The Fundamental Plane of Massive Quiescent Galaxies at z~2

TL;DR

This study investigates the Fundamental Plane and mass-to-light ratio scaling relations of massive quiescent galaxies at redshifts 1.5 to 2.5, revealing that the most massive ones require structural evolution beyond passive aging to match local galaxy relations.

Contribution

It provides the first detailed analysis of the FP and M/L relations for a large sample of high-redshift quiescent galaxies, highlighting the need for structural evolution in the most massive cases.

Findings

Most massive galaxies at z>2 cannot passively evolve to local relations.

Minor mergers and structural evolution are necessary for these galaxies.

Passive stellar aging explains the evolution of less massive galaxies.

Abstract

We examine the Fundamental Plane (FP) and mass-to-light ratio ($M/L$) scaling relations using the largest sample of massive quiescent galaxies at $1.5<z<2.5$ to date. The FP ($r_{e}, \sigma_{e}, I_{e}$) is established using $19$ $UVJ$ quiescent galaxies from COSMOS with $Hubble$ $Space$ $Telescope$ $(HST)$ $H_{F160W}$ rest-frame optical sizes and X-shooter absorption line measured stellar velocity dispersions. For a very massive, ${\rm{log}}(M_{\ast}/M_{\odot})>11.26$, subset of 8 quiescent galaxies at $z>2$, from Stockmann et al. (2020), we show that they cannot passively evolve to the local Coma cluster relation alone and must undergo significant structural evolution to mimic the sizes of local massive galaxies. The evolution of the FP and $M/L$ scaling relations, from $z=2$ to present-day, for this subset are consistent with passive aging of the stellar population and minor merger structural evolution into the most massive galaxies in the Coma cluster and other massive elliptical galaxies from the MASSIVE Survey. Modeling the luminosity evolution from minor merger added stellar populations favors a history of merging with "dry" quiescent galaxies.