Observational Prospect of NIREBL ISAS/JAXA T. MATSUMOTO, S. MATSUURA, and T. WADA

Issues to be observed Spectral shape Confirmation of the spectral gap at ~1mm real? Other spectral features? Fluctuation Spatial correlation over the wide range of angular scale Search for the large scale structure at high redshift Absolute measurements Avoid ambiguity of the model ZL Rocket experiment ASTRO-F SPICA Out of zodiacal cloud mission

ASTRO-F Formation and evolution of galaxies, stars, and planets First dedicated infrared mission of ISAS 70cm cooled infrared telescope Advanced Infrared Survey 50 times higher sensitivity, 10 times better spatial resolution, has longer wavelength band, than IRAS Instruments IRC(Infrared Camera) 512x412 InSb array camera, 1.5”/pixel band imaging: K, L, and M bands low resolution spectroscopy: R-30 slit 2x50 pixel, R-15 4x50 pixel 256x256 SiAs array FIS(Far Infrared Surveyor) Launch target : August, 2005 Orbit : sun synchronous orbit, 750km altitude Mission life: ~1.5 year (liq. He holding time) + 2 years (dedicated to NIR Observations) ISAS/ESA collaboration: 10% of the pointing observations are opened to ESA scientists

Observation of NIREBL with ASTRO-F Advantages of IRC/ASTRO-F observation Point-source rejection by high-resolution imaging observation Limiting magnitude at the K band is ~20 mag. for one pointing obseravation (~10 min.) 　 This corresponds to ~30 nW m-2 sr-1 for 1 pixel (5s) Almost all galactic stars and faint galaxies can be identified Discrimination of the fluctuation of the zodiacal light Observation of the same field at the different time epoch Observation plans 1. Detection of the NIREBLfluctuation over the wide range of angular scale Wide area survey towards north ecliptic pole (NEP) is being proposed. Coordination with galaxy deep survey group 2. Detailed study of the spectrum of IREBL Low resolution spectroscopy at different ecliptic latitudes (2~5mm) Spectrum without contamination of stars and galaxies can be obtained We welcome participation of theoreticians even in planning stage!

IRC SURVEY STRATEGIES Depth and Area Number of Pointings 1 0.02 10 100 1000 ? 100 Number of Pointings 10 1 Area (sq. deg.)

Expected fluctuation and detection capability of IRC/ASTRO-F (Cooray et al., submitted to Ap.J.)

IRC background measurements around NEP 1. Wide-band deep imaging in K, L and M bands Spectral resolution l/Dl Survey area [sq.degree] Exposure time per frame [# of pointings] Single pixel detection limit (5s) * [nW/cm2/sr] Number of galaxies per camera frame** Number of dark pixels per frame *** Wide-field Shallow（phase-3) 3 100 1 (500 s) 30 2x10^3 >1.5x10^5 Shallow (Phase-1,2) 10 Deep (Phase1,-2) 1 10 (1.4 hrs) (3-4)x10^3 >1.3x10^5 Ultra Deep (Phase-1, 2) 0.02 100 (14 hrs) (0.5-1)x10^4 >8x10^4 * in unit of surface brightness (lIl) ** FOV of the IRC camera frame is 10’x10’ *** number of pixels available for the background analysis = total number of pixels – (confusion factor) x (number of galaxies) = 1.7x10^5 – (3pics x 3pics) x (number of galaxies) 2. Spectroscopy Spectral resolution l/Dl Survey area Exposure time Detection limit (5s) [nW/cm2/sr] Number of galaxies Number of dark pixels Spectroscopy 30 (l = 2.0 – 5 mm) 3” x 73” x 100 directions (various b and b) 1 pointing (500 s) 30 (pixel binning) ~10 (10 sky average) 2 90

Out of zodiacal cloud mission Infrared observation without the zodiacal light provides decisive result for the NIREBL!

Possible mission concept of out of zodiacal cloud mission! Scientific objectives Accurate measurement of spectrum and fluctuation of IREBL Instrumentation Telescope 5cm dia. lens system Wavelength range 0.8-2.2mm Pixel FOV ~10’ Detector HgCdTe Cooling system radiation cooling Weight 3 kg