Planck is a European Space Agency (ESA) satellite, launched in May 2009, which will map the cosmic microwave background anisotropies in intensity and polarisation with unprecedented detail and ...sensitivity. It will also provide full-sky maps of astrophysical foregrounds. An accurate knowledge of the telescope beam patterns is an essential element for a correct analysis of the acquired astrophysical data. We present a detailed description of the optical design of the High Frequency Instrument (HFI) together with some of the optical performances measured during the calibration campaigns. We report on the evolution of the knowledge of the pre-launch HFI beam patterns when coupled to ideal telescope elements, and on their significance for the HFI data analysis procedure.
Cosmological constraints from Archeops Benoît, A.; Ade, P.; Amblard, A. ...
Astronomy and astrophysics (Berlin),
03/2003, Letnik:
399, Številka:
3
Journal Article
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We analyze the cosmological constraints that Archeops (Benoît et al. 2003) places on adiabatic cold dark matter models with passive power-law initial fluctuations. Because its angular power spectrum ...has small bins in $\ell$ and large $\ell$ coverage down to COBE scales, Archeops provides a precise determination of the first acoustic peak in terms of position at multipole $l_{\rm peak}=220\pm 6$, height and width. An analysis of Archeops data in combination with other CMB datasets constrains the baryon content of the Universe, $\Omega_{\rm b}h^2= 0.022^{+0.003}_{-0.004}$, compatible with Big-Bang nucleosynthesis and with a similar accuracy. Using cosmological priors obtained from recent non–CMB data leads to yet tighter constraints on the total density, e.g. $\Omega_{\rm tot}=1.00^{+0.03}_{-0.02}$ using the HST determination of the Hubble constant. An excellent absolute calibration consistency is found between Archeops and other CMB experiments, as well as with the previously quoted best fit model. The spectral index n is measured to be $1.04^{+0.10}_{-0.12}$ when the optical depth to reionization, τ, is allowed to vary as a free parameter, and $0.96^{+0.03}_{-0.04}$ when τ is fixed to zero, both in good agreement with inflation.
We examine the rest-frame far-infrared emission from powerful radio sources with 1.4-GHz luminosity densities of 25 ≤ log(L
1.4/W Hz−1) ≤ 26.5 in the extragalactic Spitzer First Look Survey field. We ...combine Herschel/SPIRE flux densities with Spitzer/Infrared Array Camera and Multiband Imaging Photometer for Spitzer infrared data to obtain total (
m) infrared luminosities for these radio sources. We separate our sources into a moderate, 0.4 < z < 0.9, and a high, 1.2 < z < 3.0, redshift sub-sample and we use Spitzer observations of a z < 0.1 3CRR sample as a local comparison. By comparison to numbers from the Square Kilometre Array (SKA) Simulated Skies, we find that our moderate-redshift sample is complete and our high-redshift sample is 14 per cent complete. We constrain the ranges of mean star formation rates (SFRs) to be 3.4-4.2, 18-41 and 80-581 M⊙ yr−1 for the local, moderate- and high-redshift samples, respectively. Hence, we observe an increase in the mean SFR with increasing redshift which we can parametrize as ∼(1 + z)
Q
, where Q = 4.2 ± 0.8. However, we observe no trends of mean SFR with radio luminosity within the moderate- or high-redshift bins. We estimate that radio-loud active galactic nuclei (AGN) in the high-redshift sample contribute 0.1-0.5 per cent to the total SFR density at that epoch. Hence, if all luminous starbursts host radio-loud AGN we infer a radio-loud phase duty cycle of 0.001-0.005.
We present a determination by the Archeops experiment of the angular power spectrum of the cosmic microwave background anisotropy in 16 bins over the multipole range $\ell=15{-}350$. Archeops was ...conceived as a precursor of the Planck HFI instrument by using the same optical design and the same technology for the detectors and their cooling. Archeops is a balloon–borne instrument consisting of a 1.5 m aperture diameter telescope and an array of 21 photometers maintained at $\sim 100$ mK that are operating in 4 frequency bands centered at 143, 217, 353 and 545 GHz. The data were taken during the Arctic night of February 7, 2002 after the instrument was launched by CNES from Esrange base (Sweden). The entire data cover ~30% of the sky. This first analysis was obtained with a small subset of the dataset using the most sensitive photometer in each CMB band (143 and 217 GHz) and 12.6% of the sky at galactic latitudes above 30 degrees where the foreground contamination is measured to be negligible. The large sky coverage and medium resolution (better than 15 arcmin) provide for the first time a high signal-to-noise ratio determination of the power spectrum over angular scales that include both the first acoustic peak and scales probed by COBE/DMR. With a binning of $\Delta \ell=7$ to 25 the error bars are dominated by sample variance for $\ell$ below 200. A companion paper details the cosmological implications.
Atmospheric emission is a dominant source of disturbance in ground-based astronomy at millimetric wavelengths. The Antarctic plateau is recognized as an ideal site for millimetric and submillimetric ...observations, and the French/Italian base of Dome Concordia (Dome C) is among the best sites on Earth for these observations. In this paper, we present measurements at Dome C of the atmospheric emission in intensity and polarization at a 2-mm wavelength. This is one of the best observational frequencies for cosmic microwave background (CMB) observations when considering cosmic signal intensity, atmospheric transmission, detector sensitivity and foreground removal. Using the B-mode radiation interferometer (BRAIN)-pathfinder experiment, we have performed measurements of the atmospheric emission at 150 GHz. Careful characterization of the airmass synchronous emission has been performed, acquiring more than 380 elevation scans (i.e. 'skydip') during the third BRAIN-pathfinder summer campaign in 2009 December/2010 January. The extremely high transparency of the Antarctic atmosphere over Dome C is proven by the very low measured optical depth, 〈τI〉= 0.050 ± 0.003 ± 0.011, where the first error is statistical and the second is the systematic error. Mid-term stability, over the summer campaign, of the atmosphere emission has also been studied. Adapting the radiative transfer atmosphere emission model am to the particular conditions found at Dome C, we also infer the level of the precipitable water vapor (PWV) content of the atmosphere, which is notoriously the main source of disturbance in millimetric astronomy (
mm). Upper limits on the airmass correlated polarized signal are also placed for the first time. The degree of circular polarization of atmospheric emission is found to be lower than 0.2 per cent 95 per cent confidence level (CL), while the degree of linear polarization is found to be lower than 0.1 per cent (95 per cent CL). These limits include signal-correlated instrumental spurious polarization.
We present the first determination of the Galactic polarized emission at 353 GHz by Archeops. The data were taken during the Arctic night of February 7, 2002 after the balloon-borne instrument was ...launched by CNES from the Swedish Esrange base near Kiruna. In addition to the 143 GHz and 217 GHz frequency bands dedicated to CMB studies, Archeops had one 545 GHz and six 353 GHz bolometers mounted in three polarization-sensitive pairs that were used for Galactic foreground studies. We present maps of the I, Q, U Stokes parameters over 17% of the sky and with a 13 arcmin resolution at 353 GHz (850 mu m). They show a significant Galactic large scale polarized emission coherent on the longitude ranges 100, 120 and 180, 200 deg. with a degree of polarization at the level of 4-5%, in agreement with expectations from starlight polarization measurements. Some regions in the Galactic plane (Gem OB1, Cassiopeia) show an even stronger degree of polarization in the range 10-20%. These findings provide strong evidence for a powerful grain alignment mechanism throughout the interstellar medium and a coherent magnetic field coplanar to the Galactic plane. This magnetic field pervades even some dense clouds. Extrapolated to high Galactic latitude, these results indicate that interstellar dust polarized emission is the major foreground for PLANCK-HFI CMB polarization measurements.
We present first results of a study of the submillimetre (submm) (rest-frame far-infrared) properties of z∼ 3 Lyman break galaxies (LBGs) and their lower redshift counterparts BX/BM galaxies, based ...on Herschel-SPIRE observations of the Northern field of the Great Observatories Origins Deep Survey (GOODS-N). We use stacking analysis to determine the properties of LBGs well below the current limit of the survey. Although LBGs are not detected individually, stacking the infrared luminous LBGs (those detected with Spitzer at 24 μm) yields a statistically significant submm detection with mean flux 〈S250〉= 5.9 ± 1.4 mJy confirming the power of SPIRE in detecting UV-selected high-redshift galaxies at submm wavelengths. In comparison, the Spitzer 24 μm detected BX/BM galaxies appear fainter with a stacked value of 〈S250〉= 2.7 ± 0.8 mJy. By fitting the spectral energy distributions (SEDs) we derive median infrared luminosities, LIR, of 2.8 × 1012 L⊙ and 1.5 × 1011 L⊙ for z∼ 3 LBGs and BX/BMs, respectively. We find that LIR estimates derived from present measurements are in good agreement with those based on UV data for z∼ 2 BX/BM galaxies, unlike the case for z∼ 3 infrared luminous LBGs where the UV underestimates the true LIR. Although sample selection effects may influence this result we suggest that differences in physical properties (such as morphologies, dust distribution and extent of star-forming regions) between z∼ 3 LBGs and z∼ 2 BX/BMs may also play a significant role.
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