We summarize the results of the Cosmic Microwave Background (CMB) working group of the ARENA project. The focus has been on precision measurements of CMB polarization (looking for the echoes of cosmological inflation) and high angular resolution CMB measurements (looking for Sunyaev Zeldovich effect in distant clusters of Galaxies, to probe the evolution of the Universe, Dark Matter and Dark Energy). For both projects the Dome C site represents the best choice worldwide.

Cosmic Microwave Background observations became the tool to probe the the first events of cosmic history. After WMAP data releases, galactic and extragalactic foregrounds are perceived as the main limiting uncertainity for the near-future search for the B-mode polarization inprints from the inflationary era, either through satellites or ground-based experiments like Brain at Dome-C. A combination of technology, scanning strategy and above all, accurate knowledge of polarized foregrounds will be necessary for an optimal mapping of B-mode CMB Polarization. In addition, the search for a better understanding of the galactic foregrounds will provide unprecedented knowledge on the Milky Way structure and star formation.

Observations of the Sunyaev-Zeldovich (S-Z) effect offer the possibility of both investigating evolution of clusters and of determining cosmological parameters when combined with X-ray observations. We describe a dedicated instrument (MITO) consisting of a 2.6-m in diameter telescope operating at 3500 m a.s.l. in the 2.1, 1.4, 1.1 and 0.8 mm channels with ˜ 10% bandwidths. Here we briefly report the results of MITO measurements towards the Coma cluster.

We discuss results from sensitive, wide-field imaging of the millimeter extragalactic background using the Max-Planck Millimeter Bolometer array (MAMBO) at the IRAM 30 m telescope.

We have mapped the source complex Sgr A (containing Sgr A West and East) at λ2.8mm, 1.3mm and 350μm using the IRAM 30m MRT (Pico Veleta, Spain) and the 3m IRTF (Mauna Kea, Hawaii) telescopes. Detailed results have been published or will be published elsewhere (Mezger et al., 1986, Paper I; Zylka and Mezger, 1988, Paper II; Mezger et al., 1988, Paper III).

During the past decade many kinds of optical surveys have discovered hundreds of quasars most of which (∼90 %) are radio quiet (<10 mJy at 5 GHz). We have observed two samples of quasars brighter than 17m.6 found by their emission lines and by their ultraviolet excess. We have also selected quasars with redshifts known to be greater than 3.00. A brief description of the observing technique is given by Sherwood et al. (1981b). We have compared our millimetre photometry of flat radio spectrum quasars with that of Ennis and Werner and find excellent agreement. For four of the 8 sources in common the data have been published: Kreysa et al. (1980) and Jones et al. (1981). In addition, analysis of our “noise” shows it to be white, gaussian distributed about zero. The three samples are summarized as follows.

Some infrared counterparts of Type II OHAR sources have been observed between 1µ and 30µ. In spite of their having very similar OH emission spectra, their energy distributions differ considerably among themselves from “flat” (1. 25µ to 4. 9µ) to “steep” (2. 2µ to 20µ). The energy distributions are compared with more familiar objects.