Measuring mass: non-circular motions of gas in disk galaxies and radial velocities of stars in a global cluster

This thesis is concerned with the motions of gas in disk galaxies and with the motions of stars in a globular cluster to learn about their mass content. First we study non-circular streaming motions of HI gas in five representative disk galaxies with a bisymmetric model. We show that this physically motivated method can represent a wide range of bar-like distortions and that its model parameters can be related to useful physical parameters of galaxies like the amplitude of the forced non-circular speed, the bar angle, and the halo ellipticity. We also model the non-circular gas flow in the strongly barred galaxy NGC~1365. The gravitational potential is based on new observations that include photometric imaging, Fabry-Perot emission line imaging spectroscopy and a detailed re-analysis of archival HI data from the VLA. We use our 2-dimensional velocity map to constrain the strength and positions of the shocks in hydrodynamical simulations and find that better agreement is found with a massive, but not fully maximal disk $(m{M/L}simeq 2.0pm 1.0)$ and a fast bar (corotation at 1.2$m{R_{bar}}$). The analysis was complicated by the discovery of an asymmetric distribution of dust and kinematics in the bar region despite the remarkably bisymmetric distribution of the I-band light. We have measured 543 radial velocities of stars in the direction of the Galactic globular cluster M80 with Fabry-Perot absorption-line imaging spectroscopy. The data is used to derive the total mean velocity of $7.39 pm 0.54$ kms, the total velocity dispersion of $10.1 pm 0.4$ kms, a declining dispersion profile, and the rotation of the cluster. M80 is rotating with an amplitude of $2.42 pm 0.81$ kms along an axis with a position angle of $246.1degr pm 17.1$ (measured from North through East), which is perpendicular to the major axis of the cluster flattening. We have fitted single- and multi-mass Michie-King models to our velocity data and to surface-brightness profiles taken from the literature. Only when we increase the expected present-day number of white dwarfs are we able to match the expected $M/L_V$ of the stellar population with the dynamically-derived value of $3.0pm0.3$. We tentatively interpret this as evidence of tidal stripping given that M80 is on an orbit that keeps it in the inner regions of the Galaxy and therefore has probably experienced significant tidal mass loss.Ph.D.Includes bibliographical referencesby Ricardo Zánmar Sánche