Browsing by Author "Gladders, MD"

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    RCS 043938-2904.9
    (2004) Barrientos, LF; Gladders, MD; Yee, HKC; Infante, L; Ellingson, E; Hall, PB; Hertling, G
    We present deep imaging and optical spectroscopy of the newly discovered Red-Sequence Cluster Survey cluster RCS 043938 - 2904.9. This cluster, drawn from an extensive preliminary list, was selected for detailed study on the basis of its apparent optical richness. Spectroscopy of 11 members places the cluster at z = 0.951 +/- 0.006 and confirms the photometric redshift estimate from the (R-z) color-magnitude diagram. Analysis of the infrared imaging data demonstrates that the cluster is extremely rich, with excess counts in the K-s band exceeding the expected background counts by 9 sigma. The properties of the galaxies in RCS 043938 - 2904.9 are consistent with those seen in other clusters at similar redshifts. Specifically, the red-sequence color, slope, and scatter and the size-magnitude relation of these galaxies are all consistent with that seen in the few other known high-redshift clusters and indeed are consistent with appropriately evolved properties of local cluster galaxies. The apparent consistency of these systems implies that the rich high-redshift RCS clusters are directly comparable to the few other systems known at, most of which have been selected on the basis of X-ray emission.
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    Slicing the cool circumgalactic medium along the major axis of a star-forming galaxy at z=0.7
    (2020) Lopez, S; Tejos, N; Barrientos, Luis Felipe; Ledoux, C; Sharon, K; Katsianis, A; Florian, MK; Rivera-Thorsen, E; Bayliss, MB; Dahle, H; Fernandez-Figueroa, A; Gladders, MD; Gronke, M; Hamel, M; Pessa, I; Rigby, JR
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    The EXPLORE project.: I.: A deep search for transiting extrasolar planets
    (2003) Mallén-Ornelas, G; Seager, S; Yee, HKC; Minniti, D; Gladders, MD; Mallén-Fullerton, GM; Brown, TM
    Planet transit searches promise to be the next breakthrough for extrasolar planet detection and will bring the characterization of short-period planets into a new era. Every transiting planet discovered will have a measured radius, which will provide constraints on planet composition, evolution, and migration history. Together with radial velocity measurements, the absolute mass of every transiting planet will be determined. In this paper we discuss the design considerations of the Extrasolar Planet Occultation Research (EXPLORE) project, a series of transiting planet searches using 4 m class telescopes to continuously monitor a single field of stars in the Galactic plane in each similar to2 week observing campaign. We discuss the general factors that determine the efficiency and the number of planets found by a transit search, including time sampling strategy and field selection. The primary goal is to select the most promising planet candidates for radial velocity follow-up observations. We show that with very high photometric precision light curves that have frequent time sampling and at least two detected transits, it is possible to uniquely solve for the main parameters of the eclipsing system (including planet radius), based on several important assumptions about the central star. Together with a measured spectral type for the star, this unique solution for orbital parameters provides a powerful method for ruling out most contaminants to transiting planet candidates. For the EXPLORE project, radial velocity follow-up observations for companion mass determination of the best candidates are done on 8 m class telescopes within 2 or 3 months of the photometric campaigns. This same-season follow-up is made possible by the use of efficient pipelines to produce high-quality light curves within weeks of the observations. We conclude by presenting early results from our first search, EXPLORE I, in which we reached better than 1% rms photometric precision (measured over a full night) on similar to37,000 stars with 14.5less than or equal toIless than or equal to18.2.
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    The optical afterglow of the gamma-ray burst GRB 012111
    (2002) Holland, ST; Soszynski, I; Gladders, MD; Barrientos, LF; Berlind, P; Bersier, D; Garnavich, PM; Jha, S; Stanek, KZ
    We present early-time optical photometry and spectroscopy of the optical afterglow of the gamma-ray burst GRB 011211. The spectrum of the optical afterglow contains several narrow metal lines that are consistent with the burst's occurring at a redshift of 2.14 +/- 0.001. The optical afterglow decays as a power law with a slope of alpha = 0.83 +/- 0.04 for the first approximate to2 days after the burst, at which time there is evidence of a break. The slope after the break is greater than or equal to 1.4. There is evidence of rapid variations in the R-band light approximately 0.5 days after the burst. These variations suggest that there are density fluctuations near the gamma-ray burst on spatial scales of approximately 40-125 AU. The magnitude of the break in the light curve, the spectral slope, and the rate of decay in the optical suggest that the burst expanded into an ambient medium that is homogeneous on large scales. We estimate that the local particle density is between approximately 0.1 and 10 cm(-3) and that the total gamma-ray energy in the burst was (1.2-1.9) x 10(50) ergs. This energy is smaller than, but consistent with, the "standard" value of (5 +/- 2) x 10(50) ergs. Comparing the observed color of the optical afterglow with predictions of the standard beaming model suggests that the rest-frame V-band extinction in the host galaxy is less than or similar to0.03 mag.