Showing papers by "Peter A. R. Ade published in 2000"

A flat Universe from high-resolution maps of the cosmic microwave background radiation

Abstract: The blackbody radiation left over from the Big Bang has been transformed by the expansion of the Universe into the nearly isotropic 2.73 K cosmic microwave background. Tiny inhomogeneities in the early Universe left their imprint on the microwave background in the form of small anisotropies in its temperature. These anisotropies contain information about basic cosmological parameters, particularly the total energy density and curvature of the Universe. Here we report the first images of resolved structure in the microwave background anisotropies over a significant part of the sky. Maps at four frequencies clearly distinguish the microwave background from foreground emission. We compute the angular power spectrum of the microwave background, and find a peak at Legendre multipole l_(peak) = (197 ± 6), with an amplitude ΔT_(200) = (69 ± 8) µK. This is consistent with that expected for cold dark matter models in a flat (euclidean) Universe, as favoured by standard inflationary models.

MAXIMA-1: A measurement of the cosmic microwave background anisotropy on angular scales of 10′-5°

Abstract: We present a map and an angular power spectrum of the anisotropy of the cosmic microwave background (CMB) from the first flight of MAXIMA. MAXIMA is a balloon-borne experiment with an array of 16 bolometric photometers operated at 100 mK. MAXIMA observed a 124 deg region of the sky with 10' resolution at frequencies of 150, 240 and 410 GHz. The data were calibrated using in-flight measurements of the CMB dipole anisotropy. A map of the CMB anisotropy was produced from three 150 and one 240 GHz photometer without need for foreground subtractions. Analysis of this CMB map yields a power spectrum for the CMB anisotropy over the range 36 {le} {ell} {le} 785. The spectrum shows a peak with an amplitude of 78 {+-} 6 {mu}K at {ell} {approx_equal} 220 and an amplitude varying between {approx} 40 {mu}K and {approx} 50 {mu}K for 400 {approx}< {ell} {approx}< 785.

Constraints on Cosmological Parameters from MAXIMA-1

Abstract: We set new constraints on a seven-dimensional space of cosmological parameters within the class of inflationary adiabatic models. We use the angular power spectrum of the cosmic microwave background measured over a wide range of l in the first flight of the MAXIMA balloon-borne experiment (MAXIMA-1) and the low-l results from the COBE Differential Microwave Radiometer experiment. We find constraints on the total energy density of the universe, Ω = 1.0img1.gif, the physical density of baryons, Ωbh2 = 0.03 ± 0.01, the physical density of cold dark matter, Ωcdmh2 = 0.2img2.gif, and the spectral index of primordial scalar fluctuations, ns = 1.08 ± 0.1, all at the 95% confidence level. By combining our results with measurements of high-redshift supernovae we constrain the value of the cosmological constant and the fractional amount of pressureless matter in the universe to 0.45 < ΩΛ < 0.75 and 0.25 < Ωm < 0.50, at the 95% confidence level. Our results are consistent with a flat universe and the shape parameter deduced from large-scale structure, and in marginal agreement with the baryon density from big bang nucleosynthesis.

A Measurement of Omega from the North American Test Flight of Boomerang.

Abstract: We use the angular power spectrum of the cosmic microwave background, measured during the North American test flight of the Boomerang experiment, to constrain the geometry of the universe. Within the class of cold dark matter models, we find that the overall fractional energy density of the universe Ω is constrained to be 0.85 ≤ Ω ≤ 1.25 at the 68% confidence level. Combined with the COBE measurement, the data on degree scales from the Microwave Anisotropy Telescope in Chile, and the high-redshift supernovae data, we obtain new constraints on the fractional matter density and the cosmological constant.

Measurement of a peak in the cosmic microwave background power spectrum from the North American test flight of Boomerang

Abstract: We describe a measurement of the angular power spectrum of anisotropies in the cosmic microwave background (CMB) at scales of 0fdg3 to 5° from the North American test flight of the Boomerang experiment. Boomerang is a balloon-borne telescope with a bolometric receiver designed to map CMB anisotropies on a long-duration balloon flight. During a 6 hr test flight of a prototype system in 1997, we mapped more than 200 deg2 at high Galactic latitudes in two bands centered at 90 and 150 GHz with a resolution of 26' and 16farcm5 FWHM, respectively. Analysis of the maps gives a power spectrum with a peak at angular scales of 1° with an amplitude 70 μKCMB.

A Flat Universe from High-Resolution Maps of the Cosmic Microwave Background Radiation

Abstract: The blackbody radiation left over from the Big Bang has been transformed by the expansion of the Universe into the nearly isotropic 2.73K Cosmic Microwave Background. Tiny inhomogeneities in the early Universe left their imprint on the microwave background in the form of small anisotropies in its temperature. These anisotropies contain information about basic cosmological parameters, particularly the total energy density and curvature of the universe. Here we report the first images of resolved structure in the microwave background anisotropies over a significant part of the sky. Maps at four frequencies clearly distinguish the microwave background from foreground emission. We compute the angular power spectrum of the microwave background, and find a peak at Legendre multipole $\ell_{peak}=(197 \pm 6)$, with an amplitude $DT_{200}=(69 \pm 8)\mu K$. This is consistent with that expected for cold dark matter models in a flat (euclidean) Universe, as favoured by standard inflationary scenarios.

A determination of the hubble constant using measurements of x-ray emission and the sunyaev-zeldovich effect at millimeter wavelengths in the cluster abell 1835

Abstract: We present a determination of the Hubble constant and central electron density in the cluster Abell 1835 (z = 0.2523) from measurements of X-ray emission and millimeter-wave observations of the Sunyaev-Zeldovich (S-Z) effect with the Sunyaev-Zeldovich Infrared Experiment (SuZIE) multifrequency array receiver. Abell 1835 is a well studied cluster in the X-ray with a large central cooling flow. Using a combination of data from ROSAT PSPC and HRI images and millimeter wave measurements we fit a King model to the emission from the ionized gas around Abell 1835 with θ0 = 022 ± 002 and β = 0.58 ± 0.02. Assuming the cluster gas to be isothermal with a temperature of 9.8 keV, we find a y-parameter of 4.9 ± 0.6 × 10-4 and a peculiar velocity of 500 ± 1000 km s-1 from measurements at three frequencies, 145, 221, and 279 GHz. Combining the S-Z measurements with X-ray data, we determine a value for the Hubble constant of H0 = 59 km s-1 Mpc-1 and a central electron density for Abell 1835 of ne0 = 5.64 × 10-2 cm-3 assuming a standard cosmology with Ωm = 1 and ΩΛ = 0. The error in the determination of the Hubble constant is dominated by the uncertainty in the temperature of the X-ray emitting cluster gas.

Constraints on Cosmological Parameters from MAXIMA-1

Abstract: We set new constraints on a seven-dimensional space of cosmological parameters within the class of inflationary adiabatic models. We use the angular power spectrum of the cosmic microwave background measured over a wide range of \ell in the first flight of the MAXIMA balloon-borne experiment (MAXIMA-1) and the low \ell results from COBE/DMR. We find constraints on the total energy density of the universe, \Omega=1.0^{+0.15}_{-0.30}, the physical density of baryons, \Omega_{b}h^2=0.03 +/- 0.01, the physical density of cold dark matter, \Omega_{cdm}h^2=0.2^{+0.2}_{-0.1}$, and the spectral index of primordial scalar fluctuations, n_s=1.08+/-0.1, all at the 95% confidence level. By combining our results with measurements of high-redshift supernovae we constrain the value of the cosmological constant and the fractional amount of pressureless matter in the universe to 0.45<\Omega_\Lambda<0.75 and 0.25<\Omega_{m}<0.50, at the 95% confidence level. Our results are consistent with a flat universe and the shape parameter deduced from large scale structure, and in marginal agreement with the baryon density from big bang nucleosynthesis.

Shaped corrugated horns for Cosmic Microwave Background anisotropy measurements

Abstract: Novel corrugated horn have been modelled, manufactured and measured which give low-sidelobe patterns required by CMB Anisotropy experiments. These horns have a Back-to-Back structure with mode filtering at their centres. They are corrugated to give axial symmetric low-sidelobe patterns, profiled to reduce their length, and have a Gaussian flare at their entrance apertures to further suppress sidelobes to -40dB. Modelling and experimental results show excellent agreement to well below 50 dB.

FIRST-SPIRE spectrometer: a novel imaging FTS for the submillimeter

Abstract: The SPIRE instrument for the FIRST mission will consist of a three band imaging submillimeter photometer and a two band imaging Fourier Transform Spectrometer (FTS) optimized for the 200 - 400 micrometers range, and with extended coverage out to 670 micrometers. The FTS will be used for follow-up spectroscopic studies of objects detected in photometric surveys by SPIRE and other facilities, and to perform medium resolving power (R approximately 500 at 250 micrometers ) imaging spectroscopy on galactic and nearby extra-galactic sources.

Minor constituent concentrations measured from a high altitude aircraft using high resolution far-infrared Fourier transform spectroscopy.

Abstract: Far-infrared emission spectroscopy has beendemonstrated to be a valuable method for remotesensing of trace species in the stratosphere, with theability to simultaneously detect a number of keychemical species. SAFIRE-A is a new far-infraredFourier Transform (FT) spectrometer which has beenspecifically designed to operate on board of a highaltitude aircraft in the lower stratosphere and uppertroposphere regions where relatively few remotesensing measurements have been made. Using newtechnology, the sensitivity of the FT spectrometermethod has been substantially improved for the longwavelength region. Results are reported formeasurements of O3, HNO3 and N2O at 17and 19 km using a detection window near 23 cm-1.Geographical and altitude variability of the volumemixing ratio of these constituents and their relativecorrelation are discussed. Ozone measurements agreewell with in situ measurements, except in regions ofstrong stirring and mixing associated with deformationof the northern vortex edge. Whilst SAFIREmeasurements of trace gases do not capture all of thelocal variability seen by rapid in-situ techniques,they can indicate horizontal variability close to, butnot intercepted by, the aircraft's flight path. Apossible detection of ClO at the low background levelsexpected outside the polar vortex is also reported.

Evaluation of prototype 100mK bolometric detector for Planck Surveyor

Abstract: The High-Frequency Instrument (HFI) for the Planck Surveyor mission will measure anisotropies of the Cosmic Microwave Background (CMB) down to scales of 6 arcmin and to an accuracy of ΔT/T=2×10−6. Channels ranging in frequency from 100 to 857 GHz will use 100 mK spider web bolometer detectors with NTD Ge thermistors. The detectors must be photon noise limited and fast enough to preserve signal information at the 1 r.p.m. scan rate of the satellite. The prime low-frequency CMB channels at 143 and 217 GHz are the most technically demanding owing to the lower background limited NEPs. For the 143 GHz channel the requirements are that the time constant τ<5.7 ms and the NEPbol <1.53×10−17 WHz−1/2 including contribution from amplifier noise. We present here thermal, electrical and optical data on a prototype detector which, although optimised for the 100 GHz channel, satisfies most of the requirements of the more demanding 143 GHz channel. The measurements are consistent with ideal thermal behaviour of the detector over the appropriate bias and temperature ranges for optimum performance. From optically blanked electrical measurements we determined the dependence of resistance and thermal conductance on temperature over a wide range, 70–200 mK. The optical responsivity and NEP were measured under photon background conditions similar to those expected in flight. Measurements of speed of response as a function of bias at different temperatures allowed us to determine the variation of total heat capacity with temperature. Extrapolation of these data show that in principal performance for all the Planck HFI channels can be met.

A low-background 3He bolometer array test facility and its use in evaluating prototype arrays for FIRST-SPIRE

Abstract: We report on the imaging detector array test and evaluation program for the Spectral and Photometric Imaging REceiver (SPIRE) instrument for the Far InfraRed and Submillimetre Telescope (FIRST) satellite. Three candidate detector array technologies are under evaluation: (i) hexagonally close-packed arrays of 2 Fλ feedhorns with NTD germanium sensors; (ii) filled absorber arrays with 0.5 Fλ square pixels with ion-implanted silicon sensors; and (iii) 0.5 Fλ filled arrays with transition-edge superconducting (TES) sensors. Detector arrays are required for SPIRE bands covering the 200–700 μm range. To meet the SPIRE performance requirements, the detectors must be background limited by the thermal emission from the 80 K low-emissivity FIRST telescope, achieve a speed of response of 20 Hz, and be fabricated in sizes up to 32×32. A novel cryogenic array test facility has been built to enable a range of experiments to be carried out under low background to enable a comprehensive evaluation and calibration programme on prototype detector arrays with a minimum of disruptive warm-up/cool-down cycles. The facility will be used to compare the performance of the different array types prior to array technology selection for SPIRE.

Modelling few-moded horns for far-IR space applications

Abstract: Few-moded or over-moded horns are now being proposed for far-IR space receiver systems, e.g. the High Frequency Instrument (HFI) on the ESA PLANCK Surveyor. In such systems individual waveguide modes can couple independently to an overmoded detector (such as a bolometer in an integrating cavity). We consider in detail the case of a cylindrically symmetric configuration consisting of a corrugated conical horn connected to waveguide filter also corrugated, such as is proposed for the HFI instrument. Such antenna feeds have the advantage of high coupling efficiency combined with low sidelobe level beam patterns. In the paper we present two alternative techniques for modelling few moded horn antennas. The first is based on a scattering matrix description of propagation in a non-uniform wave-guide structure, while the second approach uses hybrid mode solutions for a waveguide with corrugated walls. We also present computed and experimental data for an example prototype HFI horn.

Submillimeter and Far-InfraRed Experiment (SAFIRE): A PI class instrument for SOFIA

Abstract: SAFIRE is a versatile imaging Fabry-Perot spectrograph covering 145 to 655 microns, with spectral resolving powers ranging over 5-10,000. Selected as a "PI" instrument for the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA), SAFIRE will apply two-dimensional pop-up bolometer arrays to provide background-limited imaging spectrometry. Superconducting transition edge bolometers and SQUID multiplexers are being developed for these detectors. SAFIRE is expected to be a "First Light" instrument, useable during the initial SOFIA operations. Although a PI instrument rather than a "Facility Class" science instrument, it will be highly integrated with the standard SOFIA planning, observation, and data analysis tools.

Noise estimation in CMB time-streams and fast map-making

Abstract: We describe here an iterative method for jointly estimating the noise power spectrum from a CMB experiment's time-ordered data, together with the maximum-likelihood map. We test the robustness of this method on simulated Boomerang datasets with realistic noise.

Submillimeter and far-infrared experiment (SAFIRE): a PI class instrument for SOFIA

Abstract: SAFIRE is a versatile imaging Fabry-Perot spectrograph covering 145 to 655 microns, with spectral resolving powers ranging over 5 - 10,000. Selected as a `PI' instrument for the airborne Stratospheric Observatory for Infrared Astronomy (SOFIA). SAFIRE will apply 2D pop-up bolometer arrays to provide background-limited imaging spectrometry. Superconducting transition edge bolometers and SQUID multiplexers are being developed for these detectors. SAFIRE is expected to be a `First Light' instrument, usable during the initial SOFIA operations. Although a PI instrument rather than a `Facility Class' science instrument, it will be highly integrated with the standard SOFIA planning, observation, and data analysis tools.

CMB Analysis of Boomerang & Maxima & the Cosmic Parameters {Omega_tot,Omega_b h^2,Omega_cdm h^2,Omega_Lambda,n_s}

Abstract: We show how estimates of parameters characterizing inflation-based theories of structure formation localized over the past year when large scale structure (LSS) information from galaxy and cluster surveys was combined with the rapidly developing cosmic microwave background (CMB) data, especially from the recent Boomerang and Maxima balloon experiments. All current CMB data plus a relatively weak prior probability on the Hubble constant, age and LSS points to little mean curvature (Omega_{tot} = 1.08\pm 0.06) and nearly scale invariant initial fluctuations (n_s =1.03\pm 0.08), both predictions of (non-baroque) inflation theory. We emphasize the role that degeneracy among parameters in the L_{pk} = 212\pm 7 position of the (first acoustic) peak plays in defining the Ω tot range upon marginalization over other variables. Though the CDM density is in the expected range (\Omega_{cdm}h^2=0.17\pm 0.02), the baryon density Omega_bh^2=0.030\pm 0.005 is somewhat above the independent 0.019\pm 0.002 nucleosynthesis estimate. CMB+LSS gives independent evidence for dark energy (Omega_\Lambda=0.66\pm 0.06) at the same level as from supernova (SN1) observations, with a phenomenological quintessence equation of state limited by SN1+CMB+LSS to w_Q<-0.7 cf. the w_Q=-1 cosmological constant case.

First results from the BOOMERanG experiment

Abstract: We report the first results from the BOOMERanG experiment, which mapped at 90, 150, 240 and 410 GHz a wide (3%) region of the microwave sky with minimal local contamination. From the data of the best 150 GHz detector we find evidence for a well defined peak in the power spectrum of temperature fluctuations of the Cosmic Microwave Background, localized at $\ell = 197 \pm 6$, with an amplitude of $(68 \pm 8) \mu K_{CMB}$. The location, width and amplitude of the peak is suggestive of acoustic oscillations in the primeval plasma. In the framework of inflationary adiabatic cosmological models the measured spectrum allows a Bayesian estimate of the curvature of the Universe and of other cosmological parameters. With reasonable priors we find $\Omega = (1.07 \pm 0.06)$ and $n_s = (1.00 \pm 0.08)$ (68%C.L.) in excellent agreement with the expectations from the simplest inflationary theories. We also discuss the limits on the density of baryons, of cold dark matter and on the cosmological constant.

Performance of the multiband imaging photometer for SIRTF

Abstract: We describe the test approaches and results for the Multiband Imaging Photometer for SIRTF. To verify the performance within a `faster, better, cheaper' budget required innovations in the test plan, such as heavy reliance on measurements with optical photons to determine instrument alignment, and use of an integrating sphere rather than a telescope to feed the completed instrument at its operating temperature. The tests of the completed instrument were conducted in a cryostat of unique design that allowed us to achieve the ultra-low background levels the instrument will encounter in space. We controlled the instrument through simulators of the mission operations control system and the SIRTF spacecraft electronics, and used cabling virtually identical to that which will be used in SIRTF. This realistic environment led to confidence in the ultimate operability of the instrument. The test philosophy allowed complete verification of the instrument performance and showed it to be similar to pre-integration predictions and to meet the instrument requirements.