Showing papers by "Hans Ulrik Nørgaard-Nielsen published in 2000"

The European Large Area ISO Survey - I. Goals, definition and observations

Abstract: We describe the European Large Area ISO Survey (ELAIS). ELAIS was the largest single Open Time project conducted by ISO, mapping an area of 12deg^2 at 15μm with ISOCAM and at 90μm with ISOPHOT. Secondary surveys in other ISO bands were undertaken by the ELAIS team within the fields of the primary survey, with 6deg^2 being covered at 6.7μm and 1deg^2 at 175μm. This paper discusses the goals of the project and the techniques employed in its construction, as well as presenting details of the observations carried out, the data from which are now in the public domain. We outline the ELAIS `preliminary analysis' which led to the detection of over 1000 sources from the 15 and 90-μm surveys (the majority selected at 15μm with a flux limit of ~3mJy), to be fed into a ground-based follow-up campaign, as well as a programme of photometric observations of detected sources using both ISOCAM and ISOPHOT. We detail how the ELAIS survey complements other ISO surveys in terms of depth and areal coverage, and show that the extensive multi-wavelength coverage of the ELAIS fields resulting from our concerted and on-going follow-up programme has made these regions amongst the best studied areas of their size in the entire sky, and, therefore, natural targets for future surveys. This paper accompanies the release of extremely reliable subsets of the `preliminary analysis' products. Subsequent papers in this series will give further details of our data reduction techniques, reliability and completeness estimates and present the 15- and 90-μm number counts from the `preliminary analysis', while a further series of papers will discuss in detail the results from the ELAIS `final analysis', as well as from the follow-up programme.

ISOPHOT surveys and the extragalactic background

Abstract: The higher spatial resolution and sensitivity of ISO allowed several extragalactic surveys to be extended to greater depth than obtained with IRAS. With the extended wavelength range deep surveys were performed for the first time at wavelengths up to rv 200 uu». They favour galaxy models with strong evolution. With ISO's new capabilities the spectral energy distributions of larger samples of ULIRGs in the local universe and those of quasars and radio galaxies were determined. These data are applicable as templates to the more distant universe. Foreground components from zodiacal light and cirrus to the intracluster dust emission were studied in connection with their separation from the extragalactic background radiation.

Deep far infrared ISOPHOT survey in "Selected Area 57" I. Observations and source counts

Abstract: We present here the results of a deep survey in a 0.4 deg 2 blank field in Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared Space Observa- tory (ISO 1 ) at both 60 m and 90m. The resulting sky maps have a spatial resolution of 15 23 arcsrc 2 per pixel which is much higher than the 90 90 arcsec 2 pixels of the IRAS All Sky Survey. We describe the main instrumental effects en- countered in our data, outline our data reduction and analysis scheme and present astrometry and photometry of the detected point sources. With a formal signal to noise ratio of 6.75 we have source detection limits of 90 mJy at 60 m and 50 mJy at 90 m. To these limits we find cumulated number densities of 53:5 deg 2 at 60 m and 14.85:0 deg 2 at 90 m. These number densities of sources are found to be lower than previ- ously reported results from ISO but the data do not allow us to discriminate between no-evolution scenarios and various evo- lutionary models.

Deep far infrared ISOPHOT survey in Selected Area 57

Abstract: We present here the results of a deep survey in a 0.4 deg2 blank field in Selected Area 57 conducted with the ISOPHOT instrument aboard ESAs Infrared Space Observatory (ISO1) at both 60 μm and 90 μm. We describe our data reduction and analysis scheme with special emphasis on source extraction and flux calibration. With a formal signal to noise ratio of 6.75 we have source detection limits of 90 mJy at 60 μm and 50 mJy at 90 μm. To these limits we find cumulated number densities of 5±3.5 deg-2 at 60 μm and 14.8±5.0 deg-2 at 90 μm. These number densities of sources are found to be lower than previously reported results from ISO but the data do not allow us to discriminate between no-evolution scenarios and various evolutionary models.

Power filtration of CMB observational data

Abstract: We propose a power filter Gp for linear reconstruction of the CMB signal from observational maps. This Gp filter preserves the power spectrum of the CMB signal in contrast to the Wiener filter which diminishes the power spectrum of the reconstructed CMB signal. We demonstrate how peak statistics and a cluster analysis can be used to estimate the probability of the presence of a CMB signal in observational records. The efficiency of the Gp filter is demonstrated on a toy model of an observational record consisting of a CMB signal and noise in the form of foreground point sources.