Cosmological simulations

Until a few years ago, studies of galaxy formation have been affected by uncertainties both in the underlying cosmology as well as in the most relevant physical processes. Now we are in the so called "precision cosmology" era, which means that the background model is relatively well defined by a wealth of observations, in particular those of fluctuations in the cosmic micro-wave background. So, we can compute with reasonable confidence the evolution of the dynamically dominant dark matter (DM) component, ruled by gravity. Starting from a reasonable spectrum of primordial density fluctuations, over-density regions above the linear regime collapse into sheets and filaments. Then, matter mainly flows along filaments into dark matter halos. These halos merge to form bigger and bigger halos (hierarchical clustering).The general outcomes of these gravity-only simulations confirm and deepen those obtained by means of analytical analysis, yielding a broad outline of the formation of cosmic structures: galaxies and clusters. Indeed, a full understanding of the processes leading to the formation of cosmic structures, galaxies in particular, would require the much more demanding task of treating the complex physic of luminous (baryonic) matter. Galaxy formation, which occurs in DM halos, involves a complex web of processes: merging of dark matter halos, cooling of gas, collapse and star formation from cold gas, energy input into gas from SNae explosions and winds (energetic feedback), chemical enrichment of gas and stars (chemical feedback), galaxy mergers, luminosity evolution of stellar populations, absorption of starlight by dust and re-emission in IR+sub-mm, formation of super massive black holes, the ensuing AGN activity and its feedback on the interstellar medium. To follow from first principles all these processes in a fully cosmological context, it would span a dynamical range from << 1pc to >10 Mpc. Moreover, many of processes above are still poorly understood. Thus, simulations genuinely from first principles are at present impossible. Two complementary approaches are usually followed: (i) numerical simulations including gas, i.e. smooth particle hydro-dynamical (SPH) simulations, accounting for phenomenological prescriptions of sub-grid physics (e.g. star formation, feedback, SMBH growth), (ii) semi-analytical models (SAMs), using the prescription approach for every process involving baryons. At the OAPd we are deeply involved in both these projects. In particular, SPH simulations focusing on the bar growth and its evolution, for the first time in a fully cosmological frame , and the first SAM model accounting for the feedback from star formation and AGN activity, have been recently performed. Results from both these approaches help us to shed light on, and may be to solve, several crucial points concerning galaxy evolution.

Cosmological Simulations - PAST STUDIES

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  • Un telegramma astronomico pubblicato ieri dal team del satellite Agile dà notizia di un improvviso incremento nell’emissione gamma della Nebulosa del Granchio. Ce ne parla Marco Tavani dell’Inaf Iaps di Roma, responsabile scientifico della missione

  • Serena è la suite di strumenti dedicata allo studio delle particelle presenti nell'ambiente attorno a Mercurio, pronta per decollare a bordo della missione BepiColombo. A lei il compito di raccogliere informazioni sulla tenue atmosfera del pianeta e su come questa interagisca con l'attività del vicino Sole. L'intervista a Stefano Orsini, dell'Inaf, responsabile scientifico di Serena

  • Grazie alla potenza del radiotelescopio Alma, una nuova ricerca britannica ha individuato un segno distintivo negli anelli di polvere dei dischi protoplanetari che indica lo spostamento in corso di un pianeta verso una sistemazione gravitazionalmente più consona. Secondo lo studio guidato dall'Università di Warwick, a fare la differenza è la dimensione dei grani di polvere

  • Attraverso collisioni fra ioni di xeno, prodotte al Cern con Lhc e analizzate con l'esperimento Alice, è stato possibile ricostruire proprietà fondamentali del plasma di quark e gluoni che costituiva la materia dell'universo all'epoca del Big Bang

  • Con il telescopio spaziale Hubble gli studiosi cercano di capire come l’intensa emissione di raggi ultravioletti da parte delle stelle nane rosse influenzi i pianeti nella zona abitabile. Fra gli autori dello studio, Isabella Pagano dell’Inaf di Catania

  • Si chiama More, acronimo per Mercury Orbiter Radioscience Experiment, e riflettendo come uno specchio complessi segnali radio ad altissima frequenza, inviati da due enormi antenne terrestri, permetterà alla missione Esa BepiColombo di tracciare una sorta di tomografia dell’interno di Mercurio. E di mettere alla prova la Relatività generale di Einstein

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