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Caldwell, Nelson

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Caldwell

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Nelson

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Caldwell, Nelson
Author's Publications: search.filters.isAuthorOfPublication.bd2ace35-09d2-4a7f-9efc-95a9b1655537

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    Optical Spectroscopy of Type Ia Supernovae
    (IOP Publishing, 2008) Matheson, T.; Kirshner, Robert; Challis, Peter; Jha, S.; Garnavich, P. M.; Berlind, Perry; Calkins, Michael; Blondin, S.; Balog, Z.; Bragg, A. E.; Caldwell, Nelson; Concannon, K. Dendy; Falco, E. E.; Graves, G. J. M.; Huchra, J. P.; Kuraszkiewicz, Joanna; Mader, J. A.; Mahdavi, A.; Phelps, Matthew; Rines, K.; Song, I.; Wilkes, Belinda
    We present 432 low-dispersion optical spectra of 32 Type Ia supernovae (SNe Ia) that also have well-calibrated light curves. The coverage ranges from 6 epochs to 36 epochs of spectroscopy. Most of the data were obtained with the 1.5 m Tillinghast telescope at the F. L. Whipple Observatory with typical wavelength coverage of 3700-7400 Å and a resolution of ~7 Å. The earliest spectra are 13 days before B-band maximum; two-thirds of the SNe were observed before maximum brightness. Coverage for some SNe continues almost to the nebular phase. The consistency of the method of observation and the technique of reduction makes this an ideal data set for studying the spectroscopic diversity of SNe Ia.
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    Host Galaxies, Clustering, Eddington Ratios, and Evolution of Radio, X-Ray, and Infrared-selected AGNs.
    (IOP Publishing, 2009) Hickox, Ryan C.; Jones, Christine; Forman, William; Murray, Stephen; Kochanek, Christopher S.; Eisenstein, Daniel; Jannuzi, Buell T.; Dey, Arjun; Brown, Michael J. I.; Stern, Daniel; Eisenhardt, Peter R.; Gorjian, Varoujan; Brodwin, Mark; Narayan, Ramesh; Cool, Richard J.; Kenter, Almus; Caldwell, Nelson; Anderson, Michael E.
    We explore the connection between different classes of active galactic nuclei (AGNs) and the evolution of their host galaxies, by deriving host galaxy properties, clustering, and Eddington ratios of AGNs selected in the radio, Xray, and infrared (IR) wavebands. We study a sample of 585 AGNs at 0.25 10−2. We interpret these results in terms of a simple model of AGN and galaxy evolution, whereby a “quasar” phase and the growth of the stellar bulge occurs when a galaxy’s dark matter halo reaches a critical mass between ∼ 1012 and 1013 M. After this event, star formation ceases and AGN accretion shifts from radiatively efficient (optical- and IR-bright) to radiatively inefficient (optically faint, radio-bright) modes. Ke