Radio Loudness of AGNs: Host Galaxy Morphology and the Spin Paradigm Page: 4 of 7
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Stawarz, Sikora & Lasota
V s V
* + + ++
* * *-
* ** ***PQO
yis + LINERS
I I I
39 40 41 42 43 44 45 46
log L. [erg/s]
Figure 1. LR vs. LB for the analyzed sample.
4. The Spin Paradigm and Some Speculations
Is it a spin of the central SMBH which determines jet production efficiency in
AGNs? Indeed, as discussed by Blandford (1990), assuming that a jet is powered
by the rotating black hole via the Blandford-Znajek mechanism (Blandford &
Znajek 1977), one can expect the black hole spin playing a major role in this
respect (see also Wilson & Colbert 1995, Hughes & Blandford 2003). If this
is the case, then one has to explain why SMBHs in ellipticals have on average
much larger spins than SMBHs in disk-galaxies (and how the jet production
for rapidly rotating SMBHs can be intermittent, an issue which however is not
addressed in this short contribution; see Sikora et al. 2007). In other words,
one has to relate the spin parameter to the morphology of the host, since the
presence of the two revealed sequences of AGNs on the Lj - Lacc planes are
related to the type of host galaxy. (Interestingly, the spin paradigm can account
for a single 'radio-loudness sequence' in XRBs, since the black hole spin in XRBs
is not expected to evolve during the lifetime of these systems.)
In Sikora et al. (2007), we speculate that the spin evolution of SMBHs in
spiral galaxies is limited by multiple accretion events with random orientation
of angular momentum vectors and small increments of mass, m << malign ~
a Rs/Rw MBH, where Rs = 2 GMBH/c2 is the Schwarzschild radius and
RW ~ 104Rs is the distance of the warp produced by the Bardeen-Petterson
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Stawarz, L.; Sikora, M. & Lasota, J.-P. Radio Loudness of AGNs: Host Galaxy Morphology and the Spin Paradigm, article, October 15, 2007; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc890901/m1/4/: accessed December 9, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.