The extraordinary mid-infrared spectral properties of FeLoBAL quasars

Farrah, D.; Urrutia, T.; Lacy, M.; Lebouteiller, V.; Spoon, H. W. W.; Bernard-Salas, J.; Connolly, N.; Afonso, J.; Connolly, B. and Houck, J. (2010). The extraordinary mid-infrared spectral properties of FeLoBAL quasars. The Astrophysical Journal, 717(2) pp. 868–877.



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 μm 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 Myr−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) wemay be viewing over a restricted line-of-sight range.

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