475 research outputs found
Pre-Processing and Post-Processing in Group-Cluster Mergers
Galaxies in clusters are more likely to be of early type and to have lower
star formation rates than galaxies in the field. Recent observations and
simulations suggest that cluster galaxies may be `pre-processed' by group or
filament environments and that galaxies that fall into a cluster as part of a
larger group can stay coherent within the cluster for up to one orbital period
(`post-processing'). We investigate these ideas by means of a cosmological
-body simulation and idealized -body plus hydrodynamics simulations of a
group-cluster merger. We find that group environments can contribute
significantly to galaxy pre-processing by means of enhanced galaxy-galaxy
merger rates, removal of galaxies' hot halo gas by ram pressure stripping, and
tidal truncation of their galaxies. Tidal distortion of the group during infall
does not contribute to pre-processing. Post-processing is also shown to be
effective: galaxy-galaxy collisions are enhanced during a group's pericentric
passage within a cluster, the merger shock enhances the ram pressure on group
and cluster galaxies, and an increase in local density during the merger leads
to greater galactic tidal truncation.Comment: Accepted for publication in MNRAS. 25 pages, 21 figure
Simulations of the symbiotic recurrent nova V407 Cyg. I. Accretion and shock evolutions
The shock interaction and evolution of nova ejecta with a wind from a red
giant star in a symbiotic binary system are investigated via three-dimensional
hydrodynamics simulations. We specifically model the March 2010 outburst of the
symbiotic recurrent nova V407~Cygni from the quiescent phase to its eruption
phase. The circumstellar density enhancement due to wind-white dwarf
interaction is studied in detail. It is found that the density-enhancement
efficiency depends on the ratio of the orbital speed to the red giant wind
speed. Unlike another recurrent nova, RS~Ophiuchi, we do not observe a strong
disk-like density enhancement, but instead observe an aspherical density
distribution with higher density in the equatorial plane than at
the poles. To model the 2010 outburst, we consider several physical parameters,
including the red giant mass loss rate, nova eruption energy, and ejecta mass.
A detailed study of the shock interaction and evolution reveals that the
interaction of shocks with the red giant wind generates strong Rayleigh-Taylor
instabilities. In addition, the presence of the companion and circumstellar
density enhancement greatly alter the shock evolution during the nova phase.
The ejecta speed after sweeping out most of the circumstellar medium decreases
to km-s, depending on model, which is consistent with the
observed extended redward emission in [N~II] lines in April 2011.Comment: ApJ, In Press. Simulation Animation: https://youtu.be/g5Nu7vDfCO
Probing Satellite Quenching With Galaxy Clustering
Satellites within simulated massive clusters are significantly spatially
correlated with each other, even when those satellites are not gravitationally
bound to each other. This correlation is produced by satellites that entered
their hosts relatively recently, and is undetectable for satellites that have
resided in their hosts for multiple dynamical timescales. Therefore, a
measurement of clustering statistics of cluster satellites may be used to
determine the typical accretion redshifts of those satellites into their
observed hosts. We argue that such measurements may be used to determine the
fraction of satellite galaxies that were quenched by their current hosts,
thereby discriminating among models for quenching of star formation in
satellite galaxies.Comment: 7 page
Search for surviving companions in type Ia supernova remnants
The nature of the progenitor systems of type~Ia supernovae is still unclear.
One way to distinguish between the single-degenerate scenario and
double-degenerate scenario for their progenitors is to search for the surviving
companions. Using a technique that couples the results from multi-dimensional
hydrodynamics simulations with calculations of the structure and evolution of
main-sequence- and helium-rich surviving companions, the color and magnitude of
main-sequence- and helium-rich surviving companions are predicted as functions
of time. The surviving companion candidates in Galactic type~Ia supernova
remnants and nearby extragalactic type~Ia supernova remnants are discussed. We
find that the maximum detectable distance of main-sequence surviving companions
(helium-rich surviving companions) is ~Mpc (~Mpc), if the
apparent magnitude limit is 27 in the absence of extinction, suggesting that
the Large and Small Magellanic Clouds and the Andromeda Galaxy are excellent
environments in which to search for surviving companions. However, only five
Ia~SNRs have been searched for surviving companions, showing little support for
the standard channels in the singe-degenerate scenario. To better understand
the progenitors of type Ia supernovae, we encourage the search for surviving
companions in other nearby type Ia supernova remnants.Comment: 25 pages, 5 figures, and 2 tables. Accepted for publication in Ap
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