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The Extraordinary Mid-infrared Spectral Properties of FeLoBAL Quasars

D. Farrah, T. Urrutia, M. Lacy, V. Lebouteiller, H. W. W. Spoon, J. Bernard-Salas, N. Connolly, J. Afonso, B. Connolly, J. Houck

We present mid-infrared(mid-IR) spectra of six FeLoBAL quasi-stellar objects(QSOs) at 1 < z < 1.8, taken with the Spitzer Space Telescope. The spectra span a range of shapes, from hot dust-dominated active galactic nuclei(AGNs) with silicate emission at 9.7 mum to moderately obscured starbursts with strong polycyclic aromatic hydrocarbon(PAH) emission. The spectrum of one object, SDSS 1214-0001, shows the most prominent PAHs yet seen in any QSO at any redshift, implying that the starburst dominates the mid-IR emission with an associated star formation rate on the order of 2700 M sun yr-1. With the caveats that our sample is small and not robustly selected, we combine our mid-IR spectral diagnostics with previous observations to propose that FeLoBAL QSOs are at least largely comprised of systems in which(1) a merger-driven starburst is ending,(2) a luminous AGN is in the last stages of burning through its surrounding dust, and(3) we may be viewing over a restricted line-of-sight range.

galaxies: active - galaxies: evolution - infrared: galaxies - quasars: absorption: lines

The Astrophysical Journal
Volume 717, Number 2, Page 868
2010 July

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia