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Register a new userLarge angular scale fluctuations of near infrared extragalactic background light based on the IRTS observations
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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.
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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 emission, 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.
Extragalactic background light (EBL) anisotropy traces variations in the total production of photons over cosmic history, and may contain faint, extended components missed in galaxy point source surveys. Infrared EBL fluctuations have been attributed to primordial galaxies and black holes at the epoch of reionization (EOR), or alternately, intra-halo light (IHL) from stars tidally stripped from their parent galaxies at low redshift. We report new EBL anisotropy measurements from a specialized sounding rocket experiment at 1.1 and 1.6 micrometers. The observed fluctuations exceed the amplitude from known galaxy populations, are inconsistent with EOR galaxies and black holes, and are largely explained by IHL emission. The measured fluctuations are associated with an EBL intensity that is comparable to the background from known galaxies measured through number counts, and therefore a substantial contribution to the energy contained in photons in the cosmos.
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.
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 characterize 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.
We report observation of isotropic interplanetary dust (IPD) by analyzing the infrared (IR) maps of Diffuse Infrared Background Experiment (DIRBE) onboard the Cosmic Background Explorer (COBE) spacecraft. To search for the isotropic IPD, we perform new analysis in terms of solar elongation angle ($epsilon$), because we expect zodiacal light (ZL) intensity from the isotropic IPD to decrease as a function of $epsilon$. We use the DIRBE weekly-averaged maps covering $64^circ lesssim epsilon lesssim 124^circ$ and inspect the $epsilon$-dependence of residual intensity after subtracting conventional ZL components. We find the $epsilon$-dependence of the residuals, indicating the presence of the isotropic IPD. However, the mid-IR $epsilon$-dependence is different from that of the isotropic IPD model at $epsilon gtrsim 90^circ$, where the residual intensity increases as a function of $epsilon$. To explain the observed $epsilon$-dependence, we assume a spheroidal IPD cloud showing higher density further away from the sun. We estimate intensity of the near-IR extragalactic background light (EBL) by subtracting the spheroidal component, assuming the spectral energy distribution from the residual brightness at $12,{rm mu m}$. The EBL intensity is derived as $45_{-8}^{+11}$, $21_{-4}^{+3}$, and $15pm3,{rm nWm^{-2}sr^{-1}}$ at $1.25$, $2.2$, and $3.5,{rm mu m}$, respectively. The EBL is still a few times larger than integrated light of normal galaxies, suggesting existence of unaccounted extragalactic sources.
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