The relation between accretion rate and jet power in X-ray luminous elliptical galaxies

Using Chandra X-ray observations of 9 nearby, X-ray luminous ellipticals with good optical velocity dispersion measurements, we show that a tight correlation exists between the Bondi accretion rates calculated from the X-ray data and estimated black hole masses, and the power emerging from these systems in relativistic jets. The jet powers, inferred from the energies and timescales required to inflate the cavities observed in the surrounding X-ray emitting gas, can be related to the accretion rates by a power law model. A significant fraction (2.2^{+1.0}_{-0.7} per cent, for P_jet=10^{43} erg/s) of the energy associated with the rest mass of material entering the accretion radius eventually emerges in the jets. The data also hint that this fraction may rise slightly with increasing jet power. Our results have significant implications for studies of accretion, jet formation and galaxy formation. The tight correlation between P_Bondi and P_jet suggests that the Bondi formulae provide a reasonable description of the accretion process, despite the likely presence of magnetic pressure and angular momentum in the accreting gas, and that the accretion flows are approximately stable over timescales of a few million years. Our results show that the black hole `engines' at the hearts of large elliptical galaxies and groups can feed back sufficient energy to stem cooling and star formation, leading naturally to the observed exponential cut off at the bright end of the galaxy luminosity function.Comment: Accepted for publication in MNRAS. 10 pages, 4 figures. Includes an enhanced statistical analysis and some additional data. Conclusions unchange

Measuring Black Hole Spin using X-ray Reflection Spectroscopy

I review the current status of X-ray reflection (a.k.a. broad iron line) based black hole spin measurements. This is a powerful technique that allows us to measure robust black hole spins across the mass range, from the stellar-mass black holes in X-ray binaries to the supermassive black holes in active galactic nuclei. After describing the basic assumptions of this approach, I lay out the detailed methodology focusing on "best practices" that have been found necessary to obtain robust results. Reflecting my own biases, this review is slanted towards a discussion of supermassive black hole (SMBH) spin in active galactic nuclei (AGN). Pulling together all of the available XMM-Newton and Suzaku results from the literature that satisfy objective quality control criteria, it is clear that a large fraction of SMBHs are rapidly-spinning, although there are tentative hints of a more slowly spinning population at high (M>5*10^7Msun) and low (M<2*10^6Msun) mass. I also engage in a brief review of the spins of stellar-mass black holes in X-ray binaries. In general, reflection-based and continuum-fitting based spin measures are in agreement, although there remain two objects (GROJ1655-40 and 4U1543-475) for which that is not true. I end this review by discussing the exciting frontier of relativistic reverberation, particularly the discovery of broad iron line reverberation in XMM-Newton data for the Seyfert galaxies NGC4151, NGC7314 and MCG-5-23-16. As well as confirming the basic paradigm of relativistic disk reflection, this detection of reverberation demonstrates that future large-area X-ray observatories such as LOFT will make tremendous progress in studies of strong gravity using relativistic reverberation in AGN.Comment: 19 pages. To appear in proceedings of the ISSI-Bern workshop on "The Physics of Accretion onto Black Holes" (8-12 Oct 2012). Revised version adds a missing source to Table 1 and Fig.6 (IRAS13224-3809) and corrects the referencing of the discovery of soft lags in 1H0707-495 (which were in fact first reported in Fabian et al. 2009

A long hard look at MCG-6-30-15 with XMM-Newton and BeppoSAX

We summarise the primary results from a 320 ks observation of the bright Seyfert 1 galaxy MCG-6-30-15 with XMM-Newton and Beppo-SAX.Comment: 4 pages, 6 figures. Proc. of the meeting: "The Restless High-Energy Universe" (Amsterdam, The Netherlands), E.P.J. van den Heuvel, J.J.M. in 't Zand, and R.A.M.J. Wijers Ed

Atomic X-ray Spectroscopy of Accreting Black Holes

Current astrophysical research suggests that the most persistently luminous objects in the Universe are powered by the flow of matter through accretion disks onto black holes. Accretion disk systems are observed to emit copious radiation across the electromagnetic spectrum, each energy band providing access to rather distinct regimes of physical conditions and geometric scale. X-ray emission probes the innermost regions of the accretion disk, where relativistic effects prevail. While this has been known for decades, it also has been acknowledged that inferring physical conditions in the relativistic regime from the behavior of the X-ray continuum is problematic and not satisfactorily constraining. With the discovery in the 1990s of iron X-ray lines bearing signatures of relativistic distortion came the hope that such emission would more firmly constrain models of disk accretion near black holes, as well as provide observational criteria by which to test general relativity in the strong field limit. Here we provide an introduction to this phenomenon. While the presentation is intended to be primarily tutorial in nature, we aim also to acquaint the reader with trends in current research. To achieve these ends, we present the basic applications of general relativity that pertain to X-ray spectroscopic observations of black hole accretion disk systems, focusing on the Schwarzschild and Kerr solutions to the Einstein field equations. To this we add treatments of the fundamental concepts associated with the theoretical and modeling aspects of accretion disks, as well as relevant topics from observational and theoretical X-ray spectroscopy.Comment: 63 pages, 21 figures, Einstein Centennial Review Article, Canadian Journal of Physics, in pres

Weighing black holes with warm absorbers

We present a new technique for determining an upper limit for the mass of the black hole in active galactic nuclei showing warm absorption features. The method relies on the balance of radiative and gravitational forces acting on outflowing warm absorber clouds. It has been applied to 6 objects: five Seyfert 1 galaxies: IC 4329a, MCG-6-30-15, NGC 3516, NGC 4051 and NGC 5548; and one radio-quiet quasar: MR 2251-178. We discuss our result in comparison with other methods. The procedure could also be applied to any other radiatively driven optically thin outflow in which the spectral band covering the major absorption is directly observed.Comment: 13 pages, 6 figures, 7 tables. MNRAS accepte

Inversion of Plasmaspheric EUV Remote Sensing Data from the STP 72-1 Satellite

Observations of the extreme ultraviolet emission of helium ions at 30.4 nm can be used to study the global shape of the plasmasphere and its dynamical response to geomagnetic forcing. In order to retrieve number densities of plasmaspheric He+ from such observations, we have developed a new inversion technique based on discrete inverse theory, which uses the optical data to optimize a parameterized model of the He+ distribution. We apply this inversion technique to several orbits of data obtained from the Naval Research Laboratory extreme ultraviolet photometric experiment launched on the STP 72-1 satellite in October 1972. The inversion is limited to nighttime conditions where contamination from the topside ionosphere is minimal and where a simple parameterization of the He+ number density is applicable. We obtain excellent fits to the data; however, some of the retrieved model parameters have large uncertainties due to inadequate sampling of the plasmasphere. Our study shows that improved sampling using observations from different locations and view directions would significantly enhance the accuracy of the retrieved model parameters. Using a newly developed three-dimensional imaging tool to visualize the plasmaspheric regions being sampled remotely, we demonstrate that emission features observed from two of the STP 72-1 orbits originate beyond the plasmasphere. Estimated number densities of this feature are roughly consistent with observations of cold plasma seen at geosynchronous orbit by in situ experiments

Spatial differences in wind-driven sediment resuspension in a shallow, coastal estuary

Two locations approximately 11 km apart along the axis of the New River Estuary near Jacksonville, NC USA were continuously monitored for eight years. Included in the observations are vertical profiles of turbidity, temperature, salinity, chl-a, dissolved oxygen, pH and water velocity as well as local wind velocity. Differences between the two sites result from a number of factors, including bathymetry, wind strength, direction and fetch, estuarine morphology, tidal currents and sediment properties. The site near the head of the estuary, Morgan Bay, is deeper, experiences generally weaker winds and has less fetch in most directions. Stones Bay, the down-estuary site, is shallower, experiences stronger winds and has longer fetch, particularly in the prevailing wind directions. Current speeds also differ along the estuary with the down-estuary Stones Bay site being more tidal. The observations were used together with a simple wave model to analyze the estuarine turbidity response to different forcing mechanisms. Results suggest that sediments are resuspended primarily by wind-wave generated bottom stress at both locations. While turbidity is generally higher in Stones Bay than in Morgan Bay, turbidity as a function of the local wave-induced bottom stress (including forcing from all directions) is similar at both locations at low stress but diverges at higher stresses. At higher bottom stresses, turbidity in Stones Bay responds primarily to winds from the NE, S and NW while turbidity in Morgan Bay responds primarily to winds from the NW and S. Accounting for sediment resuspension within an approximate spatial advection scale around each of the observation sites, yields a similar turbidity vs bottom stress response curve for the three primary directions in Stones Bay and the S direction in Morgan Bay but a greater turbidity response for winds from the NW in Morgan Bay. In the latter case, waves are crossing the section of the New River Estuary just downstream of the confluence with the New River and are presumably encountering sediments that are more easily resuspended. Average sediment export is down-river with more sediment leaving Stones Bay than Morgan Bay

Thinking about growth : a cognitive mapping approach to understanding small business development

School of Managemen

Issues and Observations on Applications of the Constrained-Path Monte Carlo Method to Many-Fermion Systems

We report several important observations that underscore the distinctions between the constrained-path Monte Carlo method and the continuum and lattice versions of the fixed-node method. The main distinctions stem from the differences in the state space in which the random walk occurs and in the manner in which the random walkers are constrained. One consequence is that in the constrained-path method the so-called mixed estimator for the energy is not an upper bound to the exact energy, as previously claimed. Several ways of producing an energy upper bound are given, and relevant methodological aspects are illustrated with simple examples.Comment: 28 pages, REVTEX, 5 ps figure

Is the Sun Embedded in a Typical Interstellar Cloud?

The physical properties and kinematics of the partially ionized interstellar material near the Sun are typical of warm diffuse clouds in the solar vicinity. The interstellar magnetic field at the heliosphere and the kinematics of nearby clouds are naturally explained in terms of the S1 superbubble shell. The interstellar radiation field at the Sun appears to be harder than the field ionizing ambient diffuse gas, which may be a consequence of the low opacity of the tiny cloud surrounding the heliosphere. The spatial context of the Local Bubble is consistent with our location in the Orion spur.Comment: "From the Outer Heliosphere to the Local Bubble", held at International Space Sciences Institute, October 200