Lecturer: Dr. Santi Roca Affiliation: Racah Institute of Physics, The Hebrew University of Jerusalem Abstract: Simulations have shown to be one of the best tools to study properties of galactic large scale structures and their effects on the local kinematics of stars. In this thesis, using high resolution simulations obtained with different codes and initial condition techniques, we have observed two different behaviors for the rotation frequency of transient spiral arms like structures. Whereas unbarred disks present spiral arms nearly corotating with disk particles, strong barred models (bulged or bulge-less) quickly develop a bar-spiral structure dominant in density, with a pattern speed almost constant in radius (Roca- Fàbrega et al. 2013). Preliminary results also indicate that particles in barred models move inside the spiral structures. A second result we present in the thesis is that the sign of the kinematic parameter known as vertex deviation (lv) can be used to trace resonance radius of non-axisymmetric structures. This parameter changes its sign from negative to positive when crossing the spiral arms toward disk rotation, in regions where the spiral arms are in between corotation (CR) and the Outer Lindblad Resonance (OLR). By contrast, when the arm sections are inside the CR and outside the OLR, lv changes from negative to positive (Roca-Fàbrega et al. 2014). Finally we present a new cosmological Milky Way sized galaxy simulation that includes both the collisionless N-body and also the gas components. The system has been evolved inside a 28 Mpc cosmological box with a spatial resolution of 109 pc. At z=0 the system has an Mvir = 7.33•10^11 Msun. We have observed how a well-defined disk is formed inside the dark matter halo and the overall amount of gas and stars is comparable with MW observations. Several non-axisymmetric structures arise out of the disk: spirals, bars and also a warp. We have also observed that a huge reservoir of hot gas is present at large distances from the disk, embedded in the dark matter halo region, accounting for a fraction of the "missing baryons". Gas column density, emission (EM) and dispersion (DM) measure have been computed from inside the simulated disk at a position of 8 kpc from the center and in several different directions. Our preliminary results reveal that the distribution of hot gas is non-isotropic according with observations Gupta et al. 2012 and Gupta et al. 2013. Also its metallic content presents a clear bimodality what is a consequence of a recent accretion of a satellite galaxy. After a careful analysis we confirm that due to the anisotropy in the gas distribution more than 50 random observations of different sky regions are needed to recover the real distribution of hot gas in the galactic halo with a relative error lower than 5% (Roca-Fàbrega et al. 2015 in preparation). Additional details of the upcoming Astrophysics' seminars can be found on the following link. ‏האירוע הזה כולל שיחת וידאו ב-Google Hangouts. הצטרף: https://hangouts.google.com/hangouts/_/mail.huji.ac.il/astrophysics?hceid=bWFpbC5odWppLmFjLmlsX2c0czhydDlpcmhwZzRvdGNybWIzZGFqcjdvQGdyb3VwLmNhbGVuZGFyLmdvb2dsZS5jb20.7tbmqakutjolvb6vgd2p6bvrl0&hs=121