Differential Microlensing Measurements of Quasar Broad Line Kinematics in Q2237+0305

TL;DR

This paper introduces a novel differential microlensing technique to study the kinematics of quasar broad emission line regions at high redshift, providing insights into the dominant dynamics of the gas.

Contribution

The paper presents a new method using differential microlensing and integral field spectroscopy to probe the BELR kinematics in distant quasars, which was previously challenging.

Findings

Microlensing signature favors gravitationally-dominated dynamics

Single observation yields significant kinematic information

Technique applicable to high-redshift, strongly-lensed quasars

Abstract

The detailed workings of the central engines of powerful quasars remain a mystery. This is primarily due to the fact that, at their cosmological distances, the inner regions of these quasars are spatially unresolvable. Reverberation mapping is now beginning to unlock the physics of the Broad Emission Line Region (BELR) in nearby, low-luminosity quasars, however it is still unknown whether this gas is dominated by virial motion, by outflows, or infall. The challenge is greater for more distant, powerful sources due to the very long response time of the BELR to changes in the continuum. We present a new technique for probing the kinematic properties of the BELR and accretion disk of high-z quasars using differential microlensing, and show how substantial information can be gained through a single observation of a strongly-lensed quasar using integral field spectroscopy. We apply this technique to GMOS IFU observations of the multiply-imaged quasar Q2237+0305, and find that the observed microlensing signature in the CIII] broad emission line favours gravitationally-dominated dynamics over an accelerating outflow.