The fate of high-redshift massive compact galaxies

TL;DR

This study investigates the connection between high-redshift compact galaxies, known as red nuggets, and present-day massive galaxies, revealing that red nuggets can survive as dense cores within various galaxy types, including disks.

Contribution

It demonstrates that red nuggets can persist as compact cores in modern galaxies and are not exclusively linked to elliptical galaxy formation.

Findings

Compact cores matching red nugget properties are abundant in local galaxies.

Red nuggets can be embedded in both elliptical and disk galaxies.

Mass-size relations support the survival of red nuggets as galaxy cores.

Abstract

Massive high-redshift quiescent compact galaxies (nicknamed red nuggets) have been traditionally connected to present-day elliptical galaxies, often overlooking the relationships that they may have with other galaxy types. We use large bulge-disk decomposition catalogues based on the Sloan Digital Sky Survey (SDSS) to check the hypothesis that red nuggets have survived as compact cores embedded inside the haloes or disks of present-day massive galaxies. In this study, we designate a "compact core" as the bulge component that satisfies a prescribed compactness criterion. Photometric and dynamic mass-size and mass-density relations are used to show that, in the inner regions of galaxies at z ~ 0.1, there are "abundant" compact cores matching the peculiar properties of the red nuggets, an abundance comparable to that of red nuggets at z ~ 1.5. Furthermore, the morphology distribution of the present-day galaxies hosting compact cores is used to demonstrate that, in addition to the standard channel connecting red nuggets with elliptical galaxies, a comparable fraction of red nuggets might have ended up embedded in disks. This result generalises the inside-out formation scenario; present-day massive galaxies can begin as dense spheroidal cores (red nuggets), around which either a spheroidal halo or a disk are formed later.