Browsing by Author "Barthel, Peter"
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Item Disentangling the AGN and star-formation contributions to the radio-X-ray emission of radio-loud quasars at 1(2020-11-11) Azadi, Mojegan; Wilkes, Belinda; Kuraszkiewicz, Joanna; McDowell, Jonathan; Siebenmorgen, Ralf; Ashby, Matthew; Birkinshaw, Mark; Worrall, Diana; Abrams, Natasha; Barthel, Peter; Fazio, Giovanni; Haas, Martin; Hyman, Sóley; Martínez-Galarza, Rafael; Meyer, EileenTo constrain the emission mechanisms responsible for generating the energy powering the active galactic nuclei (AGN) and their host galaxies, it is essential to disentangle the contributions from both as a function of wavelength. Here we introduce a state-of-the-art AGN radio-to-X-ray spectral energy distribution fitting model (ARXSED). ARXSED uses multiple components to replicate the emission from the AGN and their hosts. At radio wavelengths, ARXSED accounts for radiation from the radio structures (e.g., lobes,jets). At near-infrared to far-infrared wavelengths, ARXSED combines a clumpy medium and a homogeneous disk to account for the radiation from the torus. At the optical-UV and X-ray, ARXSED accounts for the emission from the accretion disk. An underlying component from radio to UV wavelengths accounts for the emission from the host galaxy. Here we present the results of ARXSED fits to the panchromatic SEDs of 20 radio-loud quasars from the 3CRR sample at 170%) to the submm luminosity in half the sample, impacting the submm-based star formation rate estimates. We present the median intrinsic SED of the radio-loud quasars at z>1 and find that the median SED of \cite{Elvis1994} is unable to describe the SED of the radio-selected AGN at z>1. The AGN torus and accretion disk parameters inferred from our fitting technique agree with those in the literature for similar samples. We find that the orientation of the torus/accretion disk does not line up with the inclination of the radio jets in our sample.Item Powerful Radio-Loud Quasars are Triggered by Galaxy Mergers in the Cosmic Bright Ages(2023-05-19) Breidin, Peter; Chiaberge, Marco; Lambrides, Erini; Meyer, Eileen T.; Willner, S. P.; Hilbert, Bryan; Haas, Martin; Miley, George; Perlman, Eric S.; Barthel, Peter; O'Dea, Christopher P.; Capetti, Alessandro; Wilkes, Belinda; Baum, Stefi A.; Macchetto, Duccio F.; Tremblay, Grant; Norman, ColinWhile supermassive black holes are ubiquitous features of galactic nuclei, only a small minority are observed during episodes of luminous accretion. The physical mechanism(s) driving the onset of fueling and ignition in these active galactic nuclei (AGN) are still largely unknown for many galaxies and AGN-selection criteria. Attention has focused on AGN triggering by means of major galaxy mergers gravitationally funneling gas towards the galactic center, with evidence both for and against this scenario. However, several recent studies have found that radio-loud AGN overwhelmingly reside in ongoing or recent major galaxy mergers. In this study, we test the hypothesis that major galaxy mergers are important triggers for radio-loud AGN activity in powerful quasars during cosmic noon (1 < z < 2). To this end, we compare Hubble Space Telescope WFC3/IR observations of the z > 1 3CR radio-loud broad-lined quasars to three matched radio-quiet quasar control samples. We find strong evidence for major-merger activity in nearly all radio-loud AGN, in contrast to the much lower merger fraction in the radio-quiet AGN. These results suggest major galaxy mergers are key ingredients to launching powerful radio jets. Given many of our radio-loud quasars are blue, our results present a possible challenge to the "blow-out" paradigm of galaxy evolution models in which blue quasars are the quiescent end result following a period of red quasar feedback initiated by a galaxy merger. Finally, we find a tight correlation between black hole mass and host galaxy luminosity for these different high-redshift AGN samples inconsistent with those observed for local elliptical galaxies.