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