Observational Constraints on the Influence of Active Galactic Nuclei on the Evolution of Galaxies

Abstract

How to cite: HARRISON, CHRISTOPHER,MARK (2014) Observational constraints on the inuence of active galactic nuclei on the evolution of galaxies, Durham The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source• a link is made to the metadata record in Durham E-Theses• the full-text is not changed in any wayThe full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full Durham E-Theses policy for further details. Observational constraints on the influence of active galactic nuclei on the evolution of galaxies Christopher Mark Harrison AbstractAt the centre of every massive galaxy there resides a super-massive black hole that grew during periods of active galactic nuclei (AGN) activity. Current theoretical models of galaxy evolution invoke AGN-driven galaxy-scale feedback processes (e.g., the expulsion of gas through outflows) in order to reproduce many of the fundamental properties of galaxies and the intergalactic medium. This thesis uses observations to test some of the predictions of these feedback processes. I present integral field unit observations of AGN host galaxies to trace their ionised gas kinematics. The targets are eight high-redshift (z = 1.4 −3.4) ultra-luminous infrared galaxies, that are representative of rapidly evolving distant galaxies, and sixteen z < 0.2 luminous AGN, that were selected from a parent sample of ≈24,000 sources to be representative of the overall population. In both samples I identify galaxy-wide outflows (i.e., over kiloparsec scales), calculate their properties (e.g., mass outflow rates and energetics) and show that they are broadly consistent with theoretical predictions. I find that ionised outflows are common in z < 0.2 luminous AGN and are consistently extended over kiloparsec scales (in ≥ 70% of cases). I also use far-infrared Herschel data of X-ray detected z = 1-3 AGN to test the prediction that luminous AGN shut down star formation in their host galaxies. Using stacking techniques I show that, on average, X-ray detected AGN over a wide range of luminosities (i.e., L 2−8keV ≈ 10 42−45 erg s −1 ) have star formation rates that are consistent with non-active galaxies. This may imply that luminous AGN do not impact upon the star formation in their host galaxies. Overall, this thesis demonstrates that energetic galaxy-wide outflows are prevalent in AGN host galaxies; however, it also demonstrates that we still lack direct observational evidence that luminous AGN are suppressing star formation in their host galaxies.

Selected Chapters on Active Galactic Nuclei as Relativistic Systems

“…Figure 2: Schematic view of AGN spectral energy distribution. For a more detailed discussion see, e.g., Elvis et al (1994); Richards et al (2006); Harrison (2014). sion from a point-like source (nucleus of the galaxy), the radio image reveals two spatially separated knots of the relativistic jet.…”

Obscured Active Galactic Nuclei

“…The accretion of gas onto a SMBH is an exceptionally efficient process (≈ 5-42% of the mass is ultimately converted into emission, depending on the spin of the Schematic representation of the spectral energy distribution (SED) of an unobscured AGN (black curve), separated into the main physical components (as indicated by the colored curves) and compared to the SED of a star-forming galaxy (light grey curve). Figure from Harrison (2014), courtesy of C. M. Harrison. SMBH; e.g., Kerr 1963;Shapiro & Teukolsky 1983) and thus large luminosities can be produced for a modest amount of accretion, allowing for luminous AGN to be detected out to high redshifts. Indeed, luminous AGN are the most powerful non-explosive objects in the Universe.…”

Gamma-ray and Neutrino Signals from Accretion Disk Coronae of Active Galactic Nuclei

“…Stecker et al [27,35] made first quantitative estimate of the expected neutrino fluxes from Seyferts at the level of ∼ 3 × 10 −7 GeV cm −2 s −1 sr −1 at 1 PeV. However, in the 1990s, the detection of the X-ray spectral cutoffs [e.g., 42,43] and non-detection of Seyfert AGNs in the gamma-ray band [e.g., 44] ruled out the pair cascade scenario as a dominant source for X-ray emission of Seyferts, [38], Hickox and Alexander [39].…”

“…For the comparison, the SED of a star-forming galaxy (light grey curve) is also shown. Taken from Harrison[38], Hickox and Alexander[39].…”