A Fundamental Line for Elliptical Galaxies

TL;DR

This paper investigates the size-luminosity relation of nearby elliptical galaxies to evaluate if minor mergers can explain the observed size growth of massive galaxies, challenging hierarchical models due to low scatter.

Contribution

It provides new evidence that the scatter in the size-luminosity relation is smaller than previously thought, questioning the role of minor mergers in galaxy evolution.

Findings

Scatter in size-luminosity relation is very small

Challenges the merger-driven hierarchical galaxy formation models

Supports alternative explanations for galaxy size growth

Abstract

Recent studies have shown that massive galaxies in the distant universe are surprisingly compact, with typical sizes about a factor of three smaller than equally massive galaxies in the nearby universe. It has been suggested that these massive galaxies grow into systems resembling nearby galaxies through a series of minor mergers. In this model the size growth of galaxies is an inherently stochastic process, and the resulting size-luminosity relationship is expected to have considerable environmentally-dependent scatter. To test whether minor mergers can explain the size growth in massive galaxies, we have closely examined the scatter in the size-luminosity relation of nearby elliptical galaxies using a large new database (Nair & Abraham 2010) of accurate visual galaxy classifications. We demonstrate that this scatter is much smaller than has been previously assumed, and may even be so small as to challenge the plausibility of the merger driven hierarchical models for the formation of massive ellipticals.