UV Counterpart of an X-Ray Ultrafast Outflow in IRAS 17020+4544

Abstract

We report on the discovery of a UV absorption counterpart of a low-ionization X-ray ultrafast 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 Lyα absorption feature in the far-UV spectrum, taken with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST). The Lyα feature is found to be outflowing with a velocity of -23,430 km s^-1 (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. 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.