Revista Mexicana De Astronomia Y Astrofisica, 2009
We report optical and near-infrared imaging and photometry for the IRAS 02290+2533 source. Observ... more We report optical and near-infrared imaging and photometry for the IRAS 02290+2533 source. Observations show that this source is a system of three galaxies. Two galaxies (A and B), which are separated in projection ≈ 10 kpc, show some evidence of tidal interaction between them. The spiral-like Galaxy B presents a disk-wide Halpha emission and a high infrared luminosity, from
An introductory exposition of Chandrasekhar's gravitational dynamical friction, appropriate f... more An introductory exposition of Chandrasekhar's gravitational dynamical friction, appropriate for an undergraduate class in mec hanics, is presented. This friction results when a massive particle moving through a ``sea'' of much lighter star particles experiences a retarding force du to an exchange of energy and momentum. General features of dynamical friction are presented, both in an elementary and in a
Sinking particles have been collected at bi-weekly intervals from three different water depths in... more Sinking particles have been collected at bi-weekly intervals from three different water depths in the eastern region of the Cariaco Basin since late 1995 as part of the CARIACO time series study. A subset of samples collected from 1997 to 1999 have been analyzed by alkaline CuO oxidation to characterize the magnitude and composition of the organic matter exported from
We present results of the numerical simulation of the dynamics of newly born O+ ions in condition... more We present results of the numerical simulation of the dynamics of newly born O+ ions in conditions representative of the magnetic polar regions of the martian ionosheath. The magnetic field configuration is constructed as a superposition of a uniform component and a strongly fluctuating, turbulent component characterized by a power law spectrum. The dynamics of a large number of particles,
On the basis of the results of 2D, multispecies numerical simulations of the viscous-like interac... more On the basis of the results of 2D, multispecies numerical simulations of the viscous-like interaction of the solar wind with the upper ionosphere of Venus, we review previous estimations of Perez-de-Tejada (2004,2006) of the rate of removal of ionospheric material by the solar wind. As numerical simulations indicate, after a significant change in the IMF direction, when the erosion of
Revista Mexicana De Astronomia Y Astrofisica, 1999
Optical red spectra of a set of 18 bright barred spiral galaxies are presented. The study is aime... more Optical red spectra of a set of 18 bright barred spiral galaxies are presented. The study is aimed at determining the local kinematics, and the physical conditions of ionized gas in the compact nucleus (inside a diameter of 5") and in the circumnuclear regions (inside a diameter of 20"). Only 8 galaxies showed bright emission from their east and west
We determine both representations of the Fundamental Plane [R e ∝ σ a 0 I −b e andR e ∝ (σ 2 0 I ... more We determine both representations of the Fundamental Plane [R e ∝ σ a 0 I −b e andR e ∝ (σ 2 0 I −1 e ) λ ] and the luminosity-effective phase space density (L ∝ f −γ e ) scaling relation for N -body remnants of binary mergers of spiral-like galaxies. The main set of merger simulations involves a mass-ratio of the progenitors in the range of about 1:1 to 1:5, harboring or not a bulge-like component, and are constructed using a cosmological motivated model. Equal-mass mergers are also considered. Remnants lead to average values for the scaling indices of a ≈ 1.6, b ≈ 0.6, λ ≈ 0.7, and γ ≈ 0.65. These values are consistent with those of K-band observations ) of ellipticals: a ≈ 1.5, b ≈ 0.8, λ ≈ 0.7, and γ ≈ 0.60. The b index is, however, not well reproduced. This study does not allow us to establish a conclusive preference for models with or without a bulge as progenitors. Our results indicate that the L-f e and FP scalings might be determined to a large extent by dissipationless processes, a result that appears to be in contradiction to other dissipationless results.
We investigate the clustering properties of ∼1550 broad-line active galactic nuclei (AGNs) at z =... more We investigate the clustering properties of ∼1550 broad-line active galactic nuclei (AGNs) at z = 0.25 detected in the ROSAT All-Sky Survey (RASS) through their measured cross-correlation function with ∼46,000 luminous red galaxies (LRGs) in the Sloan Digital Sky Survey. By measuring the cross-correlation of our AGN sample with a larger tracer set of LRGs, we both minimize shot noise errors due to the relatively small AGN sample size and avoid systematic errors due to the spatially varying Galactic absorption that would affect direct measurements of the auto-correlation function (ACF) of the AGN sample. The measured ACF correlation length for the total RASS-AGN sample ( L 0.1-2.4 keV X = 1.5 × 10 44 erg s −1 ) is r 0 = 4.3 +0.4 −0.5 h −1 Mpc and the slope γ = 1.7 +0.1 −0.1 . Splitting the sample into low and high L X samples at L 0.5-10 keV X = 10 44 erg s −1 , we detect an X-ray luminosity dependence of the clustering amplitude at the ∼2.5σ level. The low L X sample has r 0 = 3.3 +0.6 −0.8 h −1 Mpc (γ = 1.7 +0.4 −0.3 ), which is similar to the correlation length of blue star-forming galaxies at low redshift. The high L X sample has r 0 = 5.4 +0.7 −1.0 h −1 Mpc (γ = 1.9 +0.2 −0.2 ), which is consistent with the clustering of red galaxies. From the observed clustering amplitude, we infer that the typical dark matter halo (DMH) mass harboring RASS-AGN with broad optical emission lines is log (M DMH /(h −1 M )) = 12.6 +0.2 −0.3 , 11.8 +0.6 −∞ , 13.1 +0.2 −0.4 for the total, low L X , and high L X RASS-AGN samples, respectively.
Optical broadband BVRI observations of 54 galaxies selected from the Catalog of Isolated Triplets... more Optical broadband BVRI observations of 54 galaxies selected from the Catalog of Isolated Triplets of Galaxies in the Northern Hemisphere have been carried out at San Pedro Mártir National Observatory to evaluate their photometric and morphological properties. We complement our analysis with Two-Micron All Sky Survey (2MASS) and Sloan Digital Sky Survey (SDSS) images and look for signatures likely related to interactions/mergers. We report apparent/absolute BVRI magnitudes and colors for the 54 galaxies. The membership of these galaxies is re-evaluated by imposing a reasonable condition of concordant redshifts upon the original selection criteria, rendering a final sample of 34 galaxies in 13 triplets, 12 galaxies in close pairs, and 8 galaxy outliers. The triplets are spiral-dominated systems in different dynamical stages from loosely interacting to almost merged objects. The incidence fraction of features likely associated with interactions is ∼56%, similar to those found in northern and southern compact groups. The average fraction of bars is 35% with a mean value of maximum bar ellipticity max ≈ 0.4. Bars are hosted in the late-type triplet spirals, almost twice more than in early-type spirals. The global fraction of rings is 20%, all in the late-type components. The overdensity of triplets with respect to the background and their current dynamical status, as devised from our estimate of their dynamical parameters, namely the harmonic radius R H , velocity dispersion σ , dimensionless crossing time H 0 τ c , and virial mass M V , appear to be sufficient to favor galaxy transformations similar to those seen in dense groups and clusters. By contrast, the lower fraction of bonafide ellipticals and the relatively higher fraction of late-type spirals make these triplets essentially different from the Hickson Compact Groups and more representative of the field. A modest 1.6 enhancement factor in the optical luminosity of the late-type triplet components relative to an isolated galaxy control sample is also interpreted as consistent with interactions in physically bounded aggregates. Our results lead us to suggest that non-negligible populations of physical triplets might be found in complete and well-observed samples. We provide individual mosaics for the 54 galaxies containing (1) logarithmic-scaled R-band images, (2) R-band sharp/filtered images, (3) (B − I) color index maps, (4) RGB images from the SDSS database, (5) co-added J + H + K images generated from the 2MASS archives that were also sharp/filtered, and (6) , position angle radial profiles from a surface photometry analysis of (a) the R band and (b) the co-added near-infrared images, all used for the present analysis.
Monthly Notices of the Royal Astronomical Society, 2006
Sérsic parameters characterising the density profiles of remnants formed in collision-less disc g... more Sérsic parameters characterising the density profiles of remnants formed in collision-less disc galaxy mergers are obtained; no bulge is included in our simulations. For the luminous component we find that the Sérsic index is n ∈ (1.5, 5.3) with n ≈ 3 ± 1 and an effective radius of R e ∈ (1.6, 12.9) kpc with R e ≈ 5 ± 3 kpc. The mean values of these quantities increases as the radial interval of fitting is reduced. A strong correlation of n with the central projected density I 0 is found (n ∝ I −0.14 0
Se estudian los efectos que fluctuaciones magnéticas turbulentas tienen sobre la dinámica de ione... more Se estudian los efectos que fluctuaciones magnéticas turbulentas tienen sobre la dinámica de iones pickup de O + en las regiones polares magnéticas de la ionofunda de Marte. En particular estudiamos su efecto en los perfiles de velocidad promedio como función de la altitud sobre los polos, con el fin de comparar con datos reciente del Mars Express; que indican que su velocidad promedio es pequeña y esencialmente en la dirección antisolar. Se encuentra que, aunque las fluctuaciones magnéticas resultan en desviaciones del simple movimiento de arrastre girotrópico, aun amplitudes de fluctuación más grandes que las medidas, no son capaces de reproducir los perfiles verticales de velocidad de los iones de O + . Concluímos que otro mecanismo físico, diferente a uno puramente de dinámica de partículas cargadas, está actuando sobre estos iones en el terminador Marciano. Una posibilidad es que exista una interacción tipo-viscosa entre el viento solar y la ionosfera Marciana a bajas altitudes.
It has been suggested that the ejection to interplanetary space of terrestrial crustal material a... more It has been suggested that the ejection to interplanetary space of terrestrial crustal material 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 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 ejecta with other planets of the Solar System. We also estimate the amount of particles falling-back to Earth as a function of time after being ejected.
Context. In this paper we study the dynamics of the υ Andromedae planetary system proposed by . W... more Context. In this paper we study the dynamics of the υ Andromedae planetary system proposed by . We focus on the study of the 3:1 Mean Motion Resonance (hereafter MMR) between υ Andromedae-d and the recently discovered υ Andromedae-e (hereafter υ And-d and υ And-e). Aims. Numerical simulations of the dynamics of the four planet system are conducted. Methods. The previously reported apsidal resonance between υ And-c and υ And-d is confirmed. In addition, we find that υ And-d and υ And-e are also in an apsidal resonance condition. Results. Our results further indicate that the υ Andromedae planetary system configuration is in the middle of a stability island in the semimajor axis-eccentricity domain. Additionally, we performed numerical integrations of the planetary configuration over 500 Myr and found it to be stable. Conclusions. We conclude that, within the uncertainties in the value of the orbital parameters, it is likely that υ Andromedae planetary system will remain stable for a long timescale.
A partir del análisis de la dinámica de iones O + de origen ionosférico en la ionofunda de Marte,... more A partir del análisis de la dinámica de iones O + de origen ionosférico en la ionofunda de Marte, acelerados por el campo eléctrico convectivo del viento solar (pick up ions), determinamos su velocidad promedio sobre los polos magnéticos del planeta. Estas velocidades se comparan con mediciones in situ de la nave Mars Express. Con base en nuestros resultados encontramos que las velocidades de los iones O + medidos sobre los polos magnéticos del planeta, que son esencialmente en la dirección antisolar, con componentes y y z muy pequeñas, no se pueden explicar en términos del movimiento girotrópico de las partículas exclusivamente. Concluimos entonces que la velocidad de los iones O + sobre los polos magnéticos del planeta resultan de la acción de fuerzas de tipo viscoso que transfieren momento entre el viento solar y el plasma ionosférico en la ionofunda de Marte.
... Héctor Aceves, Fidel Cruz, and Héctor Velázquez: Instituto de Astronomıa, Universidad Naciona... more ... Héctor Aceves, Fidel Cruz, and Héctor Velázquez: Instituto de Astronomıa, Universidad Nacional Autónoma de México, Apdo ... Aguilar, LA, & Merritt, D. 1990, ApJ, 354, 33 Bender, R. 1988, A&A, 74, 385 Binney, J., & Merrifield, M. 1998, Galactic Astronomy (Princenton: Princenton ...
Abstract. The projected (PME) and virial mass estimator (VME) are revisited and tested using an N... more Abstract. The projected (PME) and virial mass estimator (VME) are revisited and tested using an N-body equilibrium system. It is found that the PME can overestimate the mass by ≈ 40% if a cluster of galaxies is sampled only about its effective radius, Re. The exact value of ...
Abstract. The two most common mass estimators that use velocity dispersions and positions of obje... more Abstract. The two most common mass estimators that use velocity dispersions and positions of objects in a stel-lar system, the virial mass estimator (VME) and the pro-jected mass estimator (PME), are revisited and tested us-ing N-body experiments. We consider here only ...
Aims. To model the interaction of the solar wind with the plasma tail of a comet by means of nume... more Aims. To model the interaction of the solar wind with the plasma tail of a comet by means of numerical simulations, taking into account the effects of viscous-like forces.
ABSTRACT We present results from two recent projects on the correlation function analysis of AGNs... more ABSTRACT We present results from two recent projects on the correlation function analysis of AGNs from all-sky surveys to investigate the low-redshift clustering properties of AGNs. We have used ROSAT All-Sky Survey sources identified with broad line AGNs with the Sloan Digital Sky Survey (SDSS). By investigating the cross-correlation function (CCF) between these AGNs and SDSS galaxies, we have overcome the statistical limitation caused by the small number of AGNs. This has allowed us to investigate the luminosity-dependence of AGN clustering, where luminous AGNs (with Log LX ? 44) cluster more strongly, like red galaxies, than lower luminosity ones, which cluster like blue galaxies. With a novel method of applying Halo Occupation Distribution modeling to the CCF, we found, not only the mean mass of ˜10^13 Msol of DMHs occupied by the AGNs, but also the occupation distribution of the AGNs among the DMHs. As a separate project, we used AGNs in the Swift BAT Survey, which contains both un-obscured (type I) and obscured (type II) AGNs to investigate its auto-correlation function, finding similar results. We discuss the improvements on low-redshift AGN clustering studies expected from MAXI.
Revista Mexicana De Astronomia Y Astrofisica, 2009
We report optical and near-infrared imaging and photometry for the IRAS 02290+2533 source. Observ... more We report optical and near-infrared imaging and photometry for the IRAS 02290+2533 source. Observations show that this source is a system of three galaxies. Two galaxies (A and B), which are separated in projection ≈ 10 kpc, show some evidence of tidal interaction between them. The spiral-like Galaxy B presents a disk-wide Halpha emission and a high infrared luminosity, from
An introductory exposition of Chandrasekhar's gravitational dynamical friction, appropriate f... more An introductory exposition of Chandrasekhar's gravitational dynamical friction, appropriate for an undergraduate class in mec hanics, is presented. This friction results when a massive particle moving through a ``sea'' of much lighter star particles experiences a retarding force du to an exchange of energy and momentum. General features of dynamical friction are presented, both in an elementary and in a
Sinking particles have been collected at bi-weekly intervals from three different water depths in... more Sinking particles have been collected at bi-weekly intervals from three different water depths in the eastern region of the Cariaco Basin since late 1995 as part of the CARIACO time series study. A subset of samples collected from 1997 to 1999 have been analyzed by alkaline CuO oxidation to characterize the magnitude and composition of the organic matter exported from
We present results of the numerical simulation of the dynamics of newly born O+ ions in condition... more We present results of the numerical simulation of the dynamics of newly born O+ ions in conditions representative of the magnetic polar regions of the martian ionosheath. The magnetic field configuration is constructed as a superposition of a uniform component and a strongly fluctuating, turbulent component characterized by a power law spectrum. The dynamics of a large number of particles,
On the basis of the results of 2D, multispecies numerical simulations of the viscous-like interac... more On the basis of the results of 2D, multispecies numerical simulations of the viscous-like interaction of the solar wind with the upper ionosphere of Venus, we review previous estimations of Perez-de-Tejada (2004,2006) of the rate of removal of ionospheric material by the solar wind. As numerical simulations indicate, after a significant change in the IMF direction, when the erosion of
Revista Mexicana De Astronomia Y Astrofisica, 1999
Optical red spectra of a set of 18 bright barred spiral galaxies are presented. The study is aime... more Optical red spectra of a set of 18 bright barred spiral galaxies are presented. The study is aimed at determining the local kinematics, and the physical conditions of ionized gas in the compact nucleus (inside a diameter of 5") and in the circumnuclear regions (inside a diameter of 20"). Only 8 galaxies showed bright emission from their east and west
We determine both representations of the Fundamental Plane [R e ∝ σ a 0 I −b e andR e ∝ (σ 2 0 I ... more We determine both representations of the Fundamental Plane [R e ∝ σ a 0 I −b e andR e ∝ (σ 2 0 I −1 e ) λ ] and the luminosity-effective phase space density (L ∝ f −γ e ) scaling relation for N -body remnants of binary mergers of spiral-like galaxies. The main set of merger simulations involves a mass-ratio of the progenitors in the range of about 1:1 to 1:5, harboring or not a bulge-like component, and are constructed using a cosmological motivated model. Equal-mass mergers are also considered. Remnants lead to average values for the scaling indices of a ≈ 1.6, b ≈ 0.6, λ ≈ 0.7, and γ ≈ 0.65. These values are consistent with those of K-band observations ) of ellipticals: a ≈ 1.5, b ≈ 0.8, λ ≈ 0.7, and γ ≈ 0.60. The b index is, however, not well reproduced. This study does not allow us to establish a conclusive preference for models with or without a bulge as progenitors. Our results indicate that the L-f e and FP scalings might be determined to a large extent by dissipationless processes, a result that appears to be in contradiction to other dissipationless results.
We investigate the clustering properties of ∼1550 broad-line active galactic nuclei (AGNs) at z =... more We investigate the clustering properties of ∼1550 broad-line active galactic nuclei (AGNs) at z = 0.25 detected in the ROSAT All-Sky Survey (RASS) through their measured cross-correlation function with ∼46,000 luminous red galaxies (LRGs) in the Sloan Digital Sky Survey. By measuring the cross-correlation of our AGN sample with a larger tracer set of LRGs, we both minimize shot noise errors due to the relatively small AGN sample size and avoid systematic errors due to the spatially varying Galactic absorption that would affect direct measurements of the auto-correlation function (ACF) of the AGN sample. The measured ACF correlation length for the total RASS-AGN sample ( L 0.1-2.4 keV X = 1.5 × 10 44 erg s −1 ) is r 0 = 4.3 +0.4 −0.5 h −1 Mpc and the slope γ = 1.7 +0.1 −0.1 . Splitting the sample into low and high L X samples at L 0.5-10 keV X = 10 44 erg s −1 , we detect an X-ray luminosity dependence of the clustering amplitude at the ∼2.5σ level. The low L X sample has r 0 = 3.3 +0.6 −0.8 h −1 Mpc (γ = 1.7 +0.4 −0.3 ), which is similar to the correlation length of blue star-forming galaxies at low redshift. The high L X sample has r 0 = 5.4 +0.7 −1.0 h −1 Mpc (γ = 1.9 +0.2 −0.2 ), which is consistent with the clustering of red galaxies. From the observed clustering amplitude, we infer that the typical dark matter halo (DMH) mass harboring RASS-AGN with broad optical emission lines is log (M DMH /(h −1 M )) = 12.6 +0.2 −0.3 , 11.8 +0.6 −∞ , 13.1 +0.2 −0.4 for the total, low L X , and high L X RASS-AGN samples, respectively.
Optical broadband BVRI observations of 54 galaxies selected from the Catalog of Isolated Triplets... more Optical broadband BVRI observations of 54 galaxies selected from the Catalog of Isolated Triplets of Galaxies in the Northern Hemisphere have been carried out at San Pedro Mártir National Observatory to evaluate their photometric and morphological properties. We complement our analysis with Two-Micron All Sky Survey (2MASS) and Sloan Digital Sky Survey (SDSS) images and look for signatures likely related to interactions/mergers. We report apparent/absolute BVRI magnitudes and colors for the 54 galaxies. The membership of these galaxies is re-evaluated by imposing a reasonable condition of concordant redshifts upon the original selection criteria, rendering a final sample of 34 galaxies in 13 triplets, 12 galaxies in close pairs, and 8 galaxy outliers. The triplets are spiral-dominated systems in different dynamical stages from loosely interacting to almost merged objects. The incidence fraction of features likely associated with interactions is ∼56%, similar to those found in northern and southern compact groups. The average fraction of bars is 35% with a mean value of maximum bar ellipticity max ≈ 0.4. Bars are hosted in the late-type triplet spirals, almost twice more than in early-type spirals. The global fraction of rings is 20%, all in the late-type components. The overdensity of triplets with respect to the background and their current dynamical status, as devised from our estimate of their dynamical parameters, namely the harmonic radius R H , velocity dispersion σ , dimensionless crossing time H 0 τ c , and virial mass M V , appear to be sufficient to favor galaxy transformations similar to those seen in dense groups and clusters. By contrast, the lower fraction of bonafide ellipticals and the relatively higher fraction of late-type spirals make these triplets essentially different from the Hickson Compact Groups and more representative of the field. A modest 1.6 enhancement factor in the optical luminosity of the late-type triplet components relative to an isolated galaxy control sample is also interpreted as consistent with interactions in physically bounded aggregates. Our results lead us to suggest that non-negligible populations of physical triplets might be found in complete and well-observed samples. We provide individual mosaics for the 54 galaxies containing (1) logarithmic-scaled R-band images, (2) R-band sharp/filtered images, (3) (B − I) color index maps, (4) RGB images from the SDSS database, (5) co-added J + H + K images generated from the 2MASS archives that were also sharp/filtered, and (6) , position angle radial profiles from a surface photometry analysis of (a) the R band and (b) the co-added near-infrared images, all used for the present analysis.
Monthly Notices of the Royal Astronomical Society, 2006
Sérsic parameters characterising the density profiles of remnants formed in collision-less disc g... more Sérsic parameters characterising the density profiles of remnants formed in collision-less disc galaxy mergers are obtained; no bulge is included in our simulations. For the luminous component we find that the Sérsic index is n ∈ (1.5, 5.3) with n ≈ 3 ± 1 and an effective radius of R e ∈ (1.6, 12.9) kpc with R e ≈ 5 ± 3 kpc. The mean values of these quantities increases as the radial interval of fitting is reduced. A strong correlation of n with the central projected density I 0 is found (n ∝ I −0.14 0
Se estudian los efectos que fluctuaciones magnéticas turbulentas tienen sobre la dinámica de ione... more Se estudian los efectos que fluctuaciones magnéticas turbulentas tienen sobre la dinámica de iones pickup de O + en las regiones polares magnéticas de la ionofunda de Marte. En particular estudiamos su efecto en los perfiles de velocidad promedio como función de la altitud sobre los polos, con el fin de comparar con datos reciente del Mars Express; que indican que su velocidad promedio es pequeña y esencialmente en la dirección antisolar. Se encuentra que, aunque las fluctuaciones magnéticas resultan en desviaciones del simple movimiento de arrastre girotrópico, aun amplitudes de fluctuación más grandes que las medidas, no son capaces de reproducir los perfiles verticales de velocidad de los iones de O + . Concluímos que otro mecanismo físico, diferente a uno puramente de dinámica de partículas cargadas, está actuando sobre estos iones en el terminador Marciano. Una posibilidad es que exista una interacción tipo-viscosa entre el viento solar y la ionosfera Marciana a bajas altitudes.
It has been suggested that the ejection to interplanetary space of terrestrial crustal material a... more It has been suggested that the ejection to interplanetary space of terrestrial crustal material 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 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 ejecta with other planets of the Solar System. We also estimate the amount of particles falling-back to Earth as a function of time after being ejected.
Context. In this paper we study the dynamics of the υ Andromedae planetary system proposed by . W... more Context. In this paper we study the dynamics of the υ Andromedae planetary system proposed by . We focus on the study of the 3:1 Mean Motion Resonance (hereafter MMR) between υ Andromedae-d and the recently discovered υ Andromedae-e (hereafter υ And-d and υ And-e). Aims. Numerical simulations of the dynamics of the four planet system are conducted. Methods. The previously reported apsidal resonance between υ And-c and υ And-d is confirmed. In addition, we find that υ And-d and υ And-e are also in an apsidal resonance condition. Results. Our results further indicate that the υ Andromedae planetary system configuration is in the middle of a stability island in the semimajor axis-eccentricity domain. Additionally, we performed numerical integrations of the planetary configuration over 500 Myr and found it to be stable. Conclusions. We conclude that, within the uncertainties in the value of the orbital parameters, it is likely that υ Andromedae planetary system will remain stable for a long timescale.
A partir del análisis de la dinámica de iones O + de origen ionosférico en la ionofunda de Marte,... more A partir del análisis de la dinámica de iones O + de origen ionosférico en la ionofunda de Marte, acelerados por el campo eléctrico convectivo del viento solar (pick up ions), determinamos su velocidad promedio sobre los polos magnéticos del planeta. Estas velocidades se comparan con mediciones in situ de la nave Mars Express. Con base en nuestros resultados encontramos que las velocidades de los iones O + medidos sobre los polos magnéticos del planeta, que son esencialmente en la dirección antisolar, con componentes y y z muy pequeñas, no se pueden explicar en términos del movimiento girotrópico de las partículas exclusivamente. Concluimos entonces que la velocidad de los iones O + sobre los polos magnéticos del planeta resultan de la acción de fuerzas de tipo viscoso que transfieren momento entre el viento solar y el plasma ionosférico en la ionofunda de Marte.
... Héctor Aceves, Fidel Cruz, and Héctor Velázquez: Instituto de Astronomıa, Universidad Naciona... more ... Héctor Aceves, Fidel Cruz, and Héctor Velázquez: Instituto de Astronomıa, Universidad Nacional Autónoma de México, Apdo ... Aguilar, LA, & Merritt, D. 1990, ApJ, 354, 33 Bender, R. 1988, A&A, 74, 385 Binney, J., & Merrifield, M. 1998, Galactic Astronomy (Princenton: Princenton ...
Abstract. The projected (PME) and virial mass estimator (VME) are revisited and tested using an N... more Abstract. The projected (PME) and virial mass estimator (VME) are revisited and tested using an N-body equilibrium system. It is found that the PME can overestimate the mass by ≈ 40% if a cluster of galaxies is sampled only about its effective radius, Re. The exact value of ...
Abstract. The two most common mass estimators that use velocity dispersions and positions of obje... more Abstract. The two most common mass estimators that use velocity dispersions and positions of objects in a stel-lar system, the virial mass estimator (VME) and the pro-jected mass estimator (PME), are revisited and tested us-ing N-body experiments. We consider here only ...
Aims. To model the interaction of the solar wind with the plasma tail of a comet by means of nume... more Aims. To model the interaction of the solar wind with the plasma tail of a comet by means of numerical simulations, taking into account the effects of viscous-like forces.
ABSTRACT We present results from two recent projects on the correlation function analysis of AGNs... more ABSTRACT We present results from two recent projects on the correlation function analysis of AGNs from all-sky surveys to investigate the low-redshift clustering properties of AGNs. We have used ROSAT All-Sky Survey sources identified with broad line AGNs with the Sloan Digital Sky Survey (SDSS). By investigating the cross-correlation function (CCF) between these AGNs and SDSS galaxies, we have overcome the statistical limitation caused by the small number of AGNs. This has allowed us to investigate the luminosity-dependence of AGN clustering, where luminous AGNs (with Log LX ? 44) cluster more strongly, like red galaxies, than lower luminosity ones, which cluster like blue galaxies. With a novel method of applying Halo Occupation Distribution modeling to the CCF, we found, not only the mean mass of ˜10^13 Msol of DMHs occupied by the AGNs, but also the occupation distribution of the AGNs among the DMHs. As a separate project, we used AGNs in the Swift BAT Survey, which contains both un-obscured (type I) and obscured (type II) AGNs to investigate its auto-correlation function, finding similar results. We discuss the improvements on low-redshift AGN clustering studies expected from MAXI.
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Papers by Héctor Aceves