Search

COMPASS is an on-axis 2.6 meter telescope coupled to a correlation polarimeter operating at a wavelength of 1 cm. The entire instrument was built specifically for CMB polarization studies. We report here on observations of February 2001 - April 2001 using this system. We set an upper limit on E-mode polarized anisotropies of 33.5 uK (95% confidence limit) in the l-range 200-600.

Published in: Astrophys. J. 513 (1999) 23 citations recorded in [Science Citation Index] Abstract: We report simultaneous observations at 1.2 and 2 mm, with a double channel photometer on the SEST Telescope, of the X-ray cluster RXJ0658-5557 in search for the Sunyaev-Zel'dovich (S-Z). The S-Z data were analyzed using the relativistically correct expression for the Comptonization parameter and we find from the detected decrement (2.60 +/- 0.79) ~ 10^{-4}, which is consistent with that computed using the X-ray (ROSAT and ASCA) observations. The uncertainty includes contributions due to statistical uncertainty in the detection and systematics and calibration. The 1.2 {mm} channel data alone gives rise to a larger Comptonization parameter and this result is discussed in terms of contamination from foreground sources and/or dust in the cluster or from a possible systematic effect. We then make use of the combined analysis of the ROSAT and ASCA X-ray satellite observations to determine an isothermal model for the S-Z surface brightness. Since the cluster is asymmetrical and probably in a merging process, models are only approximate. The associated uncertainty can, however, be estimated by exploring a set of alternative models. We then find as the global uncertainty on the Comptonization parameter a factor of 1.3. Combining the S-Z and the X-ray measurements, we determine a value for the Hubble constant. The 2 mm data are consistent with H_0(q_0 = 1/2)= 53^{+38}_{-28} km/s Mpc^{-1}, where the uncertainty is dominated by the uncertainty in models of the X-ray plasma halo.

We report on observations of the Sunyaev-Zeldovich effect toward X-ray ROSAT clusters taken with a double-channel (1.2 and 2 mm) photometer installed at the focus of the 15 m Swedish ESO Submillimeter Telescope antenna in Chile. This paper describes the first results obtained for the high-z clusters S1077, A2744, and S295. Marginal detections were found for A2744, and at 1 mm for S1077. We discuss these data in terms of contamination of sources along the line of sight and give a constraint on the amplitude of the kinematic effect.

Millimetric observations (1-2 mm) toward the Magellanic Clouds from Antarctica show a good spatial correlation with the IRAS 100-micron emission in the same sky regions. Very likely a cold component coexisting with the warm dust detected by IRAS has been observed. 18 refs.

An infrared search for the Sunyaev-Zeldovich effect toward the intergalactic ''void'' discovered by Kirshner et al. has given a null result within 1 x 10/sup -4/ K at 1 standard deviation. The result implies that the change of the Comptonization parameter toward the hole is less than 2 x 10/sup -2/. From the hypothesis that the hot gas is absent in the hole, we get an upper limit 0.5 for the normalized density of the extragalactic gas.

A ground-based experiment has been carried out in Terra Nova Bay, Antarctica in order to detect anisotropies in cosmic background radiation at an angular scale of 1.3 deg. A 1-m-diameter flux collector and an He-3-cooled bolometric detector sensitive to radiation with a wavelength between 1.86 and 2.34 mm are used. Observations were carried out during the Antarctic summer and are limited by atmospheric emission fluctuations. 13 references.

On a analyse les correlations existant entre l'emission dans l'IR lointain de la poussiere interstellaire, les comptages de galaxies et l'emission de l'hydrogene atomique a 21 cm. On en conclut que le signal IR est le meilleur indicateur de poussiere disponible. Les correlations donnent egalement des informations concernant l'heterogeneite de la distribution des galaxies et la densite de colonne de l'hydrogene moleculaire

A new method is discussed for measuring the extragalactic diffuse radiation in the 100--1000 ..mu..m region, in the presence of the strong local sources like atmospheric, interplanetary, and galactic dust emission. The method consists of the search for a peculiar spatial signature of the extragalactic component, i.e., its dipole anisotropy due to the observers' motion, which has to be aligned with the 3 K dipole anisotropy. Using the observations available at 11 cm/sup -1/, 14 cm/sup -1/, 25 cm/sup -1/, and 50 cm/sup -1/, we derived upper limits of the order of 2 x 10/sup -12/ watts cm/sup -2/ sr/sup -1//cm/sup -1/ between 13 and 18 cm/sup -1/ for the diffuse radiation emitted by rich clusters, and of 5 x 10/sup -12/ watts cm/sup -2/ sr/sup -1//cm/sup -1/ for radiation emitted by infrared galaxies at 1 standard deviation. Our analysis excludes an extragalactic origin for the infrared excess observed by Gush at 16--17 cm/sup -1/ at 2 standard deviations.