C. Ceccarelli

An improved FIR photometer for atmospheric and astronomical studies

Abstract We describe the design, operation and performances of a FIR photometer suitable for ground-based and balloon-borne astronomical observations in the millimetric and submillimetric regions.

A FIR Photometer for Ground-Based Astronomical Observations

A description is given of a photometer which is suitable for astronomical observations through millimetric atmospheric windows. It consists of a Ge-Ga bolometer operating at 1.0 K, with a throughput AW = 0.3 cm2 sr and a NET = 1 mK Hz-1/2. Two metallic mesh filters set the windows at about 10 and 5 cm-1.

The Voids and the Cosmic Microwave Photons

Recently large voids in galaxy distribution have been found by means of red shift surveys. We consider the possible effect of the presence of one of these voids (the one found by Kirshner et al. (1982) in Bootis) on the cosmic microwave background photons.

Dust Distribution Nearby the Solar System and its Possible Implications on Cosmic Radiation Background Anisotropy

It is well known that the two darkest clouds in the sky are located in the regions of ρ-Ophiuchus (1″=354°; b″=160) and Taurus (1″=174°; b″=−13°). The approximate simmetry of these two regions around the Sun has suggested that they may be linked by a very elongated cylindrical cloud. Indirect evidence supporting this view has been obtained by studying the colour excess of nearby stars and the relation between galaxy counts and HI column density (Turon and Menessier, 1975; Lebrun, 1979).

Dust Far Infrared Emission at High Galactic Latitudes

In order to confirm the cosmological origin of the quadrupole anisotropy detected in the cosmic background radiation by Fabbri et.al.(1), we performed a balloon borne experiment devoted to the study of diffuse radiation in the far infrared. We used two germanium bolometers, in the wavelenght bandwidths 150–400 µm and 350–3000µm. The sky modulation was achieved by wobbling a metallic mirror. The modulation amplitude was 6 degrees. The sensitivity for far infrared gradients in the sky was 2×10−14W cm−2sr−1deg−1Hz−1/2. For further details see ref.(2).

New Methods of Investigation for Extragalactic Backgrounds in the Infrared

If we look at the infrared sky between 1 and 1000 µm we observe several contributions to the background coming from different parts and/or epochs of the universe. We consider the problem of distinguishing between ‘local’ contributions (planetary and galactic dust, atmospheric emission, dashed lines) and the extragalactic backgrounds. In the figure are shown the computed emissions for rich clusters of galaxies (IRG) and integrated infrared galaxies (IRG). CMB is the cosmic microwave background.

Observation of a Large Halo Around M87

During 1978 balloon borne infrared experiment we observed a signal coming from Virgo Cluster (see Ceccarelli et al., 1982).

Thermal Radiation Noise and the 3 K Background

All the measurements of the Cosmic Background (CBR) spectrum in the submillimetric region are consistent with a Planckian decrease at short wavelenghts; this agreement is, however, only qualitative (1). New, independent experimental methods are required, in order to clarify the situation and to detect indisputably the presence of distortions which could have important cosmological consequences.

Stratospheric fluctuations in the FIR

Abstract The fluctuations in the stratospheric emission in the 800–2000 μm wavelength range have been studied by means of a special correlator operating at 0.3 K. The observed noise is about three times larger than expected from a grey body at a temperature of 250 K and an emissivity of 5 × 10−4. This fact has been interpreted as proof that about 2% of the stratospheric lines were saturated.

On the Large-Scale Anisotropy of the Cosmic Background Radiation in the Far Infrared

We report preliminary results relative to a balloon-borne search for the large-scale anisotropy carried out in 1980 by means of two far infrared photometers centered at 400 and 1100 microns. While these results are consistent with those obtained in an earlier flight, the second, shorter wavelength channel included in the 1980 work provides interesting insights into the influence of galactic dust on such far infrared observations.