Constraints on supermassive black hole spins from observations of active galaxy jets

E. Kun, P. J. Wiita, L. Gergely, Z. Keresztes, Gopal-Krishna, P. L. Biermann

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

We discuss the origin of the low-energy cutoff, or LEC, seen in the radio spectra of many extragalactic jets and relate this to the spin of the supermassive black holes that presumably power them. Pion decay via proton-proton collisions is a possible mechanism to supply a secondary positron population with a low energy limit. We expect that pion production would occur in advection dominated accretion flows or ADAFs. In radiatively inefficient ADAFs the heat energy of the accreting gas is unable to radiate in less than the accretion time and the particle temperature could be high enough so that thermal protons can yield such pion production. Strong starbursts are another option for the injection of a truncated particle population into the jet. The role of both mechanisms is discussed with respect to the black hole spin estimate. The energy demanded to produce the pion decay process involves a minimum threshold for kinetic energy of the interacting protons. Therefore the mean proton speed in the flow can determine whether a LEC is generated. In ADAFs the random velocity of the protons can exceed the minimum speed limit of pion production around the jet launching region in the innermost part of the flow. Finally we summarize the additional work needed to put the model assumptions on a more rigorous basis.

Original languageEnglish
Pages (from-to)1024-1027
Number of pages4
JournalAstronomische Nachrichten
Volume334
Issue number9
DOIs
Publication statusPublished - Nov 2013

Fingerprint

active galaxies
pions
protons
energy
accretion
kinetic energy
advection
radio spectra
collision
launching
decay
radio
positrons
cut-off
gas
injection
heat
collisions
thresholds
temperature

Keywords

  • Accretion, accretion disks
  • Black hole physics
  • Galaxies: jets
  • Nuclear reactions

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Constraints on supermassive black hole spins from observations of active galaxy jets. / Kun, E.; Wiita, P. J.; Gergely, L.; Keresztes, Z.; Gopal-Krishna; Biermann, P. L.

In: Astronomische Nachrichten, Vol. 334, No. 9, 11.2013, p. 1024-1027.

Research output: Contribution to journalArticle

Kun, E. ; Wiita, P. J. ; Gergely, L. ; Keresztes, Z. ; Gopal-Krishna ; Biermann, P. L. / Constraints on supermassive black hole spins from observations of active galaxy jets. In: Astronomische Nachrichten. 2013 ; Vol. 334, No. 9. pp. 1024-1027.
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