3,319 research outputs found
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 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
Idéfix : nouvel imageur polarimétrique pour l'Observatoire du mont Mégantic
Mémoire numérisé 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
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