Home  About us  Contact
 

Ram Pressure Stripping (ram + pressure_stripping)

Distribution by Scientific Domains
Physics and Astronomy100%

Selected Abstracts

Ram pressure stripping of disk galaxies in galaxy clusters

ASTRONOMISCHE NACHRICHTEN, Issue 9-10 2009
E. Roediger
Abstract While galaxies move through the intracluster medium of their host cluster, they experience a ram pressure which removes at least a significant part of their interstellar medium. This ram pressure stripping appears to be especially important for spiral galaxies: this scenario is a good candidate to explain the differences observed between cluster spirals in the nearby universe and their field counterparts. Thus, ram pressure stripping of disk galaxies in clusters has been studied intensively during the last decade. I review advances made in this area, concentrating on theoretical work, but continuously comparing to observations (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Formation and evolution of dwarf elliptical galaxies , II.

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2009
Spatially resolved star formation histories
ABSTRACT We present optical Very Large Telescope spectroscopy of 16 dwarf elliptical galaxies (dEs) comparable in mass to NGC 205, and belonging to the Fornax cluster and to nearby groups of galaxies. Using full-spectrum fitting, we derive radial profiles of the SSP-equivalent ages and metallicities. We make a detailed analysis with ulyss and steckmap of the star formation history in the core of the galaxies and in an aperture of one effective radius. We resolved the history into one to four epochs. The statistical significance of these reconstructions was carefully tested; the two programs give remarkably consistent results. The old stellar population of the dEs, which dominates their mass, is likely coeval with that of massive ellipticals or bulges, but the star formation efficiency is lower. Important intermediate age (1,5 Gyr) populations and frequently tails of star formation until recent times are detected. These histories are reminiscent of their lower mass dwarf spheroidal counterparts of the Local Group. Most galaxies (10/16) show significant metallicity gradients, with metallicity declining by 0.5 dex over one half-light radius on average. These gradients are already present in the old population. The flattened (or discy), rotating objects (6/16) have flat metallicity profiles. This may be consistent with a distinct origin for these galaxies or it may be due to their geometry. The central single stellar population equivalent age varies between 1 and 6 Gyr, with the age slowly increasing with radius in the vast majority of objects. The group and cluster galaxies have similar radial gradients and star formation histories. The strong and old metallicity gradients place important constraints on the possible formation scenarios of dEs. Numerical simulations of the formation of spherical low-mass galaxies reproduce these gradients, but they require a longer time for them to build up. A gentle depletion of the gas, by ram pressure stripping or starvation, could drive the gas-rich, star-forming progenitors to the present dEs. [source]

Simultaneous ram pressure and tidal stripping; how dwarf spheroidals lost their gas

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2006
Lucio Mayer
ABSTRACT We perform high-resolution N -body+SPH (smoothed particle hydrodynamics) simulations of gas-rich dwarf galaxy satellites orbiting within a Milky Way-sized halo and study for the first time the combined effects of tides and ram pressure. The structure of the galaxy models and the orbital configurations are chosen in accordance with those expected in a Lambda cold dark matter (,CDM) universe. While tidal stirring of disky dwarfs produces objects whose stellar structure and kinematics resembles that of dwarf spheroidals after a few orbits, ram pressure stripping is needed to entirely remove their gas component. Gravitational tides can aid ram pressure stripping by diminishing the overall potential of the dwarf, but tides also induce bar formation which funnels gas inwards making subsequent stripping more difficult. This inflow is particularly effective when the gas can cool radiatively. Assuming a low density of the hot Galactic corona consistent with observational constraints, dwarfs with Vpeak < 30 km s,1 can be completely stripped of their gas content on orbits with pericenters of 50 kpc or less. Instead, dwarfs with more massive dark haloes and Vpeak > 30 km s,1 lose most or all of their gas content only if a heating source keeps the gas extended, partially counteracting the bar-driven inflow. We show that the ionizing radiation from the cosmic ultraviolet (UV) background at z > 2 can provide the required heating. In these objects, most of the gas is removed or becomes ionized at the first pericenter passage, explaining the early truncation of the star formation observed in Draco and Ursa Minor. Galaxies on orbits with larger pericenters and/or falling into the Milky Way halo at lower redshift can retain significant amounts of the centrally concentrated gas. These dwarfs would continue to form stars over a longer period of time, especially close to pericenter passages, as observed in Fornax and other dwarf spheroidal galaxies (dSphs) of the Local Group. The stripped gas breaks up into individual clouds pressure confined by the outer gaseous medium that have masses, sizes and densities comparable to the H i clouds recently discovered around M31. [source]

Ram pressure stripping of disk galaxies in galaxy clusters

ASTRONOMISCHE NACHRICHTEN, Issue 9-10 2009
E. Roediger
Abstract While galaxies move through the intracluster medium of their host cluster, they experience a ram pressure which removes at least a significant part of their interstellar medium. This ram pressure stripping appears to be especially important for spiral galaxies: this scenario is a good candidate to explain the differences observed between cluster spirals in the nearby universe and their field counterparts. Thus, ram pressure stripping of disk galaxies in clusters has been studied intensively during the last decade. I review advances made in this area, concentrating on theoretical work, but continuously comparing to observations (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

The effect of ram-pressure stripping and starvation on the star formation properties of cluster galaxies

ASTRONOMISCHE NACHRICHTEN, Issue 9-10 2009
A. Boselli
Abstract We have combined UV to radio centimetric observations of resolved galaxies in the Virgo cluster with multizone, chemospectrophotometric models of galaxy evolution especially tailored to take into account the effects of the cluster environment (ram pressure stripping and starvation). This exercise has shown that anemic spirals with truncated radial profiles of the gas component and of the young stellar populations, typical in rich clusters of galaxies, have been perturbed by a recent (,100 Myr) ram pressure stripping event induced by their interaction with the cluster intergalactic medium. Starvation is not able to reproduce the observed truncated radial profiles. Both ram pressure and starvation induce a decrease of the stellar surface brightness of the perturbed disc, and thus can hardly be invoked to explain the formation of lenticular galaxies inhabiting rich clusters, which are characterised by higher surface brightnesses than early type spirals of similar luminosity. In dwarfs the ram pressure stripping event is so efficient to totally remove their gas thus stopping on short time scales (<2 Gyr) their star formation activity. Low luminosity star forming discs can be transformed in dE galaxies (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]