Malin 1: interacting galaxy pair?

Malin 1 is a unique, extraordinarily large low-surface brightness galaxy. The structure and the origins of the galaxy are poorly understood. The reason for this is the absence of detailed observational data, especially of high-resolution kinematics. In this Letter, we study the stellar kinematics of the inner part (r < 15 kpc) of Malin 1. We present spectroscopic arguments in favour of a small galaxy - Malin 1B - being a companion probably interacting with the main galaxy - Malin 1. This object is clearly seen in many published images of Malin 1 but is not mentioned in any astronomical data bases. Malin 1B is located at a projected distance of 14 kpc from Malin 1's nucleus and has small - 65 +/- 16 km s-1 - relative velocity, which we determined for the first time. We suggest that the ongoing interaction with Malin 1B can explain the main morphological features of Malin 1's central region - two-armed spiral structure, a bar and an external one-armed spiral pattern. We also investigated the large-scale environment of Malin 1 and postulated that the galaxy SDSS J123708.91 + 142253.2 might be responsible for the formation of an extended low-surface brightness envelope by means of head-on collision with Malin 1 (in the framework of the collision scenario proposed by Mapelli et al.). To test the collisional origins of Malin 1's global structure, more observational data and new numerical models are needed.