A new way of detecting intergalactic baryons

Abstract

For each photon wave packet of extragalactic light, the dispersion by line-of-sight intergalactic plasma causes an increase in the envelope width and a chirp (drift) in the carrier frequency. It is shown that for continuous emission of many temporally overlapping wave packets with random epoch phases, such as quasars in the radio band, this in turn leads to quasi-periodic variations in the intensity of the arriving light on timescales between the coherence time (defined as the reciprocal of the bandwidth of frequency selection, taken here as of order 0.01 GHz for radio observations) and the stretched envelope, with most of the fluctuation power on the latter scale which is typically in the millisecond range for intergalactic dispersion. Thus, by monitoring quasar light curves on such short scales, it should be possible to determine the line-of-sight plasma column along the many directions and distances to the various quasars, affording one a 3-dimensional picture of the ionized baryons in the near universe.

ApJ Letters in press (this version incl. changes made at Proofs stage)

References in corpus (4)

• Angular Broadening of Intraday Variable AGN. II. Interstellar and Intergalactic Scattering
• Soft X-ray and extreme ultraviolet excess emission from clusters of galaxies
• Chandra X-ray observations of Abell 1835 to the virial radius
• On the lack of strong O-line excess in the Coma cluster outskirts from Suzaku

Cited by in corpus (5)

• Inference of dispersion measure from incoherent time-steady sources
• The signature of the Warm Hot Intergalactic Medium in WMAP and the forthcoming PLANCK data
• Measurement of the dispersion of radiation from a steady cosmological source
• A search for sub-second radio variability predicted to arise toward 3C 84 from intergalactic dispersion
• Does light from steady sources bear any observable imprint of the dispersive intergalactic medium?