arXiv subjects

Pablo F. Velázquez

Publications and source records attributed to Pablo F. Velázquez.

5 recordsLinked to original sources

arXiv2017

Physical properties of superbubbles in the Antennae galaxies

Mass outflow generated by the dynamical feedback from massive stars is currently a topic of high interest. Using a purpose-developed analysis technique, and taking full advantage of the high kinematic and angular resolution of our instrument we have detected a number of expanding superbubbles in the interacting pair of galaxies Arp 244 (NGC 4038/9) commonly known as the Antennae. We use a Fabry-Pérot interferometer GHαFaS to measure the profile of Hα in emission over the full extent of the object, except for the extended HI tails. The superbubbles are found centred on most of the brightest HII regions, especially in the overlap area of the two merging galaxies. We use measured sizes, expansion velocities and luminosities of the shells to estimate most of the physical parameters of the bubbles, including the kinetic energy of the expansion. In order to assess the validity of our results and approximations we perform a hydrodynamic simulation and manage to reproduce well our best measured superbubble with reasonable physical input assumptions. We also study the sources of ionization of the shells, finding that at the current, quite late stage of expansion, radiation from the remaining stars dominates, though the effect of supernova shocks can still be noted.

astro-ph.GA↗

arXiv2015

A Study of Radio Polarization in Protostellar Jets

Synchrotron radiation is commonly observed in connection with shocks of different velocities, ranging from relativistic shocks associated with active galactic nuclei, gamma-ray bursts or microquasars to weakly- or non-relativistic flows as those observed in supernova remnants. Recent observations of synchrotron emission in protostellar jets are important not only because they extend the range over which the acceleration process works, but also because they allow to determine the jet and/or interstellar magnetic field structure, thus giving insights on the jet ejection and collimation mechanisms. In this paper, we compute for the first time polarized (synchrotron) and non polarized (thermal X-ray) synthetic emission maps from axisymmetrical simulations of magnetized protostellar jets. We consider models with different jet velocities and variability, as well as toroidal or helical magnetic field. Our simulations show that variable, low-density jets with velocities $\sim$ 1000 km s$^{-1}$ and $\sim$ 10 times lighter than the environment can produce internal knots with significant synchrotron emission, and thermal X-rays in the shocked region of the leading bow shock moving in a dense medium. While models with a purely toroidal magnetic field show a very large degree of polarization, models with helical magnetic field show lower values and a decrease of the degree of polarization, in agreement with observations of protostellar jets.

astro-ph.SR↗

arXiv2011

X-ray emission and dynamics from large diameter superbubbles: The case of N 70 superbubble

The morphology, dynamics and thermal X-ray emission of the superbubble N70 is studied by means of 3D hydrodynamical simulations, carried out with the {\sc{yguazú-a}} code. We have considered different scenarios: the superbubble being the product of a single supernova remnant, of the stellar winds from an OB association, or the result of the joint action of stellar winds and a supernova event. Our results show that, in spite that all scenarios produce bubbles with the observed physical size, only those where the bubble is driven by stellar winds and a SN event are successful to explain the general morphology, dynamics and the X-ray luminosity of N70. Our models predict temperatures in excess of $10^8 \mathrm{K}$ at the interior of the superbubble, however the density is too low and the emission in thermal X-ray above $2 \mathrm{keV}$ is too faint to be detected.

astro-ph.CO↗

arXiv2008

3D hydrodynamical simulations of the large scale structure of W50-SS433

We present 3D hydrodynamical simulations of a precessing jet propagating inside a supernova remnant (SNR) shell, particularly applied to the W50-SS433 system in a search for the origin of its peculiar elongated morphology. Several runs were carried out with different values for the mass loss rate of the jet, the initial radius of the SNR, and the opening angle of the precession cone. We found that our models successfully reproduce the scale and morphology of W50 when the opening angle of the jets is set to 10$\degr$ or if this angle linearly varies with time. For these models, more realistic runs were made considering that the remnant is expanding into an interstellar medium (ISM) with an exponential density profile (as HI observations suggest). Taking into account all these ingredients, the large scale morphology of the W50-SS 433 system, including the asymmetry between the lobes (formed by the jet-SNR interaction), is well reproduced.

astro-ph↗

arXiv2005

Precessing jets from a moving source and bright X-ray filaments in galaxy clusters

We present hydrodynamical calculations carried out with the 3D yguazu-a code of a precessing jet model, which interacts with a plane parallel wind. This scenario describes an extragalactic jet, in which the jet source is in motion with respect to the surrounding intra-cluster medium. From the numerical results, synthetic emission maps and spectra in X-ray band were obtained. We compare these predictions with observations of the radio jets emanating from the radio-galaxy 4C 26.42 (in the Abell 1795 galaxy cluster). We find that the general morphology of the radio jets can be described by a point-symmetric precessing jet system interacting with a plane parallel wind (i.e., the intra-cluster medium flowing past the galaxy). We also find that our synthetic X-ray emission maps reproduce the observed large scale structures (with sizes of the order of tens of kpc).

astro-ph↗