Doctoral theses
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| Identifier |
000409521 |
| Title |
Unvealing the physics of the most active of galaxies: connecting blazar theory and observations |
| Alternative Title |
Αποκαλύπτωντας την φυσική των πιο ενεργών γαλαξιών: συνδέοντας θεωρία με παρατηρήσεις στους blazar |
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Author
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Λιοδάκης, Ιωάννης Ε.
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Thesis advisor
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Παυλίδου, Βασιλική
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Reviewer
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Παπαδάκης, Ιωσήφ
Ζέζας, Ανδρέας
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| Abstract |
Blazars are the most extreme active galactic nuclei, with relativistic jets oriented within a small angle from
our line of sight. Because of their preferential alignment, their observed properties are distorted by relativistic
effects giving rise to unique phenomena such as boosted emission throughout the electromagnetic
spectrum, fast variability, and apparently superluminal motions of resolved jet components. Small variations
in the degree of alignment with the line of sight and/or velocity of the jet can result to a large scatter
in the resulting observable quantities from otherwise similar sources, complicating our understanding of
their intrinsic properties and the processes relevant to their central engines. As a result, despite decades
of systematic study of their variability across the electromagnetic spectrum, little is known regarding the
properties of blazars in the jet rest frame. For these reasons my thesis was focused on understanding and
quantifying the relativistic effects that dominate blazar emission.
To this end, I created population models based on robust observables unaffected by variability that describe
both the BL Lacs and FSRQs. Using these models I was able to advance our physical understanding
of blazars in the following ways: a) the variability and inverse-Compton Doppler factor methods are the optimal
available techniques for obtaining observational estimates of blazar Doppler factors which shows that
blazars while flaring reach equipartition; b) a significant fraction of deboosted counter-jets will be detected
by the next generation interferometers; c) the intrinsic distribution of the timescales of any class of events
seen in blazars can be accurately recovered within flux-limited samples even if we can not resolve the relativistic
effects on a blazar-by-blazar basis; I applied these findings on various types of blazars observations:
• F-GAMMA: Using the multi-wavelength radio light curves of the F-GAMMA program, I estimated
the variability Doppler factor for 58 γ-ray loud sources with an uncertainty of 16%on average, making
them the most accurate Doppler factors available to date. With these Doppler factors I found a strong
correlation between the intrinsic broad-band radio luminosity (2.6-142.33 GHz) and the black hole
mass extending nine orders of magnitude to stellar mass black holes. I uncovered the first ever scaling
to connect observer’s and rest frames in beamed sources.
• RoboPol: I recovered the intrinsic timescale distribution of the longest (in time) rotations of the
Electric Vector Position Angle seen in blazars. I found that that distribution is most likely a narrow
Gaussian.
• OVRO: Modeling the flux-density distribution of sources monitored by the 40-m radio telescope at
the Owens Valley Radio Observatory, I found that γ-ray loud sources are systematically more variable
in radio than γ-ray quiet sources suggesting a link between radio variability and γ-ray loudness.
• Reconciling Doppler factor estimates: Using archival X-ray and VLBI radio observations I reestimated
the inverse-Compton Doppler factors for 11 γ-ray loud sources accounting for the known
sources of error in the inverse-Compton Doppler factor method. By comparing my re-estimated values
with those from the literature I was able to definitively constrain the Doppler factor for five sources,
namely 3C273, 3C345, 3C454.3, PKS1510-089, and PKS1633+382.
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| Language |
English |
| Subject |
Jets |
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Relativistic effects |
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Supermassive black holes |
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Μπλέιζαρ |
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Πίδακες |
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Σχετικιστικά φαινόμενα |
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Υπερμαζικές μελανές οπές |
| Issue date |
2017-06-12 |
| Collection
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School/Department--School of Sciences and Engineering--Department of Physics--Doctoral theses
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Type of Work--Doctoral theses
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| Permanent Link |
https://elocus.lib.uoc.gr//dlib/9/8/b/metadata-dlib-1495795555-254761-28517.tkl
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| Views |
736 |
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