Research

Co-evolution of Supermassive Black Holes and their Host Galaxies

I am broadly interested in the study of the formation and evolution of supermassive black holes across cosmic time and the connection with the evolution of their host galaxies. Using cosmological simulations of galaxy formation together with analytic models of black hole growth, we have shown that the physical mechanisms driving gas inflows from galactic scales down to the black hole accretion disk may play a more crucial role than commonly considered in feedback self-regulated models. We have proposed a scenario consistent with available observations in which the transport of angular momentum in the galaxy by gravitational instabilities regulates the long-term co-evolution of black holes and star-forming galaxies. Torque-limited growth yields black holes and host galaxies evolving on average towards the observed scaling relations with no need for mass averaging through mergers or additional self-regulation processes. You may find out more about this here.


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The impact of Outflows in High Redshift Galaxies

Massive large-scale outflows, believed to be powered by supernova explosions and radiation pressure from massive stars, are observed in star-forming galaxies from the local to the high redshift universe and likely play a central role in the evolution of galaxies and the intergalactic medium. I am broadly interested on the role of galactic winds on galaxy evolution and in particular on the impact of outflows on the morphological, dynamical, and structural properties of high redshift galaxies. Running cosmological zoom-in simulations with an extended version of the N-body + hydrodynamics code GADGET, we have shown that strong winds maintain high gas fractions, redistribute star-forming gas and metals over larger scales, and increase the velocity dispersion of simulated galaxies, more in agreement with the large turbulent disks typical of high-redshift star-forming galaxies. You may read more about this here.


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The Earliest Stages of Galactic Star Formation

Galaxy evolution models critically depend on our understanding of star formation. Stars form in dense dusty cores of molecular clouds but their origin, evolution, and detailed physical properties are still not well understood. Since my M.S. thesis at the University of Puerto Rico, I have been interested on these early stages of star formation. Using sub-millimeter dust continuum observations from the BLAST telescope together with existing data taken with SEST, IRAS, Spitzer MIPS/IRAC, and Akari, we identified and derived the physical and dynamical properties of the coldest dense cores possibly associated with the earliest stages of star formation in the Vela-D giant molecular cloud. More recently, we have used Hi-GAL data from the Herschel Space Observatory to study the mass function of large samples of starless and proto-stellar cores.


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Non-ideal Magnetohydrodynamics in Air Plasmas

During my second year in Arizona, I investigated the dynamics of shocks propagating through air at atmospheric conditions under the effects of strong magnetic fields. Low temperature air plasmas are only weakly ionized and therefore the equations of ideal magnetohydrodynamics cannot be applied to this problem. I implemented different methods into the ZEUS-MP code to model the interaction of magnetic fields and non-ideal plasmas, accounting for the thermodynamics of air plasmas including 19 different species. The extremely high resistivity of low temperature air plasmas made this numerical problem intractable using an explicit finite-difference algorithm for resistive MHD. Instead, the low magnetic Reynolds number approximation was used, were magnetic diffusion dominates over advection, the magnetic field is primarily determined by the boundary conditions, and the Lorentz force is simply added as a source term into the momentum equation. I also developed an intermediate approach in which the magnetic field is evolved in time according to the induction equation as in ideal MHD but the Lorentz force is corrected by a factor that accounts for the low ionization fraction of air plasmas at the temperatures of interest.


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