Peculiar motions and star formation in the interacting galaxy complexMK 171 = NGC 3690+IC 694.

Abstract

Spectroscopic observations in the visible and in the far ultraviolet are combined with other existing information to interpret the properties of the exceptionally active extended star formation in Mk 171. The authors show that this system corresponds to the interaction, and probably to the direct collision, of two galaxies with a total mass of ⪉4×10¹⁰M_sun;. All the properties of the system are best accounted for by the formation of O stars only in the approximate mass range 20 - 35 M_sun;, which has started about 1.5×10⁷yr ago. The total mass of stars formed is of the order of 5×10⁷M_sun;, to be compared with a total mass of atomic hydrogen of 1.4×10⁹M_sun; and a mass of molecular gas of perhaps 10¹⁰M_sun;.