Defending the Run and Pass with Quarters Coverage Mike Kuchar Immaculata High School .
Measuring magnetic power spectra of Hydra A Petr Kuchar, Torsten Ensslin.
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Transcript of Measuring magnetic power spectra of Hydra A Petr Kuchar, Torsten Ensslin.
measuring magnetic power spectra
of Hydra A
Petr Kuchar, Torsten Ensslin
Hydra A
optical x-ray
NASA/CXC/SAOLa Palma/B. McNamara
Hydra A
radio RM map
Greg Taylor, NRAO pacerman algorithm Dolag & Vogt & Ensslin
we measure this
rotation measure
we want that
previous works
• Laing 2008compare observed and computedstructure function
• Vogt & Ensslin 2005Bayesian
Bayesian approach
given RM data d
wanted power spectrum p
P(p|d)~P(d|p)P(p)
Likelihood
Jeffrey's Prior
correlation matrix
C
electron densitymagnetic density
cavity geometryprojection angle of jet
powerspectrum
maximize the posterior P(p|d)
analytical expressions for gradient and hessian
power spectrum
spectral index
projection angle
characteristics ofmagnetic field
• magnetic density:
• autocorrelation lengths
• spectral index
conclusion• maximum a posteriori method to retrieve
magnetic power spectra
• re-analysis of Hydra A data (as Vogt & Ensslin) now including cavities, noise, Galactic foreground, beam discussion, increased internal accuracy
• robust results: peaked spectrum with 3 kpc correlation length, indication of power-law inertia range on smaller scales
• required: better understanding of RM noise & beam effects, window effects on large scales