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Efstathiou, Elias C.; Polyzos, George C.

doi:10.1007/978-1-4615-0225-8_9

Cited by 6 publications

(10 citation statements)

References 8 publications

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“…4.2, we note that one explanation of the low quadrapole signal in the CMB is that the Universe has a small, but positive, curvature and a P (k) which cuts off on this curvature scale (e.g. Efstathiou 2003). Precision cosmology led by the SKA could, for example, confirm that w = −1, and that the Universe is closed.…”

Section: Cosmology Beyond Dark Energymentioning

confidence: 81%

Galaxy evolution, cosmology and dark energy with the Square Kilometer Array

Rawlings

Abdalla

Bridle

et al. 2004

New Astronomy Reviews

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The present-day Universe is seemingly dominated by dark energy and dark matter, but mapping the normal (baryonic) content remains vital for both astrophysics -understanding how galaxies form -and astro-particle physics -inferring properties of the dark components.The Square Kilometre Array (SKA) will provide the only means of studying the cosmic evolution of neutral Hydrogen (HI) which, alongside information on star formation from the radio continuum, is needed to understand how stars formed from gas within dark-matter over-densities and the rôles of gas accretion and galaxy merging.'All hemisphere' HI redshift surveys to z ∼ 1.5 are feasible with wide-field-of-view realizations of the SKA and, by measuring the galaxy power spectrum in exquisite detail, will allow the first precise studies of the equationof-state of dark energy. The SKA will be capable of other uniquely powerful cosmological studies including the measurement of the dark-matter power spectrum using weak gravitational lensing, and the precise measurement of H0 using extragalactic water masers.The SKA is likely to become the premier dark-energy-measuring machine, bringing breakthroughs in cosmology beyond those likely to be made possible by combining CMB (e.g. Planck), optical (e.g. LSST, SNAP) and other early-21 st -century datasets.

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Section: Cosmology Beyond Dark Energymentioning

confidence: 81%

Galaxy evolution, cosmology and dark energy with the Square Kilometer Array

Rawlings

Abdalla

Bridle

et al. 2004

New Astronomy Reviews

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“…Cosmic Microwave Background (CMB) experiments (see Bouchet et al 1999;Tegmark et al 2000;Efstathiou 2003;Bennet et al 2003) are of great importance for studying the early universe and its subsequent expansion. Precision cosmology with Wilkinson Microwave Anisotropy Probe (WMAP) and Planck satellite requires a good model of the microwave foreground emission to allow the subtraction of microwave foreground contamination from the CMB radiation.…”

Section: Introductionmentioning

confidence: 99%

SPINNING DUST EMISSION: EFFECTS OF IRREGULAR GRAIN SHAPE, TRANSIENT HEATING, AND COMPARISON WITHWILKINSON MICROWAVE ANISOTROPY PROBERESULTS

Hoang¹,

Lazarían²,

Draine³

2011

ApJ

106

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Planck is expected to answer crucial questions on the early Universe, but it also provides further understanding on anomalous microwave emission. Electric dipole emission from spinning dust grains continues to be the favored interpretation of anomalous microwave emission. In this paper, we present a method to calculate the rotational emission from small grains of irregular shape with moments of inertia I 1 ≥ I 2 ≥ I 3 . We show that a torque-free rotating irregular grain with a given angular momentum radiates at multiple frequency modes. The resulting spinning dust spectrum has peak frequency and emissivity increasing with the degree of grain shape irregularity, which is defined by I 1 : I 2 : I 3 . We discuss how the orientation of dipole moment µ in body coordinates affects the spinning dust spectrum for different regimes of internal thermal fluctuations. We show that the spinning dust emissivity for the case of strong thermal fluctuations is less sensitive to the orientation of µ than in the case of weak thermal fluctuations. We calculate spinning dust spectra for a range of gas density and dipole moment. The effect of compressible turbulence on spinning dust emission is investigated. We show that the emission in a turbulent medium increases by a factor from 1.2-1.4 relative to that in a uniform medium, as sonic Mach number M s increases from 2-7. Finally, spinning dust parameters are constrained by fitting our improved model to five-year Wilkinson Microwave Anisotropy Probe cross-correlation foreground spectra, for both the Hα-correlated and 100 µm-correlated emission spectra.

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“…Diffuse Galactic microwave emission in the 10 -100 GHz frequency range carries important information on the fundamental properties of the interstellar medium, but it also interferes with Cosmic Microwave Background (CMB) experiments (see Bouchet et al 1999, Tegmark et al 2000, Efstathiou 2003.…”

Section: Introductionmentioning

confidence: 99%

Improving the Model of Emission From Spinning Dust: Effects of Grain Wobbling and Transient Spin-Up

Hoang

Draine

Lazarían

2010

ApJ

119

148

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Observations continue to support the interpretation of the anomalous microwave foreground as electric dipole radiation from spinning dust grains as proposed by Draine & Lazarian (1998ab). In this paper we present a refinement of the original model by improving the treatment of a number of physical effects. First, we consider a disk-like grain rotating with angular velocity at an arbitrary angle with respect to the grain symmetry axis (i.e., grain wobbling) and derive the rotational damping and excitation coefficients arising from infrared emission, plasma-grain interactions and electric dipole emission. The angular velocity distribution function and the electric dipole emission spectrum for disk-like grains are calculated using the Langevin equation, for cases both with and without fast internal relaxation. Our results show that for fast internal relaxation, the peak emissivity of spinning dust, compared to earlier studies, increases by a factor of ∼ 2 for the Warm Neutral Medium (WNM), the Warm Ionized Medium (WIM), the Cold Neutral Medium (CNM) and the Photodissociation Region (PDR), and by a factor ∼ 4 for Reflection Nebulae (RN). The frequency at the emission peak also increases by factors ∼1.4 to ∼2 for these media. Without internal relaxation, the increase of emissivity is comparable, but the emission spectrum is more extended to higher frequency. The increased emission results from the non-sphericity of grain shape and from the anisotropy in damping and excitation along directions parallel and perpendicular to the grain symmetry axis. Second, we provide a detailed numerical study including transient spin-up of grains by single-ion collisions. The range of grain size in which single-ion collisions are important is identified. The impulses broaden the emission spectrum and increase the peak emissivity for the CNM, WNM and WIM, although the increases are not as large as those due to the grain wobbling. In addition, we present an improved treatment of rotational excitation and damping by infrared emission.

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Cited by 6 publications

References 8 publications

Galaxy evolution, cosmology and dark energy with the Square Kilometer Array

Galaxy evolution, cosmology and dark energy with the Square Kilometer Array

SPINNING DUST EMISSION: EFFECTS OF IRREGULAR GRAIN SHAPE, TRANSIENT HEATING, AND COMPARISON WITHWILKINSON MICROWAVE ANISOTROPY PROBERESULTS

Improving the Model of Emission From Spinning Dust: Effects of Grain Wobbling and Transient Spin-Up

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