interferometric data obtainedfrom the public archive of the Australia Telescope Compact Array. 210 hours ofobservations of the primary calibrator source B1934-638 were extracted fromdata obtained with the telescope from 2014--2021, and coherently combined in apower spectrum pipeline to measure the HeII power across a range of spatialscales, and at three redshifts that span the period of Helium reionization. Ourbest limit places the brightness temperature fluctuation to be less than557$\mu$K on spatial scales of 30 arcmin at $z=2.91$, and less than 755$\mu$Kon scales of 30 arcmin at $z=4.14$ (2-sigma noise-limited). We measure atemperature of 489$\mu$K at $z=2.91$. ATCA's few antennas and persistentremaining RFI in the data prevent deeper integrations improving the results.This work is a proof of principle to demonstrate how this type of experimentcan be undertaken to reach the 0.01--1$\mu$K level expected for the Heliumsignal at $z \sim 4$.

First constraints on Helium $^{+}{\rm He}^3$ evolution in $z=3-4$ using the 8.67GHz hyperfine transition