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Parsec-Scale Properties of Gamma-Ray Bright Blazars Justin D University of New Mexico UNM Digital Repository Physics & Astronomy ETDs Electronic Theses and Dissertations 1-31-2013 Parsec-scale properties of gamma-ray bright blazars Justin D. Linford Follow this and additional works at: https://digitalrepository.unm.edu/phyc_etds Recommended Citation Linford, Justin D.. "Parsec-scale properties of gamma-ray bright blazars." (2013). https://digitalrepository.unm.edu/phyc_etds/36 This Dissertation is brought to you for free and open access by the Electronic Theses and Dissertations at UNM Digital Repository. It has been accepted for inclusion in Physics & Astronomy ETDs by an authorized administrator of UNM Digital Repository. For more information, please contact [email protected]. Candidate Department This dissertation is approved, and it is acceptable in quality and form for publication: Approved by the Dissertation Committee: , Chairperson Parsec-Scale Properties of Gamma-Ray Bright Blazars by Justin Dee Linford B.S., Physics, New Mexico Institute of Mining and Technology, 2003 M.S., Physics, University of New Mexico, 2007 DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy Physics The University of New Mexico Albuquerque, New Mexico December, 2012 c 2012, Justin Dee Linford iii Dedication For my grandparents, Bob (1923 - 2003) and Gerry (1928 - 2011), who taught me that an education is the most important gift a person can give themselves. iv Acknowledgments Many thanks are in order.... To my parents, Karen and Larry, thank you for all of your love, patience, and encouragement throughout my life. Without your support and constant interest in my education, I would not have made it to this point. Also, thank you for buying me a small book called “Stars and Planets” when I was a little kid. It was what first got me interested in astrophysics (and I still have it today). To my brother, Micah, thank you for keeping me more or less sane throughout my early adult life. You have been my closest friend and ally for as long as I can remember. To my extended family, thank you for your interest in my success and for always making me welcome. Special thanks to Uncle Roy for occasionally buying me a good meal while I was at Tech. To my many friends, I could not have gotten through the tough times without you; Patrick, Ben, Leanne, Azmat, Yaz, Guillermo, Marie, Shad, Mimi, Kwah, Greg, Emily, Kathy, Tiffany, Laura, and so many others. To the good teachers I had throughout my K-12 years, thank you for your dedication and hard work. In particular, I have to thank Don Mitchell and Charles Stewart for keeping my interest in science alive and Linda Kaye for teaching me how to be comfortable in front of an audience. To the bad teachers, thanks for teaching me that sometimes a person has to educate themselves. To my professors at New Mexico Tech, thank you for not making it easy on us. Special thanks to Dan Klingle- smith for constantly reminding me that astronomy is supposed to be fun, and to Jean Eilek for being my model of a truly outstanding professor. To Dave Suszcynsky and the great folks at Los Alamos National Laboratory in the ISR-2 division, thanks for a wonderful internship and for your continuing support. To John McGraw, thank for your support in earning my MS and for your help with getting into the PhD program at UNM. To Bill Miller, thank you for your role in shaping me as an instructor. In addition, thanks to Pete Zimmer and Steve Tremblay for your advice on how to get through this whole PhD process. To my collaborators Roger Romani, Tony Readhead, Joe Helmboldt, Steve Healey, Rodrigo Reeves, Joey Richards, Frank Schinzel, and Garret Cotter, thank you for all of your hard work on our published articles. To my dissertation committee Rich Rand, Ylva Pihlstr¨om, and Mark Gilmore, thank you for helping me get this document in the best shape possible. Special thanks to Dinesh Loomba for stepping in at the last minute. To Greg Taylor, thank you for all of your support, encouragement, and gentle cattle-prodding throughout this somewhat accelerated processes. You have been an amazing advisor. To my wife, Maria, I cannot say enough. My grandfather once said that I would know I had found the woman I was going to marry when I knew I could not live without her. I truly cannot imagine life without you. To our beautiful daughter Sarah, thank you for being such a good baby and allowing your father to get some sleep. v Parsec-Scale Properties of Gamma-Ray Bright Blazars by Justin Dee Linford B.S., Physics, New Mexico Institute of Mining and Technology, 2003 M.S., Physics, University of New Mexico, 2007 Ph.D., Physics, University of New Mexico, 2012 Abstract The parsec-scale radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been investigated using observations with the Very Long Baseline Array (VLBA). Comparisons between LAT and non-LAT detected samples were made using both archival and contemporaneous data. In total, 244 sources were used in the LAT-detected sample. This very large, radio flux-limited sample of active galactic nuclei (AGN) provides insights into the mechanism that produces strong gamma-ray emission. It has been found that LAT- detected BL Lac objects are very similar to the non-LAT BL Lac objects in most properties, although LAT BL Lac objects may have longer jets. The LAT flat spec- trum radio quasars (FSRQs) are significantly different from non-LAT FSRQs and are likely extreme members of the FSRQ population. Archival radio data indicated that there was no significant correlation between radio flux density and gamma-ray flux, especially at lower flux levels. However, contemporaneous observations showed a strong correlation. Most of the differences between the LAT and non-LAT popula- tions are related to the cores of the sources, indicating that the gamma-ray emission vi may originate near the base of the jets (i.e., within a few pc of the central engine). There is some indication that LAT-detected sources may have larger jet opening angles than the non-LAT sources. Strong core polarization is significantly more common among the LAT sources, suggesting that gamma-ray emission is related to strong, uniform magnetic fields at the base of the jets of the blazars. Observations of sources in two epochs indicate that core fractional polarization was higher when the objects were detected by the LAT. The low-synchrotron peaked (LSP) BL Lac object sample shows indications of contamination by FSRQs which happen to have undetectable emission lines. There is evidence that the LSP BL Lac objects are more strongly beamed than the rest of the BL Lac object population. vii Contents List of Figures xiv List of Tables xvii Glossary xviii 1 Introduction 1 1.1 VLBI.................................... 1 1.2 Fermi Gamma-ray Space Telescope ................... 2 1.3 AGN&Blazars.............................. 3 1.4 SynchrotronEmission........................... 5 1.5 InverseComptonEmission . 12 1.5.1 SynchrotronSelfCompton . 15 1.5.2 MultipleScatterings . 18 1.6 Polarization&FaradayRotation . 20 1.6.1 MonochromaticLight. 20 viii Contents 1.6.2 TheStokesParameters . 23 1.6.3 Quasi-Monochromatic Waves and Fractional Polarization ... 24 1.6.4 FaradayRotation . 25 1.7 ThisDissertation ............................. 28 1.7.1 Goals................................ 28 1.7.2 DissertationOrganization . 29 2 Gamma-Ray Blazars in VIPS 30 2.1 Introduction................................ 31 2.2 SampleDefinition............................. 33 2.3 Gamma-rayFluxandRadioFluxDensity . 34 2.3.1 RedshiftSelectionEffect . 34 2.3.2 Gamma-rayFluxvs. RadioFluxDensity . 36 2.3.3 RadioFluxDensity. 38 2.4 MorphologicalComparison. 38 2.4.1 SourceClasses........................... 38 2.4.2 Polarization ............................ 39 2.4.3 CoreBrightnessTemperature . 40 2.4.4 JetOpeningAngle ........................ 41 2.4.5 CoreFraction ........................... 42 2.4.6 Jet Bending, Length, and Brightness Temperature . ... 43 ix Contents 2.5 NotesonIndividualSources . 44 2.5.1 LowCoreBrightnessTemperature. 44 2.5.2 HighRedshift ........................... 45 2.5.3 RadioGalaxies .......................... 45 2.6 Discussion................................. 47 2.6.1 BLLacObjects.......................... 48 2.6.2 FSRQs............................... 49 2.6.3 RadioGalaxies .......................... 51 2.6.4 Constraints on the γ-rayEmittingRegion . 51 2.7 Conclusions ................................ 52 3 ContemporaneousObservationsofLATBlazars 67 3.1 Introduction................................ 68 3.2 SampleDefinition............................. 69 3.3 VLBADataReduction .......................... 71 3.4 Gamma-rayFluxandRadioFluxDensity . 72 3.4.1 RedshiftSelectionEffect . 72 3.4.2 Gamma-rayFluxversusRadioFluxDensity . 73 3.4.3 RadioFluxDensity. 74 3.5 ArchivalversusContemporaneous . 75 3.5.1 RadioFluxDensityVariability . 75 x Contents 3.5.2 Core Brightness Temperature Variability . .. 77 3.5.3 CorePolarizationVariability. 77 3.6 LATDetectedversusnon-LATDetected . 78 3.6.1 SourceClasses........................... 78 3.6.2 CoreBrightnessTemperature . 79 3.6.3 JetBrightnessTemperature . 79 3.6.4 JetOpeningAngle,Bending,andLength . 80 3.6.5 Polarization ............................ 82 3.7 NotesonIndividualSources . 83 3.7.1 LowRedshiftObjects. 83 3.7.2 AGN................................ 84 3.7.3 AGNwithNoOpticalID. 89 3.7.4 UnidentifiedSources . 94 3.8 DiscussionandConclusions . 95 3.8.1 PolarizationandMagneticFields . 95 3.8.2 OpeningAngles.........................
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