Probing AGN physics
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Probing AGN physics

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Probing AGN physics




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Presentation on theme: "Probing AGN physics"— Presentation transcript:

Slide1

Probing AGN physicswith VLBI at Parkes

Stas Shabala

University of Tasmania

Slide2

Why 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

Slide3

AGN 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

Slide4

Multi – 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

Slide5

Multi – 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

Slide6

Step 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

Slide7

Hotspot 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

Slide8

Why 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 ?

Slide9

Which 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

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