Resolving the C IV and Mg II Absorption in NGC 4151

Abstract

Observations of the C IV and Mg II absorption lines in the Seyfert 1 galaxy NGC 4151 obtained with the GHRS in October 1994 are presented. The data from the STScI archive show multiple broad and narrow components in both species. In addition to Galactic absorption, four narrow and four broad systems associated with NGC 4151 are identified. Two broad systems dominate the total equivalent width, and their mean blueshift and width are comparable to the broad Lyman line and continuum absorption seen in far-UV spectra from the Hopkins Ultraviolet Telescope. Narrow-line C IV emission is present on the red side of the broadest absorption trough, and narrow absorption at the systemic velocity of NGC 4151, presumably in its own ISM, absorbs the core of the narrow emission line. Strong Mg II absorption is present in all but two velocity systems. Ratios relative to the corresponding C IV components suggest a low ionization parameter for the absorbing gas: U ~ 1-3 x 10^{-3}. This makes none of the identified UV absorption systems a good candidate for association with the warm X-ray absorbing gas.