The X-ray/UV absorber in NGC 4593

We present the results of a recent (March 2011) 160 ks Chandra-LETGS observation of the Seyfert galaxy NGC 4593, and the analysis of archival X-ray and UV spectra taken with XMM-Newton and HST/STIS in 2002. We find evidence of a multi-component warm absorber (WA) in the X-rays with four distinct ionisation degrees (log xi = 1.0, log xi = 1.7, log xi = 2.4, and log xi = 3.0) outflowing at several hundreds of km/s. In the UV we detect 15 kinematic components in the absorbers, blueshifted with respect to the systemic velocity of the source, ranging from -60 km/s to -1520 km/s. Although the predicted CIV and NV column densities from the low-ionisation X-ray outflow are in agreement with those measured for some components in the STIS spectrum, there are kinematic discrepancies that may prevent both the X-ray and UV absorbers from originating in the same intervening gas. We derive upper limits on the location of the absorbers finding that the high-ionisation gas lie within ~6 - 29 pc from the central ionising source, while the low-ionisation gas is located at several hundreds of pc. This is consistent with our line of sight passing through different parts of a stratified wind. The total kinetic energy of the outflows injected into the surroundings of the host galaxy only accounts for a tiny fraction of the bolometric luminosity of the source, and it is therefore unlikely that they may cause a significant impact in the interstellar medium of NGC 4593 in a given single episode of activity.