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We use an N-body/hydrodynamic simulation to forecast the future encounter between the Milky Way and the Andromeda galaxies, given present observational constraints on their relative distance, relative velocity, and masses. Allowing for a comparable amount of diffuse mass to fill the volume of the Local Group, we find that the two galaxies are likely to collide in a few billion years – within the Sun's lifetime. During the interaction, there is a chance that the Sun will be pulled away from its present orbital radius and reside in an extended tidal tail. The likelihood for this outcome increases as the merger progresses, and there is a remote possibility that our Sun will be more tightly bound to Andromeda than to the Milky Way before the final merger. Eventually, after the merger has completed, the Sun is most likely to be scattered to the outer halo and reside at much larger radii (>30 kpc). The density profiles of the stars, gas and dark matter in the merger product resemble those of elliptical galaxies. Our Local Group model therefore provides a prototype progenitor of late-forming elliptical galaxies. [ABSTRACT FROM AUTHOR]

We employ numerical simulations of galaxy mergers to explore the effect of galaxy mass ratio on merger-driven starbursts. Our numerical simulations include radiative cooling of gas, star formation, and stellar feedback to follow the interaction and merger of four disc galaxies. The galaxy models span a factor of 23 in total mass and are designed to be representative of typical galaxies in the local universe. We find that the merger-driven star formation is a strong function of merger mass ratio, with very little, if any, induced star formation for large mass ratio mergers. We define a burst efficiency that is useful to characterize the merger-driven star formation and test that it is insensitive to uncertainties in the feedback parametrization. In accord with previous work we find that the burst efficiency depends on the structure of the primary galaxy. In particular, the presence of a massive stellar bulge stabilizes the disc and suppresses merger-driven star formation for large mass ratio mergers. Direct, coplanar merging orbits produce the largest tidal disturbance and yield the most intense burst of star formation. Contrary to naive expectations, a more compact distribution of gas or an increased gas fraction both decrease the burst efficiency. Owing to the efficient feedback model and the newer version of smoothed particle hydrodynamics employed here, the burst efficiencies of the mergers presented here are smaller than in previous studies. [ABSTRACT FROM AUTHOR]

We construct a physically motivated model for predicting the properties of the remnants of gaseous galaxy mergers, given the properties of the progenitors and the orbit. The model is calibrated using a large suite of smoothed particle hydrodynamics (SPH) merger simulations. It implements generalized energy conservation while accounting for dissipative energy losses and star formation. The dissipative effects are evaluated from the initial gas fractions and from the orbital parameters via an ‘impulse’ parameter, which characterizes the strength of the encounter. Given the progenitor properties, the model predicts the remnant stellar mass, half-mass radius and velocity dispersion to an accuracy of 25 per cent. The model is valid for both major and minor mergers. We provide an explicit recipe for semi-analytic models of galaxy formation. [ABSTRACT FROM AUTHOR]

The hierarchical formation of structure suggests that dark halos, and the galaxies they host, are shaped by their merging history. While the idea that mergers between galaxies of equal mass, i.e., major merger, produce elliptical galaxies has received considerable attention, he galaxies that result from minor merger, i.e., mergers between galaxies with a large mass ratio, is much less understood. We have performed a large number of numerical simulations of minor mergers, including cooling, star formation, and black hole growth in order to study this process in more detail. This talk will present some preliminary results of this study, and in particular, the morphology and kinematics of minor merger remnants. [ABSTRACT FROM PUBLISHER]

Using hydrodynamic simulations of disc-galaxy major mergers, we investigate the star formation history and remnant properties when various parametrizations of a simple stellar feedback model are implemented. The simulations include radiative cooling, a density-dependent star formation recipe and a model for feedback from massive stars. The feedback model stores supernova feedback energy within individual gas particles and dissipates this energy on a time-scale specified by two free parameters; τfb, which sets the dissipative time-scale, and n, which sets the effective equation of state in star-forming regions. Via this model, feedback energy can provide pressure support to regions of gas that are thermally cold. Using a self-consistent disc galaxy, modelled after a local Sbc spiral, in both isolated and major-merger simulations, we investigate parametrizations of the feedback model that are selected with respect to the quiescent disc stability. These models produce a range of star formation histories for discs evolved in isolation, or during a major merger, yet all are consistent with the star formation relation found by Kennicutt. We suggest that this result is produced by the adopted recipe for star formation and is not a byproduct of the feedback model. All major mergers produce a population of new stars that is highly centrally concentrated, demonstrating a distinct break in the surface density profile, consistent with previous findings. The half-mass radius and one-dimensional velocity dispersion are affected by the feedback model used. In tests with up to an order of magnitude higher resolution, the star formation history is nearly identical, suggesting that we have achieved a numerically converged star formation history. Finally, we compare our results to those of previous simulations of star formation in disc-galaxy major mergers, addressing the effects of star formation normalization, the version of smoothed particle hydrodynamics (sph) employed and assumptions about the interstellar medium. We conclude by suggesting several methods by which future studies may better constrain feedback models. [ABSTRACT FROM AUTHOR]

We use numerical simulations to study how the spatial distribution and kinematics of globular cluster systems (GCS) are affected by galaxy mergers. Each progenitor galaxy is given a GCS modeled after the Galactic GCS. We then study how a major merger affects the spatial distribution and kinematics of the GCS. Here we present our methodology. Future work will investigate the effects of varying galaxy parameters, merger orbital parameters, and initial GCS number density profile and kinematics. We hope to be able to extract information about the merger history of a galaxy from observations of its GCS spatial distribution and kinematics. [ABSTRACT FROM PUBLISHER]

We present a merger-driven evolutionary model for the production of luminous (LIRGs) and ultraluminous infrared galaxies (ULIRGs) with warm infrared (IR) colours. Our results show that simulations of gas-rich major mergers including star formation, black hole growth and feedback can produce warm (U)LIRGs. We also find that while the warm evolutionary phase is associated with increased active galactic nucleus (AGN) activity, star formation alone may be sufficient to produce warm IR colours. However, the transition can be suppressed entirely – even when there is a significant AGN contribution – when we assume a single-phase interstellar medium, which maximizes the attenuation. Finally, our evolutionary models are consistent with the 25-to-60 flux density ratio versus relation for local LIRGs and ULIRGs, and predict the observed scatter in IR colour at fixed . Therefore, our models suggest a cautionary note in the interpretation of warm IR colours: while associated with periods of active black hole growth, they are probably produced by a complex mix of star formation and AGN activity intermediate between the cold star formation dominated phase and the birth of a bright, unobscured quasar. [ABSTRACT FROM AUTHOR]