Discovery of an Ultraviolet Counterpart to an Ultra-Fast X-ray Outflow in the Quasar PG1211+143

This is an author-created, un-copyedited version of an article published in The Astrophysical Journal. The Version of Record is available online at https://doi.org/10.3847/1538-4357/aaa42bWe observed the quasar PG 1211+143 using the Cosmic Origins Spectrograph on the Hubble Space Telescope in 2015 April as part of a joint campaign with the Chandra X-ray Observatory and the Jansky Very Large Array. Our ultraviolet spectra cover the wavelength range 912-2100 Å. We find a broad absorption feature () at an observed wavelength of 1240 Å. Interpreting this as H i Lyα, in the rest frame of PG 1211+143 (z = 0.0809), this corresponds to an outflow velocity of -16,980 (outflow redshift ), matching the moderate ionization X-ray absorption system detected in our Chandra observation and reported previously by Pounds et al. With a minimum H i column density of , and no absorption in other UV resonance lines, this Lyα absorber is consistent with arising in the same ultrafast outflow as the X-ray absorbing gas. The Lyα feature is weak or absent in archival ultraviolet spectra of PG 1211+143, strongly suggesting that this absorption is transient, and intrinsic to PG 1211+143. Such a simultaneous detection in two independent wavebands for the first time gives strong confirmation of the reality of an ultrafast outflow in an active galactic nucleus.Peer reviewe

Characteristics of He II Proximity Profiles

The proximity profile in the spectra of z~3 quasars, where fluxes extend blueward of the He II Lya wavelength 304 (1+z) A, is one of the most important spectral features in the study of the intergalactic medium. Based on the HST spectra of 24 He II quasars, we find that the majority of them display a proximity profile, corresponding to an ionization radius as large as 20 Mpc in the source's rest frame. In comparison with those in the H i spectra of the quasars at z~6, the He II proximity effect is more prominent and is observed over a considerably longer period of reionization. The He II proximity zone sizes decrease at higher redshifts, particularly at z > 3.3. This trend is similar to that for H I, signaling an onset of He II reionization at z~4. For quasar SDSS1253+6817 (z=3.48), the He II absorption trough displays a gradual decline and serves a good case for modeling the He II reionization. To model such a broad profile requires a quasar radiation field whose distribution between 4 and 1 Rydberg is considerably harder than normally assumed. The UV continuum of this quasar is indeed exceptionally steep, and the He II ionization level in the quasar vicinity is higher than the average level in the intergalactic medium. These results are evidence that a very hard EUV continuum from this quasar produces a large ionized zone around it. Distinct exceptions are the two brightest He II quasars at z~2.8, for which no significant proximity profile is present, possibly implying that they are young.Comment: 38 pages, 8 figures, 4 table