The effects of thermal conduction on radiatively inefficient accretion flows

Bryan M. Johnson, Eliot Quataert

Research output: Contribution to journalArticle

40 Scopus citations

Abstract

We quantify the effects of electron thermal conduction on the properties of hot accretion flows, under the assumption of spherical symmetry. Electron heat conduction is important for low accretion rate systems where the electron cooling time is longer than the conduction time of the plasma, such as Sgr A* in the Galactic center. For accretion flows with density profiles similar to the Bondi solution [n(r) ∝ r-3/2], we show that heat conduction leads to supervirial temperatures, implying that conduction significantly modifies the dynamics of the accretion flow. We then self-consistently solve for the dynamics of spherical accretion in the presence of saturated conduction and electron heating. We find that the accretion rate onto the central object can be reduced by ∼ 1-3 orders of magnitude relative to the canonical Bondi rate. Electron conduction may thus be an important ingredient in explaining the low radiative efficiencies and low accretion rates inferred from observations of low-luminosity galactic nuclei. The solutions presented in this paper may also describe the nonlinear saturation of the magnetothermal instability in hot accretion flows.

Original languageEnglish (US)
Pages (from-to)1273-1281
Number of pages9
JournalAstrophysical Journal
Volume660
Issue number2 I
DOIs
StatePublished - May 10 2007
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Accretion, accretion disks
  • Galaxy: center

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