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Search Results: 1 - 10 of 10098 matches for " Sergio Silich "
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On the Formation of Massive Stellar Clusters
Guillermo Tenorio,Jan Palous,Sergio Silich,Gustavo A. Medina
Revista mexicana de astronomía y astrofísica , 2004,
On the impact of radiation pressure on the dynamics and inner structure of dusty wind-driven shells
Sergio Martinez-Gonzalez,Sergiy Silich,Guillermo Tenorio-Tagle
Physics , 2014, DOI: 10.1088/0004-637X/785/2/164
Abstract: Massive young stellar clusters are strong sources of radiation and mechanical energy. Their powerful winds and radiation pressure sweep-up interstellar gas into thin expanding shells which trap the ionizing radiation produced by the central clusters affecting the dynamics and the distribution of their ionized gas. Here we continue our comparison of the star cluster winds and radiation pressure effects on the dynamics of shells around young massive clusters. We calculate the impact that radiation pressure has on the distribution of matter and thermal pressure within such shells as well as on the density weighted ionization parameter $U_w$ and put our results on the diagnostic diagram which allows one to discriminate between the wind-dominated and radiation-dominated regimes. We found that model predicted values of the ionization parameter agree well with typical values found in local starburst galaxies. Radiation pressure may affect the inner structure and the dynamics of wind-driven shells only at the earliest stages of evolution or if a major fraction of the star cluster mechanical luminosity is dissipated or radiated away within the star cluster volume and thus the star cluster mechanical energy output is significantly smaller than star cluster synthetic models predict. However, even in these cases radiation dominates over the wind dynamical pressure only if the exciting cluster is embedded into a high density ambient medium.
Infrared Observational Manifestations of Young Dusty Super Star Clusters
Sergio Martinez-Gonzalez,Guillermo Tenorio-Tagle,Sergiy Silich
Physics , 2015,
Abstract: The growing evidence pointing at core-collapse supernovae as large dust producers makes young massive stellar clusters ideal laboratories to study the evolution of dust immersed into a hot plasma. Here we address the stochastic injection of dust by supernovae and follow its evolution due to thermal sputtering within the hot and dense plasma generated by young stellar clusters. Under these considerations, dust grains are heated by means of random collisions with gas particles which results on the appearance of infrared spectral signatures. We present time-dependent infrared spectral energy distributions which are to be expected from young stellar clusters. Our results are based on hydrodynamic calculations that account for the stochastic injection of dust by supernovae. These also consider gas and dust radiative cooling, stochastic dust temperature fluctuations, the exit of dust grains out of the cluster volume due to the cluster wind and a time-dependent grain size distribution.
Winds Driven by Super-Star Clusters
Sergio Silich,Guillermo Tenorio,A. Rodru00EDguez,Casiana Muu00F1oz
Revista mexicana de astronomía y astrofísica , 2004,
On the origin of the absorption and emission line components in the spectra of PHL 293B
Guillermo Tenorio-Tagle,Sergiy Silich,Sergio Martinez-Gonzalez,Roberto Terlevich,Elena Terlevich
Physics , 2015, DOI: 10.1088/0004-637X/800/2/131
Abstract: From the structure of PHL 293B and the physical properties of its ionizing cluster and based on results of hydrodynamic models, we point at the various events required to explain in detail the emission and absorption components seen in its optical spectrum. We ascribe the narrow and well centered emission lines, showing the low metallicity of the galaxy, to an HII region that spans through the main body of the galaxy. The broad emission line components are due to two off-centered supernova remnants evolving within the ionizing cluster volume and the absorption line profiles are due to a stationary cluster wind able to recombine at a close distance from the cluster surface, as originally suggested by Silich et al. (2004). Our numerical models and analytical estimates confirm the ionized and neutral column density values and the inferred X-ray emission derived from the observations.
The Steady State Wind Model for Young Stellar Clusters with an Exponential Stellar Density Distribution
Sergiy Silich,Gennadiy Bisnovatyi-Kogan,Guillermo Tenorio-Tagle,Sergio Martinez-Gonzalez
Physics , 2011, DOI: 10.1088/0004-637X/743/2/120
Abstract: A hydrodynamic model for steady state, spherically-symmetric winds driven by young stellar clusters with an exponential stellar density distribution is presented. Unlike in most previous calculations, the position of the singular point R_sp, which separates the inner subsonic zone from the outer supersonic flow, is not associated with the star cluster edge, but calculated self-consistently. When the radiative losses of energy are negligible, the transition from the subsonic to the supersonic flow occurs always at R_sp ~ 4 R_c, where R_c is the characteristic scale for the stellar density distribution, irrespective of other star cluster parameters. This is not the case in the catastrophic cooling regime, when the temperature drops abruptly at a short distance from the star cluster center and the transition from the subsonic to the supersonic regime occurs at a much smaller distance from the star cluster center. The impact from the major star cluster parameters to the wind inner structure is thoroughly discussed. Particular attention is paid to the effects which radiative cooling provides to the flow. The results of the calculations for a set of input parameters, which lead to different hydrodynamic regimes, are presented and compared to the results from non-radiative 1D numerical simulations and to those from calculations with a homogeneous stellar mass distribution.
Young Stellar Clusters with a Schuster Mass Distribution - I: Stationary Winds
Jan Palous,Richard Wunsch,Sergio Martinez-Gonzalez,Filiberto Hueyotl-Zahuantitla,Sergiy Silich,Guillermo Tenorio-Tagle
Physics , 2013, DOI: 10.1088/0004-637X/772/2/128
Abstract: Hydrodynamic models for spherically-symmetric winds driven by young stellar clusters with a generalized Schuster stellar density profile are explored. For this we use both semi-analytic models and 1D numerical simulations. We determine the properties of quasi-adiabatic and radiative stationary winds and define the radius at which the flow turns from subsonic into supersonic for all stellar density distributions. Strongly radiative winds diminish significantly their terminal speed and thus their mechanical luminosity is strongly reduced. This also reduces their potential negative feedback into their host galaxy ISM. The critical luminosity above which radiative cooling becomes dominant within the clusters, leading to thermal instabilities which make the winds non-stationary, is determined, and its dependence on the star cluster density profile, core radius and half mass radius is discussed.
Superbubble evolution including the star-forming clouds: Is it possible to reconcile LMC observations with model predictions?
S. Silich,J. Franco
Physics , 1999, DOI: 10.1086/307694
Abstract: Here we present a possible solution to the apparent discrepancy between the observed properties of LMC bubbles and the standard, constant density bubble model. A two-dimensional model of a wind-driven bubble expanding from a flattened giant molecular cloud is examined. We conclude that the expansion velocities derived from spherically symmetric models are not always applicable to elongated young bubbles seen almost face-on due to the LMC orientation. In addition, an observational test to differentiate between spherical and elongated bubbles seen face-on is discussed.
Dusty supernovae running the thermodynamics of the matter reinserted within young and massive super stellar clusters
Guillermo Tenorio-Tagle,Sergiy Silich,Sergio Martínez González,Casiana Mu?oz-Tu?ón,Jan Palou?,Richard Wünsch
Physics , 2013, DOI: 10.1088/0004-637X/778/2/159
Abstract: Following the observational and theoretical evidence that points at core collapse supernovae as major producers of dust, here we calculate the hydrodynamics of the matter reinserted within young and massive super stellar clusters under the assumption of gas and dust radiative cooling. The large supernova rate expected in massive clusters allows for a continuous replenishment of dust immersed in the high temperature thermalized reinserted matter and warrants a stationary presence of dust within the cluster volume during the type II supernova era. We first show that such a balance determines the range of dust to gas mass ratio and this the dust cooling law. We then search for the critical line that separates stationary cluster winds from the bimodal cases in the cluster mechanical luminosity (or cluster mass) vs cluster size parameter space. In the latter, strong radiative cooling reduces considerably the cluster wind mechanical energy output and affects particularly the cluster central regions, leading to frequent thermal instabilities that diminish the pressure and inhibit the exit of the reinserted matter. Instead matter accumulates there and is expected to eventually lead to gravitational instabilities and to further stellar formation with the matter reinserted by former massive stars. The main outcome of the calculations is that the critical line is almost two orders of magnitude or more, depending on the assumed value of the adiabatic wind terminal speed, lower than when only gas radiative cooling is applied. And thus, many massive clusters are predicted to enter the bimodal regime.
The Hydrodynamics and Chemical Evolution of Starburst-driven Outflows
Sergiy Silich,Guillermo Tenorio-Tagle
Physics , 2002,
Abstract: The hydrodynamics and intrinsic properties of galactic-scale gaseous outflows generated by violent starbursts are thoroughly discussed, taking into account the hot gas chemical evolution and radiative cooling. It is shown that the metallicity of superbubbles vary with time and can easily exceed the solar value. Galactic superwinds driven by compact and powerful starbursts undergo catastrophic cooling and establish a temperature distribution radically different to that predicted by adiabatic solution. The observational properties of supergalactic winds in X-rays and visible line regimes derived from our calculations are compared with the standard adiabatic model predictions.
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