Cosmological Seed Fields versus Seed Fields Generated in Protogalaxies
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Transcript of Cosmological Seed Fields versus Seed Fields Generated in Protogalaxies
Cosmological Seed Fields versus Seed Fields Generated in Protogalaxies
Dmitry SokoloffMoscow State University
Moscow, Russiain collaboration
with D.Mossand V.Semikoz
Galactic Magnetism –Perspectives of Observation and Modeling
May 16 - 20, 2011Pushchino, Moscow region, Russia
Br BT
Ω
Differential rotation
BT Br
α
Helicity
GALACTIC DYNAMO
Basic mechanism
The excitation mechanism requires a seed magnetic field.Two options: 1. Magnetic field is created in after recombination
2. A cosmological seed field
How to decide which option is better?
A standard approach: formulate scenarios for both cases, isolate specific features and try to confront them with observations
A scenario for magnetic fields created after recombination: talks of Moss, Arshakian, …
Seeds in protogalaxies + conventional mean-field dynamo
Spatial configurations
Cosmological seeds (a standard viewpoint)
Homogeneous magnetic field.Do not destroy isotropy provided is weak
enough (< 1011G is more then sufficient).Still can be strong enough to be a seed
Homogeneous relic field+ dynamo: it works unexpectedly bad (simulations of D.Moss)
Rotation expels homogeneous field on the remote part of the galaxy(simulations of D.Moss)
A cosmological magnetic field is useful to explain the baryon asymmetrySemikoz, Sokoloff, Valle,PRD 2009
We can not distinguish between
Small-scale cosmological seed + dynamo
A battery mechanism + small scale dynamo + mean-field dynamo
A large-scale seed + small-scale dynamo +
Mean-field dynamo
What says cosmology?
1. Everything is known (this statement persists)
Nothing about homogeneous magnetic field
This idea looked strange 10 years agoIt looks attractive todayMy interpretation: the topic is completely
obscure
A possibility to go further
Neronov and D.Semikoz:Magnetic fields between galactic clusters(10-15 G)Faraday rotation?Small-scale or large-scale fields?