The birth of giant elliptical galaxies is a violent process, with most stars originating from incredible star-forming episodes and several galaxy mergers within large-scale structures (dubbed protoclusters). This formation process happened in the early epochs, when the Universe was only a few billion years old. Currently, researchers using the James Clerk Maxwell Telescope (JCMT) on Maunakea, Hawaiʻi are trying to locate the progenitors of elliptical galaxies, and thus protoclusters, using several observational techniques.
Astronomers have recently discovered a handful of rare, enormous nebulae that copiously emit in the Hydrogen Lyman-alpha transition, a tracer of intergalactic gas. These emissions cover vast distances, up to 30 times larger than the Milky Way. Most of these Enormous Lyman-Alpha Nebulae (ELANe) host multiple active galactic nuclei and are surrounded by several Lyman-alpha emission galaxies. These ELANe are prime candidates for progenitors of elliptical galaxies and massive protoclusters in the early stages of assembly. While these regions are promising, researchers are now tasked with determining the presence of protoclusters and of heavy star formation associated with each ELAN.
An international team of researchers started using the SCUBA-2 instrument on JCMT to characterize these protoclusters and the associated ELAN. Observing at 450 and 850 microns allows SCUBA-2 to capture the emission from dust powered by violent episodes of star formation, something that is not possible with optical telescopes.
Results from the targeted ELAN MAMMOTH-1 field (Fig. 1) revealed the presence of a violent starburst galaxy and emission from a veiled active galactic nuclei (Fig. 2). These sources likely power the extended Lyman-alpha emission, and could be the progenitor of an elliptical galaxy.
In addition, researchers find four times the number of dust-obscured sources in ELAN
MAMMOTH-1 compared to other standard regions. This likely confirms the presence of a rich structure surrounding ELAN MAMMOTH-1, and hints at the presence of a protocluster, hosting the progenitor of an elliptical galaxy. Figure 3 shows the distribution of Lyman-alpha emitting galaxies compared to the SCUBA-2 detections within the observed field. Hopefully, follow-up observations will confirm the relationship between these newly detected sources and a protocluster surrounding the ELAN. For now, these findings seem to agree with the expected theoretical characterizations of cosmic nurseries of giant elliptical galaxies.
European Southern Observatory/Max-Planck Institute for Astrophysics
Fabrizio Arrigoni Battaia
farrigon at eso.org
European Southern Observatory
ccchen at eso.org
James Clerk Maxwell Telescope
h.parsons at eaobservatory.org
About The Authors
The international authors of this paper are from European Southern Observatory, Germany, Durham University, UK, University of California, USA, Leiden University, Netherlands, Tsinghua University, China, and the Korea Astronomy and Space Science Institute, South Korea.