Radio Through X-ray Spectral Energy Distributions of 38 Broad Absorption Line Quasars

TL;DR

This study compiles and analyzes the broad spectral energy distributions of 38 BAL quasars from radio to X-ray, finding their properties similar to non-BAL quasars and providing insights into star formation and outflow models.

Contribution

It presents the largest multiwavelength SED sample of BAL quasars, including new infrared observations, and compares their properties with non-BAL quasars to test outflow models.

Findings

BAL quasars have similar mid-infrared properties to non-BAL quasars.

Most BAL quasars show little star formation contribution to far-infrared emission.

SED comparisons do not support the 'cocoon' outflow model, favoring the disk-wind paradigm.

Abstract

We have compiled the largest sample of multiwavelength spectral energy distributions (SEDs) of Broad Absorption Line (BAL) quasars to date, from the radio to the X-ray. We present new Spitzer MIPS (24, 70, and 160 micron) observations of 38 BAL quasars in addition to data from the literature and public archives. In general, the mid-infrared properties of BAL quasars are consistent with those of non-BAL quasars of comparable luminosity. In particular, the optical-to-mid-infrared luminosity ratios of the two populations are indistinguishable. We also measure or place upper limits on the contribution of star formation to the far-infrared power. Of 22 (57%) upper limits, seven quasars have sufficiently sensitive constraints to conclude that star formation likely contributes little (<20%) to their far-infrared power. The 17 BAL quasars (45%) with detected excess far-infrared emission likely host hyperluminous starbursts with L_fir,SF=10^{13-14} L_sun. Mid-infrared through X-ray composite BAL quasar SEDs are presented, incorporating all of the available photometry. Overall, we find no compelling evidence for inherent differences between the SEDs of BAL vs. non-BAL quasars of comparable luminosity. Therefore a ``cocoon'' picture of a typical BAL quasar outflow whereby the wind covers a large fraction of the sky is not supported by the mid-infrared SED comparison with normal quasars, and the disk-wind paradigm with a typical radio-quiet quasar hosting a BAL region remains viable.