Dynamical friction is a physical mechanism thought to be responsible for pairing of supermassive black holes (SMBHs) in the aftermath of galactic mergers. It arises when a massive perturber traveling through a background medium (either gas or stars) creates in it a density wake. The wake, which trails the perturber on its trajectory, causes it to slow down by gravitational interaction. Despite an important role played by this process in theoretical models, its impact still remains to be tested through observations, and will require detection of SMBH pairs with orbital separations < 1kpc. We model orbital evolution of a pair of SMBHs at these separations under the influence of gaseous dynamical friction for a range of physically motivated scenarios, encountered in merging galaxies. Based on it we calculate the probability of discovering a SMBH pair as a function of pair separation and make predictions for observations, which can be used to verify the impact of dynamical friction.
