We report measurements of the Diffuse Galactic Light (DGL) spectrum in the near-infrared, spanning the wavelength range 0.95-1.65 {mu}m by the Cosmic Infrared Background ExpeRiment (CIBER). Using the low-resolution spectrometer (LRS) calibrated for a
bsolute spectro-photometry, we acquired long-slit spectral images of the total diffuse sky brightness towards four high-latitude fields spread over four sounding rocket flights. To separate the DGL spectrum from the total sky brightness, we correlated the spectral images with a 100 {mu}m intensity map, which traces the dust column density in optically thin regions. The measured DGL spectrum shows no resolved features and is consistent with other DGL measurements in the optical and at near-infrared wavelengths longer than 1.8 {mu}m. Our result implies that the continuum is consistently reproduced by models of scattered starlight in the Rayleigh scattering regime with a few large grains.
We report the detection and measurement of the absolute brightness and spatial fluctuations of the cosmic infrared background (CIB) with the AKARI satellite. We have carried out observations at 65, 90, 140 and 160 um as a cosmological survey in AKARI
Deep Field South (ADF-S), which is one of the lowest cirrus regions with contiguous area on the sky. After removing bright galaxies and subtracting zodiacal and Galactic foregrounds from the measured sky brightness, we have successfully measured the CIB brightness and its fluctuations across a wide range of angular scales from arcminutes to degrees. The measured CIB brightness is consistent with previous results reported from COBE data but significantly higher than the lower limits at 70 and 160 um obtained with the Spitzer satellite from the stacking analysis of 24-um selected sources. The discrepancy with the Spitzer result is possibly due to a new galaxy population at high redshift obscured by hot dust. From power spectrum analysis at 90 um, three components are identified: shot noise due to individual galaxies; Galactic cirrus emission dominating at the largest angular scales of a few degrees; and an additional component at an intermediate angular scale of 10-30 arcminutes, possibly due to galaxy clustering. The spectral shape of the clustering component at 90 um is very similar to that at longer wavelengths as observed by Spitzer and BLAST. Moreover, the color of the fluctuations indicates that the clustering component is as red as Ultra-luminous infrared galaxies (ULIRGs) at high redshift, These galaxies are not likely to be the majority of the CIB emission at 90 um, but responsible for the clustering component. Our results provide new constraints on the evolution and clustering properties of distant infrared galaxies.
We describe the current status and the prospect for the development of monolithic Ge:Ga array detector for SAFARI. Our goal is to develop a 64x64 array for the 45 -- 110 um band, on the basis of existing technologies to make 3x20 monolithic arrays fo
r the AKARI satellite. For the AKARI detector we have achieved a responsivity of 10 A/W and a read-out noise limited NEP (noise equivalent power) of 10^-17 W/rHz. We plan to develop the detector for SAFARI with technical improvements; significantly reduced read-out noise with newly developed cold read-out electronics, mitigated spectral fringes as well as optical cross-talks with a multi-layer antireflection coat. Since most of the elemental technologies to fabricate the detector are flight-proven, high technical readiness levels (TRLs) should be achieved for fabricating the detector with the above mentioned technical demonstrations. We demonstrate some of these elemental technologies showing results of measurements for test coatings and prototype arrays.
We investigate the segregation of the extragalactic population via colour criteria to produce an efficient and inexpensive methodology to select specific source populations as a function of far-infrared flux. Combining galaxy evolution scenarios and
a detailed spectral library of galaxies, we produce simulated catalogues incorporating segregation of the extragalactic population into component types (Normal, star-forming, AGN) via color cuts. As a practical application we apply our criteria to the deepest survey to be undertaken in the far-infrared with the AKARI (formerly ASTRO-F) satellite. Using the far-infrared wavebands of the Far-Infrared Surveyor (FIS, one of the focal-plane instruments on AKARI) we successfully segregate the normal, starburst and ULIRG populations. We also show that with additional MIR imaging from AKARIs Infrared Camera (IRC), significant contamination and/or degeneracy can be further decreased and show a particular example of the separation of cool normal galaxies and cold ULIRG sources. We conclude that our criteria provide an efficient means of selecting source populations (including rare luminous objects) and produce colour-segregated source counts without the requirement of time intensive ground-based follow up to differentiate between the general galaxy population.
