Large-scale fluctuations in the X-ray background

Marie Treyer*, Caleb Scharf, Ofer Lahav, Keith Jahoda, Elihu Boldt, Tsvi Piran

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

We present an attempt to measure the large angular scale fluctuations in the X-ray background (XRB) from the HEAO 1 A2 data, expressed in terms of spherical harmonics. We model the harmonic coefficients assuming a power spectrum and an epoch-dependent bias parameter, bx(z), and using a phenomenological scenario describing the evolution of the X-ray sources. From the few low-order multipoles detected above shot noise, we estimate the power-spectrum normalization on scales intermediate between those explored by local galaxy redshift surveys (∼100 h-1 Mpc) and those probed by the COBE cosmic microwave background (CMB) measurements (∼1000 h-1 Mpc). We find that the HEAO 1 harmonics are consistent with present-epoch rms fluctuations of the X-ray sources bx(0)σ8 ∼1-2 in 8 h-1 Mpc spheres. Therefore, the observed fluctuations in the XRB are roughly as expected from interpolation between the local galaxy surveys and the COBE CMB experiment. We predict that an X-ray all-sky surface brightness survey resolving sources a factor of 10 fainter than HEAO 1 could reveal fluctuations to significantly larger scales, and therefore more strongly constrain the large-scale structure of the universe on scales of hundreds of Mpc.

Original languageEnglish
Pages (from-to)531-536
Number of pages6
JournalAstrophysical Journal
Volume509
Issue number2 PART I
DOIs
StatePublished - 1998

Keywords

  • Cosmology: observations
  • Diffuse radiation
  • Large-scale structure of universe

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