We report the discovery of a very large, spatially extended Lyα-emitting nebula at z = 2.656 associated with a luminous mid-infrared source. The bright mid-infrared source (F 24µm = 0.86 mJy) was first detected in observations made using the Spitzer Space Telescope. Existing broad-band imaging data from the NOAO Deep Wide-Field Survey revealed the mid-infrared source to be associated with a diffuse, spatially extended, optical counterpart in the B W band. Spectroscopy and further imaging of this target reveals that the optical source is an almost purely line-emitting nebula with little, if any, detectable diffuse continuum emission. The Lyα nebula has a luminosity of L Lyα ≈ 1.7 × 10 44 erg s −1 and an extent of at least 20 ′′ (160 kpc). Its central ≈ 8 ′′ shows an ordered, monotonic velocity profile; interpreted as rotation, this region encloses a mass M ≈ 6 ×10 12 M ⊙ . Several sources lie within the nebula. The central region of the nebula shows narrow (≈ 365 km s −1 ) emission lines of C IV and He II. The midinfrared source is a compact object lying within the nebula, but offset from the center by a projected distance of ≈ 2. ′′ 5 (20 kpc), and likely to be an enshrouded AGN. A young star-forming galaxy lies near the northern end of the nebula. We suggest that the nebula is a site of recent multiple galaxy and AGN formation, with the spatial distribution of galaxies within the nebula perhaps tracking the formation history of the system.

We report the discovery of a large cloud of ionized gas associated with the radio galaxy 3C 294 at a redshift of 1.786. The radio source is a powerful double with a weak core. We detect Lya emission with a total monochromatic luminosity of L Lya = 7.6 x 10 44 ergs s -1 extended over ~100 x 170 kpc. The emission-line cloud is highly elongated and is well aligned with the inner radio source axis. Long-slit spectra, taken along the major axis, show spatially extended emission lines of N v 21240, C iv 21550, He n 21640, and C m 21909. The extended Lya emission shows a large, smooth velocity gradient (1500 km s -1 ) and large intrinsic line widths (700-2600 km s -1 ). The high-ionization lines, particularly C iv, show large velocity changes that are systematically different from those of Lya.3C 294 appears to be another, even more spectacular member of a class of powerful radio galaxies at high redshift typified by 3C 326.1. We discuss our observations from the point of view of star formation and the interaction of nuclear activity with ambient material. We consider two scenarios for the ionization of the Lya cloud: ionization by a population of extremely massive stars and ionization by a nonthermal continuum from the radio nucleus. Stellar photoionization appears to be insufficient in both the total number of ionizing photons and its ability to produce highly ionized species. We propose that the 150 kpc cloud of gas is photoionized by a central nonstellar source. We detect a very red compact object at 2.2 /mi nearly coincident with the radio core. It is unclear whether the light from this object is primarily stellar or nonstellar. Subject headings: galaxies: evolution -galaxies: individual (3C 294) -galaxies: redshiftsradio sources: galaxies I. INTRODUCTION Early radio observations of 3C 294 with the Cambridge 5 km telescope were reported by Jenkins, Pooley, and Riley (1977). These observations showed it to be a strong (5 178 = 10.3 Jy) source with extended structure. Optically, the source remained unidentified until the present work, in large part because of the presence of a F = 12 mag subgiant K star, only 10" to the west of the radio centroid (Kristian, Sandage, and Katern 1974;Riley, Longair, and Gunn 1980). Current groundbased imaging with any detector is hampered by scattered light from this Galactic star.Given that many of the recently identified 3CR sources are associated with faint galaxies having strong Lya emission (Spinrad et al. 1985), and in some cases very extended Lya emission (McCarthy et al 1987a), it seemed reasonable that 3C 294 might be detectable spectroscopically, without the benefit of an optical identification. After receiving a report of a tenta-1 Based, in part, on observations obtained at Lick Observatory, which is owned and operated by the University of California, and the Multiple Mirror Observatory, a joint facility of the Smithsonian Astrophysical Observatory and the University of Arizona.

The Wide-field Infrared Survey Explorer (WISE), a NASA MIDEX mission, will survey the entire sky in four bands from 3.3 to 23 microns with a sensitivity 1000 times greater than the IRAS survey. The WISE survey will extend the Two Micron All Sky Survey into the thermal infrared and will provide an important catalog for the James Webb Space Telescope. Using 1024 2 HgCdTe and Si:As arrays at 3.3, 4.7, 12 and 23 microns, WISE will find the most luminous galaxies in the universe, the closest stars to the Sun, and it will detect most of the main belt asteroids larger than 3 km. The single WISE instrument consists of a 40 cm diamond-turned aluminum afocal telescope, a two-stage solid hydrogen cryostat, a scan mirror mechanism, and reimaging optics giving 5" resolution (full-width-half-maximum). The use of dichroics and beamsplitters allows four color images of a 47'x47' field of view to be taken every 8.8 seconds, synchronized with the orbital motion to provide total sky coverage with overlap between revolutions. WISE will be placed into a Sun-synchronous polar orbit on a Delta 7320-10 launch vehicle. The WISE survey approach is simple and efficient. The three-axis-stabilized spacecraft rotates at a constant rate while the scan mirror freezes the telescope line of sight during each exposure. WISE is currently in its Preliminary Design Phase, with the mission Preliminary Design Review scheduled for July, 2005. WISE is scheduled to launch in mid 2009; the project web site can be found at www.wise

WISE is a NASA MIDEX mission to survey the entire sky in four bands from 3 to 25 microns with sensitivity about 500 times greater than the IRAS survey. WISE will find the most luminous galaxies in the universe, find the closest stars to the Sun, and detect most of the main belt asteroids larger than 3 km. WISE launch is scheduled in November, 2009 on a Delta 7320-10 to a 525 km Sun-synchronous polar orbit.This paper gives an overview of WISE including development status and management approach. WISE flight system design is single string with selected redundancy and graceful degradation. Wherever possible, design heritage from prior missions is pursued and properly reviewed to reduce development time and cost. Further risk reduction is achieved since the WISE spacecraft has no deployable mechanisms and no propulsion. Nonetheless, a complex space mission with a sophisticated cryogenic IR telescope such as WISE demands a partnership of multiple organizations in government research, academia, and industry. With a cost cap and relatively short development schedule, it is essential for all WISE partners to work seamlessly together. This is accomplished by a single management team representing all key partners and disciplines in science, systems engineering, mission assurance, project and contract management. WISE uses a variety of management tools including frequent team interaction, schedule, milestone and critical path analysis, risk analysis, reliability analysis, earned value analysis, configuration management, and management of schedule and budget reserves. After a successful mission critical design review in June, 2007, WISE has completed building most of the flight hardware, and started integration and test within payload and spacecraft.

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Space Infrared Telescope Facility (SIRTF). IRAC is a four-channel camera that obtains simultaneous images at 3.6, 4.5, 5.8, and 8 microns. Two adjacent 5.12×5.12 arcmin fields of view in the SIRTF focal plane are viewed by the four channels in pairs (3.6 and 5.8 microns; 4.5 and 8 microns). All four detector arrays in the camera are 256×256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. We describe here the results of the instrument functionality and calibration tests completed at Goddard Space Flight Center, and provide estimates of the in-flight sensitivity and performance of IRAC in SIRTF.