UV counterpart of an X-ray ultra-fast outflow in IRAS 17020+4544

TL;DR

This paper reports the discovery of a UV absorption feature in IRAS 17020+4544 that corresponds to a low-ionization, high-velocity component of an ultra-fast outflow previously observed in X-ray, providing insights into the outflow's multi-phase structure.

Contribution

The study presents the first detection of a UV counterpart to an X-ray ultra-fast outflow in a Seyfert galaxy, linking UV and X-ray outflow components through detailed spectroscopy and modeling.

Findings

UV outflow velocity of -23430 km/s identified

UV UFO corresponds to a low-ionization, low-velocity component of X-ray UFO

Higher-ionization, higher-velocity X-ray UFO components are not detected in UV

Abstract

We report on the discovery of a UV absorption counterpart of a low-ionization X-ray ultra-fast outflow (UFO) in the Narrow-Line Seyfert-1 galaxy IRAS 17020+4544. This UV signature of the UFO is seen as a narrow and blueshifted Lyman-alpha absorption feature in the far-UV spectrum, taken with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST). The Lyman-alpha feature is found to be outflowing with a velocity of -23430 km/s (0.078 c). We carry out high-resolution UV spectroscopy and photoionization modeling to study the UFO that is seen in the HTS/COS spectrum. The results of our modeling show that the UV UFO corresponds to a low-ionization, low-velocity component of the X-ray UFO found previously with XMM-Newton's Reflection Grating Spectrometer (RGS). The other higher-velocity and higher-ionization components of the X-ray UFOs are not significantly detected in the HST/COS spectrum, consistent with predictions of our photoionization calculations. The multiple ionization and velocity components of the UFOs in IRAS 17020+4544 suggest a scenario where a powerful primary UFO entrains and shocks the ambient medium, resulting in formation of weaker secondary UFO components, such as the one found in the UV band.