We have been studying these interesting objects found in Mariska Kriek's Ph.D. thesis. These galaxies are massive, show little evidence of star-formation, but are very compact. Generally, we find that these galaxies have one-fifth the expected size as compared with galaxies today at the same mass.
I show some examples of these galaxies in the figure above, where the red circles are the half-light radii and the inset images are Keck Adaptive Optics images in the K band (or at 2.2 microns). All of our data point to these objects being massive, they are bright objects, and to these objects being very compact. If this result is correct, these objects will be a unique phase in galaxy evolution, with no counterpart in any galaxies we see in our local universe.
These results were featured in a STScI Press Release
- "Confirmation of the Remarkable Compactness of Massive Quiescent Galaxies at z ~ 2.3: Early-Type Galaxies Did not Form in a Simple Monolithic Collapse", van Dokkum, et al., ApJL 677, L5 ADS (arXiv:0802.4094)
- "A Near-Infrared Spectroscopic Survey of K-selected Galaxies at z~2.3: Redshifts and Implications for Broadband Photometric Studies", Kriek, M. et al., ApJ (arXiv:0801.1110)
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