Active galactic nuclei throughout the spectrum: M 87, PKS 2052-47, and the MOJAVE sample [Elektronische Ressource] / vorgelegt von Chin-Shin Chang

De
Publié par

Active Galactic Nuclei throughout theSpectrum: M 87, PKS 2052−47, and theMOJAVE sampleInaugural-DissertationzurErlangung des Doktorgradesder Mathematisch-Naturwissenschaftlichen Fakultätder Universität Kölnvorgelegt vonChin-Shin Changaus Taipei, Taiwan, ROCBerichterstatter: Prof. Dr. Andreas Eckart. Anton ZensusTag der mündlichen Prüfung: 25. Oktober 2010K~KáKÈÈK¥³ To my beloved father, mother, and sisterContentsSummary 7Zusammenfassung 9Summary(Chinese) 111 Introduction 131.1 AGNClassificationandtheUnifiedModel . . . . . . . . . . . . . . . . . 141.1.1 AGNClass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141.1.2 TheUnifiedModel . . . . . . . . . . . . . . . . . . . . . . . . . 161.2 RadiationProcesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171.2.1 ThermalEmission . . . . . . . . . . . . . . . . . . . . . . . . . 171.2.2 SynchrotronEmission . . . . . . . . . . . . . . . . . . . . . . . 181.2.3 InverseComptonScattering . . . . . . . . . . . . . . . . . . . . 201.2.4 X-rayEmissionofAGN . . . . . . . . . . . . . . . . . . . . . . 221.3 VeryLongBaselineInterferometry . . . . . . . . . . . . . . . . . . . . . 231.3.1 FundamentalsofRadioInterferometry . . . . . . . . . . . . . . . 231.3.2 SynthesisImaging . . . . . . . . . . . . . . . . . . . . . . . . . 261.4 TheStudyofBlazars . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261.4.1 TheEmissionofBlazars . . . . . . . . . . . . . . . . . .
Publié le : vendredi 1 janvier 2010
Lecture(s) : 14
Tags :
Source : D-NB.INFO/1013800699/34
Nombre de pages : 281
Voir plus Voir moins

Active Galactic Nuclei throughout the
Spectrum: M 87, PKS 2052−47, and the
MOJAVE sample
Inaugural-Dissertation
zur
Erlangung des Doktorgrades
der Mathematisch-Naturwissenschaftlichen Fakultät
der Universität Köln
vorgelegt von
Chin-Shin Chang
aus Taipei, Taiwan, ROCBerichterstatter: Prof. Dr. Andreas Eckart. Anton Zensus
Tag der mündlichen Prüfung: 25. Oktober 2010To my beloved father, mother, and sister
K?K??
?
?K~KContents
Summary 7
Zusammenfassung 9
Summary(Chinese) 11
1 Introduction 13
1.1 AGNClassificationandtheUnifiedModel . . . . . . . . . . . . . . . . . 14
1.1.1 AGNClass . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
1.1.2 TheUnifiedModel . . . . . . . . . . . . . . . . . . . . . . . . . 16
1.2 RadiationProcesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.2.1 ThermalEmission . . . . . . . . . . . . . . . . . . . . . . . . . 17
1.2.2 SynchrotronEmission . . . . . . . . . . . . . . . . . . . . . . . 18
1.2.3 InverseComptonScattering . . . . . . . . . . . . . . . . . . . . 20
1.2.4 X-rayEmissionofAGN . . . . . . . . . . . . . . . . . . . . . . 22
1.3 VeryLongBaselineInterferometry . . . . . . . . . . . . . . . . . . . . . 23
1.3.1 FundamentalsofRadioInterferometry . . . . . . . . . . . . . . . 23
1.3.2 SynthesisImaging . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.4 TheStudyofBlazars . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.4.1 TheEmissionofBlazars . . . . . . . . . . . . . . . . . . . . . . 26
1.4.2 TheSpectralEnergyDistributionofBlazars . . . . . . . . . . . . 28
1.4.3 Parsec-scaleJets: IntrinsicandObservedProperties . . . . . . . . 29
1.4.4 TheAGNStudyinThisThesis . . . . . . . . . . . . . . . . . . . 30
2 Amulti-bandflareoftheHST-1featureintheM 87jet 33
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
2.2 VLBIObservationsandDataAnalysis . . . . . . . . . . . . . . . . . . . 35
2.2.1 VeryLongBaselineArray . . . . . . . . . . . . . . . . . . . . . 35
2.2.2 ObservationsandDataAnalysis . . . . . . . . . . . . . . . . . . 36
2.3 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.3.1 ImagingoftheinnerjetofM87 . . . . . . . . . . . . . . . . . . 41
2.3.2oftheHST-1region . . . . . . . . . . . . . . . . . . . . 42
2.3.3 SpectralpropertiesofHST-1 . . . . . . . . . . . . . . . . . . . . 42
2.3.4 HST-1kinematics . . . . . . . . . . . . . . . . . . . . . . . . . . 44
2.4 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
2.4.1 VariabilitytimescaleandHST-1flaringregionatparsec-scales . . 47
3Contents
2.4.2 SpeedsofHST-1 . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2.4.3 Detectionlimits . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
2.4.4 HST-1parsec-scalespectrum . . . . . . . . . . . . . . . . . . . . 49
2.4.5 AblazarnatureofHST-1 . . . . . . . . . . . . . . . . . . . . . . 51
2.5 SummaryandFutureWork . . . . . . . . . . . . . . . . . . . . . . . . . 51
3 Blazar Flare: a Multiwavelength Study of the Flat Spectrum Radio Quasar
PKS2052−47 53
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.2 DataAcquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.2.1 TheMultiwavelengthCampaign . . . . . . . . . . . . . . . . . . 58
3.3 DataAnalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
3.4 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
3.4.1 TheMultibandPropertiesofPKS2052−47 . . . . . . . . . . . . 60
3.4.2 TheBroadbandSEDofPKS2052−47 . . . . . . . . . . . . . . . 62
3.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
3.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4 TheBroadbandSpectralEnergyDistributionoftheMOJAVESample 67
4.1 TheMOJAVESample . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.1.1 Parsec-scaleJetPropertiesandHighEnergyEmission . . . . . . 69
4.2 TheProject . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.3 DataAcquisition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
4.3.1 UniversityofMichiganRadioAstronomyObservatory . . . . . . 71
4.3.2 Fermi-GSTAGNMulti-frequencyMonitoringAlliance . . . . . . 72
4.3.3 TheSwift Gamma-RayBurstMission . . . . . . . . . . . . . . . 73
4.3.4 FermiGamma-raySpaceTelescope . . . . . . . . . . . . . . . . 76
4.4 DataAnalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
4.4.1 Swift/XRTDataReduction . . . . . . . . . . . . . . . . . . . . . 82
4.4.2 Swift/UVOTData . . . . . . . . . . . . . . . . . . . . 91
4.4.3 ExtinctionCorrection . . . . . . . . . . . . . . . . . . . . . . . . 92
4.4.4 Fermi/LATdata . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
4.5 TheBroadbandSEDoftheMOJAVEsources . . . . . . . . . . . . . . . 95
4.6 StatisticalPropertiesoftheMOJAVESample . . . . . . . . . . . . . . . 133
4.6.1 Histograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
4.6.2 DispersionRelation . . . . . . . . . . . . . . . . . . . . . . . . . 138
4.7 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
A TheX-raySpectraoftheMOJAVESample 147
B TheBroadbandSEDoftheMOJAVESample 171
C PreviouslyPublishedBroadbandSEDoftheMOJAVESources 189
D GlossaryofAcronyms 221
Bibliography 223
4Contents
Acknowledgements 273
Ackno(Chinese) 275
Erklarung¨ 277
CurriculumVitae 279
5Summary
Active galactic nuclei (AGN) are one of the many mysteries in the Universe. AGN hosts
a super massive black hole (SMBH) in its center surrounded by a rotating accretion disk,
andapowerfuljetisejectedalongthepoledirectionsoftheaccretiondisk. Thepowerful
jetisdefinitelythehighlightofAGN.Thoseextragalacticjetsappearstohavesuperlumi-
nal motions up to 60c, and they are very luminous and variable across the electromag-
netic spectrum. The jets can be highly polarized, which indicates the existence of strong
magnetic fields; they can have a highly bended morphology due to reasons we do not
completely understand. Astronomers have been studying AGN jets for the past decades
byperformingobservationsfromtheradiototheγ-rayband,applyingphysicaljetmodels
to the observed properties, and trying to put the pieces into the whole picture. We now
understandmanyaspectsoftheAGNphenomena,butasignificantpartisstillmissing.
The aim of this thesis is to study the extragalactic jets by using different approaches.
We investigate: (i) a bright feature in the jet of the radio galaxy M87 as observed us-
ing high-resolution VLBI technique; (ii) a multiband flare of the blazar PKS2052−47
by conducting a multifrequency campaign; (iii) the broadband spectral energy distribu-
tion (SED) of a radio-selected, statistically-complete sample of the most conspicuous
AGN in the Northern sky: the Monitoring Of Jets in Active galactic nuclei with VLBA
Experiments(MOJAVE)sample.
Very long baseline interferometry (VLBI) is a powerful technique that can resolve
distant AGN to parsec-scales by combining global radio antennas to perform together as
agianttelescopewitharadiusoftheearth. WiththeVLBItechnique,weareabletotrace
bright features being ejected from the center moving along the jet. In this thesis, we use
theVLBItechniquetodetectabrightknot80pcfromthecenteroftheradiogalaxyM87.
ItwassuggestedthattheHST-1knotwasthesitewhereaTeVflareofM87wasgenerated
from. By analyzing the VLBI data at 15GHz from 2000 to 2009, we detected HST-1
during2003and2007. Westudiedtheapparentspeed,thefluxvariability,andthespectral
propertiesofHST-1. AlthoughwefoundthatthelightcurveofthecompactHST-1region
at VLBA 15GHz peaked in 2005, we saw that the HST-1 region was very extended and
had a steep spectrum; the projected apparent speed of HST-1 was subluminal. Therefore,
ourresultsdonotcompletelysupportthehypothesis.
Studyingmultibandflaresisoneofthebestwaystodistinguishdifferentmechanisms
takenplaceinAGN.Currentjetmodelssuggestthattimedelaysbetweenmultibandflares
have different features while the emission mechanism differs. In this thesis, we studied
theflatspectrumradioquasarPKS2052−47,whichexperiencedanopticalflarefollowed
by a γ-ray flare in July 2009. We arranged a multiwavelength campaign from radio to
γ-rayaftertheblazar’sflare. Inthecampaign,VLBIobservationsbytheTrackingActive
Galactic Nuclei with Austral Milliarcsecond Interferometry (TANAMI) program are in-
7Summary
cluded in order to trace any change of jet morphology, if any; the millimeter radio flux
density was measured by the Atacama Pathfinder EXperiment (APEX); the optical and
the X-ray band observations were obtained by the Swift UV/Optical telescope (UVOT)
and X-ray telescope (XRT); the γ-ray observations were obtained by the Fermi Large
Area Telescope (LAT). We do not see significant change in the X-ray photon indices and
fluxesduringthe5-daySwift monitoringofthesource.
The broadband spectral energy distribution reflects the emission properties of AGN,
anditshowstheenergyoutputindifferentwavebands. Bysimulatingphysicaljetmodels
and reconstructing the broadband SED, one can probe the emission mechanism, the jet
composition,themagneticfield,thebulkvelocityinjet,andthestructureofAGN.Inthis
thesis, we study the broadband SED from the radio to the γ-ray band of a radio-selected
sample. TheMOJAVEprogramhasbeenmonitoring135radio-bright,statistically-complete
sampleofAGNusingtheVeryLongBaselineArray(VLBA)at15GHzforadecade,and
the MOJAVE sample is consisted of mostly blazars, which are AGN as seen jet-on. The
typical broadband SED of a blazar has a double-hump profile. It is believed that the
lower-energy hump is caused by the synchrotron emission from the AGN jet, and the
higher-energy hump is produced by the inverse-Compton (IC) up-scattering of the seed
photons from the jet or other external sources. We constructed a broadband SED catalog
of the MOJAVE sample, and we applied polynomial fits to the observed data at the low
and the high energy humps of the SED as a first approach to understand the properties of
the sources. The peak positions of the two humps can be derived from the polynomial fit
formanyoftheMOJAVEsourcesexceptforsomesourceshavingdeviatedSEDprofiles.
In this thesis, we try to understand the AGN puzzles by using different approaches.
We contributed in understanding the emission nature of AGN with novel techniques and
instruments,andoureffortshelptomakeastepforwardtorevealthewholepicture.
Keywords: VLBI,radio,X-ray,γ-ray,SED,broadband,multifrequency,M87,PKS2052−47,
MOJAVE.
8

Soyez le premier à déposer un commentaire !

17/1000 caractères maximum.