Medium Scale Anisotropy Measurement Research Articles

Cosmic microwave background anisotropy window functions revisited

The primary results of most observations of cosmic microwave background (CMB) anisotropy are estimates of the angular power spectrum averaged through some broad band, called band-powers. These estimates are in turn what are used to produce constraints on cosmological parameters due to all CMB observations. Essential to this estimation of cosmological parameters is the calculation of the expected band-power for a given experiment, given a theoretical power spectrum. Here we derive the "band power" window function which should be used for this calculation, and point out that it is not equivalent to the window function used to calculate the variance. This important distinction has been absent from much of the literature: the variance window function is often used as the band-power window function. We discuss the validity of this assumed equivalence, the role of window functions for experiments that constrain the power in {\it multiple} bands, and summarize a prescription for reporting experimental results. The analysis methods detailed here are applied in a companion paper to three years of data from the Medium Scale Anisotropy Measurement.

New Cosmic Microwave Background Power Spectrum Constraints from MSAM1

We present new cosmic microwave background (CMB) anisotropy results from the combined analysis of the three flights of the first Medium Scale Anisotropy Measurement (MSAM1). This balloon-borne bolometric instrument measured about 10 deg2 of sky at half-degree resolution in four frequency bands from 5.2 to 20 cm-1 with a high signal-to-noise ratio. Here we present an overview of our analysis methods, compare the results from the three flights, derive new constraints on the CMB power spectrum from the combined data, and reduce the data to total power Wiener-filtered maps of the CMB. A key feature of this new analysis is a determination of the amplitude of CMB fluctuations at l ~ 400. The analysis technique is described in a companion paper (L. Knox).

Detection of Cosmic Microwave Background Anisotropy by the Third Flight of the Medium-Scale Anisotropy Measurement

The third flight of the Medium-Scale Anisotropy Measurement (MSAM1), in 1995 June, observed a new strip of sky, doubling the sky coverage of the original MSAM1 data set. MSAM1 observes with a 05 beam size in four bands from 5 to 20 cm-1. From these four bands we derive measurements of cosmic microwave background radiation (CMBR) anisotropy and interstellar dust emission. Our measurement of dust emission correlates well with the 100 μm IRAS Sky Survey Atlas; from this comparison we determine an effective emissivity spectral index between 100 μm and 444 μm of 1.46±0.28. Analysis of our measurement of CMBR anisotropy shows that for Gaussian-shaped correlation functions with θc = 03, we place a limit on total rms anisotropy of 2.2×10−5<ΔT/T<3.9×10−5 (90% confidence interval, including calibration error). The band-power limits are ⟨δT⟩ ≡ ⟨l(l+1)Cl/2π⟩½=50+16−11 μK at l=160, and ⟨δT⟩=65+18−13 μK at l=270 (1 σ limits, including calibration error). The corresponding limits with statistical errors only are ⟨δT⟩=50+ 13−9 μK and ⟨δT⟩=65+ 14−10 μK, respectively. These measurements are consistent with a standard adiabatic cold dark matter model; we discuss constraints on h, n, and the redshift of reionization.

Millimeter/Submillimeter Search for the Sunyaev‐Zeldovich Effect in the Coma Cluster

Observations from the first flight of the Medium Scale Anisotropy Measurement (MSAM1-92) are analyzed to search for the Sunyaev-Zeldovich (SZ) effect toward the Coma cluster. This balloon-borne instrument uses a 28' FWHM beam and a three-position chopping pattern with a throw of ±40'. With spectral channels at 5.7, 9.3, 16.5, and 22.6 cm-1, the observations simultaneously sample the frequency range where the SZ spectral distortion in the intensity transitions from a decrement to an increment and where the fractional intensity change is substantially larger than in the Rayleigh-Jeans region. We set limits on the Comptonization parameter integrated over our antenna pattern, Δy ≤ 8.0 × 10-5 (2 σ). For a spherically symmetric isothermal model, this implies a central Comptonization parameter y0 ≤ 2.0 × 10-4 or a central electron density n0 ≤ 5.8 × 10-3 cm-3 h50, a result consistent with central densities implied by X-ray brightness measurements and central Comptonization estimates from lower frequency observations of the SZ effect.

A Detection of Bright Features in the Microwave Background

We report the characterization of bright, compact features in the cosmic microwave background radiation (CMBR) detected during the June 1992 and June 1994 balloon flights of the Medium Scale Anisotropy Measurement (MSAM1-92 and MSAM1-94, respectively). Spectral flux densities are determined for each feature at 5.7, 9.3, and 16.5 cm$^{-1}$. No viable counterparts for these features were found in source catalogs at 5 GHz or at 100 $\mu$m. The measured spectrum of each feature is consistent with a temperature fluctuation in the CMBR. The existence of these features is consistent with adiabatic fluctuation models of anisotropy in the CMBR.

A Cosmic Microwave Background Radiation Measurement Reproduced: A Statistical Comparison of MSAM1-94 to MSAM1-92

The goal of the second flight of the medium-scale anisotropy measurement (MSAM1-94) was to confirm the measurement of cosmic microwave background radiation (CMBR) anisotropy made in the first flight (MSAM1-92). The CMBR anisotropy and interstellar dust emission signals from the two flights are compared by forming the sum and difference of those portions of the data with the same pointings on the sky. The difference data are consistent with a null detection, while the summed data show significant signal. We conclude that MSAM1-92 and MSAM1-94 measured the same celestial signal.

A Balloon-borne Millimeter-Wave Telescope for Cosmic Microwave Background Anisotropy Measurements

view Abstract Citations (37) References (20) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Balloon-borne Millimeter-Wave Telescope for Cosmic Microwave Background Anisotropy Measurements Fixsen, D. J. ; Cheng, E. S. ; Cottingham, D. A. ; Folz, W. C. ; Inman, C. A. ; Kowitt, M. S. ; Meyer, S. S. ; Page, L. A. ; Puchalla, J. L. ; Ruhl, J. E. ; Silverberg, R. F. Abstract We report on the characteristics and design details of the Medium Scale Anisotropy Measurement telescope, a millimeter-wave, balloon-borne experiment that measures anisotropy in the cosmic microwave background radiation on 0.5^deg^ angular scales. The gondola is capable of maintaining orientation to 2' rms and determining absolute pointing to 2.5' accuracy during a one-night flight. Emphasis is placed on the optical and pointing performance as well as the weight and power budgets. We also discuss the total balloon/gondola mechanical system. The pendulation from this system is a ubiquitous perturbation on the pointing system. A detailed understanding in these areas is needed for developing the next generation of balloon-borne instruments. Publication: The Astrophysical Journal Pub Date: October 1996 DOI: 10.1086/177850 arXiv: arXiv:astro-ph/9512006 Bibcode: 1996ApJ...470...63F Keywords: BALLOONS; COSMOLOGY: COSMIC MICROWAVE BACKGROUND; INSTRUMENTATION: MISCELLANEOUS; TELESCOPES; Astrophysics E-Print: 37 pages, 15 figures, uses BoxedEPS.tex full text sources arXiv | ADS |

MSAM1-94: Repeated Measurement of Medium-Scale Anisotropy in the Cosmic Microwave Background Radiation

The second flight of the Medium-Scale Anisotropy Measurement (MSAM1-94) observed the same field as the first flight (MSAM1-92) to confirm our earlier measurement of cosmic microwave background radiation (CMBR) anisotropy. This instrument chops a 30' beam in a three-position pattern with a throw of ±40' and simultaneously measures single- and double-differenced sky signals. We observe in four spectral channels centered at 5.6, 9.0, 16.5, and 22.5 cm-1, providing sensitivity to the peak of the CMBR and to thermal emission from interstellar dust. The dust component correlates well with the IRAS 100 μm map. The CMBR observations in our double-difference channel correlate well with the earlier observations, but the single-difference channel shows some discrepancies. We obtain a detection of fluctuations in the MSAM1-94 data set that match CMBR in our spectral bands of ΔT/T = 1.9−0.7+1.3 × 10−5 (90% confidence interval, including calibration uncertainty) for total rms Gaussian fluctuations with correlation angle 03, using the double-difference demodulation.

An arcminute-resolution search at 4.7 inverse centimeters for point source confusion to mesurements of CMB anisotropy

We have searched for millimeter-wave emission from compact objects in two fields, each approximately 1 sq deg in size, taken form regions of the sky in which degree-scale structure in the cosmic microwave background (CMB) has recently been reported. The observations were made at a frequency of 4.7 1 cm and an angular resolution of 1.7 min, using the Sunyaev-Zeldovich Infrared Experiment (SuZIE) bolometer array at the Caltech Submillimeter Observatory (CSO). The first field was centered on 14.92 hours, +82 deg (1994.0), one of two regions in which Cheng et al. (1994) identify the signature of an unresolved point source seen during 0.5 deg resolution observations at 5.6 1 cm with the Medium Scale Anisotropy Measurement (MSAM) experiment. The second field was centered on 15.47 hours, +72.4 deg (1994.0), part of the Gamma Ursae Minoris (GUM) region in which structure has been detected by Devlin et al. (1994) in 0.55 deg resolution observations at 3.5 and 6 1 cm with the Millimeter Anisotropy eXperiment (MAX). We find that there is no point source in either field that can account for the structure observed at 0.5 deg resolution, and that the structure must arise from objects with an angular size greater than 2 mins.

A measurement of the medium-scale anisotropy in the cosmic microwave background radiation

Observations from the first flight of the Medium Scale Anisotropy Measurement (MSAM) are analyzed to place limits on Gaussian fluctuations in the Cosmic Microwave Background Radiation (CMBR). This instrument chops a 30\arcmin beam in a 3 position pattern with a throw of $\pm40\arcmin$; the resulting data is analyzed in statistically independent single and double difference datasets. We observe in four spectral channels at 5.6, 9.0, 16.5, and 22.5~\icm, allowing the separation of interstellar dust emission from CMBR fluctuations. The dust component is correlated with the \IRAS 100~\micron map. The CMBR component has two regions where the signature of an unresolved source is seen. Rejecting these two source regions, we obtain a detection of fluctuations which match CMBR in our spectral bands of $0.6 \times 10^{-5} < \Delta T/T < 2.2 \times 10^{-5}$ (90\% CL interval) for total rms Gaussian fluctuations with correlation angle 0\fdg5, using the single difference demodulation. For the double difference demodulation, the result is $1.1 \times 10^{-5} < \Delta T/T < 3.1 \times 10^{-5}$ (90\% CL interval) at a correlation angle of 0\fdg3.