Examinando por Autor "Degroot, A."

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    Evidence for the universality of properties of red-sequence galaxies in x-ray- and red-sequence-selected clusters at z ∼ 1
    (Institute of Physics Publishing, 2015-10) Foltz, R.; Rettura, A.; Wilson, G.; Van Der Burg, R.F.J.; Muzzin, A.; Lidman, C.; Demarco, R.; Nantais, Julie; Degroot, A.; Yee, H.
    We study the slope, intercept, and scatter of the color-magnitude and color-mass relations for a sample of 10 infrared red-sequence-selected clusters at z ∼ 1. The quiescent galaxies in these clusters formed the bulk of their stars above z 3 with an age spread Δt 1 Gyr. We compare UVJ color-color and spectroscopic-based galaxy selection techniques, and find a 15% difference in the galaxy populations classified as quiescent by these methods. We compare the color-magnitude relations from our red-sequence selected sample with X-ray- and photometric-redshift-selected cluster samples of similar mass and redshift. Within uncertainties, we are unable to detect any difference in the ages and star formation histories of quiescent cluster members in clusters selected by different methods, suggesting that the dominant quenching mechanism is insensitive to cluster baryon partitioning at z ∼ 1. © 2015. The American Astronomical Society. All rights reserved..
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    Galaxy Merger Candidates in High-redshift Cluster Environments
    (Institute of Physics Publishing, 2017-07) Delahaye, A.G.; Webb, T.M.A.; Nantais, J.; Degroot, A.; Wilson, G.; Muzzin, A.; Yee, H.K.C.; Foltz, R.; Noble, A.G.; Demarco, R.; Tudorica, A.; Cooper, M.C.; Lidman, C.; Perlmutter, S.; Hayden, B.; Boone, K.; Surace, J.
    We compile a sample of spectroscopically and photometrically selected cluster galaxies from four high-redshift galaxy clusters (1.59 < z < 1.71) from the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS), and a comparison field sample selected from the UKIDSS Deep Survey. Using near-infrared imaging from the Hubble Space Telescope, we classify potential mergers involving massive (M∗ ≥ 3 × 1010M⊙) cluster members by eye, based on morphological properties such as tidal distortions, double nuclei, and projected near neighbors within 20 kpc. With a catalog of 23 spectroscopic and 32 photometric massive cluster members across the four clusters and 65 spectroscopic and 26 photometric comparable field galaxies, we find that after taking into account contamination from interlopers, 11+7.0-5.6% of the cluster members are involved in potential mergers, compared to 24.7+5.3-4.6% of the field galaxies. We see no evidence of merger enhancement in the central cluster environment with respect to the field, suggesting that galaxy-galaxy merging is not a stronger source of galaxy evolution in cluster environments compared to the field at these redshifts.