X-ray images of hot accretion flows

Feryal Özel, Tiziana Di Matteo

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


We consider the X-ray emission due to bremsstrahlung processes from spherically symmetric, low radiative efficiency hot accretion flows around supermassive and galactic black holes. We calculate surface brightness profiles and Michelson visibility functions for a range of density profiles, p ̃ r -3/2 + p, with 0 < p < 1, to allow for the presence of outflows. We find that although the 1 ke V emitting region in these flows can always extend up to 106 Schwarzschild radii (Rs), their surface brightness profiles and visibility functions are strongly affected by the specific density profile. The advection-dominated solutions with no outflows (p = 0) lead to centrally peaked profiles with characteristic sizes of only a few tens of Rs. Solutions with strong outflows (p ̃ 1) lead to flat intensity profiles with significantly larger characteristic sizes of up to 106Rs. This implies that low-luminosity galactic nuclei, such as M87, may appear as extended X-ray sources when observed with current X-ray imaging instruments. We show that X-ray brightness profiles and their associated visibility functions may be powerful probes for determining the relevant mode of accretion and, in turn, the properties of hot accretion flows. We discuss the implications of our results for observations with the Chandra X-Ray Observatory and the proposed X-ray interferometer MAXIM.

Original languageEnglish (US)
Pages (from-to)213-218
Number of pages6
JournalAstrophysical Journal
Issue number1 PART 1
StatePublished - Feb 10 2001


  • Accretion, accretion disks
  • Black hole physics
  • Galaxies: nuclei
  • Radiation mechanisms: thermal
  • X-rays: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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