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

Autor: Julie Wardlow, James E. Geach, Daniel J. Smith, Kristen Coppin, Jamie Stevens, Ryan C. Hickox, D. M. Alexander, Duncan Farrah, Giulio Violino
Jazyk: angličtina
Rok vydání: 2015
Předmět:
Zdroj: Monthly notices of the Royal Astronomical Society, 2016, Vol.457(2), pp.1371-1384 [Peer Reviewed Journal]
NASA Astrophysics Data System
Popis: It is thought that a class of broad absorption line (BAL) QSOs, characterised 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 SCUBA-2 850 $\mu$m observations of a sample of 17 FeLoBAL QSOs with 0.89 $\leq$ z $\leq$ 2.78 and -23.31 $\leq$ M$_{B}$ $\leq$-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 submillimetre, none of them are individually detected at 850 $\mu$m, nor as a population through stacking ($F_{s}=1.14\pm0.58$ 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 SED fitting analysis shows that the FIR emission is dominated by AGN 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$\geq$10$^{12}$L$_{\odot}$, 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 a ULIRG and an unobscured QSO; in particular, FeLoBALs are not characterized by a cold starburst which would support this hypothesis.
Comment: 15 pages, 7 figures, MNRAS in press
Databáze: OpenAIRE