摘要:

Although the Planck Surveyor mission is optimized to map the cosmic microwave background anisotropies, it will also provide extremely valuable information on astrophysical phenomena. We review our present understanding of Galactic and extragalactic foregrounds relevant to the mission and discuss on one side, Planck’s impact on the study of their properties and, on the other side, to what extent foreground contamination may affect Planck’s ability to accurately determine cosmological parameters. Planck’s multifrequency surveys will be unique in their coverage of large areas of the sky (actually, of the full sky); this will extend by two or more orders of magnitude the flux density interval over which mm/sub-mm counts of extragalactic sources can be determined by instruments already available (like SCUBA) or planned for the next decade (like the LSA-MMA or the space mission FIRST), which go much deeper but over very limited areas. Planck will thus provide essential complementary information on the epoch-dependent luminosity functions. Bright radio sources will be studied over a poorly explored frequency range where spectral signatures, essential to understand the physical processes that are going on, show up. The Sunyaev-Zeldovich effect, with its extremely rich information content, will be observed in the direction of a large number of rich clusters of Galaxies. Thanks again to its all sky coverage, Planck will provide unique information on the structure and on the emission properties of the interstellar medium in the Galaxy. At the same time, the foregrounds are unlikely to substantially limit Planck’s ability to measure the cosmological signals. Even measurements of polarization of the primordial Cosmic Microwave background fluctuations appear to be feasible. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59327

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

We describe the MAXIMA experiment, a balloon-borne measurement designed to map temperature anisotropy in the Cosmic Microwave Background (CMB) froml=80 tol=800. The experiment consists of a 1.3 m diameter off-axis Gregorian telescope and a receiver with a 16 element array of bolometers cooled to 100 mK. The frequency bands are centered at 150, 240, and 410 GHz. The 10′FWHM beam sizes are well matched to the scale of acoustic peaks expected in the angular power spectrum of the CMB. The first flight of the experiment in its full configuration was launched in August 1998. A 122 deg2map of the sky was made near the Draco constellation during the 7 hour flight in a region of extremely low galactic dust contamination. This map covers 0.3&percent; of the sky and has 3200 independent beamsize pixels. We describe the MAXIMA instrument and its performance during the recent flight. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59349

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The BOOMERanG experiment is a stratospheric balloon telescope intended to measure the Cosmic Microwave Background anisotropy at angular scales between a few degrees and ten arcminutes. The experiment features a wide focal plane with 16 detectors in the frequency bands centered at 90, 150, 220, 400 GHz, with FWHM ranging between 18 and 10 arcmin. It will be flown on a long duration (7–14 days) flight circumnavigating Antarctica at the end of 1998. The instrument was flown with a reduced focal plane (6 detectors, 90 and 150 GHz bands, 25 to 15 arcmin FWHM) on a qualification flight from Texas, in August 1997. A wide (∼300 deg2, i.e. about 5000 independent beams at 150 GHz) sky area was mapped in the constellations of Capricornus, Aquarius, Cetus, with very low foreground contamination. The instrument was calibrated using the CMB dipole and observations of Jupiter. The LDB version of the instrument has been qualified and shipped to Antarctica. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59328

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Although the broad outlines of the appropriate pipeline for cosmological likelihood analysis with CMB data has been known for several years, only recently have we had to contend with the full, large-scale, computationally challenging problem involving both highly-correlated noise and extremely large datasets(N>1000).In this talk we concentrate on the beginning and end of this process. First, we discuss estimating the noise covariance from the data itself in a rigorous and unbiased way; this is essentially an iterated minimum-variance mapmaking approach. We also discuss the unbiased determination of cosmological parameters from estimates of the power spectrum or experimental bandpowers. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59329

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The most known inflationary model leaves traces in the form of Gaussian scale-invariant perturbations. It univoquely marks the CMB angular power spectrum. However, high energy physics may be more complicated and may leave other (and richer) traces, in the form of non-Gaussian scale-dependent perturbations. In this work we change our mind to the second issue. Instead of the CMB angular power spectrum only, we predict the temperature and polarization anisotropies from single well shaped spatially limited structures. These are generally characterized by some symmetries, and here we concentrate on the spherical ones. The treatment developed allows to express the anisotropy pattern as a function of (i) the geometrical coordinates of the particular structure under investigation, including its position relative to the last scattering surface, and (ii) the photon propagation directionn⁁.Due to the wave-like behavior of the relevant equations, the general phenomenology that turns out is that for a localized initial inhomogeneity, the corresponding CMB perturbation propagatesbeyond the initial size, generating waves traveling outward with the sound velocitycs,and reaching the size of the sound horizon at the time we are examinating it. This behavior is a common feature of both the pure temperature and polarization anisotropies. The natural test of these computations will be the comparison with the observational data from the forthcoming high resolution CMB maps from the Planck mission. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59330

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Ongoing observations of the Cosmic Microwave Background, such as the MAXIMA and BOOMERanG projects, are providing datasets of unprecedented quality and ever-increasing size. Exact analysis of the data they produce is a serious computational challenge, currently scaling as the number of sky pixels squared in memory and cubed in time. Here we discuss the origins of these scaling relations and their implications for our efforts to extract precise cosmological parameters from observations of the CMB. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59331

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Experiments to measure anistropies in the cosmic background radiation have discovered a new “anomalous” component of galactic emission in the 15–90 GHz region. This component is correlated with interstellar dust, but has an intensity and spectrum very different from what interstellar dust had been expected to emit at these frequencies. The “anomalous emission” has been interpreted by the some as free-free emission, but free-free emission from interstellar plasma cannot possibly be this strong. The “anomalous emission” can be quite naturally explained as the “rotational” emission from the population of ultrasmall dust grains which is independently required by observations of 3–60 &mgr;m diffuse infrared emission. Alternatively, some of the observed 15–90 GHz emission could be due to magnetic dipole emission from magnetic materials in interstellar grains. Experiments to distinguish between these two emission processes are discussed. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59332

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

I review our recent claim that there is evidence of non-Gaussianity in the 4 Year COBE DMR data. I describe the statistic we apply, the result we obtain and make a detailed list of the systematics we have analyzed. I finish with a qualitative understanding of what it might be and its implications. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59333

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

Much progress has been made on observing the Sunyaev-Zel’dovich effect(s) in clusters of galaxies, and recent theoretical work has placed the interpretation of the new data on a more secure footing. The deductions that can be made about the baryonic mass fractions of clusters and the value of the Hubble constant are reaching interesting levels of accuracy. In the present article I review the data, theory, and deductions and make some suggestions about where substantial progress is needed over the next few years by pointing out some of the pitfalls in the use of the effect. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59334

出版商:AIP    

年代:1999

数据来源: AIP

摘要:

The spectral and spatial signatures imprinted on the cosmic microwave background radiation by hot gas in clusters of galaxies—the Sunyaev-Zeldovich effect—are of immense astrophysical and cosmological significance. In recent years observations of the effect have improved tremendously; high signal-to-noise images of the effect can now be obtained by interferometric arrays. Sensitive X-ray spectral and spatial measurements of clusters are expected in the near future, following the launch of two new X-ray satellites. These observational advances, together with a more accurate theoretical description of the effect, will yield a significantly improved value ofH0,and reliable estimates of the total masses and peculiar velocities of clusters. The recent developments which have advanced the use of the effect as a valuable cosmological probe are briefly reviewed, along with a discussion of prospects for significant progress in the near future. ©1999 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.59335

出版商:AIP    

年代:1999

数据来源: AIP