Lee R. Spitler, Ivo Labbé, Karl Glazebrook, S. Eric Persson, Andy Monson, Casey Papovich, Kim-Vy H. Tran, Greg B. Poole, Ryan Quadri, Pieter van Dokkum, Daniel D. Kelson, Glenn G. Kacprzak, Patrick J. McCarthy, David Murphy, Caroline Straatman, Vithal Tilvi
We report the first results from the Z-FOURGE survey: the discovery of a
candidate galaxy cluster at z = 2.2 consisting of two compact overdensities
with red galaxies detected at > 20{\sigma} above the mean surface density. The
discovery was made possible by a new deep (Ks < 24.8 AB 5{\sigma})
Magellan/FourStar near-IR imaging survey with 5 custom medium-bandwidth
filters. The filters pinpoint the location of the Balmer/4000\AA\ break in
evolved stellar populations at 1.5 < z < 3.5, yielding significantly more
accurate photometric redshifts than possible with broadband imaging alone. The
overdensities are within 1' of each other in the COSMOS field and appear to be
embedded in a larger structure that contains at least one additional
overdensity (~10{\sigma}). Considering the global properties of the
overdensities, the z = 2.2 system appears to be the most distant example of a
galaxy cluster with a red sequence. A comparison to a large {\Lambda}CDM
simulation suggests that the system may consist of merging subclusters, with
properties in between those of z > 2 protoclusters with more diffuse
distributions of blue galaxies and the lower-redshift galaxy clusters with
prominent red sequences. Remarkably the structure is completely absent in
public optical catalogs in COSMOS and only weakly visible in a shallower
near-IR survey. The discovery showcases the potential of our deep near-IR
survey to advance the understanding of environment and galaxy evolution at z >
1.5.
View original:
http://arxiv.org/abs/1112.2691
No comments:
Post a Comment