Hector Aceves

The spatial clustering of ROSAT All-Sky Survey Active Galactic Nuclei IV. More massive black holes reside in more massive dark matter halos

This is the fourth paper in a series that reports on our investigation of the clustering properties of active galactic nuclei (AGN) identified in the ROSAT All-Sky Survey (RASS) and Sloan Digital Sky Survey (SDSS). In this paper we investigate the cause of the X-ray luminosity dependence of the clustering of broad-line, luminous AGN at 0.16<z<0.36. We fit the H-alpha line profile in the SDSS spectra for all X-ray and optically-selected broad-line AGN, determine the mass of the super-massive black hole (SMBH), M_BH, and infer the accretion rate relative to Eddington (L/L_EDD). Since M_BH and L/L_EDD are correlated, we create AGN subsamples in one parameter while maintaining the same distribution in the other parameter. In both the X-ray and optically-selected AGN samples we detect a weak clustering dependence with M_BH and no statistically significant dependence on L/L_EDD. We find a difference of up to 2.7sigma when comparing the objects that belong to the 30% least and 30% most massive M_BH subsamples, in that luminous broad-line AGN with more massive black holes reside in more massive parent dark matter halos at these redshifts. These results provide evidence that higher accretion rates in AGN do not necessarily require dense galaxy environments in which more galaxy mergers and interactions are expected to channel large amounts of gas onto the SMBH. We also present semi-analytic models which predict a positive M_DMH dependence on M_BH, which is most prominent at M_BH ~ 10^{8-9} M_SUN.

From the Tully–Fisher relation to the Fundamental Plane through mergers

We set up a series of self-consistent N-body simulations to investigate the Fundamental Plane of merger remnants of spiral galaxies. These last ones are obtained from a theoretical Tully- Fisher relation at z = 1, assuming a constant mass-to-light ratio within thecold dark matter cosmogony. Using a Sersic growth curve and an orthogonal fitting method, we find that the Fun- damental Plane of our merger remnants is described by the relation R e ∝ σ 1.48±0.01 I −0.75±0.01 , which is in good agreement with that reported from the Sloan Digital Sky Survey, R e ∝ σ 1.49±0.05 I −0.75±0.01 .H owever, the R 1/4 -profile leads to a Fundamental Plane given by R e ∝ σ 1.79±0.01 I −0.60±0.01 .I ngeneral, the correlation found in our merger remnants arises from ho- mology breaking (V 2 ∝ σ ν, R g ∝ R η )i ncombination with a mass scaling relation between the total and luminous mass, M ∝ M γ . Considering an orthogonal fitting method, it is found that 1.74 ν 1.79, 0.21 η 0.52 and 0.80 γ 0.90 depending on the adopted profile (Sersic or R 1/4 ). Ke yw ords: methods: N-body simulations - galaxies: elliptical and lenticular, cD - galaxies: formation - galaxies: fundamental parameters.

A dynamical stability study of Kepler Circumbinary planetary systems with one planet

To date, 17 circumbinary planets have been discovered. In this paper, we focus our attention on the stability of the Kepler circumbinary planetary systems with only one planet, i.e. Kepler-16, Kepler-34, Kepler-35, Kepler-38, Kepler-64 and Kepler-413. In addition to their intrinsic interest, the study of such systems is an opportunity to test our understanding of planetary system formation and evolution around binaries. The investigation is done by means of numerical simulations. We perform numerical integrations of the full equations of motion of each system with the aim of checking the stability of the planetary orbit. The investigation of the stability of the above systems consists of three numerical experiments. In the first one, we perform a long-term (1Gyr) numerical integration of the nominal solution of the six Kepler systems under investigation. In the second experiment, we look for the critical semimajor axis of the six planetary orbits, and finally, in the third experiment, we construct two-dimensional stability maps on the eccentricity–pericentre distance plane. Additionally, using numerical integrations of the nominal solutions we checked if these solutions were close to the exact resonance.

Dynamics of escaping Earth ejecta and their collision probabilities with different Solar System bodies

Abstract It has been suggested that the ejection of terrestrial crustal material to interplanetary space, accelerated in a large impact, may result in the interchange of biological material between Earth and other Solar System bodies. In this paper, we analyze the fate of debris ejected from Earth by means of direct numerical simulations of the dynamics of a large collection of test particles. This allows us to determine the probability and conditions for the collision of Earth ejecta with other planets of the Solar System. We also estimate the amount of particles falling back to Earth and colliding with the Moon as a function of time after being ejected. The Mercury-6 code is used to compute the dynamics of test particles under the gravitational effect of the planets in the Solar System and the Sun. A series of simulations are conducted with different ejection speeds, considering more than 10 5 particles in each case. We find that in general, the collision rates of Earth ejecta with Venus and the Moon, as well as the fall-back rates, are within an order of magnitude of results reported in the literature. By considering a larger number of particles than in all previous calculations we have also determined, on the basis of direct numerical simulations, the collision probability with Mars and, for the first time, computed collision probabilities with Jupiter and Saturn. We find that the collision probability with Mars is greater than values determined from collision cross section estimations previously reported.

STABILITY OF THE OUTER PLANETS IN MULTIRESONANT CONFIGURATIONS WITH A SELF-GRAVITATING PLANETESIMAL DISK

We study the effect of a massive planetesimal disk on the dynamical stability of the outer planets assuming, as has been suggested recently, that these were initially locked in a compact and multiresonant configuration as a result of gas-driven migration in a protoplanetary disk. The gravitational interaction among all bodies in our simulations is included self-consistently using the Mercury6.5 code. Several initial multiresonant configurations and planetesimal disk models are considered. Under such conditions a strong dynamical instability, manifested as a rapid giant planet migration and planetesimal disk dispersal, develops on a timescale of less than 40 Myr in most cases. Dynamical disk heating due to the gravitational interactions among planetesimals leads to more frequent interactions between the planetesimals and the ice giants Uranus and Neptune, in comparison to models in which planetesitmal-planetesimal interactions are neglected. On account of the rapid evolution of the multiresonant configurations obtained with fully self-consistent simulations, our results are inconsistent with the dynamical instability origin of the Late Heavy Bombardment as currently considered by the Nice model for the Solar System.

Numerical simulation of viscous-like flow in and around the plasma tail of a comet

Aims. We model the interaction of the solar wind with the plasma tail of a comet using numerical simulations, taking into account the effects of viscous-like forces. Methods. We developed a 2D hydrodynamical, two species, finite difference code to solve the time-dependent continuity, momentum, and energy conservation equations, and model the interaction of the solar wind with a cometary plasma tail. We compute the evolution of the plasma of cometary origin in the tail as well as the properties of the shocked solar wind plasma around it, as it transfers momentum on its passage by the tail. Velocity, density and temperature profiles across the tail are obtained. Several models with different flow parameters are considered to study the relative importance of viscous-like effects and the coupling between species on the flow dynamics. Results. Assuming a Mach number equal to 2 for the incident solar wind as it flows past the comet’s nucleus, the flow exhibits three transitions with location and properties depending on the Reynolds number of each species and on the ratio of the timescale for interspecies coupling to the crossing time of the free-flowing solar wind. By comparing our results with the measurements taken in situ by the Giotto spacecraft during its flyby of comet Halley, we constrain the flow parameters for both plasmas. Conclusions. In the context of our approximations, we find that our model is qualitatively consistent with the in situ measurements as long as the Reynolds number of both solar wind protons and cometary H2O+ ions is low, less than 100, suggesting that viscous-like momentum transport processes may play an important role in the interaction of the solar wind and the plasma environment of comets.

Formation of S0 galaxies through mergers - Evolution in the Tully-Fisher relation since z ~ 1

(Abridged version) We explore whether a scenario that combines an origin by mergers at

SCALING RELATIONS IN DISSIPATIONLESS SPIRAL-LIKE GALAXY MERGERS

z\sim

Spatial clustering and halo occupation distribution modelling of local AGN via cross-correlation measurements with 2MASS galaxies

1.8-1.5 with a subsequent passive evolution of the resulting S0 remnants since

Halo Occupation Distribution of AGNs throught Numerical Simulations

z \sim