Detecting the Rise and Fall of 21 cm Fluctuations with the Murchison Widefield Array

By A. Lidz, Oliver Zahn, M. McQuinn, M. Zaldarriaga, L. Hernquist. 2007

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We forecast the sensitivity with which the Murchison Widefield Array (MWA) can measure the 21 cm power spectrum of cosmic hydrogen. The MWA is sensitive to roughly a decade in scale (wavenumbers of k ∼ 0.1-1 h Mpc−1). This amounts primarily to constraints on two numbers: the amplitude and the slope of the 21 cm power spectrum on the scales probed. We find, however, that the redshift evolution in these quantities can yield important information about reionization. We examine a range of theoretical models, spanning uncertainties in the nature of the ionizing sources and the abundance of minihalos during reionization. Although the power spectrum differs substantially among these models, a generic prediction is that the amplitude of the 21 cm power spectrum on MWA scales (k ∼ 0.4 h Mpc−1) peaks near the epoch when the intergalactic medium (IGM) is ≈50% ionized. Moreover, the slope of the 21 cm power spectrum flattens as the ionization fraction increases and the sizes of the H II regions grow. With regards to detection sensitivity, we show that the optimal MWA antenna configuration for power spectrum measurements would pack all 500 antenna tiles as closely as possible in a compact core. Detecting the characteristic redshift evolution of our models will help to confirm that observed 21 cm fluctuations originate from the IGM, and not from foregrounds, and will provide an indirect constraint on the evolution of the volume-filling factor of H II regions during reionization. After two years of observations, the MWA can constrain the filling factor at an epoch when ∼ 0.5 to within roughly ±δ ∼ 0.1 at 2 σ confidence.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/04ae9e6a5143693d569d2844da46373e4ab0d204

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Citations in the corpus

Comparison of reionization models: radiative transfer simulations and approximate, seminumeric models (2010, background): “…the power spectrum as this is a simple, often-studied statistic, which can encode information about the reionization state of the Universe (e.g., Lidz et al. 2008) Ignoring redshift-space distortions, the excess 21 cm brightness temperature over that of the cosmic microwave background from…”
Inside-out or outside-in: the topology of reionization in the photon-starved regime suggested by Lyα forest data (2008, methodology): “For a given filtering scaleR, we equate it to the mean free path, i.e.,λmfp = R (Lidz et al. 2008).”
The Evolution of the Intergalactic Medium (2015, unknown): “…derive from multiple independent measurements, from a detection in cross-correlation with a co-spatial galaxy survey (Furlanetto & Lidz 2007; Lidz et al. 2009), or from a detection of temporal evolution in the signal that is consistent with the predictions of reionization models (Lidz et al. 2008).”
INTENSITY MAPPING WITH CARBON MONOXIDE EMISSION LINES AND THE REDSHIFTED 21 cm LINE (2011, methodology): “The 21 cm fluctuations are generally largest in amplitude on most relevant scales around reionization’s mid-point, when 〈xi〉 = 0.5 (e.g. Lidz et al. 2008).”
Reionization and Cosmology with 21-cm Fluctuations (2009, background): “The majority of the information about reionization from the first generation EoR observations will come from the evolution of the power spectrum amplitude and slope (Lidz et al. 2008, and Figure 4).”
New Limits on 21cm EoR From PAPER-32 Consistent with an X-Ray Heated IGM at z=7.7 (2013, methodology): “…do not know whether the ionization fraction at z ≈ 8 is near to the ionization fractions we investigate (although models such as Zahn et al. 2007 and Lidz et al. 2008 do predict xi = 0.5 near z ≈ 8), the implication of our measurements is that the IGM may have been heated with respect to…”
Science with the Murchison Widefield Array (2012, background): “Lidz et al. (2008) found that a null detection with the MWA at z ≤ 8 would be able to constrain the neutral fraction to .”
21 cm cosmology in the 21st century (2011, background): “single k-mode with line of sight component k|| = μk is given by [141]:”
BRIGHT SOURCE SUBTRACTION REQUIREMENTS FOR REDSHIFTED 21 cm MEASUREMENTS (2010, background): “As discussed in Lidz et al. (2008), the MWA-512 will be sensitive primarily to scales 0 .”
Reionization and the Cosmic Dawn with the Square Kilometre Array (2012, background): “At this point in time no standard framework exists to interpret observed power spectra, but steps in the direction of such a framework have been taken, see e.g. (Lidz et al. 2008; Iliev et al. 2012).”
Signatures of X-rays in the early Universe (2012, background): “Our results are in excellent agreement with those in Lidz et al. (2008), who only considered reionization assuming TS Tγ (see their Fig.”
21CMMC: an MCMC analysis tool enabling astrophysical parameter studies of the cosmic 21 cm signal (2015, background): “…driven by relatively massive galaxies should result in larger, more uniform ionized regions (e.g. McQuinn et al. 2007; Iliev et al. 2012) and the large-scale PS should peak at the midpoint of the EoR (e.g. Lidz et al. 2008), unless reionization is driven by X-rays (Mesinger et al. 2013).”
PAPER-64 CONSTRAINTS ON REIONIZATION: THE 21 cm POWER SPECTRUM AT z = 8.4 (2015, background): “During our cosmic dawn, IGM characteristics depend on the matter density field, the mass and clustering of the first galaxies (Lidz et al. 2008), their ultraviolet luminosities (McQuinn et al. 2007), the abundance of X-ray sources and other sources of heating (Pritchard & Loeb 2008; Mesinger et al.…”
The GMRT Epoch of Reionization experiment: a new upper limit on the neutral hydrogen power spectrum at z≈ 8.6 (2010, background): “…see, e.g., Zaroubi & Silk 2005; Harker et al. 2010), MWA2 (Lonsdale et al. 2009; for the EoR case see, e.g., Morales et al. 2006; Bowman et al. 2006; Lidz et al. 2008), PAPER3 (Parsons et al. 2010), 21CMA4 (a.k.a. PaST; Peterson et al. 2004), in addition to the current GMRT5 program, and the first…”
WHAT NEXT-GENERATION 21 cm POWER SPECTRUM MEASUREMENTS CAN TEACH US ABOUT THE EPOCH OF REIONIZATION (2013, methodology): “We utilize the latter set, and “extrapolate” each neutral fraction to a variety of redshifts by scaling the amplitude with the square of the mean temperature of the IGM as (1+z), as anticipated when ionization fractions dominate the power spectrum (McQuinn et al. 2006; Lidz et al. 2008).”
Inhomogeneous recombinations during cosmic reionization (2014, background): “The amplitude and slope of the power spectrum around k ∼ 0.1 Mpc−1 are fundamental observables of the first generation 21cm interferometers (e.g. Lidz et al. 2008).”
A SENSITIVITY AND ARRAY-CONFIGURATION STUDY FOR MEASURING THE POWER SPECTRUM OF 21 cm EMISSION FROM REIONIZATION (2011, background): “Compact antenna configurations improve sensitivity by increasing sampling redundancy, motivating the centrally-condensed configurations explored for interferometers targeting the 21cm EoR signal (Bowman et al. 2006; Lidz et al. 2008).”
CRITICAL STAR FORMATION RATES FOR REIONIZATION: FULL REIONIZATION OCCURS AT REDSHIFT z ≈ 7 (2012, background): “The peak signal from redshifted 21 cm emission would likely occur during the heating period between z = 7.7 and z = 8.8 (145–163 MHz) when the hydrogen neutral fraction xH i ≈ 0.5 (Pritchard et al. 2010; Lidz et al. 2008).”