Measuring Stellar and Dark Mass Fractions in Spiral Galaxies
ArXiv astro-ph/0011250 (2000)
Abstract:
We explore the relative importance of the stellar mass density as compared to the inner dark halo, for the observed gas kinematics thoughout the disks of spiral galaxies. We perform hydrodynamical simulations of the gas flow in a sequence of potentials with varying the stellar contribution to the total potential. The stellar portion of the potential was derived empirically from K-band photometry. The output of the simulations - namely the gas density and the gas velocity field - are then compared to the observed spiral arm morphology and the H-alpha gas kinematics. We solve for the best matching spiral pattern speed and draw conclusions on how massive the stellar disk can be at most. For the case of the galaxy NGC 4254 (Messier 99) we demonstrate that the prominent spiral arms of the stellar component would overpredict the non-circular gas motions unless an axisymmetric dark halo component adds significantly in the radial range R_exp < R < 3*R_exp.Star Formation in Viscous Galaxy Disks
ArXiv astro-ph/0009330 (2000)
Abstract:
The Lin and Pringle model (1987) of galactic disk formation postulates that if star formation proceeds on the same timescale as the viscous redistribution of mass and angular momentum in disk galaxies, then the stars attain an exponential density profile. Their claim is that this result holds generally: regardless of the disk galaxy's initial gas and dark matter distribution and independent of the nature of the viscous processes acting in the disk. We present new results from a set of 2D hydro-simulations which investigate their analytic result.Time-independent gravitational fields in the BGK scheme for hydrodynamics
Astronomy and Astrophysics Supplement Series 139:1 (1999) 199-217
Abstract:
We incorporate a time-independent gravitational field into the BGK scheme for numerical hydrodynamics. In the BGK scheme the gas evolves via an approximation to the collisional Boltzmann equation, namely the Bhatnagar-Gross-Krook (BGK) equation. Time-dependent hydrodynamical fluxes are computed from local solutions of the BGK equation. By accounting for particle collisions, the fundamental mechanism for generating dissipation in gas flow, a scheme based on the BGK equation gives solutions to the Navier-Stokes equations: the fluxes carry both advective and dissipative terms. We perform numerical experiments in both 1D Cartesian geometries and axisymmetric cylindrical coordinates.Time-Independent Gravitational Fields in the BGK Scheme for Hydrodynamics
ArXiv astro-ph/9905247 (1999)
Abstract:
We incorporate a time-independent gravitational field into the BGK scheme for numerical hydrodynamics. In the BGK scheme the gas evolves via an approximation to the collisional Boltzmann equation, namely the Bhatnagar-Gross-Krook (BGK) equation. Time-dependent hydrodynamical fluxes are computed from local solutions of the BGK equation. By accounting for particle collisions, the fundamental mechanism for generating dissipation in gas flow, a scheme based on the BGK equation gives solutions to the Navier-Stokes equations: the fluxes carry both advective and dissipative terms. We perform numerical experiments in both 1D Cartesian geometries and axisymmetric cylindrical coordinates.A catalog of intracluster gas temperatures
Astrophysical Journal 412:2 (1993) 479-488