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We have constructed merger trees for galaxies in the Illustris Simulation by directly tracking the baryonic content of subhalos. These merger trees are used to calculate the galaxy-galaxy merger rate as a function of descendant stellar mass, progenitor stellar mass ratio, and redshift. We demonstrate that the most appropriate definition for the mass ratio of a galaxy-galaxy merger consists in taking both progenitor masses at the time when the secondary progenitor reaches its maximum stellar mass. Additionally, we avoid effects from `orphaned galaxies by allowing some objects to `skip a snapshot when finding a descendant, and by only considering mergers which show a well-defined `infall moment. Adopting these definitions, we obtain well-converged predictions for the galaxy-galaxy merger rate with the following main features, which are qualitatively similar to the halo-halo merger rate except for the last one: a strong correlation with redshift that evolves as $sim (1+z)^{2.4-2.8}$, a power law with respect to mass ratio, and an increasing dependence on descendant stellar mass, which steepens significantly for descendant stellar masses greater than $sim 2 times 10^{11} , {rm M_{odot}}$. These trends are consistent with observational constraints for medium-sized galaxies ($M_{ast} gtrsim 10^{10} , {rm M_{odot}}$), but in tension with some recent observations of the close pair fraction for massive galaxies ($M_{ast} gtrsim 10^{11} , {rm M_{odot}}$), which report a nearly constant or decreasing evolution with redshift. Finally, we provide a fitting function for the galaxy-galaxy merger rate which is accurate over a wide range of stellar masses, progenitor mass ratios, and redshifts.
(Abridged) Any viable cosmological model in which galaxies interact predicts the existence of primordial and tidal dwarf galaxies (TDGs). In particular, in the standard model of cosmology ($Lambda$CDM), according to the dual dwarf galaxy theorem, the
We have generated synthetic images of $sim$27,000 galaxies from the IllustrisTNG and the original Illustris hydrodynamic cosmological simulations, designed to match Pan-STARRS observations of $log_{10}(M_{ast}/{rm M}_{odot}) approx 9.8$-$11.3$ galaxi
Quenching is a key topic in exploring the formation and evolution of galaxies. In this work, we study the quenching rate, i.e., the variation in the fraction of quenched galaxies per unit time, of the Illustris-1 simulation. By building the quenched
There is a consensus in the literature that starburst galaxies are triggered by inter- action events. However, it remains an open question as to what extent both merging and non-merging interactions have in triggering starbursts? In this study, we ma
The flux ratios in the multiple images of gravitationally lensed quasars can provide evidence for dark matter substructure in the halo of the lensing galaxy if the flux ratios differ from those predicted by a smooth model of the lensing galaxy mass d