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Ragone-Figueroa C.,Institute Investigaciones en Astronomia Teorica y Experimental | Ragone-Figueroa C.,CONICET | Plionis M.,National institute for astrophysics | Plionis M.,National Institute of Astrophysics, Optics and Electronics | And 4 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

We use dark matter haloes identified in the M. areN. ostrum U. niversex and galaxy groups identified in the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) galaxy catalogue to study the relation between halo shape and halo dynamics, parametrizing the mass of the systems. A strong shape-dynamics correlation, independent of mass, is present in the simulation data, which we find to be due to different halo-formation times. Early formation-time haloes are, at the present epoch, more spherical and have higher velocity dispersions than late formation-time haloes. The halo shape-dynamics correlation survives the projection into two dimensions (i.e. between projected shape and 1D velocity dispersion), albeit weaker. A similar shape-dynamics correlation, independent of mass, is also found in the SDSS DR7 groups of galaxies, and in order to investigate its cause we have tested and used, as a proxy of the group formation time, a concentration parameter. We have found, as in the case of the simulated haloes, that less concentrated groups, corresponding to late formation times, have lower velocity dispersions and higher elongations than groups with higher values of concentration, corresponding to early formation times. © 2010 The Authors. Journal compilation © 2010 RAS. Source


Krause G.,National University of Cordoba | Krause G.,CONICET | Cecere M.,CONICET | Cecere M.,Institute Investigaciones en Astronomia Teorica y Experimental | And 9 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2015

We examine the capability of a blast-wave scenario - associated with a coronal flare or to the expansion of CME flanks - to reproduce a chromospheric Moreton phenomenon. We also simulate the Moreton event of 2006 December 06, considering both the corona and the chromosphere. To obtain a sufficiently strong coronal shock - able to generate a detectable chromospheric Moreton wave - a relatively low magnetic field intensity is required, in comparison with the active region values. Employing reasonable coronal constraints, we show that a flare ignited blast-wave or the expansion of the CME flanks emulated as an instantaneous or a temporal piston model, respectively, are capable to reproduce the observations. © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Source

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