First Constraints on Helium ^{+}He^{3} Evolution in z = 34 Using the 8.67 GHz Hyperfine Transition
Abstract
We present the first constraints on the crosscorrelation power spectrum of the He II (^{+}He^{3}) signal strength using the redshifted 8.67 GHz hyperfine transition between z = 2.9 and 4.1 and with interferometric data obtained from the public archive of the Australia Telescope Compact Array (ATCA). 210 hr of observations of the primary calibrator source B1934638 were extracted from data obtained with the telescope from 20142021, and coherently combined in a power spectrum pipeline to measure the He II power across a range of spatial scales, and at three redshifts that span the period of helium reionization. Our best limit places the fluctuation of the brightness temperature to be less than 557 μK on spatial scales of 30' at z = 2.91, and less than 755 μK on scales of 30' at z = 4.14 (2σ noise limited). We measure a temperature of 489 μK at z = 2.91. ATCA's few antennas and persistent remaining radio frequency interference in the data prevent deeper integrations improving the results. This work is a proof of principle to demonstrate how this type of experiment can be undertaken to reach the 0.011 μK level expected for the helium signal at z ~ 4.
 Publication:

The Astrophysical Journal
 Pub Date:
 January 2024
 DOI:
 10.3847/15384357/ad0ecf
 arXiv:
 arXiv:2309.05960
 Bibcode:
 2024ApJ...960...10T
 Keywords:

 Cosmology;
 Reionization;
 Astronomical instrumentation;
 Radio interferometers;
 343;
 1383;
 799;
 1345;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Instrumentation and Methods for Astrophysics
 EPrint:
 10 pages, 4 figures, accepted in ApJ