PROBING THE DARK AGES AT z ∼ 20: THE SCI-HI 21 cm ALL-SKY SPECTRUM EXPERIMENT

Tabitha C Voytek,Jeffrey B Peterson,Aravind Natarajan,Omar López-Cruz,José Miguel Jáuregui García

doi:10.1088/2041-8205/782/1/l9

Abstract

We present first results from the SCI-HI experiment, which we used to measure the all-sky-averaged \cm brightness temperature in the redshift range 14.8<z<22.7. The instrument consists of a single broadband sub-wavelength size antenna and a sampling system for real-time data processing and recording. Preliminary observations were completed in June 2013 at Isla Guadalupe, a Mexican biosphere reserve located in the Pacific Ocean. The data was cleaned to excise channels contaminated by radio frequency interference (RFI), and the system response was calibrated by comparing the measured brightness temperature to the Global Sky Model of the Galaxy and by independent measurement of Johnson noise from a calibration terminator. We present our results, discuss the cosmological implications, and describe plans for future work.

Highlights

IntroductionEmission and absorption due to the 21 cm spin flip transition of neutral Hydrogen (HI) have emerged as valuable tools to probe the physics of the Universe across a set of cosmological eras ranging from the pre-star dark ages to the epoch of reionization to the era of acceleration (Loeb & Zaldarriaga 2004; Cooray 2004; Bharadwaj & Ali 2004; Carilli et al 2004; Furlanetto & Briggs 2004; Furlanetto et al 2006; Pritchard & Loeb 2010, 2012; Liu et al 2013)
The Galactic Global Sky Model (GSM) provides a set of maps of the Galaxy at frequencies between 10 MHz and 100 GHz, created by interpolating data derived from publicly available large area radio surveys
GSM software is used to produce a set of maps of the sky in the frequency range relevant to our GlobalGSlkoybMalodSekly(7M0 ModHezl)(70 MHz)

Summary

Introduction

Emission and absorption due to the 21 cm spin flip transition of neutral Hydrogen (HI) have emerged as valuable tools to probe the physics of the Universe across a set of cosmological eras ranging from the pre-star dark ages to the epoch of reionization to the era of acceleration (Loeb & Zaldarriaga 2004; Cooray 2004; Bharadwaj & Ali 2004; Carilli et al 2004; Furlanetto & Briggs 2004; Furlanetto et al 2006; Pritchard & Loeb 2010, 2012; Liu et al 2013). The first stars to form are composed almost entirely of primordial elements These stars, called Pop. III., are thought to form in dark matter minihalos of mass ≈ 106 − 108M at a redshift z ≈ 20-30 (Bromm et al 1999, 2002; Bromm & Larson 2004; Abel et al 2002; Omukai & Palla 2001, 2003; Tan & McKee 2004; McKee & Tan 2008; Bromm 2013), and provide UV illumination of the HI in their surroundings. Supernovae from these short lived, massive stars enriched the Universe

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Conclusion