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NASA’s Wide-Field Infrared Survey Telescope (WFIRST) is a space-based observatory currently under design and initial stages of fabrication, targeted to launch in the mid-2020s. The U.S. National Academy of Science’s Astro2010 decadal survey identified WFIRST as the highest-priority mission to investigate three fundamental problems in astronomy: the dark energy content of the Universe, the evolution of the high-redshift galaxy and quasar population, and the demographics of exoplanets in our own galaxy. Ball Aerospace is currently developing the mechanical/optical assembly for WFIRST’s key imager, the Wide Field Instrument. With its leading-edge mosaic of IR detectors, this imager will provide a field of view over 100 times greater than the competing instruments on the Hubble Space Telescope, thus opening an exciting new era in sky surveys from space. To achieve the mission’s ambitious science objectives, WFI must observe celestial objects over an exceptional range of brightness with extraordinary photometric precision. Ball Aerospace and Utah State University’s Space Dynamics Laboratory (SDL) are collaborating to design and build an onboard light source system capable of helping WFI meet these stringent photometric performance requirements. This Relative Calibration System (RCS) generates light matched to the wavelengths of each of the imager’s six filters, illuminating the WFI Focal Plane Assembly (FPA) with temporally stable illumination at six logarithmically-spaced signal levels. Measuring these light levels will define a detector response ratio we’ll use to define a transfer standard relating faint objects to bright ones. This talk will highlight the engineering methods we’ve employed to select the sources for use in the calibration system, some unexpected consequences of these choices, the lessons learned from the trade studies, and what challenges lie ahead in completing the RCS.

NASA’s Wide-Field Infrared Survey Telescope (WFIRST) is a space-based observatory now being designed for launch in the mid-2020s. As the U.S. astronomical community’s top-priority mission for this decade, WFIRST is designed not only as a “discovery machine” for general PI-driven science but also as a survey platform to address three fundamental problems at the forefront of modern astrophysics: the dark energy content of the Universe, the evolution of the high-redshift galaxy and quasar population, and the demographics of exoplanets in our own galaxy. WFIRST’s primary camera, the Wide-Field Instrument (WFI), is a near-IR imager under development by Ball Aerospace and NASA’s Goddard Space Flight Center that will provide a field of view over 100 times greater than that of the Hubble Space Telescope. Achieving WFIRST’s key science objectives will require WFI to obtain imagery of faint galaxies, stars, and supernovae with unprecedented photometric precision. Attaining this level of accuracy demands calibrating the data at a level never previously accomplished in space. To meet these requirements, Ball Aerospace and Utah State University’s Space Dynamics Laboratory (SDL) are collaborating to design and build the Relative Calibration System (RCS) for WFI. The RCS is a self-calibrating unit which will generate temporally and spatially stable illumination of the WFI focal plane at a variety of wavelengths over an exceptionally large range of intensity. The RCS will enable not only standard tests of pixel-to-pixel sensitivity and gain from space, but also assessments of interpixel non-linearity, charge persistence, total-count-dependent non-linearity, and count-rate-dependent non-linearity throughout the mission’s lifetime. This talk will explore novel aspects of the RCS hardware design that permit the system to meet these demanding requirements.

We describe the design and data analysis of the DEEP2 Galaxy Redshift Survey, the densest and largest high-precision redshift survey of galaxies at z ∼ 1 completed to date. The survey was designed to conduct a comprehensive census of massive galaxies, their properties, environments, and large-scale structure down to absolute magnitude MB = -20 at z ∼ 1 via ∼90 nights of observation on the Keck telescope. The survey covers an area of 2.8 deg2 divided into four separate fields observed to a limiting apparent magnitude of RAB = 24.1. Objects with z ≲ 0.7 are readily identifiable using BRI photometry and rejected in three of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ∼2.5 times more efficiently than in a purely magnitude-limited sample. Approximately 60% of eligible targets are chosen for spectroscopy, yielding nearly 53,000 spectra and more than 38,000 reliable redshift measurements. Most of the targets that fail to yield secure redshifts are blue objects that lie beyond z ∼ 1.45, where the [O II] 3727 Å doublet lies in the infrared. The DEIMOS 1200 line mm-1 grating used for the survey delivers high spectral resolution (R ∼ 6000), accurate and secure redshifts, and unique internal kinematic information. Extensive ancillary data are available in the DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into one of the richest multiwavelength regions on the sky. This paper is intended as a handbook for users of the DEEP2 Data Release 4, which includes all DEEP2 spectra and redshifts, as well as for the DEEP2 DEIMOS data reduction pipelines. Extensive details are provided on object selection, mask design, biases in target selection and redshift measurements, the spec2d two-dimensional data-reduction pipeline, the spec1d automated redshift pipeline, and the zspec visual redshift verification process, along with examples of instrumental signatures or other artifacts that in some cases remain after data reduction. Redshift errors and catastrophic failure rates are assessed through more than 2000 objects with duplicate observations. Sky subtraction is essentially photon-limited even under bright OH sky lines; we describe the strategies that permitted this, based on high image stability, accurate wavelength solutions, and powerful B-spline modeling methods. We also investigate the impact of targets that appear to be single objects in ground-based targeting imaging but prove to be composite in Hubble Space Telescope data; they constitute several percent of targets at z ∼ 1, approaching ∼5%-10% at z > 1.5. Summary data are given that demonstrate the superiority of DEEP2 over other deep high-precision redshift surveys at z ∼ 1 in terms of redshift accuracy, sample number density, and amount of spectral information. We also provide an overview of the scientific highlights of the DEEP2 survey thus far. © 2013. The American Astronomical Society. All rights reserved.

We have undertaken a Keck spectral survey of galaxies to R~24 near the central region of Cl0024+1654 at z=0.4. The spectral resolution and slits have been selected to yield kinematics such as the velocity dispersions of early-type systems and rotation curves of disks. The spectra also provide a suite of lines that yield star formation, age, and metallicity information., Comment: 2 pages, to appear in the ASP Conference Series, "Tracing Cosmic Evolution with Galaxy Clusters", Sesto, Italy, 3-6 July 2001, eds, S. Borgani, M. Mezzetti, R. Valdarnini

We present HST images of 24 confirmed members of the distant galaxy cluster Cl0016+16 at redshift 0.55. The Balmer-strong (``E+A'') and emission- line galaxies frequently show unusual visual morphology, implying that galaxian interactions produce ``active'' galaxies in moderate-redshift clusters. We use the image concentration index as a quantitative measure of morphology to show that these unusual galaxies appear disklike, while the normal red galaxies resemble E/S0s. Although consistent with HST observations by Dressler et al. in Cl0939+4713 ($z=0.41$), our results differ from the Couch et al. finding that most Balmer-strong galaxies in AC114 ($z=0.31$) resemble ellipticals. The entire ``E+A'' sample is small, but if future studies confirm their diversity, it will suggest that they have different origins., Comment: 11 pages, uuencoded compressed PostScript, accepted to ApJ Letters, LICK-32