1,475 research outputs found
Narrative persuasion by corporate CSR messages: The impact of narrative richness on attitudes and behavioral intentions <i>via</i> character identification, transportation, and message credibility
Planck pre-launch status: The HFI instrument, from specification to actual performance
Context. The High Frequency Instrument (HFI) is one of the two focal instruments of the Planck mission. It will observe the whole sky in six
bands in the 100 GHz−1 THz range.
Aims. The HFI instrument is designed to measure the cosmic microwave background (CMB) with a sensitivity limited only by fundamental
sources: the photon noise of the CMB itself and the residuals left after the removal of foregrounds. The two high frequency bands will provide
full maps of the submillimetre sky, featuring mainly extended and point source foregrounds. Systematic effects must be kept at negligible levels
or accurately monitored so that the signal can be corrected. This paper describes the HFI design and its characteristics deduced from ground tests
and calibration.
Methods. The HFI instrumental concept and architecture are feasible only by pushing new techniques to their extreme capabilities, mainly:
(i) bolometers working at 100 mK and absorbing the radiation in grids; (ii) a dilution cooler providing 100 mK in microgravity conditions;
(iii) a new type of AC biased readout electronics and (iv) optical channels using devices inspired from radio and infrared techniques.
Results. The Planck-HFI instrument performance exceeds requirements for sensitivity and control of systematic effects. During ground-based
calibration and tests, it was measured at instrument and system levels to be close to or better than the goal specification
The 3.3 micron emission feature: Map of the galactic disk, 10 deg less than 1 less than 35 deg, - 6 deg less than b less than 6 deg
The 3.3 micron aromatic feature has been detected in the diffuse galactic emission with the AROME balloon-borne instrument. The results are presented in the form of an map of the 3.3 micron feature's intensity. The AROME instrument consists in a Cassegrain telescope with wobbling secondary mirrors and a liquid/solid nitrogen cooled photometer. The instrumental output is modified by the impulse response of the system. So the galactic surface brightness was restored in Fourier space by an inverse optimal filtering. The map of the feature's intensity is presented for a region of galactic coordinates. All the known H II giant molecular cloud complexes are visible in the 3.3 micron feature emission showing a good correlation with the infrared dust emission
A Sunyaev-Zel'dovich map of the massive core in the luminous X-ray cluster RXJ1347-1145
We have mapped the Sunyaev-Zel'dovich decrement (hereafter SZ) in the
direction of the most luminous X-ray cluster known to date, RXJ1347-1145, at
z=0.451. This has been achieved with an angular resolution of about 23'' using
the Diabolo photometer running on the IRAM 30 meter radio telescope. We present
here a map of the cluster central region at 2.1mm. The Comptonization parameter
towards the cluster center, \yc=(12.7^{+2.9}_{-3.1})\times 10^{-4},
corresponds to the deepest SZ decrement ever observed. Using the gas density
distribution derived from X-ray data, this measurement implies a gas
temperature \te=16.2 \pm 3.8 keV. The resulting total mass of the cluster is,
under hydrostatic equilibrium, for a corresponding gas fraction .Comment: 16 pages, 2 figures, accepted for publication in ApJ Letter
The Diabolo photometer and the future of ground-based millimetric bolometer devices
The millimetric atmospheric windows at 1 and 2 mm are interesting targets for
cosmological studies. Two broad areas appear leading this field: 1) the search
for high redshift star-forming galaxies and 2) the measurement of
Sunyaev-Zel'dovich (SZ) effect in clusters of galaxies at all redshifts. The
Diabolo photometer is a dual-channel photometer working at 1.2 and 2.1 mm and
dedicated to high angular resolution measurements of the Sunyaev--Zel'dovich
effect towards distant clusters. It uses 2 by 3 bolometers cooled down to 0.1 K
with a compact open dilution cryostat. The high resolution is provided by the
IRAM 30 m telescope. The result of several Winter campaigns are reported here,
including the first millimetric map of the SZ effect that was obtained by
Pointecouteau et al. (2001) on RXJ1347-1145, the non-detection of a millimetric
counterpart to the radio decrement towards PC1643+4631 and 2 mm number count
upper limits. We discuss limitations in ground-based single-dish millimetre
observations, namely sky noise and the number of detectors. We advocate the use
of fully sampled arrays of (100 to 1000) bolometers as a big step forward in
the millimetre continuum science. Efforts in France are briefly mentionned.Comment: 7 pages, 6 figures, to appear in the Proceedings of the 2K1BC
``Experimental Astronomy at millimeter wavelengths'', Breuil-Cervinia (AO)
Italy - July 9 - 13, 2001, Eds. M. De Petris et a
Observations of the Sunyaev-Zel'dovich effect at high angular resolution towards the galaxy clusters A665, A2163 and CL0016+16
We report on the first observation of the Sunyaev-Zel'dovich effect with the
Diabolo experiment at the IRAM 30 metre telescope. A significant brightness
decrement is detected in the direction of three clusters (Abell 665, Abell 2163
and CL0016+16). With a 30 arcsecond beam and 3 arcminute beamthrow, this is the
highest angular resolution observation to date of the SZ effect.Comment: 23 pages, 8 figures, 6 tables, accepted to New Astronom
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