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Using high resolution numerical simulations -- addressing the dynamics, the star formation, and the chemical evolution -- we follow the formation of disc galaxies during wet major mergers in which each protogalaxy is embedded in a hot gaseous halo. We witness the destruction of the discs of the protogalaxies and the inside-out formation of a new disc, which is both massive and extended. We also witness the formation of a classical bulge component whose mass relative to the disc varies from one run to another, taking values that cover all the range from lenticulars to spiral galaxies.
While photometric surveys of normal stars for exoplanet transits have revealed many candidate planets, the effort is limited by non-Gaussian noise. This typically arises from stellar magnetic activity for space-based missions (Kepler, Corot, TESS) and from atmospheric effects for ground-based projects (WASP, HAT, AST3-1). Most treatments of these extraneous noise use nonparametric techniques, but we have found that parametric autoregressive ARIMA models are often very effective. This talk reviews the fitting of ARIMA models to reduce autocorrelated noise, the development of a Transit Com
I will discuss the astrophysical importance of the recent LIGO/Virgo direct detections of gravitational-waves. Despite the fact that massive BH-BH dominance in gravitational-wave signal was predicted prior the detections, it is not at all clear which one of the several formation scenarios produces these massive mergers. This inhibits astrophysical information inference from LIGO/Virgo observations, as conclusions are different within each formation scenario. There is quite an opposite problem with the recent detection of NS-NS merger in an old elliptical host galaxy.
The Sun is an intense and steady source of gamma rays, likely due to hadronic interactions between Galactic cosmic rays and the solar atmosphere.The gamma-ray flux measured by Fermi, however, is much larger than previous theoretical estimates.
Gravitational microlensing provides a unique probe to study the population of lens objects and the emission region of the innermost parts of quasar accretion disks. We show that the current X-ray observations of microlensing signatures of emission close to the innermost stable orbit are able to constrain the population of lens objects down to planet mass scales.
The Chemistry properties of galaxies are regulated by many fundamental physical processes, including gas accretion, gas outflow, and star formation. These processes are known to be critical to shape the galaxies to be what we see today. Due to a lack of direct observations and complexity in the interplays between these processes, we still do not fully understand the properties of these processes and the exact roles they played in driving galaxy evolution. In this talk, I would like to discuss what we could learn in terms of this issue by studying the chemical properties of galaxies.