F. X. Desert

FIRBACK Source Counts and Cosmological Implications

FIRBACK is a one of the deepest survey performed at 170 μm with ISOPHOT onboard ISO, and is aimed at the study of the cosmic far infrared background sources. About 300 galaxies are detected in an area of four square degrees, and source counts present a strong slope of 2.2 of the integral ”logN-logS” plot, which cannot be due to the effect of the cosmological evolution if no K-correction is present. The resolved sources account for less that 10% of the Cosmic Infrared Backgound at 170 μm. In order to understand the nature of the sources contributing to the CIB, and to explain deep source counts at other wavelengths, we have developped a phenomenological model, which constrains in a simple way the luminosity function evolution with the redshift, and fits all the existing deep source counts from the mid-infrared to the submillimetre range.

Dust distribution during reionization

Context. The dust produced by the first generation of stars will be a foreground to cosmic microwave background. Aims. In order to evaluate the effect of this early dust, we calculate the power spectrum of the dust emission anisotropies and compare it with the sensitivity limit of the Planck satellite. Methods. The spatial distribution of the dust is estimated through the distribution of dark matter. Results. At small angular scales (� 1000) the dust signal is found to be noticeable with the Planck detector for certain values of dust lifetime and production rates. The dust signal is also compared to sensitivities of other instruments. The early dust emission anisotropies are finally compared to those of local dust and they are found to be similar in magnitude at mm wavelengths.

The Extragalactic Background and Its Fluctuations in the Far-Infrared Wavelengths

A Cosmic Far-InfraRed Background (CFIRB) has long been predicted that would traces the intial phases of galaxy formation. It has been first detected by Puget et al.(1996) using COBE data and has been later confirmed by several recent studies (Fixsen et al. 1998, Hauser et al. 1998, Lagache et al. 1999). We will present a new determination of the CFIRB that uses for the first time, in addition to COBE data, two independent gas tracers: the HI survey of Leiden/Dwingeloo (hartmann, 1998) and the WHAM H

ISOCAM--the Infrared Space Observatory camera: results of testing and calibrations

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TENTATIVE DETECTION OF A COSMIC FAR-INFRARED BACKGROUND WITH COBE

survey (Reynolds et al 1998). We will see that the CFIRB above 100 micron is now very well constrained. The next step is to see if we can detect its fluctuations. To search for the CFIRB fluctuations, we have used the FIRBACK observations. FIRBACK is a deep cosmological survey conducted at 170 micron with ISOPHOT (Dole et al., 2000). We show that the emission of unresolved extra-galactic sources clearly dominates, at arcminute scales, the background fluctuations in the lowest galactic emission regions. This is the first detection of the CFIRB fluctuations.

Interstellar dust models for extinction and emission

ISOCAM, the ISO camera is designed to map selected regions of the sky in the spectral regions 2.5 to 17 microns. It will make images, within the 3 arcmin field of view of ISO with two 32 X 32 infrared array detectors, one for the short wavelength range, below 5 microns, the second for the long wavelength range, above 4.5 microns. Filter wheels and lens wheels allow to change the spectral resolution and the pixel field of view. Circular variable filters are also mounted on the filter wheel. The instrument is ready for delivery to ESA, after a thorough testing and calibration phase. Test has been conducted in a facility that simulate the ISO environment. A particular care has been taken to ensure the appropriate level of IR background inside the calibration cryostat, to check the detectors in the actual IR flux range that they will experience in flight. This paper presents the results on this test and calibration campaign, with a particular emphasis on the optical performances and on the behavior of the detectors. Photometric performances have been obtained for all the observing modes of ISOCAM. Some of these results, like stabilization of the detectors, have strong impacts on the observing strategy with ISOCAM.