Harmonic analysis of the Ha velocity field of NGC 4254

The ionized gas kinematics of the Virgo Cluster galaxy NGC 4254 (Messier 99) is analyzed by an harmonic decomposition of the velocity field into Fourier coefficients. The aims of this study are to measure the kinematical asymmetries of Virgo cluster galaxies and to connect them to the environment. The analysis reveals significant $m=1,2,4$ terms which origins are discussed.Comment: 3 pages, 2 figures, to appear in "Science Perspectives for 3D Spectroscopy", ESO Astrophysics Symposia, M. Kissler-Patig, M.M. Roth & J.R. Walsh ed

A galactic weigh-in: mass models of SINGS galaxies using chemospectrophotometric galactic evolution models

The baryonic mass-to-light ratio used to perform the photometry-to-mass conversion has a tremendous influence on the measurement of the baryonic content and distribution, as well as on the determination of the dark halo parameters. Since numerous clues hint at an inside-out formation process for galaxies, a radius-dependant mass-to-light ratio is needed to physically represent the radially varying stellar population. In this article, we use chemo-spectrophotometric galactic evolution (CSPE) models to determine the mass-to-light ratio for a wide range of masses and sizes in the scenario of an inside-out formation process by gas accretion. We apply our method on a SINGS subsample of ten spiral and dwarf galaxies for stellar bands covering from the UV to the MIR. The CSPE models prove to be a good tool to weight the different photometric bands in order to obtain consistent stellar discs' masses regardless of the spectral band used. On the other hand, we show that colour index vs. the mass-to-light ratio relation is an imperfect tool to assign masses to young stellar populations because of the degeneracy affecting mass-to-light ratio in all bands at low colour index. Resulting discs from our analysis are compatible with the maximum disc hypothesis provided that adequate bulge/disc decomposition is performed and correction for the presence of a bar is not neglected since it disturbs the internal disc kinematics. Disc-mass models including mass-to-light ratio-as a free parameter as well as models using our physically motivated radial variation of mass-to-light ratio are presented and discussed for each galaxy.Comment: 27 pages, 15 figures, accepted for publication in the Astrophysical Journa

Modelling and Control of the Moisture in a Test Bench Flow with Time-delay

International audienceMoisture control in systems with time delay is studied in this work to be assessed in a process-control system (Test bench). To further investigate the phenomenon of transport delay in flows, the test bench system has been studied. In this work it is presented the design and validation of a model which describes the dynamics of mass transport phenomena. In order to control the moisture in the test bench, it is design a state-feedback controller such that the closed-loop system is robustly stable has an upper bound for the time delay

Cinématique et dynamique des galaxies spirales barrées

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Quantifying Resonant Structure in NGC 6946 from Two-dimensional Kinematics

We study the two-dimensional kinematics of the H-alpha-emitting gas in the nearby barred Scd galaxy, NGC 6946, in order to determine the pattern speed of the primary m=2 perturbation mode. The pattern speed is a crucial parameter for constraining the internal dynamics, estimating the impact velocities of the gravitational perturbation at the resonance radii, and to set up an evolutionary scenario for NGC 6946. Our data allows us to derive the best fitting kinematic position angle and the geometry of the underlying gaseous disk, which we use to derive the pattern speed using the Tremaine-Weinberg method. We find a main pattern speed Omega_p=22 km/s/kpc, but our data clearly reveal the presence of an additional pattern speed Omega_p=47 km/s/kpc in a zone within 1.25 kpc of the nucleus. Using the epicyclic approximation, we deduce the location of the resonance radii and confirm that inside the outer Inner Lindblad Resonance radius of the main oval, a primary bar has formed rotating at more than twice the outer pattern speed. We further confirm that a nuclear bar has formed inside the Inner Lindblad Resonance radius of the primary bar, coinciding with the inner Inner Lindblad Resonance radius of the large-scale m=2 mode oval.Comment: Accepted for publication in ApJ Letter