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| ==Wolf effect and Quasars== | ==Wolf effect and Quasars== | ||
| The effect has been regarded by a small number of researchers as being possibly significant in the spectra of ]s. Wolf has gone as far as to advocate the effect as a ''] ]'',<ref name="wolf87nature" /> |
The effect has been regarded by a small number of researchers as being possibly significant in the spectra of ]s. Wolf has gone as far as to advocate the effect as a ''] ]'',<ref name="wolf87nature" />. Wolf and James note <ref name="wolf96james" /> that: | ||
| ⚫ | :".. the observed spectral shifts may be due to other causes has been a subject of intense controversy. Discussions of this topic are given, for example, in Field ''et al'' (1973), Arp (1987), Burbidge (1988), Narlikar (1989) and Sulentic (1994). Although we make no claim that correlation-induced spectral shifts account for all, or even for a majority, of the observed shifts of lines in the spectra of extra-galactic objects, we note the possibility that correlation-induced spectral shifts may contribute to the shifts observed in the spectra of some astronomical objects such as quasars. They might help to resolve a long-standing controversy relating to pairs of astronomical objects whose spectra have different redshifts, but which appear to be physically connected, such as the pair consisting of the galaxy NGC 4319 (''z'' = 0.006) and the quasar Markarian 205 (''z ''= 0.007/ (Arp 1971, Sulentic 1983). The possible 'excess' redshift observed in the spectrum of the quasar in such a galaxy-quasar pair may perhaps be induced by the mechanism that we have just discussed". | ||
| An example of such a medium which could produce Doppler-like shifts was found in 1990 by Daniel James, Malcolm Savedoff, Malcolm and Emil Wolf,<ref name="james1990savedoff" /> and involved a highly ''statistically ]'' scattering medium, that is compatible with current models of quasars. A "no blueshift" condition has also been found by Datta, S. ''et al.'', <ref>Datta, S., Roy, S., Roy, M., and Moles, M., "" (1998) ''Physical Review A'' 58 (1): 720—723.</ref> <ref name="roy99" />. | An example of such a medium which could produce Doppler-like shifts was found in 1990 by Daniel James, Malcolm Savedoff, Malcolm and Emil Wolf,<ref name="james1990savedoff" /> and involved a highly ''statistically ]'' scattering medium, that is compatible with current models of quasars. A "no blueshift" condition has also been found by Datta, S. ''et al.'', <ref>Datta, S., Roy, S., Roy, M., and Moles, M., "" (1998) ''Physical Review A'' 58 (1): 720—723.</ref> <ref name="roy99" />. | ||
| Wolf and James note <ref name="wolf96james" /> that: | |||
| ⚫ | :"Although we make no claim that correlation-induced spectral shifts account for all, or even for a majority, of the observed shifts of lines in the spectra of extra-galactic objects, we note the possibility that correlation-induced spectral shifts may contribute to the shifts observed in the spectra of some astronomical objects such as quasars. They might help to resolve a long-standing controversy relating to pairs of astronomical objects whose spectra have different redshifts, but which appear to be physically connected, such as the pair consisting of the galaxy NGC 4319 (''z'' = 0.006) and the quasar Markarian 205 (''z ''= 0.007/ (Arp 1971, Sulentic 1983). The possible 'excess' redshift observed in the spectrum of the quasar in such a galaxy-quasar pair may perhaps be induced by the mechanism that we have just discussed". | ||
| ==Notes== | ==Notes== | ||
Revision as of 14:43, 19 August 2006
The Wolf Effect (sometimes Wolf shift) is a frequency shift in the electromagnetic spectrum, that has been consider to be a new redshift mechanism. The phenomenon occurs in several closely related phenomena in radiation physics, with analogous effects occurring in the scattering of light. It was first predicted by Emil Wolf in 1987 and subsequently confirmed in the laboratory by Dean Faklis and G. Michael Morris in 1988 . Under certain conditions, the shift may be distortion free, and occur in free space, Wolf and James write:
- "A review is also presented of recent research, which has revealed that under certain circumstances the changes in the spectrum of light scattered on random media may imitate the Doppler effect, even though the source, the medium and the observer are all at rest with respect to one another. This expression shows that the relative frequency shift is independent of the central frequency ω0 of the incident light and thus imitates the Doppler effect. it is now firmly established that spectra of radiation may change on propagation, even in free space .."
Sisir Roy et al also note that:
- "The frequency shift of spectral lines from astronomical objects is most often explained by the Doppler Effect arising in relative motion and the broadening of a particular line is supposed to depend on the absolute temperature, pressure or the different line of sight velocities. The Wolf effect on the other hand deals with correlation induced spectral changes and explains both the broadening and shift of the spectral lines."
Wolf and James note that the Wolf effect ".. has superficial analogies with effects such as Brillouin scattering, which can also produce Doppler-like shifts in certain circumstances (Boyd 1992)", and ".. that this mechanism cannot be explained either by naive considerations involving photon fluxes or by radiative transfer or coherent wave propagation".
Theoretical description
In optics, two non-Lambertian sources that emit beamed energy can interact in a way that causes a shift in the spectral lines. It is analogous to a pair of tuning forks with similar frequencies (pitches), connected together mechanically with a sounding board; there is a strong coupling that results in the resonant frequencies getting "dragged down" in pitch.
The Wolf Effect requires that the waves from the sources are partially coherent - the wavefronts being partially in phase. Laser light is coherent while candle light is incoherent, each photon having random phase.
The Wolf Effect can produce either redshifts or blueshifts, depending on the observer's point of view, but is redshifted when the observer is head-on. A subsequent 1999 article by Sisir Roy et al. have suggested that the Wolf Effect may explain discordant redshift in certain quasars .
For two sources interacting while separated by a vacuum, the Wolf effect cannot produce shifts greater than the linewidth of the source spectral line, since it is a position-dependent change in the distribution of the source spectrum, not a method by which new frequencies may be generated. However, when interacting with a medium, in combination with effects such as Brillouin scattering it may produce shifts greater than the linewidth of the source.
Wolf effect and Quasars
The effect has been regarded by a small number of researchers as being possibly significant in the spectra of quasars. Wolf has gone as far as to advocate the effect as a non-cosmological redshift,. Wolf and James note that:
- ".. the observed spectral shifts may be due to other causes has been a subject of intense controversy. Discussions of this topic are given, for example, in Field et al (1973), Arp (1987), Burbidge (1988), Narlikar (1989) and Sulentic (1994). Although we make no claim that correlation-induced spectral shifts account for all, or even for a majority, of the observed shifts of lines in the spectra of extra-galactic objects, we note the possibility that correlation-induced spectral shifts may contribute to the shifts observed in the spectra of some astronomical objects such as quasars. They might help to resolve a long-standing controversy relating to pairs of astronomical objects whose spectra have different redshifts, but which appear to be physically connected, such as the pair consisting of the galaxy NGC 4319 (z = 0.006) and the quasar Markarian 205 (z = 0.007/ (Arp 1971, Sulentic 1983). The possible 'excess' redshift observed in the spectrum of the quasar in such a galaxy-quasar pair may perhaps be induced by the mechanism that we have just discussed".
An example of such a medium which could produce Doppler-like shifts was found in 1990 by Daniel James, Malcolm Savedoff, Malcolm and Emil Wolf, and involved a highly statistically anisotropic scattering medium, that is compatible with current models of quasars. A "no blueshift" condition has also been found by Datta, S. et al., .
Notes
- Emil Wolf himself writes:
- "In 1986 I predicted the existing of a new mechanism for producing redshifts of spectral lines. It arises from the coherence properties of sources and from somewhat similar properties of their atmospheres. What perhaps is most remarkable is that in some cases this mechanism may be shown to completely imitate the Doppler effect, even though the source is not moving away from us. This implies that if one detects a redshift of a spectral line from an astronomical source one cannot always be certain that the shift is due to recessional motion; it could be due to the new effect, which has nothing to do with motion." See Emil Wolf, "Selected Works of Emil Wolf: With Commentary" (2001) p.638, ISBN 981-02-4204-2.
- "A New Optical Redshift Mechanism .. An important discovery made in 1986 that its finder calls correleation-induced spectral changes .. by Emil Wolf, professor of optical physics at the University of Rochester, and generally appears to have been ignored or incorrectly explained. .. According to Wolf's theory, in some well-defined circumstances, one may generate "shifts of spectral lines which are indistinguishable from those that would be produced by the Doppler effect" .. those theoretical predictions were subsequently verified by experiments conducted by two of Wolf's colleagues G.M. Morris and D.Falkis" Physics Before and After Einstein (2005) edited by M. Mamone Capria, p.303 ISBN: 1-58603-462-6.
- ".. this new mechanism for redshift .. proposed by E. Wolf in the mid-eighties that has no connection with relative motion and gravitation". See S. Roy, S. Data, in Gravitation and Cosmology: From the Hubble Radius to the Planck Scale (2002) by Colin Ray Wilks, Richard L Amoroso, Geoffrey Hunter, Menas Kafatos; page 104, ISBN: 1-4020-0885-6
- James, Daniel, "The Wolf effect and the redshift of quasars" (1998) Pure Appl. Opt. 7: 959-970. (Full text, PDF)
- ^ Wolf, Emil "Noncosmological redshifts of spectral lines" (1987) Nature 326: 363—365.
- Wolf, Emil, "Redshifts and blueshifts of spectral lines caused by source correlations" (1987) Optics Communications 62: 12—16.
- Bocko, Mark F., Douglass, David H., and Knox, Robert S., "Observation of frequency shifts of spectral lines due to source correlations" (1987) Physical Review Letters 58: 2649—2651.
- Faklis, Dean, and Morris, G. Michael, "Observation of frequency shifts of spectral lines due to source correlations" (1988) Optics Letters 13 (1): 4—6.
- ^ Wolf, Emil, and James, Daniel F. V., "Correlation-induced spectral changes" (1996) Reports on Progress in Physics 59: 771—818. (Full text, PDF)
- ^ Roy, S., Kafatos, M., and Datta, S., "Shift of Spectral Lines due to Dynamic Multiple Scattering and Screening Effect: Implications for Discordant Redshifts" (1999) astro-ph/9904061
- ^ James, Daniel F. V., Savedoff, Malcolm P., and Wolf, Emil, "Shifts of spectral lines caused by scattering from fluctuating random media" (1990) Astrophysical Journal 359: 67—71. (Full text, PDF)
- Roy, Sisir, Kafatos, Menas, and Datta, Suman, "Shift of spectral lines due to dynamic multiple scattering and screening effect: implications for discordant redshifts" (2000) Astronomy and Astrophysics, v.353, p.1134-1138 353: 1134—1138.
- Datta, S., Roy, S., Roy, M., and Moles, M., "Effect of multiple scattering on broadening and the frequency shift of spectral lines" (1998) Physical Review A 58 (1): 720—723.