arXiv subjects

Y. Revaz

Publications and source records attributed to Y. Revaz.

21 records · Page 2Linked to original sources

arXiv2004

Bending instabilities at the origin of persistent warps

Based on N-body simulations, we show that realistic galactic disks are subject to bending instabilities of fire-hose type when the disks are substantially self-gravitating, that is, if they contain dark matter distributed in the disk. Depending on the degree of instability, S and U-shaped, as well as asymmetric warps are generated. In some cases, the warp may last several galactic rotations, particularly when the instability is marginal. Since the bending instability is very sensitive to the disk flattening, the fractions of dark matter distributed in the disk and in the dark halo are constrained. For a Milky Way like galaxy the extended dark halo can not exceed 30-40% of the total mass within 35 kpc if the Milky Way warp results from a bending instability. This mode of warping provides a unified picture of spiral galaxies, where bars, spiral arms and warps result all from disk gravitational instabilities, radial or transverse, which are constantly regenerated by the dissipative gas component.

astro-ph↗

arXiv2004

The Baryonic Tully-Fisher relation revisited

The Baryonic Tully-Fisher relation (BTF) can be substantially improved when considering that the galactic baryonic mass is likely to consist not only from the detected baryons, stars and gas, but also from a dark baryonic component proportional to the HI gas. The BTF relation is optimally improved when the HI mass is multiplied by a factor of about 3, but larger factors up to 11-16 still improve the fit over the original one using only the detected baryons. The strength of this improved relation is quantified with up-to-date statistical tests such as the Akaike Information Criterion or the Bayesian Information Criterion. In particular they allow to show that supposing a variable $M_\star/L$ ratio instead is much less significant. This result reinforces the suggestion made in several recent works that mass within galactic disks must be a multiple of the HI mass, and that galactic disks are substantially, but not necessarily fully, self-gravitating.

astro-ph↗

arXiv2001

Periodic orbits in warped disk

It is often assumed that a warped galaxy can be modeled by a set of rings. This paper verifies numerically the validity of this assumption by the study of periodic orbits populating a heavy self-gravitating warped disk. The phase space structure of a warped model reveals that the circular periodic orbits of a flat disk are transformed in quasi annular periodic orbits which conserve their stability. This lets us also explore the problem of the persistence of a large outer warp. In particular, the consistency of its orbits with the density distribution is checked as a function of the pattern speed.

astro-ph↗