Escape, Accretion or Star Formation? The Competing Depleters of Gas in the Quasar Markarian 231

TL;DR

This study uses high-resolution millimeter observations to analyze molecular gas dynamics in the quasar Markarian 231, revealing details about gas depletion, star formation, and outflow properties.

Contribution

It provides detailed measurements of dense gas mass, outflow structure, and escape rates, offering new insights into gas depletion mechanisms in quasar host galaxies.

Findings

15% of molecular gas exceeds escape velocity

Depletion timescale of 49 Myr aligns with poststarburst age

Molecular disk forms stars at normal efficiency

Abstract

We report on high resolution CO(1-0), CS(2-1) and 3mm continuum Combined Array for Research in Millimeter Astronomy (CARMA) observations of the molecular outflow host and nearest quasar Markarian 231. We use the CS(2-1) measurements to derive a dense gas mass within Mrk231 of $1.8\pm0.3\times10^{10}~M_\odot$, consistent with previous measurements. The CS(2-1) data also seem to indicate that the molecular disk of Mrk231 is forming stars at about normal efficiency. The high resolution CARMA observations were able to resolve the CO(1-0) outflow into two distinct lobes, allowing for a size estimate to be made and further constraining the molecular outflow dynamical time, further constraining the molecular gas escape rate. We find that 15% of the molecular gas within the Mrk231 outflow actually exceeds the escape velocity in the central kiloparsec. Assuming that molecular gas is not constantly being accelerated, we find the depletion timescale of molecular gas in Mrk231 to be 49Myr, rather than 32Myr, more consistent with the poststarburst stellar population observed in the system.