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Register a new userThe effect of point sources on satellite observations of the cosmic microwave background
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We study the effect of extragalactic point sources on satellite observations of the cosmic microwave background (CMB). In order to separate the contributions due to different foreground components, a maximum-entropy method is applied to simulated observations by the Planck Surveyor satellite. In addition to point sources, the simulations include emission from the CMB and the kinetic and thermal Sunyaev-Zeldovich (SZ) effects from galaxy clusters, as well as Galactic dust, free-free and synchrotron emission. We find that the main input components are faithfully recovered and, in particular, that the quality of the CMB reconstruction is only slightly reduced by the presence of point sources. In addition, we find that it is possible to recover accurate point source catalogues at each of the Planck Surveyor observing frequencies.
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A maximum entropy method (MEM) is presented for separating the emission due to different foreground components from simulated satellite observations of the cosmic microwave background radiation (CMBR). In particular, the method is applied to simulated observations by the proposed Planck Surveyor satellite. The simulations, performed by Bouchet and Gispert (1998), include emission from the CMBR, the kinetic and thermal Sunyaev-Zeldovich (SZ) effects from galaxy clusters, as well as Galactic dust, free-free and synchrotron emission. We find that the MEM technique performs well and produces faithful reconstructions of the main input components. The method is also compared with traditional Wiener filtering and is shown to produce consistently better results, particularly in the recovery of the thermal SZ effect.
Simulated observations of a $10dg times 10dg$ field by the Microwave Anisotropy Probe (MAP) are analysed in order to separate cosmic microwave background (CMB) emission from foreground contaminants and instrumental noise and thereby determine how accurately the CMB emission can be recovered. The simulations include emission from the CMB, the kinetic and thermal Sunyaev-Zeldovich (SZ) effects from galaxy clusters, as well as Galactic dust, free-free and synchrotron. We find that, even in the presence of these contaminating foregrounds, the CMB map is reconstructed with an rms accuracy of about 20 $mu$K per 12.6 arcmin pixel, which represents a substantial improvement as compared to the individual temperature sensitivities of the raw data channels. We also find, for the single $10dg times 10dg$ field, that the CMB power spectrum is accurately recovered for $ell la 600$.
Modern (sub-)millimeter interferometers enable the measurement of the cool gas and dust emission of high-redshift galaxies (z>5). However, at these redshifts the cosmic microwave background (CMB) temperature is higher, approaching, and even exceeding, the temperature of cold dust and molecular gas observed in the local Universe. In this paper, we discuss the impact of the warmer CMB on (sub-)millimeter observations of high-redshift galaxies. The CMB affects the observed (sub-)millimeter dust continuum and the line emission (e.g. carbon monoxide, CO) in two ways: (i) it provides an additional source of (both dust and gas) heating; and (ii) it is a non-negligible background against which the line and continuum emission are measured. We show that these two competing processes affect the way we interpret the dust and gas properties of high-redshift galaxies using spectral energy distribution models. We quantify these effects and provide correction factors to compute what fraction of the intrinsic dust (and line) emission can be detected against the CMB as a function of frequency, redshift and temperature. We discuss implications on the derived properties of high-redshift galaxies from (sub-)millimeter data. Specifically, the inferred dust and molecular gas masses can be severely underestimated for cold systems if the impact of the CMB is not properly taken into account.
In this paper we introduce a new linear filtering technique, the so-called matrix filters, that maximizes the signal-to-interference ratio of compact sources of unknown intensity embedded in a set of images by taking into account the cross-correlations between the different channels. By construction, the new filtering technique outperforms (or at least equals) the standard matched filter applied on individual images. An immediate application is the detection of extragalactic point sources in Cosmic Microwave Background images obtained at different wavelengths. We test the new technique in two simulated cases: a simple two-channel case with ideal correlated color noise and more realistic simulations of the sky as it will be observed by the LFI instrument of the upcoming ESAs Planck mission. In both cases we observe an improvement with respect to the standard matched filter in terms of signal-to-noise interference, number of detections and number of false alarms.
Radio interferometers are well suited to studies of both total intensity and polarized intensity fluctuations of the cosmic microwave background radiation, and they have been used successfully in measurements of both the primary and secondary anisotropy. Recent observations with the Cosmic Background Imager operating in the Chilean Andes, the Degree Angular Scale Interferometer operating at the South Pole, and the Very Small Array operating in Tenerife have probed the primary anisotropy over a wide range of angular scales. The advantages of interferometers for microwave background observations of both total intensity and polarized radiation are discussed, and the cosmological results from these three instruments are presented. The results show that, subject to a reasonable value for the Hubble constant, which is degenerate with the geometry in closed models, the geometry of the Universe is flat to high precision (~5%) and the primordial fluctuation spectrum is very close to the scale-invariant Harrison-Zeldovich spectrum. Both of these findings are concordant with inflationary predictions. The results also show that the baryonic matter content is consistent with that found from primordial nucleosynthesis, while the cold dark matter component can account for no more than ~40% of the energy density of the Universe. It is a requirement of these observations, therefore, that ~60% of the energy content of the Universe is not related to matter, either baryonic or nonbaryonic. This dark energy component of the energy density is attributed to a nonzero cosmological constant.
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