Discovery of Metastable He I* λ10830 Mini-broad Absorption Lines and Very Narrow Paschen α Emission Lines in the ULIRG Quasar IRAS F11119+3257

Abstract

Abstract IRAS F11119+3257 is a quasar-dominated ultraluminous infrared galaxy, with a partially obscured narrow-line Seyfert 1 nucleus. In this paper, we present the near-IR (NIR) spectroscopy of F11119+3257, in which we find unusual Paschen emission lines and metastable He i* λ10830 absorption associated with the previously reported atomic sodium and molecular OH mini-BAL (broad absorption line) outflow. Photoionization diagnosis confirms previous findings that the outflows are at kiloparsec scales. Such large-scale outflows should produce emission lines. We indeed find that high-ionization emission lines ([O III], [Ne III], and [Ne V]) are dominated by blueshifted components at similar speeds to the mini-BALs. The blueshifted components are also detected in some low-ionization emission lines, such as [O II] λ3727 and some Balmer lines (Hα, Hβ, and Hγ), even though their cores are dominated by narrow (FWHMNEL = 570 ± 40 km s−1) or broad components at the systemic redshift of z = 0.18966 ± 0.00006. The mass flow rate (230–730 M ⊙ yr−1) and the kinetic luminosity ( erg s−1) are then inferred jointly from the blueshifted emission and absorption lines. In the NIR spectrum of F11119+3257, we also find that the Paschen emission lines are unique, in which a very narrow (FWHM = 260 ± 20 km s−1) component is shown in only Paα. This narrow component most probably comes from heavily obscured star formation. Based on the Paα and Paβ emissions, we obtain an extinction at the H band, A H > 2.1 (or a reddenning of > 3.7), and a star formation rate of SFR > 130 M ⊙ yr−1 that resembles the estimates inferred from the far-IR emissions (SFRFIR = 190 ± 90 M ⊙ yr−1).