Galactic bulges, spinning black holes and star forming galaxies in their cosmological context: insights from a semi-analytical perspective

• Autores: David Izquierdo Villalba
• Directores de la Tesis: Silvia Bonoli (dir. tes.) , Carlos Hernández Monteagudo (codir. tes.)
• Lectura: En la Universidad de Zaragoza ( España ) en 2020
• Idioma: español
• Tribunal Calificador de la Tesis: Mar Mezcua (presid.) , Miguel Ángel Pérez Torres (secret.) , Pau Amaro Seoane (voc.)
• Enlaces
  • Tesis en acceso abierto en: Zaguán
• Resumen

  • During the last decades, astrophysicists have developed a theory about how galaxies form and evolve within the Lambda-CDM cosmological framework. Despite being successful in many aspects, this general picutre has still some missing pieces that observational and theoretical works are trying to put all together. In this thesis, we try to answer to some open problems by addressing three different topics: galactic bulges, supermassive black holes and the development of mocks for the new generation of multi-narrow band surveys. We have tackled all these subjects by using the L-Galaxies semi-analytical model (SAM). Roughly, SAMs consist of dark matter merger trees populated with galaxies through analytical recipes. L-Galaxies is one of the state-of-the-art models whose capability to predict the correct galaxy properties at different redshifts has been proven during the last decade in many works. One of the main advantages of L-Galaxies is its flexibility to be run on the dark matter merger trees of the Millennium suite of simulations whose different box sizes and dark matter mass resolution offer the capability to explore different physical processes undergone by galaxies over a wide range of scales and environments.

    In the first part of the thesis, we address the cosmological build-up of galactic bulges with special focus on pseudobulges, whose cosmological evolution in a Lambda-CDM Universe has not been fully explored yet. In particular, we study their formation process and characterize the properties of their host galaxies at different redshifts. Within the L-Galaxies framework, galaxies are allowed to develop a bulge component via mergers and disk instabilities (DIs). Under the hypothesis that pseudobulges can only form and grow via secular evolution, we have modified the treatment of galaxy DIs. In detail, we assumed that only secular DI events lead to the development and growth of pseudobulges through the formation of long-lasting bar structures. We have applied this pseudobulge formation scenario to L-Galaxies, run on top of the Millennium and Millennium II dark matter merger trees. The outcomes of the model are in agreement with observations, showing that z=0 pseudobulges are small structures ~0.5 [kpc] hosted in main-sequence Milky Way-type galaxies. These results give support to our main underlying assumption that pseudobulge structure mainly form via secular evolution. We have extended our analysis of pseudobulge structures studying the performance of the DI criterion used by L-Galaxies when it is applied on a barred and unbarred galaxy sample of the cosmological hydrodynamical simulation TNG100. Despite finding a correlation between the analytical criteria predictions and the actual bar assembly (non-assembly) shown in the barred (unbarred) galaxies, we have detected cases where the analytical criterion fails, either claiming disk stability for barred galaxies or disk instability for the stable unbarred disks. We have proposed a new extra condition whose combination with the L-Galaxies criterion improves the detectability of bar structures and reduces both the contamination of fake barred galaxies and the number of undetected bar formation events.

    The second part of the thesis explores the mass assembly and spin evolution of supermassive black holes (BHs) across cosmic time. For this objective, we have updated L-Galaxies with new physical prescriptions. We have assumed that BH-mass assembly is mainly triggered by gas accretion after galaxy mergers or disk instabilities, and it takes place through a stage of rapid growth followed by a regime of slow accretion rates. During these phases, the BH spin evolution is followed by linking it with the morphological properties of the hosting bulge. The model predictions display a good consistency with some local observables, such as the black hole mass function, spin values distribution, BH-bulge mass relation and quasar luminosity functions. One of the main novelties of this thesis has been to use the BH model previously explained for exploring the formation and evolution of the wandering black hole population, i.e the population of BH outside of galaxies in bound orbits within the dark matter subhalos. We have found that the formation of these type of wandering black holes leave an imprint in the co-evolution between the black hole and the host galaxy which can be detected by current and future galaxy surveys.

    Finally, the third part of the thesis tackles the construction of mocks specially designed for the new generation of narrow-bands surveys. For this, we have inserted the lightcone assembly inside L-Galaxies, including in the photometry of the simulated galaxies the effect of emission lines produced in starforming regions. The latter has ensured the mock capability to correctly predict the galaxy photometry in narrow band filters. To determine the exact flux of emission lines we have used a model for the nebular emission in star-forming regions, coupled with a dust attenuation model, able to predict the flux emitted in 9 different lines. The validation of our lightcone has been done by comparing galaxy number counts, angular clustering, and Halpha, Hbeta, OII and OIII luminosity functions to a compilation of observations. We have applied all these procedures to generate catalogues tailored for J-PLUS, a large optical galaxy survey featuring a large number of narrow band filters. By analysing the J-PLUS mock catalogues, we have proved the ability of the survey to correctly identify a population of emission-line galaxies at various redshifts.

    As we summarize above, in this thesis we have tackled several aspects related to the details of galaxy formation, trying to bridge theoretical and observational approaches. The advance of theoretical models combined with the data from future experiments will certainly help to complete a detailed picture of how structures in our Universe form and evolve.