RGB “color” images of one of the three candidate clusters around COSMOS-FR I 03 . The image was obtained using Spitzer 3.6μm, Subaru r and B band images for the R, G and B channels respectively. White circles indicate objects with 1.6 < zphot < 2.3. The projected size of the fields are 18000 × 18000 (~ 1.5 × 1.5 Mpc2 at z ~ 1.8), North is up.
Credit: COSMOS team.
A team of astronomers from several organizations presented three candidate clusters of galaxies at redshifts between 1.7 and 2.0, which corresponds to a fundamentally unexplored epoch of clusters evolution. The candidates were found by studying the environment around our newly selected sample of “beacons” low-luminosity (FR I) radio galaxies. Detection of galaxy clusters from this epoch doesn't have a completely convincing method and the search for clusters of galaxies at z > 1 has proven to be particularly difficult, mainly because of the reduced contrast between cluster members and field galaxies.
The team has now proposed a method that seems suitable to make detections of these galaxy clusters. (read more)
The article in arXiv:
Chiaberge, M., Capetti,A., Macchetto,D., Rosati,P., Tozzi, P., Tremblay,P.R. (2010).Three candidate clusters of galaxies at redshift ~1.8: The missing link between protoclusters and local clusters?,Accepted for publication in ApJL.