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A SCUBA-2 survey of FeLoBAL QSOs. Are FeLoBALs in a `transition phase' between ULIRGs and QSOs?

Research output: Contribution to Journal/MagazineJournal articlepeer-review

  • Giulio Violino
  • Kristen E. K. Coppin
  • Jason A. Stevens
  • Duncan Farrah
  • James E. Geach
  • Dave M. Alexander
  • Ryan Hickox
  • Daniel J. B. Smith
  • Julie L. Wardlow
<mark>Journal publication date</mark>1/04/2016
<mark>Journal</mark>Monthly Notices of the Royal Astronomical Society
Issue number2
Pages (from-to)1371-1384
Publication StatusPublished
Early online date4/02/16
<mark>Original language</mark>English


It is thought that a class of broad absorption line (BAL) QSOs, characterized by Fe absorption features in their UV spectra (called `FeLoBALs'), could mark a transition stage between the end of an obscured starburst event and a youthful QSO beginning to shed its dust cocoon, where Fe has been injected into the interstellar medium by the starburst. To test this hypothesis, we have undertaken deep Submillimetre Common-User Bolometer Array 2 (SCUBA-2) 850 μm observations of a sample of 17 FeLoBAL QSOs with 0.89 ≤ z ≤ 2.78 and -23.31 ≤ MB ≤ -28.50 to directly detect an excess in the thermal emission of the dust which would probe enhanced star formation activity. We find that FeLoBALs are not luminous sources in the sub-mm, none of them are individually detected at 850 μm, nor as a population through stacking (Fs = 1.14 ± 0.58 mJy). Statistical and survival analyses reveal that FeLoBALs have sub-mm properties consistent with BAL and non-BAL QSOs with matched redshifts and magnitudes. An Spectral Energy Distribution fitting analysis shows that the far-infrared emission is dominated by active galactic nuclei activity, and a starburst component is required only in 6/17 sources of our sample; moreover the integrated total luminosity of 16/17 sources is L ≥ 1012 L⊙, high enough to classify FeLoBALs as infrared luminous. In conclusion, we do not find any evidence in support of FeLoBAL QSOs being a transition population between an ultraluminous infrared galaxy (ULIRG) and an unobscured QSO; in particular, FeLoBALs are not characterized by a cold starburst which would support this hypothesis.