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تسجيل مستخدم جديدNew Spectral Evidence of an Unaccounted Component of the Near-infrared Extragalactic Background Light from the CIBER
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The Extragalactic Background Light (EBL) captures the total integrated emission from stars and galaxies throughout the cosmic history. The amplitude of the near-infrared EBL from space absolute photometry observations has been controversial and depends strongly on the modeling and subtraction of the Zodiacal light foreground. We report the first measurement of the diffuse background spectrum at 0.8-1.7 um from the CIBER experiment. The observations were obtained with an absolute spectrometer over two flights in multiple sky fields to enable the subtraction of Zodiacal light, stars, terrestrial emission, and diffuse Galactic light. After subtracting foregrounds and accounting for systematic errors, we find the nominal EBL brightness, assuming the Kelsall Zodiacal light model, is 42.7+11.9/-10.6 nW/m2/sr at 1.4 um. We also analyzed the data using the Wright Zodiacal light model, which results in a worse statistical fit to the data and an unphysical EBL, falling below the known background light from galaxies at <1.3 um. Using a model-independent analysis based on the minimum EBL brightness, we find an EBL brightness of 28.7+5.1/-3.3 nW/m2/sr at 1.4 um. While the derived EBL amplitude strongly depends on the Zodiacal light model, we find that we cannot fit the spectral data to Zodiacal light, Galactic emission, and EBL from solely integrated galactic light from galaxy counts. The results require a new diffuse component, such as an additional foreground or an excess EBL with a redder spectrum than that of Zodiacal light.
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The Cosmic Infrared Background Experiment (CIBER) is a suite of four instruments designed to study the near infrared (IR) background light from above the Earths atmosphere. The instrument package comprises two imaging telescopes designed to character
ize spatial anisotropy in the extragalactic IR background caused by cosmological structure during the epoch of reionization, a low resolution spectrometer to measure the absolute spectrum of the extragalactic IR background, and a narrow band spectrometer optimized to measure the absolute brightness of the Zodiacal light foreground. In this paper we describe the design and characterization of the CIBER payload. The detailed mechanical, cryogenic, and electrical design of the system are presented, including all system components common to the four instruments. We present the methods and equipment used to characterize the instruments before and after flight, and give a detailed description of CIBERs flight profile and configurations. CIBER is designed to be recoverable and has flown twice, with modifications to the payload having been informed by analysis of the first flight data. All four instruments performed to specifications during the second flight, and the scientific data from this flight are currently being analyzed.
The Cosmic Infrared Background ExpeRiment (CIBER) is a rocket-borne absolute photometry imaging and spectroscopy experiment optimized to detect signatures of first-light galaxies present during reionization in the unresolved IR background. CIBER-I co
nsists of a wide-field two-color camera for fluctuation measurements, a low-resolution absolute spectrometer for absolute EBL measurements, and a narrow-band imaging spectrometer to measure and correct scattered emission from the foreground zodiacal cloud. CIBER-I was successfully flown on February 25th, 2009 and has one more planned flight in early 2010. We propose, after several additional flights of CIBER-I, an improved CIBER-II camera consisting of a wide-field 30 cm imager operating in 4 bands between 0.5 and 2.1 microns. It is designed for a high significance detection of unresolved IR background fluctuations at the minimum level necessary for reionization. With a FOV 50 to 2000 times largerthan existing IR instruments on satellites, CIBER-II will carry out the definitive study to establish the surface density of sources responsible for reionization.
We reanalyze data of near-infrared background taken by Infrared Telescope in Space (IRTS) based on up-to-date observational results of zodiacal light, integrated star light and diffuse Galactic light. We confirm the existence of residual isotropic em
ission, which is slightly lower but almost the same as previously reported. At wavelengths longer than 2 {mu}m, the result is fairly consistent with the recent observation with AKARI. We also perform the same analysis using a different zodiacal light model by Wright and detected residual isotropic emission that is slightly lower than that based on the original Kelsall model. Both models show the residual isotropic emission that is significantly brighter than the integrated light of galaxies.
We measure the spatial fluctuations of the Near-Infrared Extragalactic Background Light (NIREBL) from 2$^{circ}$ to 20$^{circ}$ in angular scale at the 1.6 and 2.2 $mu$m using data obtained with Near-Infrared Spectrometer (NIRS) on board the Infrared
Telescope in Space (IRTS). The brightness of the NIREBL is estimated by subtracting foreground components such as zodiacal light, diffuse Galactic light, and integrated star light from the observed sky. The foreground components are estimated using well-established models and archive data. The NIREBL fluctuations for the 1.6 and 2.2 $mu$m connect well toward the sub-degree scale measurements from previous studies. Overall, the fluctuations show a wide bump with a center at around 1$^{circ}$ and the power decreases toward larger angular scales with nearly a single power-law spectrum (i.e. textit{F($sqrt{l(l+1)C_l/2pi}$)} $sim$ $theta^{-1}$) indicating that the large scale power is dominated by the random spatial distribution of the sources. After examining several known sources, contributors such as normal galaxies, high redshift objects, intra-halo light, and far-IR cosmic background, we conclude that the excess fluctuation at around the 1$^{circ}$ scale cannot be explained by any of them.
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 mea
sured using instruments situated above the Earths 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.
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