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Número de entradas: 2

15
Marzo 2019

Chemical Complexity in Space and Earth Induced by Solid State Surfaces. Investigations by means of Quantum Chemistry


Inicio: 12:15h
Ponente: Albert Rimola (Chemistry Department, UAB)
Lugar: Sala Alberto Lobo

Our universe is molecularly rich [1-3], comprising from the most essential molecules (such as H2, H2O and NH3), passing through complex organic molecules (namely, COMs, molecules between 6 – 13 atoms where at least one is C rendering its organic character), reaching more evolved complex organic compounds,…
Inicio: 12:15h
Ponente: Albert Rimola (Chemistry Department, UAB)
Lugar: Sala Alberto Lobo

Our universe is molecularly rich [1-3], comprising from the most essential molecules (such as H2, H2O and NH3), passing through complex organic molecules (namely, COMs, molecules between 6 – 13 atoms where at least one is C rendering its organic character), reaching more evolved complex organic compounds, in which in some cases are of biological relevance, such as amino acids, nucleobases and sugars. Formation of early Solar-type systems involves successive steps, mainly represented by the prestellar, protostellar, protoplanetary disk, and planetesimal and planet formation phases. This evolution goes hand-in-hand with an increase of the molecular complexity, in which more complex molecules form at each step [4]. The usual interpretation of the complex scenario of molecular reactions occurring in space is through a cascade of gas-phase reactions [5]. Nevertheless, it has since long recognized, with kinetic models, that gas-phase process alone cannot justify the abundance in the universe of even the simplest molecule, H2, but resort to reactions occurring on cosmic grain surfaces is mandatory to reconcile prediction with observation [6]. Accordingly, a key role of the chemical complexity is also played by cosmic solid state materials, as their surfaces provide catalytic sites that favor pivotal chemical reactions. A possible fate of the cosmic biomolecules is to reach Earth through meteorites or comets to become one of the building blocks for the formation of the pristine biopolymers. Biopolymer formation is very difficult, as these reactions are thermodynamically disfavoured in water with high kinetic barriers [7]. However, it has been long proposed that naturally-occurring minerals could have played a key role favouring these reactions, as they present specific surface sites that can adsorb and concentrate prebiotic organic compounds [8,9]. Computational quantum chemical methods may help in clarifying possible reactive channels towards molecule formations using proper atomistic structural models of the systems (including the extended surfaces), as they allow us to characterize chemical paths along the potential energy surfaces.In the talk, we discuss few examples from our own work for simulating essential molecules and COMs on interstellar grains as well as formation of polypeptides via condensation reaction of amino acids on mineral surfaces.
25
Enero 2019

Feeding and feedback from little monsters: black holes in dwarf galaxies


Inicio: 12:15h
Ponente: Mar Mezcua Pallerola
Lugar: Sala Alberto Lobo

Supermassive black holes of 10^10 solar masses already existed when the Universe was ~1 Gyr old and are also found in local brightest cluster galaxies. To reach this mass, they should have started as seed intermediate-mass black holes (IMBHs) of 100-10^6 solar masses at z~10 and grow very fast via accretion…
Inicio: 12:15h
Ponente: Mar Mezcua Pallerola
Lugar: Sala Alberto Lobo

Supermassive black holes of 10^10 solar masses already existed when the Universe was ~1 Gyr old and are also found in local brightest cluster galaxies. To reach this mass, they should have started as seed intermediate-mass black holes (IMBHs) of 100-10^6 solar masses at z~10 and grow very fast via accretion and mergers. Detecting such IMBHs in the early Universe is extremely challenging; however, those seed black holes that did not become supermassive should be found in local dwarf galaxies resembling the first galaxies formed at early epochs. 
I will show that a population of actively accreting IMBHs exists in local dwarf galaxies and that they can be detected out to z~3 with the use of deep multiwavelength surveys like COSMOS. The black hole occupation fraction of these dwarf galaxies suggests that the early Universe seed black holes formed from direct collapse of pre-galactic gas disk, which is reinforced by the finding that the scaling relations between supermassive black hole mass and host galaxy properties flatten at the low-mass end. This scenario is however challenged by the recent suggestion that dwarf galaxy mergers and black hole feedback can yield significant growth of the primordial seeds. In this case, IMBHs in local dwarf galaxies should not be treated as the fossils of the early Universe seed black holes. 
Institute of Space Sciences (IEEC-CSIC)

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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya