Thesis (Ph. D.)--University of Hawaii at Manoa, 2001. / Includes bibliographical references (leaves 180-195). Also available on microfiche.

Supermassive black holes (BHs) and their host-galaxies are thought to evolve in tandem, with the energy output from the rapidly-accreting BH regulating star formation and the growth of the BH itself. The goal of better understanding this process has led to much work focussing on the properties of quasars at high redshifts, $z\gtrsim 2$, when cosmic star formation and BH accretion both peaked. At these redshifts, however, ground-based statistical studies of the quasar population generally have no access to the rest-frame optical spectral region, which is needed to measure H$\beta$-based BH masses and narrow line region outflow properties. The cornerstone of this thesis has been a new near-infrared spectroscopic catalogue providing rest-frame optical data on 434 luminous quasars at redshifts $1.5 \lesssim z \lesssim 4$. At high redshift, $z \gtrsim 2$, quasar BH masses are derived using the velocity-width of the CIV broad emission-line, based on the assumption that the observed velocity-widths arise from virial-induced motions. However, CIV exhibits significant asymmetric structure which suggests that the associated gas is not tracing virial motions. By combining near-infrared spectroscopic data (covering the hydrogen Balmer lines) with optical spectroscopy from SDSS (covering CIV), we have quantified the bias in CIV BH masses as a function of the CIV blueshift. CIV BH masses are shown to be over-estimated by almost an order of magnitude at the most extreme blueshifts. Using the monotonically increasing relationship between the CIV blueshift and the mass ratio BH(CIV)/BH(H$\alpha$) we derive an empirical correction to all CIV BH-masses. The correction depends only on the CIV line properties and therefore enables the derivation of un-biased virial BH mass estimates for the majority of high-luminosity, high-redshift, spectroscopically confirmed quasars. Quasars driving powerful outflows over galactic scales is a central tenet of galaxy evolution models involving 'quasar feedback' and significant resources have been devoted to searching for observational evidence of this phenomenon. We have used [OIII] emission to probe ionised gas extended over kilo-parsec scales in luminous $z\gtrsim2$ quasars. Broad [OIII] velocity-widths and asymmetric structure indicate that strong outflows are prevalent in this population. We estimate the kinetic power of the outflows to be up to a few percent of the quasar bolometric luminosity, which is similar to the efficiencies required in recent quasar-feedback models. [OIII] emission is very weak in quasars with large CIV blueshifts, suggesting that quasar-driven winds are capable of sweeping away gas extended over kilo-parsec scales in the host galaxies. Using data from a number of recent wide-field photometric surveys, we have built a parametric SED model that is able to reproduce the median optical to infrared colours of tens of thousands of AGN at redshifts $1 < z < 3$. In individual objects, we find significant variation in the near-infrared SED, which is dominated by emission from hot dust. We find that the hot dust abundance is strongly correlated with the strength of outflows in the quasar broad line region, suggesting that the hot dust may be in a wind emerging from the outer edges of the accretion disc.

Analysis and results are presented from EXOSAT observations of Seyfert type active galactic nuclei (AGN). The sample chosen for study axe 48 hard X-ray selected Seyfert type AGN including all 29 of the emission line AGN in the Piccinotti sample making this the largest such survey to date. EXOSAT, its detectors and methods of data analysis axe detailed, with emphasis on background subtraction techniques. One of the most important new results from EXOSAT data is the discovery that rapid variability (factor 2 over a few thousand seconds) is common in AGN. No evidence is found in the sample sources for any characteristic timescales of variability. Combining EXOSAT LE and ME data allowed us to obtain broad band X-ray spectra over the range 0.1-10 keV. Spectra in the &sim; 2-10 keV range are found to be well described by a simple power-law. The distribution of spectral indices across the sample can be approximated by a Gaussian distribution of mean a = 0.70 and a = 0.17. The spectra are not all consistent with this mean at the 90% confidence level and there must some intrinsic spread in AGN slopes. This spread can be constrained to 0.14. EXOSAT has also revealed a significant number of sources with complex soft X-ray spectra. These include spectra with a second spectral component at soft X-ray energies and sources with ''leaky" absorbing columns. Evidence that soft excess components occur in at least 50% of Seyfert type AGN, together with detection of rapid variability in the soft component provides the strongest support to date for an accretion disc model for AGN.

Modeling the highly energetic particles known as galactic cosmic rays is a highly nontrivial task. This process may require numerical simulations of the complex processes occurring continuously in the heliosphere due to changes in solar wind reflecting the solar activity. However, if reasonable assumptions are employed, considering only the diffusion and convection processes, the above phenomenon can be reduced to a simplified scenario that can be modeled analytically. The variable solar wind may be responsible for solar modulation of galactic cosmic rays. The aforementioned, in addition to the postulated role of cosmic rays in climate change, has led to the following questions: what is the relationship between galactic cosmic rays and solar wind? What are the possible effects of solar wind on galactic cosmic ray flux? In an attempt to address these questions, we have modeled the transport of galactic cosmic rays in the heliosphere theoretically. Our model describes solar modulation and transport of galactic cosmic rays in the heliosphere mainly in terms of the size of the heliosphere, timedependent solar wind, and a uniform diffusion coefficient. Our results suggest that solar wind causes significant decrease in galactic cosmic ray flux at r ≈ 1AU. In further investigation, we examine a short-time variation of the calculated flux, and the result is reflected by exposing a negative correlation of −0.988 ± 0.001 between galactic cosmic ray flux variation and the solar wind variation at r ≈ 1AU. This outcome may suggest that the higher the solar wind, the lower the galactic cosmic ray flux and vice-versa. For completeness, we compared our results with available observational data that shows a good fit to the model. Thus, based on our model results, it may be possible to predict that galactic cosmic ray flux variation and solar wind variation at Earth are negatively correlated.

>Magister Scientiae - MSc / The radio emission of radio-quiet active galactic nuclei (AGN) is thought to be from star formation and AGN related emission. I investigate these sources using 1.4 GHz radio data from FIRST and three optical quasars samples from the SDSS: (i) a volume-limited sample in the redshift range 0:2 < z < 0:4 defined by Mi < -23 (ii) magnitude-limited sample in the redshift range 1:8 < z < 2:5 defined by mr ≤ 18:5 and (iii) a uniform sample in the redshift range 0:2 < z < 3:5 (divided into 12 redshift bins). I constructed radio source counts and radio luminosity functions (RLFs) using the optical quasars detected in FIRST, which are consistent with literature results obtained using SDSS and NVSS quasars. There are differences at the low uxs end because of the different resolutions of FIRST and NVSS. I applied a median stack method to the 12 redshift bins of the uniform sample and found that the median ux decreases from 182 µJy in the lowest redshift bin to 39 µJy and the highest redshift bin. This is because the high redshift quasars although more luminous than their low redshift counterparts, they are much further away so they have lower uxes. I probed the quasar radio source counts to lower levels using reconstructed source counts obtained by applying the Bayesian stack technique. The reconstructed radio source counts were then used to constructed the quasar RLF to lower levels, where I found: (i) for z < 1 the constructed quasar RLF has the same slope as the detected quasars, suggesting that like the detect quasars their radio emission is dominated by AGN related emission (ii) above z = 1 the constructed RLF steepens with redshift, which suggests the strong link between accretion rate and radio jet power is gradually breaking down towards faint optical luminosities at high redshift. / National Astrophysics and Space Science Program (NASSP) and SKA Africa

Philosophiae Doctor - PhD / The faint radio population consisting of star forming galaxies (SFG) and radio-quiet active galactic nuclei (AGN) is important in the study of galaxy evolution. However, the bulk of the faint population is below the detection threshold of the current radio surveys. I study this population through a Bayesian-stacking technique that I have adapted to probe the radio luminosity function (RLF) below the typical 5σ detection threshold. The technique works by fitting RLF models to radio flux densities extracted at the position of galaxies selected from an auxiliary catalogue. I test the technique by adding Gaussian noise (σ) to simulated data and the RLF models are in agreement with the simulated data for up to three orders of magnitude (3 dex) below the detection threshold (5σ). The source of radio emission from radio quiet quasars (subset of AGN) is widely debated. I apply the technique to 1.4-GHz flux densities from the Faint Images of the Radio Sky at Twenty-cm survey (FIRST) at the positions of the optical quasars from the Sloan Digital Sky Survey (SDSS). The RLF models are constrained to 2 dex below the FIRST detection threshold. I found that the radio luminosity where radio-quiet quasars emerge coincides with the luminosity where SFGs are expected to start to dominate the RLF. This Implies that the radio emission of radio-quiet quasars and radio-quiet AGN, in general, could have a significant contribution from star formation in the host galaxies.

It is now well established that a substantial fraction of all galaxy assembly occurs in intense bursts of star formation and black hole accretion, but the role of these two modes and how much they affect one another remains unclear. We thus investigate this in three complementary studies. In the first, we assemble a sample of 513 quasars identified by the Sloan Digital Sky Survey with detections by Herschel. These objects span a redshift range of 0 < z < 4, and their SEDs give a mean SFR of ~1000M☉/year. When comparing these SFRs to the intrinsic properties of the quasars, we find no clear connections between the quasars and the ongoing star formation events in their hosts. We then look for evidence of AGN feedback in broad absorption line (BAL) quasars, as such features are indicative of outflowing material. We find that high-ionization BAL quasars have indistinguishable properties to those of classical quasars. In our second study, which describes an iron low-ionization BAL quasar, SDSS J121441.42-000137.8, our results are again consistent with no feedback. Thus, it seems unlikely that feedback plays a dominant role in quenching star formation at the extreme SFRs seen in our BAL objects. We lastly study the host of an optically-bright quasar, SDSS J160705.16+355358.6, with evidence of an ongoing merger. We create the Point Spread Function (PSF) using a star that is in the same part of the field as our object, a method which is relatively unexplored. By subtracting the PSF, we are able to extract some of the host properties. We compare two PSF creation methods and find the empirical approach to be superior. Fits to the SEDs of the two galaxies are consistent with both falling on or above the main sequence of star formation. It is additionally plausible that these two galaxies could coalesce into a single massive quiescent galaxy by z ~ 2, and thus serve as progenitors to this class of galaxy that has proven challenging to our understanding of galaxy assembly. / Doctor of Philosophy / Quasars are among some of the brightest objects in the Universe and are powered by supermassive black holes that are rapidly accreting new material. The light from these distant objects can be detected across the electromagnetic spectrum, with each wavelength regime offering new insight into their properties. Further, if we look at their spectra, the features appear redshifted, i.e. they are at longer wavelengths compared to the expected values on Earth. More distant objects have higher redshifts. This, coupled with the constant speed of light, tells us that light from a quasar that has reached us on Earth must have been emitted many years ago; in other words, quasars offer glimpses into the past and can be used study how our Universe has assembled over time. Star formation and quasar activity in galaxies have been shown to coexist across all redshifts. This suggests a deep connection between a galaxy's stellar and black hole mass assemblies. Both peak at z ~ 2, implying that a substantial amount of all galaxy assembly took place in high-redshift, dusty bursts of star formation and quasar activity. This dust absorbs light originally emitted at optical/UV wavelengths and reradiates it in the infrared, making infrared wavelengths the perfect regime in which to investigate the connection between the two processes. In this dissertation, I have focused specifically on quasars with detections at both optical and far-infrared (FIR) wavelengths to determine what effect, if any, quasars have on the galaxies in which they reside. The optical emission of these systems describes the properties of the quasars, while the FIR estimates star formation rates (SFRs) in their hosts. Many astronomers invoke something called feedback, in which the quasar regulates the host star formation, to align theory with observations. We search for evidence of this process in the very bright quasars located within extremely star-forming systems. We, however, find no such evidence. This could imply that, at the high luminosities of our systems, feedback is not the dominant effect in regulating star formation, but perhaps some host self-regulation is instead. It could also imply that the feedback timescale is much shorter than that of either quasar or extreme star formation activity, making direct observations of feedback difficult.

This dissertation investigates the signatures of electromagnetic radiation that may accompany two specific sources of gravitational radiation: the inspiral and merger of massive black hole binaries (MBHBs) in galactic nuclei, and the coalescence of black hole neutron star (BHNS) pairs. Part I considers the interaction of MBHBs, at sub-pc separations, with a circumbinary gas disk. Accretion rates onto the MBHB are calculated from two-dimensional hydrodynamical simulations as a function of the relative masses of the black holes. The results are applied to interpretation of the recent, sub-pc separation MBHB candidate in the nucleus of the periodically variable Quasar PG 1302-102. We advance an interpretation of the variability observed in PG 1302-102 as being caused by Doppler-boosted emission sourced by the orbital velocity of the smaller black hole in a MBHB with disparate relative masses. Part II considers BHNS binaries in which the black hole is large enough to swallow the neutron star whole before it is disrupted. As the pair nears merger, orbital motion of the black hole through the magnetosphere of the neutron star generates an electromotive force, a black-hole-battery, which, for the strongest neutron star magnetic field strengths, could power luminosities large enough to make the merging pair observable out to cosmic distances. Relativistic solutions for vacuum fields of a magnetic dipole near a horizon are given, and a mechanism for harnessing the power of the black-hole-battery is put forth in the form of a fireball emitting in hard X-rays to to gamma-rays.

Observations millimétriques de l'émission continue intégrée du plan galactique avec l'expérience Emilie

Thesis (Ph. D.)--Michigan State University. Dept. of Physics and Astronomy, 2008. / Title from PDF t.p. (viewed on July 22, 2009) Includes bibliographical references (leaves 170-174). Also issued in print.