arXiv subjects

Yves Revaz

Publications and source records attributed to Yves Revaz.

43 records · Page 3Linked to original sources

arXiv2011

The Dynamical and Chemical Evolution of Dwarf Spheroidal Galaxies with GEAR

We present a fully parallel chemo-dynamical Tree/SPH code, GEAR, which allows to perform high resolution simulations with detailed chemical diagnostics. Starting from the public version of Gadget-2, we included the complex treatment of the baryon physics: gas cooling, star formation law, chemical evolution and supernovae feedback. We qualified the performances of GEAR with the case of dSph galaxies. GEAR conserves the total energy budget of the systems to better than 5% over 14Gyr and proved excellent convergence of the results with numerical resolution. We showed that models of dSphs in a static Euclidean space, where the expansion of the universe is neglected are valid. In addition, we tackled some of the existing open questions in the field, like the stellar mass fraction of dSphs and its link with the predicted dark matter halo mass function, the effect of the supernova feedback, the spatial distribution of the stellar populations, and the origin of the diversity in star formation histories and chemical abundance patterns. Strong supernovae driven winds seem incompatible with the observed metallicities and luminosities. Despite the fact that newly formed stars are preferentially found in the galaxy central parts, turbulent motions in the gas can quickly erase any metallicity gradient. The variety in dSph properties result from a range of total masses as well as from a dispersion in central densities. The latter is also seen in the haloes emerging from a LCDM cosmogony.

astro-ph.CO↗

arXiv2009

A Population of Compact Elliptical Galaxies Detected with the Virtual Observatory

Compact elliptical galaxies are characterized by small sizes and high stellar densities. They are thought to form through tidal stripping of massive progenitors. However, only a handful of them were known, preventing us from understanding the role played by this mechanism in galaxy evolution. We present a population of 21 compact elliptical galaxies gathered with the Virtual Observatory. Follow-up spectroscopy and data mining, using high-resolution images and large databases, show that all the galaxies exhibit old metal-rich stellar populations different from those of dwarf elliptical galaxies of similar masses but similar to those of more massive early-type galaxies, supporting the tidal stripping scenario. Their internal properties are reproduced by numerical simulations, which result in compact dynamically hot remnants resembling the galaxies in our sample.

astro-ph.CO↗

arXiv2006

Formation of cold molecular filaments in cooling flow clusters

New CO observations at the center of cooling flow in Perseus cluster \cite{salome06} show a clear correlation of the molecular gas with the previously detected H-$α$ filaments \cite{conselice01}. In this poster, we present high resolution multi-phase simulations of the Perseus Cluster, taking into account the AGN feedback in form of hot buoyant bubbles. These simulations show that significant amount of gas can cool far from the center. The AGN feedback provides some heating, but also trigger the hot gas compression, that favours cooling (positive feedback), even at high radius ($R>30 \rm{kpc}$). The cooled gas flows into the cluster core forming the observed filaments.

astro-ph↗

arXiv2005

A new scenario for the origin of galactic warps

Galactic warps represent an old unresolved problem, since the discovery, at the end of the fifties, of the HI warp of the Milky Way. In this paper, we propose a new scenario explaining a large fraction of the observed optical warps. Based on N-body simulations, we show that realistic galactic disks, where the dark matter is essentially distributed in a disk, are subject to bending instabilities. S, U-shaped, as well as asymmetric warps are spontaneously generated and in some cases are long-lived. While this scenario presents the advantage of explaining the three observed types of warps, it also brings new constraints on the dark matter distribution in spiral galaxies. Finally, it gives us a unified picture of galaxies where galactic asymmetries, like bars, spirals and warps result from gravitational instabilities.

astro-ph↗

arXiv2004

A Unified Picture of Disk Galaxies where Bars, Spirals and Warps Result from the Same Fundamental Causes

Bars and spiral arms have played an important role as constraints on the dynamics and on the distribution of dark matter in the optical parts of disk galaxies. Dynamics linked to the dissipative nature of gas, and its transformation into stars provide clues that spiral galaxies are driven by dissipation close to a state of \textit{marginal stability} with respect to the dynamics in the galaxy plane. Here we present numerical evidences that warps play a similar role but in the transverse direction. N-body simulations show that typical galactic disks are also marginally stable with respect to a bending instability leading to typical observed warps. The frequent occurrence of warps and asymmetries in the outer galactic disks give therefore, like bars in the inner disks, new constraints on the dark matter, but this time in the outer disks. If disks are marginally stable with respect to bending instabilities, our models suggest that the mass within the HI disks must be a multiple of the detected HI and stars, i.e., disks must be heavier than seen. But the models do not rule out a traditional thick halo with a mass within the HI disk radius similar to the total disk mass.

astro-ph↗

arXiv2004

Bending instabilities at the origin of persistent warps: a new constraint on dark matter halos

A substantial fraction of the warps in spiral galaxies may result from bending instabilities if the disks are essentially self-gravitating. With N-body simulations, we show that galaxies with self-gravitating disks as thick as HI disks are subject to bending instabilities generating S-shaped, U-shaped or asymmetric warps. S-shaped warps persist during several rotations and keep the line of node straight. The warp amplitudes generated by bending instabilities remain however modest. Other factors must be invoked for extreme warped disks. However, bending instabilities can account for most of the cases reported in optical surveys, where the warp angle is generally less than $5^\circ$. This mode of warping is very sensitive to the disk flattening. It also constrains the fraction of dark matter distributed in the disk and in the dark halo.

astro-ph↗

arXiv2000

N-body simulations of warped galaxies

Two methods generating warped galaxies with N-body simulations are presented. One uses an external potential as a disturber while the other is based on material accretion. The results of both methods are compared. A particular attention is given on the shape of the line of node (LON).

astro-ph↗