PhD defense by Andreas Skielboe – University of Copenhagen

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PhD defense by Andreas Skielboe

Andreas Skielboe will defend his PhD thesis on Friday, January 13 at 1:00 PM in the DARK Lounge

Thesis title: Colossal creations of gravity -- From clusters of galaxies to active galactic nuclei

Supervisor: Darach Watson, DARK
Co-supervisor: Kristian Pedersen, DTU

PhD Committee:
Opponent: Andrea Biviano, INAF-Trieste
Opponent: Mike Goad, University of Leicester
Committee Chair: Marianne Vestergaard, DARK

Abstract: Gravity governs the evolution of the universe on the largest scales, and powers some of the most extreme objects at the centers of galaxies. Determining the masses and kinematics of galaxy clusters provides essential constraints on the large-scale structure of the universe, and act as direct probes of cosmological models, through the cluster mass function. Here, I present the first ever measurement of anisotropic kinematics in clusters of galaxies, providing evidence for anisotropic structure formation, and allowing assessment of systematics in galaxy cluster catalogs. While clusters of galaxies are the largest bound structures, supermassive black holes in active galactic nuclei (AGN) are the most massive compact objects. Probing the structure of AGN through reverberation mapping allows independent measurements of supermassive black hole masses. The masses of black holes in AGN have been shown to correlate with properties of the AGN host galaxy across orders of magnitude. In addition, black hole masses scale with the intrinsic luminosity of the AGN, suggesting that AGN can be used as independent distance probes for cosmology. Improving understanding of the structure of AGN paves the way for improved black hole mass measurements, as well as AGN cosmology. Here, I develop a new method for probing the structure of AGN using reverberation mapping. The method is based on regularized linear inversion with statistical modeling of the light curves. The method is applied to five nearby AGN, yielding velocity-resolved response maps for the Hβ emission line. The results can be compared to physical models of the broad emission line region in AGN, improving our understanding of active galaxies. While useful for studying AGN structure in individual objects, spectroscopic reverberation mapping campaigns require high cadence spectroscopy to isolate broad line emission from the underlying AGN continuum. This makes traditional reverberation mapping prohibitively expensive at higher redshifts ≳ 1, where the time delays between variations in the continuum and broad line emission is of the order of years. To address this issue, new methods for photometric reverberation mapping have recently been developed. I test the method of photometric reverberation mapping on data obtained from three nearby AGN, and discuss the possibility of using photometric reverberation mapping to constrain scaling relations at high redshift. These results show that photometric reverberation mapping can be a useful and cheap alternative to traditional spectroscopic reverberation mapping campaigns.

Link to thesis ––>>here