2019MNRAS.487.5041H

Quasar outflows are fundamental components of quasar environments that might play an important role in feedback to galaxy evolution. We report on the emergence of a remarkable new outflow absorption-line system in the quasar PG1411+442 (redshift ∼0.089) detected in the UV and visible with the Hubble Space Telescope Cosmic Origins Spectrograph and the Gemini Multi-Object Spectrograph, respectively. This new 'transient' system contains thousands of lines, including Fe II and Fe II^* from excited states up to 3.89 eV, H I^* Balmer lines, Na I D λλ5890, 5896, and the first detection of He I^* λ5876 in a quasar. The transient absorber is spatially inhomogeneous and compact, with sizes <=0.003 pc, based on covering fractions on the quasar continuum source ranging from ∼0.45 in strong UV lines to ∼0.04 in Na I D. CLOUDY photoionization simulations show that large total column densities log N_H(cm^–2) >= 23.4 and an intense radiation field <=0.4 pc from the quasar are needed to produce the observed lines in thick zones of both fully ionized and partially ionized gas. The densities are conservatively log n_H(cm^–3) >= 7 based on Fe II^*, H I^*, and He I^* but they might reach log n_H(cm^–3) >= 10 based on Na I D. The transient lines appear at roughly the same velocity shift, v ∼ -1900 km s^–1, as a 'mini-BAL' outflow detected previously, but with narrower Doppler widths, b ∼ 100 km s^–1, and larger column densities in more compact outflow structures. We propose that the transient lines identify a clumpy outflow from the broad emission-line region that, at its current speed and location, is still gravitationally bound to the central black hole.