Connecting radio emission to AGN wind properties with Broad Absorption Line Quasars

Abstract

Broad Absorption Line Quasars (BALQSOs) show strong signatures of powerful outflows, with the potential to alter the cosmic history of their host galaxies. These signatures are only seen in ∼10% of optically selected quasars, although the fraction significantly increases in IR and radio selected samples. A proven physical explanation for this observed fraction has yet to be found, along with a determination of why this fraction increases at radio wavelengths. We present the largest sample of radio matched BALQSOs using the LOFAR Two-metre Sky Survey Data Release 2 and employ it to investigate radio properties of BALQSOs. Within the DR2 footprint, there are 3537 BALQSOs from Sloan Digital Sky Survey DR12 with continuum signal to noise ≥ 5. We find radio-detections for 1108 BALQSOs, with an important sub-population of 120 LoBALs, an unprecedented sample size for radio matched BALQSOs given the sky coverage to date. BALQSOs are a radio-quiet population that show an increase of ×1.50 radio-detection fraction compared to non-BALQSOs. LoBALs show an increase of ×2.22 that of non-BALQSO quasars. We show that this detection fraction correlates with wind-strength, reddening and C emission properties of BALQSOs and that these features may be connected, although no single property can fully explain the enhanced radio detection fraction. We create composite spectra for sub-classes of BALQSOs based on wind strength and colour, finding differences in the absorption profiles of radio-detected and radio-undetected sources, particularly for LoBALs. Overall, we favour a wind-ISM interaction explanation for the increased radio-detection fraction of BALQSOs.

A panchromatic view of infrared quasars: excess star formation and radio emission in the most heavily obscured systems

“…This result is particularly intriguing because the radio emission is optically thin; therefore, we do not expect the AGN radio properties to change with obscuration. Given that most of our quasars are in the radio-quiet regime, any nuclear-enhanced radio emission from obscured quasars is likely to be produced by either small-scale jets or shocks due to AGN-driven outflows (e.g., Zakamska & Greene 2014;Nims et al 2015;Jarvis et al 2021;Petley et al 2022). As we can not easily resolve the small-scale structure of our sample, distinguishing between compact jets and outflows is challenging.…”