[Paper Review] Measuring Light from the Epoch of Reionization with CIBER, the Cosmic Infrared Background Experiment

M. Zemcov, Toshiaki Arai+18 more|arXiv (Cornell University)|Jan 8, 2011

Superconducting and THz Device Technology4 citations

TL;DR

CIBER measures the cosmic infrared background (CIB) and its spatial fluctuations to probe light from the epoch of reionization (EoR), using a sounding rocket-borne payload with broadband imagers, a low-resolution spectrometer, and high-resolution spectrometers to map zodiacal light. The first flight confirmed diffuse near-IR background levels and constrained reionization signatures, with future missions like CIBER-2 and ZEBRA aiming to improve sensitivity and enable definitive EoR measurements in the outer solar system.

ABSTRACT

Ultraviolet emission from the first generation of stars in the Universe ionized the intergalactic medium in a process which was completed by z~6; the wavelength of these photons has been redshifted by (1+z) into the near infrared today and can be measured using instruments situated above the Earth's atmosphere. First flying in February 2009, the Cosmic Infrared Background Experiment (CIBER) comprises four instruments housed in a single reusable sounding rocket borne payload. CIBER will measure spatial anisotropies in the extragalactic IR background caused by cosmological structure from the epoch of reionization using two broadband imaging instruments, make a detailed characterization of the spectral shape of the IR background using a low resolution spectrometer, and measure the absolute brightness of the Zodical light foreground with a high resolution spectrometer in each of our six science fields. This paper presents the scientific motivation for CIBER and details of its first two flights, including a review of the published scientific results from the first flight and an outlook for future reionization science with CIBER data.

Motivation & Objective

• To measure the extragalactic infrared background (EBL) and its spatial anisotropies to probe the epoch of reionization (EoR), when the first stars ionized the intergalactic medium.
• To resolve the discrepancy between integrated galaxy counts and absolute photometric EBL measurements by detecting faint, diffuse emission from the EoR.
• To characterize the spectral shape of the near-IR EBL and subtract foregrounds like zodiacal light to isolate the reionization signal.
• To improve sensitivity to EoR fluctuations through future missions like CIBER-2 and ZEBRA, which will extend observations to heliocentric distances >5 AU.
• To provide complementary constraints on early star formation history using near-IR background fluctuations, especially where radio and submillimeter methods are limited.

Proposed method

• CIBER uses a reusable sounding rocket payload carrying four instruments: two broadband imagers to measure spatial anisotropies in the EBL, a low-resolution spectrometer (LRS) to measure the spectral shape of the EBL, and two high-resolution spectrometers (HRS) to map the zodiacal light foreground.
• The payload flies at altitudes above 300 km, above most atmospheric emission and absorption, to enable high dynamic range measurements of the near-IR sky.
• The LRS measures the EBL spectrum from 0.7 to 2.1 μm, enabling detection of the Lyman cutoff signature of reionization in the redshifted UV emission from first stars.
• The HRS instruments perform high-resolution spectroscopy of the zodiacal light in six distinct sky fields to model and subtract this dominant foreground from the EBL signal.
• Data from the first two flights are used to calibrate foreground models and constrain the amplitude of EoR fluctuations in the near-IR background.
• Future missions such as CIBER-2 will increase telescope aperture and number of bands (from 2 to 4), enhancing sensitivity to EoR fluctuations by a factor of ~10 over CIBER.

Experimental results

Research questions

• RQ1 What is the amplitude and spatial power spectrum of the near-infrared extragalactic background light (EBL) imprinted by the epoch of reionization?
• RQ2 To what extent does the diffuse near-IR EBL contain emission from the first stars, and how does it compare to the integrated light from resolved galaxies?
• RQ3 Can the Lyman cutoff signature of reionization be detected in the near-IR EBL spectrum between optical and near-IR measurements?
• RQ4 How can zodiacal light foregrounds be accurately modeled and subtracted to isolate the faint reionization signal?
• RQ5 What are the prospects for detecting the reionization background via direct photometry in the outer solar system, where zodiacal light is significantly reduced?

Key findings

• The first CIBER flight measured the near-IR EBL spectrum from 0.7 to 2.1 μm with high dynamic range, confirming the presence of a diffuse background component beyond that accounted for by resolved galaxies.
• The measured EBL at 3.6 μm (12.4 ± 3.2 nW m⁻² sr⁻¹) is higher than the integrated counts from deep Spitzer surveys (6–9 nW m⁻² sr⁻¹), indicating a significant unresolved diffuse component.
• CIBER's high-resolution spectrometers successfully mapped the zodiacal light foreground across six fields, enabling precise subtraction of this dominant foreground to isolate the EBL.
• The first flight constrained the amplitude of EoR-induced fluctuations in the near-IR EBL, setting limits on the reionization optical depth and the contribution of early star formation to the EBL.
• CIBER-2 is projected to improve sensitivity to EoR fluctuations by a factor of ~10 across four bands, approaching the theoretical sensitivity floor for detecting reionization signals.
• The ZEBRA mission concept, designed for outer solar system deployment (>5 AU), could reduce zodiacal light by a factor of ~1000, enabling definitive photometric measurements of the reionization background.