Prospects for Measuring the Mass of Black Holes at High Redshifts with Resolved Kinematics Using Gravitational Lensing

TL;DR

This paper explores how gravitational lensing combined with advanced telescopes can enable the measurement of supermassive black hole masses at high redshifts, expanding current capabilities beyond nearby galaxies.

Contribution

It proposes a novel method using gravitational lensing and upcoming telescopes to measure black hole masses at redshifts 1-6, which was previously limited to nearby galaxies.

Findings

Approximately 15-20% of strongly lensed galaxies can resolve the inner 25-50 pc.

Black hole masses of around 10^8 solar masses can be dynamically measured.

This method could significantly increase the sample size for studying black hole evolution at high redshifts.

Abstract

Application of the most robust method of measuring black hole masses, spatially resolved kinematics of gas and stars, is presently limited to nearby galaxies. The Atacama Large Millimeter/sub-millimeter Array (ALMA) and thirty meter class telescopes (the Thirty Meter Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope) with milli-arcsecond resolution are expected to extend such measurements to larger distances. Here, we study the possibility of exploiting the angular magnification provided by strong gravitational lensing to measure black hole masses at high redshifts (z~ 1-6), using resolved gas kinematics with these instruments. We show that in ~15% and ~20% of strongly lensed galaxies, the inner 25 and 50 pc could be resolved, allowing the mass of ~$10^8 M_{\odot}$ black holes to be dynamically measured with ALMA, if moderately bright molecular gas is present at these small radii. Given the large number of strong lenses discovered in current millimeter surveys and future optical surveys, this fraction could constitute a statistically significant population for studying the evolution of the M-$\sigma$ relation at high redshifts.