Constraints on Cosmological Models from Cosmic Flows

2005 ◽  
Vol 201 ◽  
pp. 471-472
Author(s):  
Michael J. Hudson ◽  
Russell J. Smith ◽  
John R. Lucey ◽  
David J. Schlegel ◽  
Roger L. Davies
Keyword(s):  
Cosmic Microwave Background ◽  
Measurement Errors ◽  
Cosmological Models ◽  
Bulk Velocity ◽  
Microwave Background ◽  
Peculiar Velocity ◽  
Cluster Sample ◽  
Large Bulk

The SMAC cluster sample (Hudson et al. 1999), with a depth of ˜ 12000km s-1, has a bulk velocity of ˜ 600 km s-1, with respect to the Cosmic Microwave Background (CMB) frame. Other surveys (Willick 1999, hereafter LP10k; Lauer & Postman 1994, hereafter ACIF) have also yielded large bulk motions on similarly large scales. Taken at face value, these results appear to be in conflict with bulk flows expected from favoured cosmological models. However, at the same time, other surveys (notably Dale et al. 1999, hereafter SC) have found rather small bulk motions on large scales. We have measured bulk flows from the above mentioned surveys plus SNIa (Riess et al. 1995) in a consistent way. The results are given in Table 1. The measurement errors are due to peculiar velocity errors. Note that these are the errors typically quoted. Based on these errors alone, there appears to be conflict between some of the surveys (e.g. SC vs SMAC).

scholarly journals THE TOPOLOGY OF THE COSMIC MICROWAVE BACKGROUND ANISOTROPY ON THE SCALE ~1°

1996 ◽  
Vol 05 (04) ◽  
pp. 319-362 ◽  
Author(s):  
D.I. NOVIKOV ◽  
H.E. JØRGENSEN
Keyword(s):  
Cosmic Microwave Background ◽  
Random Field ◽  
Gaussian Noise ◽  
Gaussian Random Field ◽  
Cosmological Models ◽  
Topological Method ◽  
Microwave Background ◽  
Cosmic Microwave Background Anisotropy ◽  
Non Gaussian

In this paper we develop the theory of clusterization of peaks in a Gaussian random field. We have obtained new mathematical results from this theory and the theory of percolation and have proposed a topological method of analysis of sky maps based on these results. We have simulated 10°×10° sky maps of the cosmic microwave background anisotropy expected from different cosmological models with 0.5°–1° resolution in order to demonstrate how this method can be used for detection of non-Gaussian noise in the maps and detection of the Doppler-peak in the spectrum of perturbation of ΔT/T.

scholarly journals Cosmological parameters from the comparison of peculiar velocities with predictions from the 2M++ density field

2014 ◽  
Vol 11 (S308) ◽  
pp. 318-321
Author(s):  
Michael J. Hudson ◽  
Jonathan Carrick ◽  
Stephen J. Turnbull ◽  
Guilhem Lavaux
Keyword(s):  
Cosmic Microwave Background ◽  
Local Group ◽  
Cosmological Parameters ◽  
Density Field ◽  
Bulk Flow ◽  
Microwave Background ◽  
Peculiar Velocity ◽  
Peculiar Velocities ◽  
Best Fit ◽  
Good Agreement

AbstractUsing redshifts from the 2M++ redshift compilation, we reconstruct the density of galaxies within 200 h−1 Mpc, and compare the predicted peculiar velocities Tully-Fisher and SNe peculiar velocities. The comparison yields a best-fit value of β ≡ Ωm0.55/b* = 0.431 ± 0.021, suggesting Ωm0.55σ8,lin = 0.401 ± 0.024, in good agreement with other probes. The predicted peculiar velocity of the Local Group from sources within the 2M++ volume is 540 ± 40 km s−1, towards l = 268° ± 4°, b = 38° ± 6°, which is misaligned by only 10° with the Cosmic Microwave Background dipole. To account for sources outside the 2M++ volume, we fit simultaneously for β* and an external bulk flow in our analysis. The external bulk flow has a velocity of 159 ± 23 km s−1 towards l = 304° ± 11°, b6° ± 13°.

scholarly journals The Izaña Cosmic Microwave Background Fluctuations Experiment: A Progress Report

1988 ◽  
Vol 130 ◽  
pp. 25-26
Author(s):  
R.A. Watson ◽  
R. Rebolo ◽  
R.D. Davies ◽  
A.N. Lasenby ◽  
J.E. Beckman
Keyword(s):  
Cosmic Microwave Background ◽  
Progress Report ◽  
Cosmological Models ◽  
Angular Range ◽  
Beam Size ◽  
Microwave Background ◽  
Angular Scale

The Jodrell-IAC anisotropy experiment operating with twin 8° beams at 10.45 GHz over a two-year period, produced the reported limit of δ T/T≤3.7×10−5 (Davies et al., 1987: Nature 326, 462). Given the ability of this angular scale to strongly constrain cosmological models, it was decided to continue and expand the experiment by extending the horns to reduce the beam-size to 5°, while retaining the 8° separation. This improves the sensitivity to fluctuations by extending the angular range and decreasing beam-smearing.

scholarly journals Physics of the cosmic microwave background anisotropy

2015 ◽  
Vol 24 (02) ◽  
pp. 1530004 ◽  
Author(s):  
Martin Bucher
Keyword(s):  
Cosmic Microwave Background ◽  
Frequency Spectrum ◽  
Early Universe ◽  
Cosmological Models ◽  
Experimental Techniques ◽  
Current Status ◽  
Microwave Background ◽  
Cosmic Microwave Background Anisotropy ◽  
Cmb Polarization ◽  
Modern Cosmology

Observations of the cosmic microwave background (CMB), especially of its frequency spectrum and its anisotropies, both in temperature and in polarization, have played a key role in the development of modern cosmology and of our understanding of the very early universe. We review the underlying physics of the CMB and how the primordial temperature and polarization anisotropies were imprinted. Possibilities for distinguishing competing cosmological models are emphasized. The current status of CMB experiments and experimental techniques with an emphasis toward future observations, particularly in polarization, is reviewed. The physics of foreground emissions, especially of polarized dust, is discussed in detail, since this area is likely to become crucial for measurements of the B modes of the CMB polarization at ever greater sensitivity.

scholarly journals Cosmic Microwave Background at Low Frequencies

2002 ◽  
Vol 199 ◽  
pp. 58-65 ◽  
Author(s):  
R. Subrahmanyan
Keyword(s):  
Cosmic Microwave Background ◽  
Radio Telescope ◽  
Low Frequency ◽  
Cosmological Models ◽  
Large Element ◽  
Radio Telescopes ◽  
Next Generation ◽  
Microwave Background ◽  
Low Frequencies

The next generation low-frequency radio telescopes may probe cosmological models by means of observations of the cosmic microwave background (CMB). I discuss the prospects for observations of CMB imprints —- recombination lines from the epoch of recombination, μ distortions and angular temperature anisotropies —- at low frequencies. A future low-frequency radio telescope, like the proposed SKA, may be capable of attempting some difficult CMB measurements because of the large collecting area and large element numbers; however, this will require a telescope design that will allow specialized calibration strategies and will give emphasis to the control of spurious responses.

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