Quadratic genetic modifications: a streamlined route to cosmological simulations with controlled merger history

Understand

Recent work has studied the interplay between a galaxy's history and its observable properties using "genetically modified" cosmological zoom simulations.

• The approach systematically generates alternative histories for a halo, while keeping its cosmological environment fixed.
• Applications to date altered linear properties of the initial conditions such as the mean overdensity of specified regions; we extend the formulation to include quadratic features such as local variance, which determines the overall importance of smooth accretion relative to mergers in a galaxy's history.
• We introduce an efficient algorithm for this new class of modification and demonstrate its ability to control the variance of a region in a one-dimensional toy model.