with VLBI at . Parkes. Stas Shabala. University of Tasmania. Why study AGN. . AGN physics. Brightest objects in the Universe, yet we don’t know:. Composition. Accretion / outflow connection. Details of interaction with environment. ID: 334573
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Probing AGN physicswith VLBI at Parkes
Stas Shabala
University of Tasmania
Slide2Why study AGN
AGN physicsBrightest objects in the Universe, yet we don’t know:CompositionAccretion / outflow connectionDetails of interaction with environment FeedbackGalaxiesClusters ProbesISMHI in and outside galaxiesHigh z UniverseEarth !
SKA Key ScienceProbing the Dark Ages ✓Galaxy evolution + cosmology ✓Cosmic magnetism ✓Gravity with pulsars/BHs ✓Cradle of life
Croton et al. 2006
Beutler
2004
Slide3AGN at high angular resolution
Cores
Survey
follow up: AGN and/or SF (Falcke+04, Middelberg+12)Self – absorptionAGN energetics and feedback (Lobanov 96, Kovalev+08)Geodesy (Porcas 09)JetsComposition: Faraday depolarization, jet powers (O’Sullivan+11)Propagation + interaction: KHI, entrainment (Lobanov 96, Croston+03)Physics: B-field, central engine modulation, standing shocks, binary BHs… (O’Sullivan & Gabuzda 09, Godfrey+12)LobesAgeing: backflow + large-scale dynamics (Alexander & Leahy 87)HotspotsAGN energetics (Godfrey & Shabala 12)
Godfrey et al. 2012,
ApJ 758, 27
Image: R. Perley / NRAO
Kovalev
et al. 2008, A&A 383, 759
Slide4Multi – frequency VLBI
Cores
Survey
follow up: AGN and/or SFSelf – absorptionAGN energetics and feedbackGeodesyJetsComposition: Faraday depolarization, jet powersPropagation + interaction: KHI, entrainmentPhysics: B-field, central engine modulation, standing shocks, binary BHs…LobesAgeing: backflow + large-scale dynamicsHotspotsAGN energetics
Godfrey et al. 2012,
ApJ 758, 27
Image: R. Perley / NRAO
frequency – dependent core shift
s
pectral index
b
reak frequency
r
otation measures
GPS sources: turnover frequency
z
Slide5Multi – frequency VLBI
Cores
Survey
follow up: AGN and/or SFSelf – absorptionAGN energetics and feedbackGeodesyJetsComposition: Faraday depolarization, jet powersPropagation + interaction: KHI, entrainmentPhysics: B-field, central engine modulation, standing shocks, binary BHs…LobesAgeing: backflow + large-scale dynamicsHotspotsAGN energetics
Godfrey et al. 2012,
ApJ 758, 27
Image: R. Perley / NRAO
frequency – dependent core shift
s
pectral index
b
reak frequency
r
otation measures
GPS sources: turnover frequency
z
Slide6Step 1 : relate other variables to B (equipartition)Step 2 : find B from core shift
Core shift jet powers
Kovalev
et al. 2008, A&A 383, 759
particles
B-field
rest mass
Shabala+ 2012
,
ApJ
756, 161
Jet power
Weak
jets at high
z
are Doppler boosted
LBA v469: core shifts without optically thin jets
Slide7Hotspot size + luminosity + spectral index Jet power
Hotspot jet powers
s
pectral index
Godfrey & Shabala
2012
, submitted to
ApJ
Comparison
:Hotspot vs core shift jet powers
Slide8Why southern hemisphere
VLBA issues
SKA pathfinders
Geodesy
Structure + core shiftSouthern Hemisphere most affected (O. Titov’s talk)Flux density + geodetic + LBA
Scintillation10 μas
Intrinsic
100 μas
Intrinsic
1 mas
Geodesy
AGN physics
s
table
quasar
unstable quasar
Parkes
jet evolution
VLBI core shift ?
Slide9Which receivers ?
Multi – frequency science
Core shifts, Faraday depolarization hotspots, lobesLBA: 1.4 – 22 GHzGeodesy + astrophysicsVLBI 2010: S / X 2 – 14 GHzTimelines uncertainConsequences of losing S / XAuScope needs Parkes for sensitivity (12 x 64 m)astrometry ~ SNRno simultaneous multi – λ on long baselinesE.g. with 4 GHz broadband receiver (need 2.3 GHz)Geodesy impossible without S / X AGN physics loses outAGN studies need quasi-simultaneous multi – λ observationsCore shift ~ ν-1
AuScope
12m:
Yarragadee
+KatherineLBA Sep 2012
Slide10Slide11Slide12Slide13Slide14Slide15
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