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Internal Structure and Dynamics of Extragalactic Relativistic Jets

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Internal Structure and Dynamics of Extragalactic Relativistic Jets Internal structure and dynamics of extragalactic relativistic jets INAUGURAL-DISSERTATION zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakult¨at der Universit¨atzu K¨oln vorgelegt von Mertens Florent aus Tulle, France K¨oln 2015 Berichterstatter: Prof. Dr. J. Anton Zensus Prof. Dr. Andreas Eckart Tag der m¨undlichen Pr¨ufung:26. Juni 2015 Abstract Radio-loud AGN typically manifest powerful relativistic jets extending up to mil- lions of light years and often showing superluminal motions organised in a complex kinematic pattern. A number of physical models are still competing to explain the jet structure and kinematics revealed by radio images using the Very Long Baseline Interferometer (VLBI) technique. Robust measurements of longitudinal and transverse velocity field in the jets would provide crucial information for these models. This is a difficult task, partic- ularly for transversely resolved jets in objects like 3C 273 and M87. To address this task, we have developed a new wavelet-based image segmentation and evaluation (WISE) technique for identifying significant structural patterns (SSP) of smooth, transversely resolved flows and obtaining a velocity field from cross-correlation of these regions in multi-epoch observations. Detection of individual SSP is performed using the wavelet decomposition and multiscale segmentation of the observed struc- ture. The cross-correlation algorithm combines structural information on different scales of the wavelet decomposition, providing a robust and reliable identification of related SSP in multi-epoch images. A stacked cross correlation (SCC) method is also introduced to recover multiple velocity components from partially overlapping, optically thin emitting regions. Test performed on simulated image of jets revealed excellent performance of WISE. The algorithm enables recovering structural evolution on scales down to 0.25 FWHM of the image point spread function (PSF). It also performs well on sparse or irregular sets of observations, providing robust identification for structural displace- ments as large as 3 PSF size. The performance of WISE was further tested on astronomical images by applying it to several image sequences obtained as part of the MOJAVE long-term monitor- ing program of extragalactic jets with VLBI observations. The particular focus of the analysis was made on prominent radio jets in the quasar 3C 273 and the radio galaxies 3C 120 and 3C 111. Results showed the robustness and fidelity of results obtained from WISE compared with those coming from the \standard" procedure of using multiple Gaussian components to represent the observed structure. These tests demonstrated also the excellent efficiency of the method, with WISE analysis taking only a few minutes of computing time to recover the same structural information which required weeks of model fitting efforts. Going beyond global one dimensional kinematic analysis, WISE revealed trans- verse structure in the the jet of 3C 273, with three distinct flow lines clearly present inside the jet and evolving in a regular fashion, suggesting a pattern that may rise as a result of Kelvin-Helmholtz (K-H) instability that has previously been detected in this jet. The positional precision of the WISE decomposition was also critical on modeling the helical trajectory of the components in the jet of 3C 120, revealing an helical surface mode of the K-H instability with an apparent wavelength λapp = 15:8 mas iii w and evolving at an apparent speed βapp = 2:0 c. We finally present in this thesis the first detailed transverse velocity fields of the 3 4 jet in M87 on scales of 10 {10 rg. Its proximity combined with a large mass of the central black hole make it one of the primary source to probe the jet formation and acceleration region. We analyzed 11 epochs of the M87 jet VLBA movie project observed at 3 weeks intervals revealing a structured and stratified flow, compatible with a magnetically launched, accelerated and collimated jet. Based on the structural analysis obtained with WISE, important physical param- eters of the flow could be determined. Using the velocity detected in the counter-jet and the intensity ratio between the jet and counter-jet, we estimated the viewing angle θ = 18°. Differential velocity in the northern and southern limbs of the flow was explained by the jet rotation consistent with a field line with angular velocity 6 1 Ω 10− s− and corresponding to a launching location in the inner part of the ∼ accretion disk. The stratification in the flow was unveiled from a SCC analysis that detected a slow mildly relativistic layer (β 0:5c) associated either with the instability pattern ∼ speed or an outer wind, and a fast accelerating stream line (γ 2:5). ∼ The acceleration of the jet together with the collimation profile of the flow, was successfully modeled by solving the magnetohydrodynamics wind equation, indicat- ing a total specific energy µ 6, and a transition from Poynting to kinetic energy at ∼ a distance z 3000R , in a good agreement with previous analytic and simulation eq ∼ s work. iv Zusammenfassung Radio-laute aktive Galaxiekerne (AGN) weisen starke relativistische Jets auf, die sich ¨uber Millionen Lichtjahre erstrecken und sich h¨aufigin komplexen kinetischen Mustern anordnen, die sich mit Uberlichtgeschwindigkeit¨ fortbewegen. Mehrere physikalische Modelle versuchen derzeit die Morphologie und Kinematik von very long baseline interferometry (VLBI) Radio Aufnahmen dieser Objekte zu erkl¨aren. Robuste Messungen longitudinaler und transversaler Geschwindigkeitsfelder in- nerhalb dieser Jets liefern wichtige Informationen ¨uber diese Modelle. Dies stellt eine schwierige Aufgabe dar, insbesondere f¨urtransversal aufgel¨osteJets, wie sie in 3C 273 und M87 zu finden sind. Um dieses Problem zu l¨osenhaben wir eine wavelet basierte Bildsegmentierungs- und Bewertungstechnik (WISE) f¨urcharak- teristische strukturelle Muster (SSP) glatter und transversal aufgel¨osterFl¨usseen- twickelt. Außerdem l¨asstsich hierdurch anhand von Aufnahmen, die sich ¨uber mehrere Epochen erstrecken, durch Kreuzkorrelation ein Geschwindigkeitsfeld dieser Regionen bestimmen. Die Detektion individueller SSPs erfolgt ¨uber eine Wavelet- dekomposition und Segmentation auf verschiedenen Skalen der beobachteten Struk- tur. Der Kreuzkorrelationsalgorithmus kombiniert strukturelle Informationen aus verschiedenen Skalen der Wavelet-dekomposition und liefert hierdurch eine belast- bare und verl¨assliche Identifikation von im Zusammenhang stehenden SSPs aus Auf- nahmen von mehreren Epochen. Eine stacked cross correlation (SCC) wird ebenfalls benutzt um mehrere Geschwindigkeitskomponenten teilweise ¨uberlappender Emis- sionsregionen zu rekonstruieren. Tests mit simulierten Aufnahmen von Jets zeigen, dass WISE diese Aufgabe ausgezeichnet erledigt. Der Algorithmus rekonstruiert die strukturelle Evolution auf Skalen bis zum 0.25 fachen des FWHM der PSF dieser Bilder. Es zeigt gut Leistung beim Umgang mit vereinzelt oder irregul¨arbeobachteten Datens¨atzenund erm¨oglicht eine robuste Identifikation von Dislokationen bis zur dreifachen PSF Gr¨oße. WISE wurde des weiteren an astronomischen Aufnahmen getestet, in dem es auf verschiedene Sequenzen von VLBI Aufnahmen angewendet wurde, welche im Rah- men des MOJAVE Langzeitaufnahmeprogramms extra galaktischer Jets entstanden sind. Besonderer Fokus wurde auf die bekannten Radio-Jets des Quasars 3C 273 und der Radiogalaxien 3C 120 und 3C 111 gelegt. Die Ergebnisse best¨atigendie mit WISE erreichbare Belastbarkeit und Genauigkeit im Vergleich mit den ¨ublichen Methoden, welche multiple Gauss Komponenten nutzen um die beobachtete Struk- tur darzustellen. WISE ist außerdem hocheffizient. Es ist m¨oglich innerhalb von Minuten die gleiche strukturelle Information zu rekonstruieren f¨urdie ansonsten ein Model-fitting Aufwand von Wochen ben¨otigtw¨urde. Uber¨ die globale eindimensionale kinematische Analyse hinaus zeigte WISE eine transversale Struktur innerhalb des Jets von 3C 273 mit drei unterscheidbaren Flus- slinien auf, welche sich klar innerhalb des Jets befinden und in regul¨arer Form en- twickeln. Dies legt ein Muster nahe, das sich aus Kelvin-Helmholtz (K-H) Insta- bilit¨atenentwickelt, welche fr¨uherbereits in diesem Jet detektiert worden sind. v Die Positionsgenauigkeit der Dekomposition von WISE war ein kritischer Faktor in der Modellierung der spiralf¨ormigenTrajektorien der Komponenten des Jets in 3C 120 und zeigte eine spiralf¨ormige Oberfl¨achen-Mode der K-H Instabilit¨atmit einer scheinbaren Wellenl¨ange λapp = 15:8 mas und einer scheinbaren Geschwindigkeit von βapp = 2 c auf. Abschließend pr¨asentieren wir das erste transversale Geschwindigkeitsfeld des Jets 3 4 in M87 auf Skalen von 10 {10 rg. Die Kombination aus der unmittelbaren N¨ahedes Objektes zu uns und der großen Masse des zentralen super-massereichen schwarzen Loches (SMBH) machen es zu einer der prim¨arenQuellen um die Entstehung und die Beschleunigungsregion von Jets zu untersuchen. Wir haben 11 Epochen des M87 Jets im Rhythmus von 3 Wochen analysiert, welche einen strukturierten und geschichteten Fluss aufzeigen, der in guter Ubereinstimmung¨ mit einem magnetisch in Gang gesetzten, beschleunigten und kollimierten Jet ist. Wichtige physikalische Parameter des Flusses konnten bestimmt werden. Durch Nutzung der Geschwindigkeiten, welche im Gegenjet detektiert wurden und des Intensit¨atsverh¨altnisses zwischen Jet und Gegenjet haben wir einen Beobach- tungswinkel von θ = 18° ermittelt. Die differentielle Geschwindigkeit im n¨ordlichen
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