CANDELS Observations Of The Structural Properties Of Cluster Galaxies At Z=1.62

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Papovich, Casey
Bassett, Robert
Lotz, Jennifer M.
van der Wel, A.
Tran, K. V.
Finkelstein, Steven L.
Bell, Eric F.
Conselice, Christopher J.
Dekel, Avishai
Dunlop, J. S.

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We discuss the structural and morphological properties of galaxies in a z = 1.62 proto-cluster using near-IR imaging data from Hubble Space Telescope Wide Field Camera 3 data of the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS). The cluster galaxies exhibit a clear color-morphology relation: galaxies with colors of quiescent stellar populations generally have morphologies consistent with spheroids, and galaxies with colors consistent with ongoing star formation have disk-like and irregular morphologies. The size distribution of the quiescent cluster galaxies shows a deficit of compact (less than or similar to 1 kpc), massive galaxies compared to CANDELS field galaxies at z = 1.6. As a result, the cluster quiescent galaxies have larger average effective sizes compared to field galaxies at fixed mass at greater than 90% significance. Combined with data from the literature, the size evolution of quiescent cluster galaxies is relatively slow from z similar or equal to 1.6 to the present, growing as (1 + z)(-0.6 +/- 0.1). If this result is generalizable, then it implies that physical processes associated with the denser cluster region seem to have caused accelerated size growth in quiescent galaxies prior to z = 1.6 and slower subsequent growth at z < 1.6 compared to galaxies in the lower density field. The quiescent cluster galaxies at z = 1.6 have higher ellipticities compared to lower redshift samples at fixed mass, and their surface-brightness profiles suggest that they contain extended stellar disks. We argue that the cluster galaxies require dissipationless (i.e., gas-poor or "dry") mergers to reorganize the disk material and to match the relations for ellipticity, stellar mass, size, and color of early-type galaxies in z < 1 clusters.



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Papovich, C., R. Bassett, J. M. Lotz, A. van der Wel, K-V. Tran, S. L. Finkelstein, E. F. Bell et al. "CANDELS Observations of the Structural Properties of Cluster Galaxies at z= 1.62." The Astrophysical Journal, Vol. 750, No. 2 (May., 2012): 93.