G. Dall’Oglio

Computer program for optimization of small cryostat design

Abstract This work describes a computer program for the design of four types of 4 He cooled cryostats. Contributions to the thermal balance are computed and the positions of the 4 He gas cooled shields are determined by optimizing the time for which the helium stays in the main bath. The four types of cryostat considered are also described, along with some examples to illustrate how to make good use of this program.

CBR anisotropy and galactic emission observations from Antarctica

In this paper we report the results of an experiment on the CBR anisotropy at 2 mm and 2.5 degrees angular resolution carried out during the Antarctic summer of 1987-88. We find evidence of statistical fluctuations at a level of T/T=2x10{sup {minus}4}, most of which can be ascribed to both atmospheric residual noise and/or patch galactic emission. In addition, we observed the Magellanic Clouds and obtained an excess of mm-wave radiation in dicating the presence of a cold dust component coexisting with the IRAS wa rm dust. (AIP)

Italian plans for astrophysical observations from Antarctica

The characteristics which make Antarctica interesting for astrophysical research are: i) atmospheric transparency, ii) remoteness iii) geographical and geomagnetic position. Because of previous experience of observation from arctic sites in northern Europe and from isolated mountain sites, groups of Italian astrophysicists were immediately ready to go to Antarctica and bring their equipment to places not easily accessible, in a difficult environment when, about ten years, ago, the antarctic regions became more accessible.

A Balloon-Borne Experiment Devoted to the Search for Extragalactic Background Anisotropies in the Far IR

Several cosmological scenarios have been proposed, in which a strong extragalactic background in the far infrared region is expected (see Bond, Carr, Hogan (1986) for a review). The Berkeley-Nagoya group claimed to have detected such an emission in a recent rocket-borne experiment carried out in the submillimetre range (Matsumoto et al. (1988)).

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.

Measurement of the 3 K Cosmic Background Noise in the Far Infrared

Quantum fluctuations of the cosmic background have been measured in the 900 to 2000 micron range (H.P.B.W.) by means of a balloon-borne correlator operating between 5 and 150 Hz. Preliminary results indicate an upper limit √ ≤ 2.1 × 10-17 watt/(cm2 srad Hz)1/2, corresponding to the noise of a blackbody at a temperature T ≤ 3.1 K at 1σ.