Physics affecting heavy impurity migration in tokamaks: Benchmarking test-ion code ASCOT against TEXTOR tracer experiment

•ASCOT simulations of TEXTOR molybdenum transport experiments were carried out.•Central and SOL plasma parameters were varied to study the impact on high-Z impurity transport in the simulations.•Toroidal plasma movement, either within the LCFS or as SOL flow, is negligible.•SOL profile and marker starting energy have modest impact on deposition.•Source distribution has a large impact in combination with radial electric field profiles.•The E⇀×B⇀ drift has the highest impact on the deposition profiles.