Multiple Velocity Components in the CIV Absorption Line of NGC55481

We have observed the much studied Seyfert 1 galaxy NGC5548 with the GHRS spectrometer on HST. Our 14ksec observation covers the CIV emission line at a resolution of >20,000. Our purpose was to study the absorption line found at lower resolution by IUE and HST/FOS. We found that the CIV absorption line resolves into 6 separate doublets with EWs of 0.07Å–0.38Å. The absorption lines have blueshifts relative to the systemic velocity of the galaxy of 380 – 1250 km s−1, except for one which has a redshift of 250 km s−1, suggesting both inflow and outflow. The inflowing component may be related to the accretion flow into the nuclear black hole. All the doublet lines are resolved by the GHRS. Three doublets are narrow with FWHM<∼100 km s −1, and three are broad, FWHM ∼160–290 km s−1 . We find evidence of partial covering by the narrow absorption lines. Either (but not both) of the two strongest broad doublets could be from the same material that produces the X-ray ionized absorber seen in soft X-rays. The remaining five systems must be at least 10 times less ionized (and so of lower total column density) to remain consistent with the X-ray spectra. Subject headings: galaxies: Seyfert, galaxies: individual (NGC5548), galaxies: absorption lines, ultraviolet: galaxies Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. [email protected]