The MG II line profile in the Seyfert galaxy NGC 4151 : a new outflowing component.

Abstract

This paper examines the Mg II λλ2795, 2802 doublet in the Seyfert galaxy NGC 4151 at a higher resolution than has previously been used, searching for velocity systems in absorption and emission. Evidence is presented for a new, narrow, outflowing absorption system in Mg II having a velocity of 825 km s^-1 relative to the Sun, -165 km s^-1 relative to the systemic velocity of NGC 4151. This feature is not present in Lyα or C IV and possible explanations for this are considered. For the Mg II and C IV lines a model decomposition of the line profile is presented.