Star formation in luminous LoBAL quasars at 2.0 < z < 2.5

Abstract

ABSTRACT Low-ionization broad absorption line quasars (LoBALs) mark an important, yet poorly understood, population of quasars showing direct evidence for energetic mass outflows. We outline a sample of 12 luminous (Lbol > 1046 ergs−1) LoBALs at 2.0 < z < 2.5 – a key epoch in both star formation and black hole accretion, which have been imaged as part of a targeted program with the Herschel Spectral and Photometric Imaging REceiver (SPIRE). We present K-band NOTCam spectra for three of these targets, calculating their spectroscopic redshifts, black hole masses, and bolometric luminosities, and increasing the total number of LoBAL targets in our sample with spectral information from five to eight. Based on FIR observations from Herschel SPIRE, we derive prolific star formation rates (SFRs) ranging 740–2380 M⊙ yr−1 for the detected targets, consistent with LoBALs existing in an evolutionary phase associated with starburst activity. Furthermore, an upper limit of <440 M⊙ yr−1 is derived for the non-detections, meaning moderate-to-high SFRs cannot be ruled out, even among the undetected targets. Indeed, we detect an enhancement in both the SFRs and FIR fluxes of LoBALs compared to HiBAL and non-BAL quasars, further supporting the evolutionary LoBAL paradigm. Despite this enhancement in SFR, however, the environments of LoBALs appear entirely consistent with the general galaxy population at 2.0 < z < 2.5.