A Multiwavelength Study of Binary Quasars and Their Environments

TL;DR

This study uses multiwavelength observations to analyze binary quasars, finding their properties similar to isolated quasars and no preference for rich environments, suggesting different triggering mechanisms.

Contribution

It provides the first comprehensive multiwavelength analysis of binary quasars, comparing their properties and environments to isolated quasars, and discusses implications for quasar triggering.

Findings

Binary quasars have similar X-ray properties to isolated quasars.

No significant environmental richness difference between binary and isolated quasars.

Star formation contributions are significant but comparable to isolated QSOs.

Abstract

We present Chandra X-ray imaging and spectroscopy for 14 quasars in spatially resolved pairs, part of a complete sample of binary quasars with small transverse separations drawn from Sloan Digital Sky Survey (DR6) photometry. We find no significant difference in X-ray properties when compared with large control samples of isolated quasars. We present infrared photometry from our observations with SWIRC at the MMT, and from the WISE Preliminary Data Release, and fit simple spectral energy distributions to all 14 QSOs. We find preliminary evidence that substantial contributions from star formation are required, but possibly no more so than for isolated X-ray-detected QSOs. Sensitive searches of the X-ray images for extended emission, and the optical images for optical galaxy excess show that these binary QSOs are not preferentially found in rich cluster environments. While larger binary QSO samples with richer far-IR and sub-millimeter multiwavelength data might better reveal signatures of merging and triggering, optical color-selection of QSO pairs may be biased against such signatures. X-ray and/or variability selection of QSO pairs, while challenging, should be attempted. We present in our Appendix a primer on X-ray flux and luminosity calculations.