Foreground and Sensitivity Analysis for Broadband (2D) 21 cm–Lyα and 21 cm–Hα Correlation Experiments Probing the Epoch of Reionization

Journal Article · Wed Nov 01 04:00:00 EDT 2017 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/AA8F9C· OSTI ID:22875634

Neben, Abraham R.; Hewitt, Jacqueline N. ^[1]; Stalder, Brian; Tonry, John L. ^[2]

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1. MIT Kavli Institute, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)
2. Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

A detection of the predicted anticorrelation between 21 cm and either Lyα or Hα from the epoch of reionization (EOR) would be a powerful probe of the first galaxies. While 3D intensity maps isolate foregrounds in low-k{sub ∥} modes, infrared surveys cannot yet match the field of view and redshift resolution of radio intensity mapping experiments. In contrast, 2D (i.e., broadband) infrared intensity maps can be measured with current experiments and are limited by foregrounds instead of photon or thermal noise. We show that 2D experiments can measure most of the 3D fluctuation power at k<0.2 Mpc{sup −1} while preserving its correlation properties. However, we show that foregrounds pose two challenges: (1) simple geometric effects produce percent-level correlations between radio and infrared fluxes, even if their luminosities are uncorrelated; and (2) radio and infrared foreground residuals contribute sample variance noise to the cross spectrum. The first challenge demands better foreground masking and subtraction, while the second demands large fields of view to average away uncorrelated radio and infrared power. Using radio observations from the Murchison Widefield Array and near-infrared observations from the Asteroid Terrestrial-impact Last Alert System, we set an upper limit on residual foregrounds of the 21 cm–Lyα cross-power spectrum at z∼7 of Δ{sup 2}<181 (kJy sr{sup −1} mK) (95%) at ℓ∼800. We predict levels of foreground correlation and sample variance noise in future experiments, showing that higher-resolution surveys such as LOFAR, SKA-LOW, and the Dark Energy Survey can start to probe models of the 21 cm–Lyα EOR cross spectrum.

• OSTI ID: 22875634
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 849; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ASTEROIDS
CORRELATIONS
COSMOLOGY
FLUCTUATIONS
GALAXIES
LUMINOSITY
LYMAN LINES
NONLUMINOUS MATTER
RED SHIFT
RESOLUTION
SENSITIVITY ANALYSIS
SPECTRA
STARS