Showing papers in "Revista Mexicana De Astronomia Y Astrofisica in 2006"

Closed newton-cotes trigonometrically-fitted formulae for long-time integration of orbital problems

Abstract: The connection between closed Newton-Cotes, trigonometrically-tted dierential methods and symplectic integrators is investigated in this paper It is known from the literature that several one step symplectic integrators have been obtained based on symplectic geometry However, the investigation of multistep symplectic integrators is very poor Zhu et al (1996) presented the well known open NewtonCotes dieren tial methods as multilayer symplectic integrators Also, Chiou & Wu (1997) investigated the construction of multistep symplectic integrators based on the open Newton-Cotes integration methods In this paper we investigate the closed Newton-Cotes formulae and we write them as symplectic multilayer structures After this we construct trigonometrically-tted symplectic methods which are based on the closed Newton-Cotes formulae We apply the symplectic schemes in order to solve Hamilton’s equations of motion which are linear in position and momentum We observe that the Hamiltonian energy of the system remains almost constant as integration procceeds

Morpho-Kinematic Modeling of Gaseous Nebulae with Shape

Abstract: We present a powerful new tool to analyse and disentangle the 3-D geometry and kinematic structure of gaseous nebulae. The method consists in combining commercially available digital animation software to simulate the 3-D structure and expansion pattern of the nebula with a dedicated, purpose-built rendering software that produces the final images and long slit spectra which are compared to the real data. We show results for the complex planetary nebulae NGC 6369 and Abell 30

Revised Diagnostic Diagrams for Planetary Nebulae

Abstract: Diagnostic diagrams of electron density-excitation for a sample of 613 planetary nebulae are presented. The present extensive sample allows the denition of new statistical limits for the distribution of planetary nebulae in the log [H /[S ii]] versus log [H /[N ii]], log [H /[S ii]] versus [S ii] 6717/6731, and log [H /[N ii]] versus [S ii] 6717/6731 planes. The diagrams provide a good representation of the ranges of physical conditions, indicated by these emission line ratios, present in planetary nebulae during dieren t evolutionary stages.

Low redshift bal qsos in the eigenvector 1 context

Abstract: We attempt to characterize the geometry of Broad Absorption Line (BAL) QSOs by studying a low redshift sample of 12 sources. We nd that the majority of these sources are Population A quasars as dened in Sulentic et al. (2000a, broad H FWHM 4000 km s 1 ). A possible correlation between terminal velocity and absolute V magnitude suggests that the bolometric luminosity to black hole mass ratio Lbol=MBH is a governing factor with classical BAL sources showing the highest values. Civ 1549 emission in classical BAL sources shows a prole blueshift that supports a disk wind/outo w scenario with a half opening angle of < 50 . Observation of \secondary" mini-BAL features in the Civ 1549 emission prole motivates us to model BALs with an additional component that may be involved with the BLR outo w and co-axial with the accretion disk.

Galactic Planetary Nebulae with Wolf-Rayet Nuclei III: Kinematical Analysis of a Large Sample of Nebulae

Abstract: Expansion velocities (Vexp) of dieren t ions and line widths at the base of the lines are measured and analyzed for 24 PNe with [WC]-type nuclei (WRPNe), 9 PNe ionized by WELS (WLPNe) and 14 ordinary PNe. A comparative study of the kinematical behavior of the sample clearly demonstrates that WRPNe have on average 40{45% larger Vexp, and possibly more turbulence than WLPNe and ordinary PNe. WLPNe have velocity elds very much like the ones of ordinary PNe, rather than the ones of WRPNe. All the samples (WRPNe, WLPNe and ordinary PNe) show expansion velocities increasing with age indicators, for example is larger for low-density nebulae and also it is larger for nebulae around hightemperature stars. This age eect is much stronger for evolved WRPNe, suggesting that the [WC] winds have been accelerating the nebulae for a long time, while for non-WRPNe the acceleration seems to stop at some point when the star reaches a temperature of about 90,000 { 100,000 K. Non-WR nebulae reach a maximum Vexp 30 km s 1 while evolved WRPNe reach maximum Vexp of about 40 km s 1 . For all kinds of objects (WRPNe and non-WRPNe) it is found that on average Vexp(N + ) is slightly larger than Vexp(O ++ ), indicating that the nebulae present acceleration of the external shells.

The Status of Speckle Imaging in Binary Star Research

Abstract: Speckle imaging continues to be an important tool in binary star research despite the rise of adaptive optics and other high-resolution techniques The last decade of speckle work will be surveyed and a picture of where speckle sits in the broader context will be drawn The advent of CCD-based speckle imaging and the publication of the Hipparcos Catalogue have played important roles in the ongoing vitality of the speckle technique The possibilities of the future of the eld will also be discussed

CCD photometry of the globular cluster M15: RR lyrae fourier decomposition and physical parameters

Abstract: Results of CCD photometry using V and R lters are reported for 33 RR Lyrae stars in M15. The periodicities of some variables have been revised and new ephemerides are given. The Blazhko eect, previously reported in V12, was not detected. Applying the approach of Fourier decomposition of the light curves, the physical parameters of the type RRab and RRc variables were estimated. The cluster is Oosterho type II and the values for the iron content and distance are: [Fe/H]= 1:98 0:24 and d = 8:67 0:41 kpc, respectively. The mean values of the physical parameters determined for the RR Lyrae stars place the cluster precisely into the sequences Oosterho type |metallicity and metallicity| eectiv e temperature, valid for globular clusters. Evidences of evolution from the ZAHB are found for the RRc but not for the RRab stars.

Frida: diffraction limited imaging and integral field spectroscopy with gtc

Abstract: FRIDA is a diffraction-limited imager and integral-field spectrometer that is being built for the adaptive-optics focus of the Gran Telescopio Canarias. In imaging mode FRIDA will provide scales of 0.010, 0.020 and 0.040 arcsec/pixel and in IFS mode spectral resolutions of 1500, 4000 and 30,000. FRIDA is starting systems integration and is scheduled to complete fully integrated system tests at the laboratory by the end of 2017 and to be delivered to GTC shortly thereafter. In this contribution we present a summary of its design, fabrication, current status and potential scientific applications.

Preservation of Cuspy Profiles in Disk Galaxy Mergers

Abstract: We carried out three self-consistent N-body simulations of galaxy mergers, with a cuspy dark matter prole, in order to study if the inner dark density slope is preserved in the remnants. In these simulations the progenitors include both a stellar disk and an intrinsic angular momentum for the halos, unlike previous similar studies. The mass-ratios of progenitor galaxies are about 1:1, 1:3, and 1:10. We nd that the initial cuspy density prole of the dark halos is preserved in the remnants for the cases considered here.

Expansion parallax for the compact planetary nebula M2-43

Abstract: LICA-UCM is the brand new laboratory for scientific advanced instrumentation (Laboratorio de Investigacion Cientifica Avanzada) at Universidad Complutense de Madrid where MEGARA integration will take place.

Photometric and Spectroscopic Study of the Shakhbazian Compact Galaxy Groups ShCG 254, ShCG 257, ShCG 351, and ShCG 371

Abstract: We continue the presentation of the results of detailed spectroscopic and photometric study of Shakhbazian compact galaxy groups. They belong to the interesting class of compact groups. Because of their large number (the catalogue contains 377 entries) we are able to study the groups in dieren t stages of evolution. Here we give the results of a detailed study of v e groups, ShCG 74E, ShCG 74W, ShCG 188, ShCG 251, and ShCG 348. We present the redshifts of individual galaxies in groups, the results of the surface photometry in R, the contour plots of the surface brightness, and some physical parameters of groups, such as the radial velocity dispersions, the crossing times, and the mass-to-luminosity ratios of groups. The general properties of 18 ShCGs obtained in this and previous works are discussed.

San Pedro Mártir mid-infrared photometric system

Abstract: Resumen es: Con el objetivo de definir el Sistema Fotometrico para el Mediano-Infrarrojo de San Pedro Martir, se realizaron observaciones de estrellas de calibracion...

A simple model to determine chaotic motions around asteroids

Abstract: It is well known that the 3-D motion around the asteroid (433) Eros is chaotic for a wide set of inclinations. The main feature of this body is its elongated shape, which originates that the usual procedure of expanding the potential function in spherical harmonics is useless. This is the reason why we consider a simple model to describe its elongated shape, namely, a rotating nite straight segment. By so doing, it is possible to obtain the potential in closed form, with no need of further expansions. For this model, from the analysis of families of periodic orbits, we can nd an explanation for most of dynamics already found for orbits around Eros.

Understanding the stellar initial mass function

Abstract: The essential features of the stellar Initial Mass Function are, rather generally, (1) a peak at mass of a few tenths of a solar mass, and (2) a power-law tail toward higher masses that is similar to the original Salpeter function. Recent work suggests that the IMF peak reects a preferred scale of fragmentation associated with the transition from a cooling phase of collapse at low densities to a nearly isothermal phase at higher densities, where the gas becomes thermally coupled to the dust. The Salpeter power law is plausibly produced, at least in part, by scale-free accretion processes that build up massive stars in dense environments. The young stars at the Galactic Center appear to have unusually high masses, possibly because of a high minimum mass resulting from the high opacity of the dense star-forming gas.

The n(h2)/i(co) conversion factor: a treatment that includes radiative transfer

Abstract: A treatment that better explains the N(H2)=I(CO) conversion factor is given that includes radiative transfer. At rst glance, involving radiative transfer seems superuous for an optically thick line such as CO J = 1 ! 0 line. However, given that the interstellar medium is inhomogeneous, the individual gas fragments (i.e., clumps) can still be optically thin toward their edges and in the wings of their line proles. The statistical treatment by Martin et al.(1984) of the radiative transfer through a clumpy molecular cloud is used to derive an expression for the conversion factor that overcomes the shortcomings in the more traditional explanations based on Dickman et al. (1986). While possibly representing important step forward in understanding the N(H2)=I(CO) conversion factor, the treatment here also has shortcomings of its own that are briey discussed.

Shadows and photoevaporated flows from neutral clumps exposed to two ionizing sources

Abstract: Neutral clumps immersed in H II regions are frequently found in star formation regions. We investigate here the formation of tails of neutral gas, which are not reached by the direct ionizing ux coming from two massive stars, using both an analytical approximation that allows us to estimate the shadow geometry behind the clumps for dieren t initial geometric congurations, and three-dimensional numerical simulations. We nd a good agreement between both approaches to this theoretically interesting problem. A particularly important application could be the proplyds that are found in the Trapezium cluster in Orion, which are being photoevaporated primordially by the O stars 1 Ori C and 2 Ori A.

Searching for balmer self-absorption in planetary nebulae

Abstract: We analyse the distribution of 482 planetary nebulae (PNe) within the H =H H =H and H =H H =H planes. Whilst most sources appear to possess case B line ratios, and normal reddening decrements, certain of them also appear to be aected by Balmer self-absorption. We are able to identify 9 possible cases, and 11 probable examples where such absorption is important. Approximately half of these nebulae are compact, and probably quite young. Most previous identications of self-absorption are shown to be open to doubt, and there is no overlap at all between our present candidates, and those of previous analyses.

Near-field cosmology with horizontal branch and rr lyrae stars

Abstract: The importance of horizontal branch and RR Lyrae stars is discussed in the context of cosmological arguments for the formation of the Galactic halo and its satellite dwarf galaxies. It is shown, in particular, that the Galactic halo globular cluster system cannot have formed from the accretion of \protogalactic fragments" resembling the very early counterparts of the present-day dwarf satellite galaxies of the Milky Way, or else its RR Lyrae properties would be very dieren t from what is currently observed.

Multifrequency study of the blue compact dwarf haro 2: nir imaging and optical spectroscopy

Abstract: We carried out near infrared (NIR) imaging of the BCD Haro 2 in J and H bands which conrms that the J-H color is typical of a slightly blue S0 galaxy. The absence of asymmetries in the central NIR light distribution is similar to what is seen in unperturbed early-type galaxies, in spite of being a gas rich galaxy (in both H i and CO), with a high SFR. To better understand this peculiar object we obtained medium-resolution optical spectroscopy, which suggests continuous star formation over the past few 10 8 yr. This age for the burst is consistent with the observed oxygen abundance and with the nitrogen to oxygen ratio. We reanalyze VLA H i data which, compared with the NIR images and CO(1{0) maps, conrm a major gas accretion event, most likely the result of an interaction with a gas rich companion. Our observations indicate that Haro 2 is likely a dwarf elliptical which suered a y-b y interaction a few times 10 8 years ago; this resulted in the accretion of a substantial amount of gas and the subsequent triggering of star formation.

The problem with reddening distances to planetary nebulae

Abstract: It is noted that the vast majority of Galactic PNe are located outside of the interstellar reddening layer, to the extent that local gradients in EB V are low to undetectable. This is likely to invalidate certain previous estimates of their reddening distances DRED. It also means that larger scale analyses, such as those of Pottasch (1984) and Acker (1973), lead to values of DRED which are signican tly too small. A similar critique applies to analyses based on measures of Na D-line absorp

Deep photometric studies in the Third Quadrant: NGC 2467

Abstract: Resumen es: La region de NGC 2467, ubicada en la \ventana de Puppis" del tercer cuadrante, contiene cumulos abiertos jovenes y estructuras nebulares reportados a...

Morpho-Kinematic modeling of planetary nebulae

Abstract: Resumen es: Presentamos una nueva herramienta para desenredar la geometra 3-D y la estructura cinematica de nebulosas gaseosas. El metodo consiste en combinar s...

Stellar populations in elliptical galaxies of compact groups

Abstract: Resumen en: A spectroscopic analysis is presented, where elliptical galaxies in Hickson Compact Groups (HCG) are compared with their counterparts in the eld. The s...

Evidence for rotation-induced mixing in evolved intermediate mass stars

Abstract: Resumen es: Muchos resultados observacionales parecen indicar procesos de mezclado mas e cientes en estrellas de masas intermedias (5-20 M ) que los esperados de l...

The evolution of galaxies in compact and fossil groups

Abstract: Resumen es: Presentamos observaciones en el optico de algunos de los grupos compactos cercanos mas evolucionados que se conocen actualmente, HCG 31, HCG 79 y HCG ...

The maternities of high-mass stars

Abstract: The understanding of the birth process of massive stars, known to be formed in clusters, requires a detailed knowledge of the physical conditions of the parental cloud which are thought to play a critical role in determining the formation mechanism. In this contribution I will review recent results from observations of the gas and dust emission towards massive star forming regions which are providing key evidence concerning the initial conditions for the formation of cluster of massive stars. These observations have allowed to characterize the physical properties of massive and dense cores and to identify them in dieren t stages of their early evolution.

Probing galactic structure with musyc

Abstract: We present some preliminary results of the Galactic program within the MUSYC collaboration. Using the multi-colour photometry of MUSYC we are able to classify objects and select samples of a given type. We apply colour selection to establish a sample of M-stars in the MUSYC eld CDFS-E which was then used to study the distribution along the pencil beam. The distribution shows three components for which we derived scale heights indicating that these components are the Thin and Thick Disk and the Halo.

The use of Ks Band Photometric Excesses to Investigate H2 Emission in Planetary Nebulae

Abstract: We have determined the distribution of H2 emission in 14 planetary nebulae (PNe), using imaging and photometry published by the 2MASS infrared survey. This technique is only applicable under certain stringent conditions, and requires precise broad band photometry, and accurate spatial registration between the KS and H band images. It is, in addition, only applicable to certain sources, and excludes outo ws in which central star and grain thermal excesses are appreciable. Our results for NGC 3132, NGC 6720, IC 4406 and M 2 9 are closely similar to those of previous narrow band imaging, and conrm that H2 emission is conned to narrow, highly fragmented shells. Similar results are obtained for M 1 7, M 1 8, and M 3 5. Our spatial proles also conrm that the emission extends outside of the primary ionised shells. Where envelopes are large, and the PNe are more evolved, then the fractional extensions = appear to be at their smallest. They are also similar to the radial widths predicted for H2 abundance proles, and to the values R/R determined through magnetohydrodynamic modelling of shocks. There appears, nally , to be evidence for an evolution in this parameter, such that = varies with increasing envelope size d(H) as / / d(H) 2:2 .

Oh maser emission toward the young planetary nebula K3-35

Abstract: K 3-35 is one of the two planetary nebulae (PNe) where water maser emission has been reported, suggesting that these kind of objets departed from the AGB phase only some decades ago. We present VLA (Very Large Array) observations of the 1720, 1667, 1665 and 1612 MHz OH maser emission from the central region of K 3-35. The OH 1665 MHz maser spots are distributed in an elongated structure, along the minor axis of the radio continuum bipolar outo w, and they exhibit high circular polarization suggesting the presence of a toroidal magnetic eld in K 3-35. An estimate of the magnitude of the magnetic eld, derived from the 1665 line, toward this young planetary nebula is 0.14 mG at a radius of 250 AU.

The most luminous radio galaxies

Abstract: The properties of the brightest extragalactic radio sources and their host galaxies are discussed These sources are associated with the most massive galaxies known out to a redshift of at least 2 They provide a unique class of object for studying the most extreme active galactic nuclei and their host galaxies and present challenges for understanding the formation of the most massive galaxies