• Review Home
• Introduction
• Observables
  • Cosmological Paradigm
  • Temperature Field
  • Polarization Field
• Acoustic Peaks
  • Introduction
  • Basics
  • Initial Conditions
  • Gravitational Forcing
  • Baryon Loading
  • Radiation Driving
  • Damping
  • Polarization
  • Integral Approach
  • Parameter Sensitivity
• Matter Power Spectrum
  • Introduction
  • Physical Description
  • Cosmological Implications
• Gravitational Secondaries
  • Introduction
  • ISW Effect
  • RS/Moving Halo
  • Gravitational Waves
  • Gravitational Lensing
• Scattering Secondaries
  • Introduction
  • Peak Suppression
  • Large Angle Polarization
  • Doppler Effect
  • Modulated Doppler Effect
  • SZ Effect
• Non-Gaussianity
• Data Analysis
  • Introduction
  • Mapmaking
  • Bandpower Estimation
  • Parameter Estimation
• Discussion
  • Discussion
  • Bibliography

Doppler Effect

Naively, velocity fields of order (see e.g. [Strauss & Willick, 1995] for a review) and optical depths of a few percent would imply a Doppler effect that rivals the acoustic peaks themselves. That this is not the case is the joint consequence of the cancellation described in §4.2.1 and the fact that the acoustic peaks are not ``Doppler peaks'' (see §3.8). Since the Doppler effect comes from the peculiar velocity along the line of sight, it retains no contributions from linear modes with wavevectors perpendicular to the line of sight. But as we have seen, these are the only modes that survive cancellation (see Plate 3 and [Kaiser, 1984]). Consequently, the Doppler effect from reionization is strongly suppressed and is entirely negligible below unless the optical depth in the reionization epoch approaches unity (see Plate 5b).