Sachs–Wolfe effect
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The Sachs–Wolfe effect, named after
Non-integrated Sachs–Wolfe effect
The non-integrated Sachs–Wolfe effect is caused by gravitational redshift occurring at the surface of last scattering. The effect is not constant across the sky due to differences in the matter/energy density at the time of last scattering.
Integrated Sachs–Wolfe effect
The integrated Sachs–Wolfe (ISW) effect is also caused by gravitational redshift, but it occurs between the surface of last scattering and the
There are two contributions to the ISW effect. The "early-time" ISW occurs immediately after the (non-integrated) Sachs–Wolfe effect produces the primordial CMB, as photons course through density fluctuations while there is still enough radiation around to affect the Universe's expansion. Although it is physically the same as the late-time ISW, for observational purposes it is usually lumped in with the primordial CMB, since the matter fluctuations that cause it are in practice undetectable.
Late-time integrated Sachs–Wolfe effect
The "late-time" ISW effect arises quite recently in cosmic history, as
A signature of the late-time ISW is a non-zero cross-correlation function between the galaxy density (the number of galaxies per square degree) and the temperature of the CMB,[3] because superclusters gently heat photons, while supervoids gently cool them. This correlation has been detected at moderate to high significance.[4][5][6][7][8]
In May 2008, Granett, Neyrinck & Szapudi showed that the late-time ISW can be pinned to discrete supervoids and superclusters identified in the SDSS Luminous Red Galaxy catalog.[9] Their ISW detection traces the localised ISW effect produced by supervoids and superclusters have on the CMB. However, the amplitude of this localised detection is controversial, as it is significantly larger than the expectations and depends on several assumptions of the analysis.
See also
References
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Sachs, R. K.; Wolfe, A. M. (1967). "Perturbations of a Cosmological Model and Angular Variations of the Microwave Background". doi:10.1086/148982.
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Rees, M. J.; Sciama, D. W. (1968). "Large-scale Density Inhomogeneities in the Universe". S2CID 4168044.
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Crittenden, R. G.; Turok, N. (1996). "Looking for a Cosmological Constant with the Rees–Sciama Effect". PMID 10061494.
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Fosalba, P.; et al. (2003). "Detection of the Integrated Sachs–Wolfe and Sunyaev–Zeldovich Effects from the Cosmic Microwave Background-Galaxy Correlation". doi:10.1086/379848.
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Scranton, R.; arXiv:astro-ph/0307335.
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Ho, S.; et al. (2008). "Correlation of CMB with large-scale structure. I. Integrated Sachs–Wolfe tomography and cosmological implications". S2CID 38383124.
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Giannantonio, T.; et al. (2008). "Combined analysis of the integrated Sachs–Wolfe effect and cosmological implications". S2CID 21763795.
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Raccanelli, A.; et al. (2008). "A reassessment of the evidence of the Integrated Sachs–Wolfe effect through the WMAP–NVSS correlation". S2CID 15054396.
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Granett, B. R.; Neyrinck, M. C.; Szapudi, I. (2008). "An Imprint of Superstructures on the Microwave Background due to the Integrated Sachs–Wolfe Effect". S2CID 15976818.
External links
- Sam LaRoque, The Integrated Sachs–Wolfe Effect. University of Chicago, IL.
- Aguiar, Paulo, and Paulo Crawford, Sachs–Wolfe effect in some anisotropic models. (PDFformat)
- White, Martin; Hu, Wayne (1997). "The Sachs–Wolfe effect" (PDF). Astronomy and Astrophysics. 321: 89.
- Sachs–Wolfe effect Level 5.
- "Dark Energy and the Imprint of Super-Structures on the Microwave Background", a webpage by Granett, Neyrinck & Szapudi.