Unravelling elliptical galaxy formation using galaxy protoclusters and submillimetre galaxies

Tracing the histories of massive elliptical galaxies in the local Universe is a monumental task. Identifying the progenitors of these galaxies is a crucial step towards achieving this goal, but is made difficult by their complex evolution. Since massive elliptical galaxies typically reside in galaxy clusters, it is therefore expected that their progenitor populations should typically reside in protoclusters at high redshift. Submillimetre galaxies (SMGs) are the sites of some of the most extreme star formation in the Universe, and represent one such population of candidate progenitors. In this talk, I present results from two studies in which we explore the link between SMGs and massive elliptical galaxies through searches for protoclusters. The first is a narrowband VLT/HAWK-I search for overdensities of H-alpha and [OIII] emitters around an unbiased sample of three spectroscopically-confirmed SMGs at z ~ 2–3, which we use to verify whether SMGs are likely progenitors of massive elliptical galaxies in clusters. The second is a JCMT/SCUBA-2 search for overdensities of SMGs in the environments of massive, radio-quiet galaxies at z ~ 1–3, conducted as part of the RAdio Galaxy Environment Reference Survey (RAGERS). This study is motivated by the observation that while high-redshift radio galaxies (HzRGs) tend to reside in SMG-rich, protocluster-like environments – making them strong candidates for the progenitors of brightest cluster galaxies – it is not clear whether this is primarily driven by their high stellar masses or their AGN activity. Measuring the SMG density in the environments of similarly massive, radio-quiet counterparts thus enables us to disentangle these two effects.