Computación para Astronomía y Meteorología : Lenguaje Fortran

Este libro describe los usos de programación en lenguaje Fortran con el fin de utilizar las computadoras como instrumentos de cálculo. Se discuten las sentencias, sus usos y cuidados. Además, se detallan los problemas de eficiencia de diversos algoritmos, los problemas de la inestabilidad numérica por el redondeo y se incluye una introducción a la realización de modelos con números al azar.Facultad de Ciencias Astronómicas y Geofísica

La ciencia en la ciencia ficción : Relaciones entre científicos, escritores y sus temas en el caso de las ciencias del espacio

En esta charla trataremos el caso de la comunicación entre escritores y científicos, pero no sólo desde el punto de vista de los logros que se han realizado desde el punto de buscar que la CF sea predictiva, sino al revés donde la ciencia es la que inspira la CF, Para entender este panorama trataremos primero una serie de pautas que nos permiten evaluar el contexto en que se realiza esta comunicación.Facultad de Ingenierí

Identification and analysis of the young population in the starburst galaxy NGC 253

We present a study of the young population in the starburst galaxy NGC 253. In particular, we focused our attention on searching young star groups, obtaining their main properties and studying their hierarchical organization. For this task, we used multiband images and their corresponding photometric data obtained with the Advanced Camera for Surveys of the Hubble Space Telescope (ACS/HST).We have first derived the absorption affecting the different regions of the galaxy. Then, we applied an automatic and objective searching method over the corrected data in order to detect young star groups. We complemented this result with the construction of the stellar density map for the blue young population. A statistical procedure to decontaminate the photometric diagrams from field stars was applied over the detected groups and we estimated their fundamental parameters.As a result, we built a catalog of 875 new identified young groups with their main characteristics, including coordinates, sizes, estimated number of members, stellar densities, luminosity function (LF) slopes and galactocentric distances. We observed these groups delineate different structures of the galaxy, and they are the last step in the hierarchical way in which the young population is organized. From their size distribution, we found they have typical radius of ∼ 40 − 50 pc. These values are consistent with those ones found in others nearby galaxies. We estimated a mean value of the LF slope of 0.21 and an average density of 0.0006 stars/pc³ for the identified young groups taking into account stars earlier than B6.Fil: Rodriguez, Maria Jimena. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Baume, Gustavo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Feinstein Baigorri, Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; Argentin

Shock ionization in the extended emission-line region of 3C 305: the last piece of the (optical) puzzle

We present new Gemini spectroscopical data of the extended emission-line region of the 3C 305 radio galaxy in order to achieve a final answer to the long-standing question about the ionizing mechanism. The spectra show strong kinematic disturbances within the most intense line-emitting region. The relative intensities of the emission lines agree with the hypothesis that the gas is shocked during the interaction of powerful radio jets with the ambient medium. The emission from the recombination region acts as a very effective cooling mechanism, which is supported by the presence of a neutral outflow. However, the observed intensity is almost an order of magnitude lower than expected in a pure shock model. So, autoionizing shock models, in low-density and low-abundance regimes, are required in order to account for the observed emission within the region. This scenario also supports the hypothesis that the optical emitting gas and the X-ray plasma are in pressure balance.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

The fingerprints of photoionization and shock-ionization in two CSS sources

We investigate the ionization state of the extended emission-line regions (EELRs) around two compact steep-spectrum (CSS) radio galaxies, 3C 268.3 and 3C 303.1, in order to identify the contribution of photoionization and shock-ionization. We perform a new spectroscopical (long-slit) analysis with GMOS/Gemini with the slit oriented in the radio-jet direction, where outflows are known to exist. The [Ne V] λ3426 emission is the most interesting feature of the spectra and the one key to breaking the degeneracy between the models: since this emission-line is more extended than He II, it challenges the ionization structure proposed by any photoionization model, also its intensity relative to H β does not behave as expected with respect to the ionization parameter U in the same scenario. On the contrary, when it is compared to the intensity of [O II] λ3727/H β and all these results are joined, the whole scenario is plausible to be explained as emission coming from the hot, compressed, shocked gas in shock-ionization models. Although the model fitting is strongly sensitive to the chosen line ratios, it argues for the presence of external and strong ionizing fields, such as the precursor field created by the shock or/and the AGN radiation field. In this paper, we show how AGN photoionization and shock-ionization triggered by jet–cloud interaction work together in these EELRs in order to explain the observed trends and line-ratio behaviours in a kinematically acceptable way.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

Searching for evidence of jet-cloud interaction in radio galaxies : First results for 3C 381

We present results of Gemini spectroscopy and Hubble Space Telescope imaging of the 3C 381 radio galaxy. Possible ionizing mechanisms for the extended emission-line region were studied through state-of-the-art diagnostic analysis employing line ratios. Photoionization from the central engine as well as mixed medium photoionization models fail in reproducing both the strengths and the behaviour of the highest excitation lines, such as [Ne v]λ3424, He ii and [O iii]λ5007, which are measured at very large distances from the active galactic nucleus. Shock-ionization models provide a better fit to the observation. Expanding shocks with velocities higher than 500 km s-1 are capable of reaching the observed intensity ratios for lines with different ionization states and excitation degrees. This model also provides a direct explanation of the mechanical energy input needed to explain the high-velocity line-splitting observed in the velocity field.Facultad de Ciencias Astronómicas y Geofísica

The fingerprints of photoionization and shock-ionization in two CSS sources

We investigate the ionization state of the extended emission-line regions (EELRs) around two compact steep-spectrum (CSS) radio galaxies, 3C 268.3 and 3C 303.1, in order to identify the contribution of photoionization and shock-ionization. We perform a new spectroscopical (long-slit) analysis with GMOS/Gemini with the slit oriented in the radio-jet direction, where outflows are known to exist. The [Ne V] λ3426 emission is the most interesting feature of the spectra and the one key to breaking the degeneracy between the models: since this emission-line is more extended than He II, it challenges the ionization structure proposed by any photoionization model, also its intensity relative to H β does not behave as expected with respect to the ionization parameter U in the same scenario. On the contrary, when it is compared to the intensity of [O II] λ3727/H β and all these results are joined, the whole scenario is plausible to be explained as emission coming from the hot, compressed, shocked gas in shock-ionization models. Although the model fitting is strongly sensitive to the chosen line ratios, it argues for the presence of external and strong ionizing fields, such as the precursor field created by the shock or/and the AGN radiation field. In this paper, we show how AGN photoionization and shock-ionization triggered by jet–cloud interaction work together in these EELRs in order to explain the observed trends and line-ratio behaviours in a kinematically acceptable way.Facultad de Ciencias Astronómicas y GeofísicasInstituto de Astrofísica de La Plat

The interaction between jets and clouds in the 3CR galaxies

From the HST/WFPC2 3CR Snapshot Survey, data taken with the filter F555W, F702W and narrow-ramp, a set of galaxies with noticeable extended structure were selected (e.g. 3C 79, 3C 135, 3C 234, etc). All of these objects show large regions of [OIII] λ 5007˚A emission (narrow ramp filter) and the broad-band filters data show similar structures indicating the presence of strong emission in several lines over these regions. The morphology observed seems to be related (e.g. same position angle, direct overlapping or similar shape) with the radio-jet. For some candidates with these properties GMOS/Gemini spectroscopy was taken. These data (both HST direct imaging and Gemini spectroscopy) can be tested with diagnostic diagrams and total UV photons budget to understand the source of energy that is ionizing the gas. This source of ionization was commonly believed to be the UV photons emitted by the powerful active galactic nuclei (AGN), but several of these objects show clearly that shocks produced by the radio jet are the main cause of the observed gas line emission. We show in this work, the results obtained over some of these radio-galaxies: 3C 135, 3C 180, 3C 234 and 3C 284.Fil: Hägele, G. F.. Universidad Autónoma de Madrid; EspañaFil: Feinstein Baigorri, Carlos. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Macchetto, D. F.. Space Telescope Science Institute; Estados UnidosFil: Montero, F.. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Función de luminosidad Hα en galaxias australes

Hα images of 20 nearby Southern galaxies were obtained using narrow interferometric filters. Positions, fluxes and diameters of the objects were obtained from these frames. A study of the completeness of the sample is made and after a proper calibration, the absolute fluxes and the Hα luminosity function were obtained for each galaxy. Two galaxies in the sample (NGC 1672, NGC 5861) show profiles of type II luminosity function while NGC 6221 shows extended Hα emission.Asociación Argentina de Astronomí

Significado de la función de luminosidad Hα en galaxias australes

By means of CCD frames and image processing techniques we measured the luminosity function of H-alpha of HII regions of nearby galaxies with a high S/N. Several studies were done recently assuming that the shape of the observed luminosity function can be use to determine physical parameters (e.g. mass distribution, stellar evolution, stellar mass distribution, etc) of the hidden stellar population. Some of the models only consider the distribution of the integrated stellar mass of the HII regions and others only the evolution of the stellar ionizating population of H11 region. In this work we consider the two effects simultaneously plus the effect of taking in account different stellar formation rate for the host galaxy. This a summary of the results: - The turnover point discover by Kennicutt et al. (1989) appears to have an explanation as the convolution of the stellar formation rate and the stellar mass distribution. - From comparison with observational data (from Feinstein et al. - 1992, this issue and Thesis) some galaxies NGC 2997, NGC 6070, NGC 6384, NGC 7552 seem to have luminosity functions compatible with a constant SFR. NGC 1672 exhibits to have a more complex situation, not compatible with a constant SFR. - In the case of constant SFR, the slope of-2 (Kennicutt et al., 1989, Apj 337,761) can only fit the luminosity function in the bright side of the distribution.Asociación Argentina de Astronomí