Catálogo de publicaciones - libros

Our knowledge of the phenomenology of accretion onto black holes has increased considerably thanks to ten years of observations with the RXTE satellite. In particular, it has been possible to schematize the outburst evolution of transient systems on the basis of their spectral and timing properties, and link them to the ejection of relativistic jets as observed in the radio. Here I concentrate on some aspects of this scheme, concentrating on the timing properties and on their link with jet ejection.

We analyse the effects of central AGN heating on the formation of galaxy clusters by means of hydrodynamical simulations. Besides self-gravity of dark matter and baryons, our approach includes radiative cooling and heating processes of the gas component and a multiphase model for a self-consistent treatment of star formation and SNe feedback [1]. Additionally, we incorporate a periodic feedback mechanism in the form of hot buoyant bubbles, injected into the ICM during the active phases of accreting central AGN. We find that AGN heating can substantially affect the properties of the stellar and gaseous components, in particular reducing the mass deposition rate onto the central cD galaxy, thereby offering an energetically plausible solution to the cooling flow problem.

The collapse of massive stars produces the most bizarre objects in the Universe.In the last ten years, astronomers have been successfully searching for real black holes in the Universe. There is now clear evidence for about 20 stellar mass black holes and a hundred thousand of supermassive black holes in galactic centers. All these black holes are expected to be rapidly rotating objects, and the energy stored in the rotation can be extracted by means of pulsar–like processes when strong magnetic fields are advected by accretion. In the last few years, progress in the simulation of such processes has enabled us to test the fundamental idea of the Blandford-Znajek mechanism and its relation to the launch and collimation of jets.

We propose a cosmological model in which Bose-Einstein condensation works as Dark Energy. We obtain a novel mechanism of inflation, very early formation of highly non-linear objects, and log-z periodicity in the BEC collapsing time.

We present a theoretical model for powering relativistic jets in Active Galactic Nuclei (AGN) from the accretion flow power, which can be increased by the power coming from the spindown of the black hole (BH). The BH rotational energy is transferred to the accretion disk through closed magnetic field lines that connect them. Adding these two energy sources, the accreting mass flow energy and the rotational energy, we derive the jets-launching power, as well as the efficiency of the jets drive for both the Eddington accretion rate and low accretion rates. In the case of low accretion rates, the efficiency of the jets drive can reach unity, that means almost all of the power used to drive the jets comes from the BH rotational energy.

Here we present our latest studies of relativistic jet formation in the vicinity of a rotating black hole where the reconnection process has been taken into account. In order to simplify the problem, we use Lagrangian formalism and develop a method which enables us to consider a magnetized plasma as a set of magnetic flux tubes [5,6]. Within the limits of the Lagrangian approach, we perform numerical simulations of the flux tube (nonlinear string) behavior which clearly demonstrates the process of relativistic jet formation in the form of outgoing torsional nonlinear aves. It turns out that the jet is produced deep inside the ergosphere where the flux tube takes away spinning energy from the black hole due to the nonlocal Penrose process [2]. This is similar to the Blandford-Znajek (BZ) mechanism to some extent [8], however, the string mechanism is essentially time dependent. It is shown that the leading part of the accreting tube gains negative energy and therefore has to stay in the ergosphere forever. Simultaneously, another part of the tube propagates along the spinning axis away from the hole with nearly the speed of light. As a result, the tube is continuously stretching and our mechanism is essentially time dependent. Obviously, such process cannot last infinitely long and we have to take into account the reconnection process. Due to reconnection, the topology of the flux tube is changed and it gives rise to a plasmoid creation which propagates along spin axis of the hole with relativistic speed carrying off the energy and angular momentum away from the black hole.

A semi-analytic approach to the relativistic transport equation with isotropic diffusion and consistent radiative losses is presented. It is based on the eigenvalue method first introduced in Kirk & Schneider [5]and Heavens & Drury [3]. We demonstrate the pitch-angle dependence of the cut-off in relativistic shocks.

We report a numerical result of jet formation driven by magnetic field due to a current loop around a rapidly rotating black hole. Beside the current loop, there are magnetic flux tubes that bridge the region between the ergosphere and the rotating disk, which we call ‘magnetic bridges’. The numerical result shows that the magnetic bridges can not be stationary and expand explosively to form a jet when the black hole rotates apidly.

A semi-analytic approach to the relativistic transport equation with isotropic diffusion and consistent radiative losses is presented. It is based on the eigenvalue method first introduced in Kirk & Schneider [5]and Heavens & Drury [3]. We demonstrate the pitch-angle dependence of the cut-off in relativistic shocks.

Past years have brought an increasingly wider recognition of the ubiquity of relativistic outflows (jets) in galactic nuclei, which has turned jets into an effective tool for investigating the physics of nuclear regions in galaxies. A brief summary is given here of recent results from studies of jets and nuclear regions in several active galaxies with prominent outflows.