Quasars |
In General > s.a. black holes [alternatives];
black-hole phenomenology and types.
* Idea: Objects characterized
by pointlike appearance (almost stellar, earlier called quasi-stellar objects
or QSOs) and large redshifts (peaking at z ~ 2).
* Nature: They are almost
certainly brilliant luminous cores of galaxies, powered by infalling matter.
* Evidence: Other galaxies have
similar central engines, with a wide range of luminosities, and all quasars
within z ~ 0.7 show a faint fuzzy nebulosity, which often resembles
a normal galaxy in appearance and spectrum.
* Energy source: Cannot be just
nuclear reactions, and the most attractive possibility is the presence of large
(~ 10 MSun) black holes, with matter
falling into them and converting up to 50% of its mass into radiation.
* Interactions: The fraction of
them in interaction with other galaxies is far greater than the corresponding
fraction for all galaxies; This indicates that the presence of a quasar nucleus
is strongly related to the interaction with another galaxy; The mechanism could
be that if there is already a compact massive nucleus, matter coming from the
other, smaller galaxy could be funneled into it.
* Puzzle: 1996, Some quasars
seem to be (visually) associated with other galaxies, but have a very different
redshift; No good explanation has been found yet.
References
@ General, reviews: Weedman 86 [III];
Rech(92)oct, p1118; Disney SA(98)jun;
Osmer IAU-ap/99;
Lacy ap/06;
Makarov a1202-conf [quasometry].
@ History: Kellermann JAHH-a1304;
Hazard et al IAU(14)-a1412 [discovery of the first Quasar 3C273];
Kellermann IAU(14)-a1412;
Antonucci a1501
[and AGN, unsatisfactory progress in understanding].
@ Unconventional redshift interpretation:
Arp et al ap/05 [periodicities];
Arp a0711 [evolving intrinsic redshift];
Hartnett ASS(08)-a0712,
Hartnett & Hirano ASS(09) [periodicities].
@ Other unconventional: Moret-Bailly ap/03,
ap/04 [as neutron stars!].
@ Related topics: Dau et al PRL(12)-a1204 [using quasars as standard clocks for measuring redshifts].
> Related topics:
see cosmic strings [quasar alignment].
Microquasars
* Idea: Galactic miniatures
of the far more distant quasars, obtained when accreting neutron stars eject
relativistic particles orthogonal to the accretion disk, instead of confining
disk-material down to the magnetic poles and creating the two emitting caps
typical for a X-ray pulsar.
@ Reviews: Ribo ASP-ap/04;
Massi Hab(05)ap,
ap/06-proc;
Mirabel PoS-ap/07.
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send feedback and suggestions to bombelli at olemiss.edu – modified 9 nov 2018