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Author(s): Schlegel, David J; Kollmeier, Juna A; Aldering, Greg; Bailey, Stephen; Baltay, Charles; Bebek, Christopher; BenZvi, Segev; Besuner, Robert; Blanc, Guillermo; Bolton, Adam S; Bouri, Mohamed; Brooks, David; Buckley-Geer, Elizabeth; Cai, Zheng; Crane, Jeffrey; Dey, Arjun; Doel, Peter; Fan, Xiaohui; Ferraro, Simone; Font-Ribera, Andreu; Gutierrez, Gaston; Guy, Julien; Heetderks, Henry; Huterer, Dragan; Infante, Leopoldo; Jelinsky, Patrick; Johns, Matthew; Karagiannis, Dionysios; Kent, Stephen M; Kim, Alex G; Kneib, Jean-Paul; Kronig, Luzius; Konidaris, Nick; Lahav, Ofer; Lampton, Michael L; Lang, Dustin; Leauthaud, Alexie; Liguori, Michele; Linder, Eric V; Magneville, Christophe; Martini, Paul; Mateo, Mario; McDonald, Patrick; Miller, Christopher J; Moustakas, John; Myers, Adam D; Mulchaey, John; Newman, Jeffrey A; Nugent, Peter E; Palanque-Delabrouille, Nathalie; Padmanabhan, Nikhil; Piro, Anthony L; Poppett, Claire; Prochaska, Jason X; Pullen, Anthony R; Rabinowitz, David; Ramirez, Solange; Rix, Hans-Walter; Ross, Ashley J; Samushia, Lado; Schaan, Emmanuel; Schubnell, Michael; Seljak, Uros; Seo, Hee-Jong; Shectman, Stephen A; Silber, Joseph; Simon, Joshua D; Slepian, Zachary; Soares-Santos, Marcelle; Tarle, Greg; Thompson, Ian; Valluri, Monica; Wechsler, Risa H; White, Martin; Wilson, Michael J; Yeche, Christophe; Zaritsky, Dennis | Abstract: MegaMapper is a proposed ground-based experiment to measure Inflation parameters and Dark Energy from galaxy redshifts at 2

The Dark Energy Survey Instrument (DESI) is a 5000-fibre optical multi object spectrograph for the 4m Mayall telecope at the Kitt Peak National Observatory. Ten identical three channel spectrographs will be equipped with 500-element fibre slits. Here we focus on the architecture of the science slits and the interchangeable auxiliary slits required for calibration.

International audience; The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation probe. The KPNO Mayall telescope will deliver light to 5000 fibers feeding ten broadband spectrographs. A consortium of Aix-Marseille University (AMU) and CNRS laboratories (LAM, OHP and CPPM) together with the WINLIGHT Systems company (Pertuis-France) has committed to integrate and validate the performance requirements of the full spectrographs, equipped with their cryostats, shutters and other mechanisms. An AIT plan has been defined and dedicated test equipment has been designed and implemented. This equipment simulates the fiber input illumination from the telescope, and offers a variety of continuum and line sources. Flux levels are adjustable and can illuminate one or several fibers along the test slit. It is fully remotely controlled and interfaced to the Instrument Control System. Specific analysis tools have also been developed to verify and monitor the performance and stability of the spectrographs. All these developments are described in details.

We have developed a photon-counting High-temporal and High-spatial resolution, High-throughput 3-Dimensional detector (H33D) for biological imaging of fluorescent samples. The design is based on a 25 mm diameter S20 photocathode followed by a 3-microchannel plate stack, and a cross delay line anode. We describe the bench performance of the H33D detector, as well as preliminary imaging results obtained with fluorescent beads, quantum dots and live cells and discuss applications of future generation detectors for single-molecule imaging and high-throughput study of biomolecular interactions.

We present version 1.0 of the NASA Galaxy Evolution Explorer (GALEX) ultraviolet variability (GUVV) catalog, which contains information on 84 time-variable and transient sources gained with simultaneous near-ultraviolet (NUV) and far-ultraviolet (FUV) photometric observations. These time-variable sources were serendipitously revealed in the various 12 diameter star fields currently being surveyed by the GALEX satellite in two ultraviolet bands (NUV 1750–2750 A, FUV 1350–1750 A) with limiting AB magnitudes of 23–25. The largest amplitude variable objects currently detected by GALEX are M dwarf flare stars, which can brighten by 5–10 mag in both the NUV and FUV bands during short-duration (

We present the first Galaxy Evolution Explorer (GALEX) UV images of the well-known interacting group of galaxies, Stephan's Quintet (SQ). We detect widespread UV emission throughout the group. However, there is no consistent coincidence between UV structure and emission in the optical, Hα, or H I. Excluding the foreground galaxy NGC 7320 (Sd), most of the UV emission is found in regions associated with the two spiral members of the group, NGC 7319 and NGC 7318b, and the intragroup medium starburst SQ-A. The extinction-corrected UV data are analyzed to investigate the overall star formation activity in SQ. We find that the total star formation rate (SFR) of SQ is 6.69 ± 0.65 M☉ yr-1. Of this, 1.34 ± 0.16 M☉ yr-1 is due to SQ-A. This is in excellent agreement with that derived from the extinction-corrected Hα luminosity of SQ-A. The SFR in regions related to NGC 7319 is 1.98 ± 0.58 M☉ yr-1, most of which (68%) is contributed by the disk. The contribution from the young tail is only 15%. In the UV, the young tail is more extended (~100 kpc) and shows a looplike structure, including the optical tail, the extragalactic H II regions recently discovered in Hα, and other UV emission regions discovered for the first time. The UV and optical colors of the old tail are consistent with a single stellar population of age t 108.5±0.4 yr. The UV emission associated with NGC 7318b is found in a very large (~80 kpc) disk, with a net SFR of 3.37 ± 0.25 M☉ yr-1. Several large UV emission regions are 30-40 kpc away from the nucleus of NGC 7318b. Although both NGC 7319 and NGC 7318b show peculiar UV morphology, their SFR is consistent with that of normal Sbc galaxies, indicating that the strength of star formation activity is not enhanced by interactions.

We present GALEX FUV (1530 A) and NUV (2310 A) observations of the archetypal merging system NGC 4038/39, ``The Antennae". Both tails are relatively bright in the UV, especially in the vicinity of the Tidal Dwarf Galaxy candidates at the end of the southern tail. The UV light generally falls within the optically delineated tails, although the UV light is considerably more structured, with a remarkably similar morphology to the tidal HI. The UV colors suggest that there has been continuing star formation within the tidal tails, even outside the previously studied Tidal Dwarf regions. Within the inner disk regions, there are interesting UV features which appear to be related to the extended soft X-ray loops and halo recently discovered by CHANDRA.

We present Galaxy Evolution Explorer (GALEX) far-UV and near-UV mosaic observations covering the entirety of M31 and M33. For both targets, we measure the decline of surface brightness (in FUV and NUV) and changes in FUV--NUV color as a function of galactocentric radius. These UV radial profiles are compared to the distribution of ionized gas traced by H-alpha emission. We find that the extent of the UV emission, in both targets, is greater than the extent of the observed HII regions and diffuse ionized gas. We determine the ultraviolet diffuse fraction in M33 using our FUV observations and compare it to the H-alpha diffuse fraction obtained from wide-field narrow-band imaging. The FUV diffuse fraction appears to be remarkably constant near 0.65 over a large range in galactocentric radius, with departures to higher values in circumnuclear regions and, most notably, at the limit of the H-alpha disk. We suggest that the increase in FUV diffuse fraction at large galactocentric radii could indicate that a substantial portion of the diffuse emission beyond this point is not generated in situ but rather scattered from dust, after originating in the vicinity of the disk's outermost HII regions. Radial variation of the H-alpha diffuse fraction was also measured. We found the H-alpha diffuse fraction generally near 0.4 but rising toward the galaxy center, up to 0.6. We made no attempt to correct our diffuse fraction measurements for position-dependent extinction, so the quoted values are best interpreted as upper limits given the plausibly higher extinction for stellar clusters relative to their surroundings.

We present measurements of the UV galaxy luminosity function and the evolution of luminosity density from GALEX observations matched to the Sloan Digital Sky Survey (SDSS). We analyze galaxies in the Medium Imaging Survey overlapping the SDSS DR1 with a total coverage of 44 deg^2. Using the combined GALEX+SDSS photometry, we compute photometric redshifts and study the LF in three redshift shells between z=0.07 and 0.25. The Schechter function fits indicate that the faint-end slope alpha is consistent with -1.1 at all redshifts but the characteristic UV luminosity M* brightens by 0.2 mag from z=0.07 to 0.25. In the lowest redshift bin, early and late type galaxies are studied separately and we confirm that red galaxies tend to be brighter and have a shallower slope alpha than blue ones. The derived luminosity densities are consistent with other GALEX results based on a local spectroscopic sample from 2dF and the evolution follows the trend reported by deeper studies., This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http://www.galex.caltech.edu/PUBLICATIONS/ after November 22, 2004

We have used the GALEX UV photometric data to construct a first near-ultraviolet (NUV) color-magnitude relation (CMR) for the galaxies pre-classified as early-type by SDSS studies. The NUV CMR is a powerful tool for tracking the recent star formation history in early-type galaxies, owing to its high sensitivity to the presence of young stellar populations. Our NUV CMR for UV-weak galaxies shows a well-defined slope and thus will be useful for interpreting the restframe NUV data of distant galaxies and studying their star formation history. Compared to optical CMRs, the NUV CMR shows a substantially larger scatter, which we interpret as evidence of recent star formation activities. Roughly 15% of the recent epoch (z < 0.13) bright (M[r] < -22) early-type galaxies show a sign of recent (< 1Gyr) star formation at the 1-2% level (lower limit) in mass compared to the total stellar mass. This implies that low level residual star formation was common during the last few billion years even in bright early-type galaxies.

The Galaxy Evolution Explorer (GALEX) Nearby Galaxies Survey is providing deep far-UV and near-UV imaging for a representative sample of galaxies in the local universe. We present early results for M51 and M101, from GALEX UV imaging and Sloan Digital Sky Survey optical data in five bands. The multiband photometry of compact stellar complexes in M101 is compared to population synthesis models, to derive ages, reddening, reddening-corrected luminosities, and current/initial masses. The GALEX UV photometry provides a complete census of young compact complexes on a ≈160 pc scale. A galactocentric gradient of the far-UV/near-UV color indicates younger stellar populations toward the outer parts of the galaxy disks, the effect being more pronounced in M101 than in M51.

We present ultraviolet photometry for globular clusters (GCs) in M31 from 15 square deg of imaging using the Galaxy Evolution Explorer (GALEX). We detect 200 and 94 GCs with certainty in the near-ultraviolet (NUV; 1750 - 2750 Angstroms) and far-ultraviolet (FUV; 1350 - 1750 Angstroms) bandpasses, respectively. Our rate of detection is about 50% in the NUV and 23% in the FUV, to an approximate limiting V magnitude of 19. Out of six clusters with [Fe/H]>-1 seen in the NUV, none is detected in the FUV bandpass. Furthermore, we find no candidate metal-rich clusters with significant FUV flux, because of the contribution of blue horizontal-branch (HB) stars, such as NGC 6388 and NGC 6441, which are metal-rich Galactic GCs with hot HB stars. We show that our GALEX photometry follows the general color trends established in previous UV studies of GCs in M31 and the Galaxy. Comparing our data with Galactic GCs in the UV and with population synthesis models, we suggest that the age range of M31 and Galactic halo GCs are similar.

Number Counts of galaxies in two GALEX bands (FUV: 1530A and NUV: 2310A, both in AB magnitudes) are reported. They provide for the first time in the literature homogeneously calibrated number counts of UV galaxies covering continuously a very wide range of UV magnitude (14 -- 23.8). Both the FUV and NUV counts are inconsistent with a non-evolution model, while they are in good agreement with evolution models (essentially luminosity evolution) derived from the high-z UV luminosity functions of Arnouts et al. (2004). It is found that the contribution from galaxies detected by GALEX to the UV background is 0.68+-0.10 nW m-2 sr-1 at 1530A and 0.99+-0.15 nW m-2 sr-1 at 2310A. These are 66+-9% and 44+-6% of the total contributions of galaxies to the the UV background at 1530A, respectively, as estimated using the evolution models. ...

We have matched 358,046 objects in 143 deg2 of overlap between the Galaxy Evolution Explorer (GALEX) and the Sloan Digital Sky Survey (SDSS). This Letter provides matching statistics at Medium Imaging Survey and All-sky Imaging Survey depths for SDSS-classified stars and galaxies as well as spectroscopic star, galaxy, and QSO subsamples. Distributions of magnitudes, redshifts, and colors are provided. Near-ultraviolet (NUV)-based color-color diagrams reveal (1) the segregation of main-sequence, horizontal-branch, subdwarf, white dwarf, M dwarf, and M dwarf-white dwarf binary stellar populations, (2) a bimodal distribution of galaxies, and (3) the higher signal quality of the GALEX NUV compared to the SDSS u band.

The KPNO Nicholas U. Mayall 4-meter telescope is to be the host facility for the Dark Energy Spectroscopic Instrument (DESI). DESI will record broadband spectra simultaneously for 5000 objects distributed over a 3-degree diameter field of view; it will record the spectra of approximately 20 million galaxies and quasi-stellar objects during a five-year survey. This survey will improve the combined precision of measurement on the dark energy equation of state today (w 0 ) and its evolution with redshift (w a ) by approximately a factor of ten over existing spectroscopy baryon acoustic oscillation surveys (e.g., BOSS 1 ) in both co-moving volume surveyed and number of galaxies mapped. Installation of DESI on the telescope is a complex procedure, involving a complete replacement of the telescope top end, routing of massive fiber cables, and installation of banks of spectrographs in an environmentally-controlled lab area within the dome. Furthermore, assembly of the instrument and major subsystems must be carried out on-site given their size and complexity. A detailed installation plan is being developed early in the project in order to ensure that DESI and its subsystems are designed so they can be safely and efficiently installed, and to ensure that all telescope and facility modifications required to enable installation are identified and completed in time.

The Berkeley spectrograph aboard the ORFEUS telescope made its second flight on the 14-day ORFEUS-SPAS II mission of the Space Shuttle Columbia in November/December 1996. Approximately half of the available observing time was dedicated to the Berkeley spectrograph, which was used by both Principal and Guest Investigators. The spectrograph's full bandpass is 390-1218 A; here we discuss its in-flight performance at far-ultraviolet (FUV) wavelengths, where most of the observations were performed. The instrument's effective area peaks at 8.9 +/- 0.5 cm^2 near 1020 A, and the mean spectral resolution is 95 km/s FWHM for point sources. Over most of the spectral range, the typical night-time background event rate in each spectral resolution element was about 0.003/s. Simultaneous background observations of an adjacent blank field were provided through a secondary, off-axis aperture. The Berkeley spectrograph's unique combination of sensitivity and resolution provided valuable observations of approximately 105 distinct astronomical targets, ranging in distance from the earth's own moon to some of the brightest AGN.

The Extreme Ultraviolet Explorer (EUVE) observatory, successfully launched on 1992 June 7, provided astronomers with the first observatory dedicated to observation in the extreme ultraviolet. The scientific objectives of EUVE include an all-sky survey in four spectral bands, a deep survey in two spectral bands, and a spectroscopic survey carried out through a NASA guest observer program. We describe here the hardware components of the four telescopes used to carry out both the all-sky survey and the deep survey, and we present the imaging and photometric performance characteristics of the instruments as determined from ground calibration and in-orbit data.

[The BigBOSS experiment is a redshift survey designed to map the large scale structure of the universe and probe the nature of dark energy. Using massively-multiplexed _ber spectroscopy over 14,000 deg2 of sky, the survey will deliver more than 20 million galaxy and quasar redshifts. The resulting three dimensional sky map will contain signatures from primordial baryon acoustic oscillations (BAO) that set a "standard ruler" distance scale. Using the BAO signature, BigBOSS will measure the cosmological distance scale to < 1% accuracy from 0.5

BigBOSS is a proposed ground-based dark energy experiment to study baryon acoustic oscillations (BAO) and the growth of structure with a 14,000 square degree galaxy and quasi-stellar object redshift survey. It consists of a 5,000- fiber-positioner focal plane feeding the spectrographs. The optical fibers are separated into ten 500 fiber slit heads at the entrance of ten identical spectrographs in a thermally insulated room. Each of the ten spectrographs has a spectral resolution (λ/Δλ) between 1500 and 4000 over a wavelength range from 360 - 980 nm. Each spectrograph uses two dichroic beam splitters to separate the spectrograph into three arms. It uses volume phase holographic (VPH) gratings for high efficiency and compactness. Each arm uses a 4096x4096 15 μm pixel charge coupled device (CCD) for the detector. We describe the requirements and current design of the BigBOSS spectrograph. Design trades (e.g. refractive versus reflective) and manufacturability are also discussed.

BigBOSS is a Stage IV dark energy experiment based on proven techniques to study baryon acoustic oscillations and the growth of large scale structure. The 2010 Astronomy and Astrophysics Decadal Survey labeled dark energy as a key area of exploration. BigBOSS is designed to perform a 14,000 square degree survey of 20 million galaxies and quasi-stellar objects. The project involves installation of a new instrument on the Mayall 4m telescope, operated by the National Optical Astronomy Observatory. The instrument includes a new optical widefield corrector, a 5,000 fiber actuator system, and a multi-object spectrometer. Systems engineering flowdown from data set requirements to instrument requirements are discussed, along with the trade considerations and a pre-conceptual baseline design of the widefield optical corrector, spectrometer and fiber positioner systems.

BigBOSS is a Stage IV Dark Energy instrument based on the Baryon Acoustic Oscillations (BAO) and Red Shift Distortions (RSD) techniques using spectroscopic data of 20 million ELG and LRG galaxies at 0.5≤z≤1.6 in addition to several hundred thousand QSOs at 0.5≤z≤3.5. When designing BigBOSS instrumentation, it is imperative to maximize throughput whilst maintaining a resolving power of between R=1500 and 4000 over a wavelength range of 360-980 nm. Volume phase Holographic (VPH) gratings have been identified as a key technology which will enable the efficiency requirement to be met, however it is important to be able to accurately predict their performance. In this paper we quantitatively compare different modelling techniques in order to assess the parameter space over which they are more capable of accurately predicting measured performance. Finally we present baseline parameters for grating designs that are most suitable for the BigBOSS instrument.

We describe a non-contact optical measurement method used to determine the surface flatness of a cryogenic sensor array developed for the JDEM mission. Large focal planes envisioned for future visible to near infra-red astronomical large area point-source surveys such as JDEM, WFIRST, or EUCLID must operate at cryogenic temperatures while maintaining focal plane flatness within a few 10's of μm over half-meter scales. These constraints are imposed by sensitivity conditions that demand low noise observations from the sensors and the large-field, fast optical telescopes necessary to obtain the science yield. Verifying cryogenic focal plane flatness is challenging because μm level excursions need to be measured within and across many multi-cm sized sensors using no physical contact and while situated within a high-vacuum chamber. We have used an optical metrology Shack-Hartmann scheme to measure the 36x18 cm focal plane developed for the JDEM mission at the Lawrence Berkeley National Laboratory. The focal plane holds a 4x8 array of CCDs and HgCdTe detectors. The flatness measurement scheme uses a telescope-fed micro-lens array that samples the focal plane to determine slope changes of individual sensor zones.

Mission concepts for NASA's Wide Field Infrared Survey Telescope (WFIRST) 1,2 , ESA's Euclid 3,4 mission, as well as next-generation ground-based surveys require large mosaic focal planes sensitive in both visible and near infrared (NIR) wavelengths. We have developed space-qualified detectors, readout electronics and focal plane design techniques that can be used to intermingle CCDs and NIR detectors on a single, silicon carbide (SiC) cold plate. This enables optimized, wideband observing strategies. The CCDs, developed at Lawrence Berkeley National Laboratory, are fully-depleted, pchannel devices that are backside illuminated and capable of operating at temperatures down to 120K. The NIR detectors are 1.7 μm and 2.0 μm wavelength cutoff H2RG® HgCdTe, manufactured by Teledyne Imaging Sensors under contract to LBNL. Both the CCDs and NIR detectors are packaged on 4-side abuttable SiC pedestals with a common mounting footprint supporting a 44 mm mosaic pitch. Both types of detectors have direct-attached readout electronics that convert the detector signal directly to serial, digital data streams and allow a flexible, low cost data acquisition strategy to enable large data rates. A mosaic of these detectors can be operated at a common temperature that achieves the required dark current and read noise performance necessary for dark energy observations. We report here the qualification testing and performance verification for a focal plane that accommodates a 4x8 array of CCDs and HgCdTe detectors.

BigBOSS is a proposed DOE-NSF Stage IV ground-based dark energy experiment designed to study baryon acoustic oscillations (BAO) and the growth of large scale structure with a 14,000 square degree survey of the redshifts of galaxies and quasi-stellar objects. The project involves modification of existing facilities operated by the National Optical Astronomy Observatory (NOAO). Design and systems engineering of a preliminary 3 degree field of view refractive corrector, atmospheric dispersion corrector (ADC), and 5000 actuator fiber positioning system are presented.

Fully depleted, back-illuminated, p-channel CCDs developed at Lawrence Berkeley National Laboratory exhibit high quantum efficiency in the near-infrared (700-1050nm), low fringing effects, low lateral charge diffusion (and hence small, well-controlled point spread function), and high radiation tolerance. Building on previous efforts, we have developed techniques and hardware that have produced space-qualified 4-side abuttable, high-precision detector packages for 10.5μm pixel, 3.5k x 3.5k p-channel LBNL CCDs. These packages are built around a silicon carbide mounting pedestal, providing excellent rigidity, thermal stability, and heat transfer. Precision fixturing produces packages with detector surface flatness better than 10μm P-V. These packages with active areas of 36.8mm square may be packed on a detector pitch as small as 44mm. LBNL-developed Front End Electronics (FEE) packages can mount directly to the detector packages within the same footprint and detector pitch. This combination, along with identically interfaced NIR detector/FEE packages offers excellent opportunities for high density, high pixel count focal planes for space-based, ground-based, and airborne astronomy.

Single-molecule observation, characterization and manipulation techniques have recently come to the forefront of several research domains spanning chemistry, biology and physics. Due to the exquisite sensitivity, specificity, and unmasking of ensemble averaging, single-molecule fluorescence imaging and spectroscopy have become, in a short period of time, important tools in cell biology, biochemistry and biophysics. These methods led to new ways of thinking about biological processes such as viral infection, receptor diffusion and oligomerization, cellular signaling, protein-protein or protein-nucleic acid interactions, and molecular machines. Such achievements require a combination of several factors to be met, among which detector sensitivity and bandwidth are crucial. We examine here the needed performance of photodetectors used in these types of experiments, the current state of the art for different categories of detectors, and actual and future developments of single-photon counting detectors for single-molecule imaging and spectroscopy.

The Extreme Ultraviolet Explorer mission is described. For the first six months, an all-sky survey will be carried out covering 90 to 750 Å, or essentially the entire extreme ultraviolet (EUV) bandpass. This EUV survey will be made in four bands, or colors: λλ 90-150 Å, 170-250 Å, 400-600 Å, and 550-750 Å. A portion of the sky which is free from the normally intense 304 Å geocoronal helium background will be surveyed at greater sensitivity; the wavelength coverage of this band is from 90 to 400 Å. Following the sky survey portion of the mission, spectroscopy of individual sources will be carried out. Three spectrometers employing novel variable line-space gratings will provide spectra with ~1 Å resolution over the band from 70 to 760 Å. This spectroscopy will be carried out by guest observers chosen by NASA in a manner roughly analogous to the International Ultraviolet Explorer (IUE) guest observer program.

SNAP is a proposed space-based experiment designed to quantify dark energy by measuring the redshift-magnitude diagram of supernovae and to quantify the growth of structure in the universe by measuring weak gravitational lensing over cosmological distances. The baseline SNAP telescope is an ambient temperature three-mirror anastigmat (TMA). The goal of the stray light design is to ensure that stray light in the 0.4 to 1.7 micron wavelength range does not exceed a small fraction of Zodiacal radiation within the mission's target field near the North ecliptic pole. At visible wavelengths, we expect the primary source of stray light will be starlight scattered by the primary mirror. In our longest wavelength NIR band we expect thermal emission from the mirrors and structure will dominate. Scattered stray light is mitigated by an internal field stop, and a cold (140K) internal aperture stop. Stray light scattered by mirror roughness and particulate contamination, as well as scattering from the telescope baffles are modeled and quantified. The baseline design and analyses contained herein ensure that stray light will be less than 10% of Zodiacal in all bands.

We have recently developed a wide-field photon-counting detector (the H33D detector) having high-temporal and high-spatial resolutions and capable of recording up to 500,000 photons per sec. Its temporal performance has been previously characterized using solutions of fluorescent materials with different lifetimes, and its spatial resolution using sub-diffraction objects (beads and quantum dots). Here we show its application to fluorescence lifetime imaging of live cells and compare its performance to a scanning confocal TCSPC approach. With the expected improvements in photocathode sensitivity and increase in detector throughput, this technology appears as a promising alternative to the current lifetime imaging solutions.

We study two samples of local galaxies, one is UV (GALEX) selected and the other FIR (IRAS) selected, to address the question whether UV and FIR surveys see the two sides ('bright' and 'dark') of the star formation of the same population of galaxies or two different populations of star forming galaxies. No significant difference between the L$_{tot}$ ($=L_{60}+L_{FUV}$) luminosity functions of the UV and FIR samples is found. Also, after the correction for the `Malmquist bias' (bias for flux limited samples), the FIR-to-UV ratio v.s. L$_{tot}$ relations of the two samples are consistent with each other. In the range of $9 \la \log(L_{tot}/L_\sun) \la 12$, both can be approximated by a simple linear relation of $\log (L_{60}/L_{FUV})=\log(L_{tot}/L_\sun)-9.66$. These are consistent with the hypothesis that the two samples represent the same population of star forming galaxies, and their well documented differences in L$_{tot}$ and in FIR-to-UV ratio are due only to the selection effect. A comparison between the UV luminosity functions shows marginal evidence for a population of faint UV galaxies missing in the FIR selected sample. The contribution from these 'FIR-quiet' galaxies to the overall UV population is insignificant, given that the K-band luminosity functions (i.e. the stellar mass functions) of the two samples do not show any significant difference.

We have recently developed a wide-field photon-counting detector having high-temporal and high-spatial resolutions and capable of high-throughput (the H33D detector). Its design is based on a 25 mm diameter multi-alkali photocathode producing one photo electron per detected photon, which are then multiplied up to 107 times by a 3-microchannel plate stack. The resulting electron cloud is proximity focused on a cross delay line anode, which allows determining the incident photon position with high accuracy. The imaging and fluorescence lifetime measurement performances of the H33D detector installed on a standard epifluorescence microscope will be presented. We compare them to those of standard single-molecule detectors such as single-photon avalanche photodiode (SPAD) or electron-multiplying camera using model samples (fluorescent beads, quantum dots and live cells). Finally, we discuss the design and applications of future generation of H33D detectors for single-molecule imaging and high-throughput study of biomolecular interactions.

SNAP is a proposed space-based experiment designed to study dark energy and alternate explanations of the acceleration of the universe's expansion by performing a series of complementary systematic-controlled astrophysical measurements. The principal mission activities are the construction of an accurate Type Ia supernova Hubble diagram (the supernova program), and conducting a wide-area weak gravitational lensing (WL) survey. WL measurements benefit from a highly constant point spread function (PSF). The goal of this study is to quantify the anticipated variations in PSF arising from on-orbit thermal variations and and shrinkage associated with dryout of the composite telescope metering structure. A combined thermo-mechanical-optical analysis tool was developed, and WL metrics whisker and effective anisotropy quantified for thermal and composite structure dryout effects. Stability limits necessary for WL are defined, and compared to stability tolerances defined for the supernova program. The mission is designed for operations at at the Earth-Sun L2 Lagrange point, where thermal disturbances from Earth are minimal. In this study, the effects of seasonal variations in solar flux, transients introduced when pointing the body-fixed Ka-band antenna toward Earth and 90° roll maneuvers (planned every three months of operations) are quantified, and introduced into the optical system. Whisker and effective anisotropy were computed, and found to be well below the WL requirement for stability. The effects of composite structure shrinkage due to on-orbit H 2 O desorption are discussed, and estimated to be below WL limits for daily observations, at the beginning of the WL phase of the mission.

The Supernova/Acceleration Probe (SNAP) is a proposed space-based experiment designed to study the dark energy and alternative explanations of the acceleration of the Universe's expansion by performing a series of complementary systematics-controlled astrophysical measurements. We here describe a self-consistent reference mission design that can accomplish this goal with the two leading measurement approaches being the Type Ia supernova Hubble diagram and a wide-area weak gravitational lensing survey. This design has been optimized to first order and is now under study for further modification and optimization. A 2-m three-mirror anastigmat wide-field telescope feeds a focal plane consisting of a 0.7 square-degree imager tiled with equal areas of optical CCDs and near infrared sensors, and a high-efficiency low-resolution integral field spectrograph. The instrumentation suite provides simultaneous discovery and light-curve measurements of supernovae and then can target individual objects for detailed spectral characterization. The SNAP mission will discover thousands of Type Ia supernovae out to z = 3 and will obtain high-signal-to-noise calibrated light-curves and spectra for a subset of > 2000 supernovae at redshifts between z = 0.1 and 1.7 in a northern field and in a southern field. A wide-field survey covering one thousand square degrees in both northern and southern fields resolves {approx} 100 galaxies per square arcminute, or a total of more than 300 million galaxies. With the PSF stability afforded by a space observatory, SNAP will provide precise and accurate measurements of gravitational lensing. The high-quality data available in space, combined with the large sample of supernovae, will enable stringent control of systematic uncertainties. The resulting data set will be used to determine the energy density of dark energy and parameters that describe its dynamical behavior. The data also provide a direct test of theoretical models for the dark energy, including discrimination of vacuum energy due to the cosmological constant and various classes of dynamical scalar fields. If we assume we live in a cosmological-constant-dominated Universe, the matter density, dark energy density, and flatness of space can all be measured with SNAP supernova and weak-lensing measurements to a systematics-limited accuracy of 1%. For a flat universe, the density-to-pressure ratio of dark energy or equation of state w(z) can be similarly measured to 5% for the present value w{sub 0} and {approx} 0.1 for the time variation w' {triple_bond} dw/d ln a|{sub z=1}. For a fiducial SUGRA-inspired universe, w{sub 0} and w' can be measured to an even tighter uncertainty of 0.03 and 0.06 respectively. Note that no external priors are needed. As more accurate theoretical predictions for the small-scale weak-lensing shear develop, the conservative estimates adopted here for space-based systematics should improve, allowing even tighter constraints. While the survey strategy is tailored for supernova and weak gravitational lensing observations, the large survey area, depth, spatial resolution, time-sampling, and nine-band optical to NIR photometry will support additional independent and/or complementary dark-energy measurement approaches as well as a broad range of auxiliary science programs.

We present GALEX near-ultraviolet (2310 Å) and far-ultraviolet (1530 Å) images of the interacting galaxy NGC 4438 (Arp 120) in the center of the Virgo Cluster. These images show an extended (20 kpc) tidal tail at the northwest edge of the galaxy that was previously undetected at other wavelengths; this tail is 15-25 kpc from NGC 4438's nucleus. Except for in the nucleus, the UV morphology of NGC 4438 is totally different from the Hα + [N II] morphology, which is more similar to the X-ray emission, confirming its gas cooling origin. We study the star formation history of NGC 4438 by combining spectrophotometric data in the UV-visible-near-IR wavelength range with population synthesis and galaxy evolution models. The data are consistent with a recent (~10 Myr), instantaneous burst of star formation in the newly discovered UV northwestern tail that is significantly younger than the age of the tidal interaction with NGC 4435, dated by dynamical models at ~100 Myr ago. Recent star formation events are also present at the edge of the northern arm and in the southern tail, while totally lacking in the other regions, which are dominated by the old stellar population that was perturbed during the dynamical interaction with NGC 4435. The contribution of this recent starburst to the total galaxy stellar mass is lower than 0.1%, an extremely low value for such a violent interaction. High-velocity, off-center tidal encounters such as that observed in Arp 120 are thus not sufficient to significantly increase the star formation activity of cluster galaxies.

Ultraviolet imaging with the Galaxy Evolution Explorer (GALEX) has revealed an extensive sample of UV-bright stellar complexes in the extreme outer disk of M83, extending to about four times the radius where the majority of HII regions are detected (R_HII = 5.1' or 6.6 kpc). These sources are typically associated with large-scale filamentary HI structures in the warped outer disk of M83, and are distributed beyond the galactocentric radii at which molecular ISM has yet been detected. We present measured properties of these stellar complexes, including FUV and NUV magnitudes and local gas surface density. Only a subset of the outer disk UV sources have corresponding HII regions detected in H-alpha imaging, consistent with a sample of mixed age in which some sources are a few Myr old and others are much more evolved (~ 10^8 yr)., Comment: This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http://www.galex.caltech.edu/PUBLICATIONS/ after November 22, 2004

We use the far-UV (FUV) and near-UV images of M83 obtained by the Galaxy Evolution Explorer (GALEX) to compute the radial profile of the UV spectral slope in the star-forming disk. We briefly present a model of its chemical evolution, which allows us to obtain realistic intrinsic properties of the stellar populations. Using corollary data, we also compute the profiles of Hα/Hβ and total-IR/FUV ratios. Both the data and model are used to estimate and compare the extinction gradients at the FUV wavelength obtained from these various indicators. We discuss the implications for the determination of the star formation rate.

In order to investigate the origin of the far-UV (FUV) flux from the early-type galaxies, Galaxy Evolution Explorer (GALEX) is collecting the UV data for the elliptical-rich clusters at moderate redshifts (z < 0.2) where the dominant FUV source is predicted to be hot horizontal-branch (HB) stars and their post-HB progeny. Here we present our first result for the early-type galaxies in Abell 2670 at z = 0.076. Compared to NGC 1399, a nearby giant elliptical galaxy in the Fornax cluster, it appears that the rest-frame FUV - V color of the giant ellipticals gets redder by ~ 0.7 mag at the distance of Abell 2670 (z = 0.076; look-back time ~ 1.0 Gyr). Although a detailed comparison with the models is postponed until more cluster data are accumulated, it is interesting to note that this value is consistent with the variation predicted by the population synthesis models where the mean temperature of HB stars declines rapidly with increasing look-back time.

The NASA Galaxy Evolution Explorer (GALEX) satellite has obtained simultaneous near and far ultraviolet light curves of the ROTSE-I Catalog RR Lyrae ab-type variable star J143753.84+345924.8. A series of 38 GALEX Deep Imaging Survey observations well distributed in phase within the star's 0.56432d period shows an AB=4.9mag variation in the far UV (1350-1750A) band and an AB=1.8mag variation in the near UV (1750-2750A) band, compared with only a 0.8mag variation in the broad, unfiltered ROTSE-I (4500-10000A) band. These GALEX UV observations are the first to reveal a large RR Lyrae amplitude variation at wavelengths below 1800A. We compare the GALEX and ROTSE-I observations to predictions made by recent Kurucz stellar atmosphere models. We use published physical parameters for the comparable period (0.57433d), well-observed RR Lyrae star WY Antliae to compute predicted FUV, NUV, and ROTSE-I light curves for J143753.84+345924.8. The observed light curves agree with the Kurucz predictions for [Fe/H]=-1.25 to within AB=0.2mag in the GALEX NUV and ROTSE-I bands, and within 0.5mag in the FUV. At all metallicities between solar and one hundredth solar, the Kurucz models predict 6-8mag of variation at wavelengths between 1000-1700A. Other variable stars with similar temperature variations, such as Cepheids, should also have large-amplitude FUV light curves, observable during the ongoing GALEX imaging surveys., This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http:/www.galex.caltech.edu/PUBLICATIONS after November 22, 2004

We test the empirical relation between ultraviolet color and attenuation as derived for starburst galaxies with a wide assortment of galaxy types detected by the Galaxy Evolution Explorer and find that it systematically overestimates the far-ultraviolet attenuation of our sample by ~0.5 mag. Our efforts to find an additional parameter that could improve the starburst reddening relation were unsuccessful. In particular, UV-Ks colors (in nonmatching apertures) show no correlation with the offset from the starburst reddening relation, suggesting either that UV-Ks colors are a poor tracer of present to past average star formation history (the ``b'' parameter) or that the intrinsic dust distribution/geometry may be responsible for moving galaxies off the correlation. It is possible to reduce the systematic overestimate of AFUV by using the linear correlation derived from our sample, which simply lowers the starburst predicted values of AFUV by 0.58 mag. The scatter, however, remains large at 0.89 mag.

We give an overview of the Galaxy Evolution Explorer (GALEX), a NASA Explorer Mission launched on April 28, 2003. GALEX is performing the first space UV sky-survey, including imaging and grism surveys in two bands (1350-1750 Angstroms and 1750-2750 Angstroms). The surveys include an all-sky imaging survey (m[AB] ~ 20.5), a medium imaging survey of 1000 square degrees (m[AB] ~ 23), a deep imaging survey of 100 square degrees (m[AB] ~ 25), and a nearby galaxy survey. Spectroscopic grism surveys (R=100-200) are underway with various depths and sky coverage. Many targets overlap existing or planned surveys. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in local galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the redshift range 0 < z < 1.5, and probe the physical drivers of star formation in galaxies. The GALEX mission includes a Guest Investigator program supporting the wide variety of programs made possible by the first UV sky survey., This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http:/www.galex.caltech.edu/PUBLICATIONS/ after November 22, 2004

We present Galaxy Evolution Explorer (GALEX) images of the prototypical edge-on starburst galaxies M82 and NGC253. Our initial analysis is restricted to the complex of ultraviolet (UV) filaments in the starburst-driven outflows in the galaxy halos. The UV luminosities in the halo are too high to be provided by shock-heated or photoionized gas except perhaps in the brightest filaments in M82, suggesting that most of the UV light is the stellar continuum of the starburst scattered into our line of sight by dust in the outflow. This interpretation agrees with previous results from optical imaging polarimetry in M82. The morphology of the UV filaments in both galaxies shows a high degree of spatial correlation with H-alpha and X-ray emission. This indicates that these outflows contain cold gas and dust, some of which may be vented into the intergalactic medium (IGM). UV light is seen in the ``H-alpha cap'' 11 kpc North of M82. If this cap is a result of the wind fluid running into a pre-existing gas cloud, the gas cloud contains dust and is not primordial in nature but was probably stripped from M82 or M81. If starburst winds efficiently expel dust into the IGM, this could have significant consequences for the observation of cosmologically distant objects., This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at http://www.galex.caltech.edu/PUBLICATIONS/ after November 22, 2004

M32, the compact elliptical-galaxy companion to the Andromeda spiral galaxy has been imaged by the Galaxy Evolution Explorer (GALEX) in two ultraviolet bands, centered at ~1500 (FUV) and 2300 Angstroms (NUV). The imaging data have been carefully decomposed so as to properly account for the complicated background contamination from the disk of M31. We have derived the surface brightness and color profiles finding a slightly positive color gradient of Delta(FUV-B)/Delta log(r)=+0.15+/-0.03 within one effective radius. Earlier data from the Ultraviolet Imaging Telescope suggested that M32 had an extremely large (negative) FUV-optical color gradient (Delta(FUV-B)/Delta log(r)

The total ultraviolet (UV) flux (from 1412 to 2718 AA) of M 101 is compared on a pixel-to-pixel basis with the total far-infrared (FIR) flux (from 60 to 170 micron), using the maps of the galaxy taken by GALEX in the near-UV and far-UV and by ISOPHOT at 60, 100 and 170 micron. The main result of this investigation is the discovery of a tight dependence of the FIR/UV ratio on radius, with values monotonically decreasing from around 4 in the nuclear region to nearly zero towards the edge of the optical disk. Although the tightness of this dependence is in part attributable to resolution effects, the result is consistent with the presence of a large-scale distribution of diffuse dust having a face-on optical depth which decreases with radius and which dominates over the more localized variations in opacity between the arm and interarm regions. We also find a trend for the FIR/UV ratio to take on higher values in the regions of diffuse interarm emission than in the spiral-arm regions, at a given radius. This is interpreted quantitatively in terms of the escape probability of UV photons from spiral arms and their subsequent scattering in the interarm regions, and in terms of the larger relative contribution of optical photons to the heating of the dust in the interarm regions., This paper will be published as part of the Galaxy Evolution Explorer (GALEX) ApJ Letters Special Issue. Links to the full set of papers will be available at http://www.galex.caltech.edu/PUBLICATIONS/ after Nov. 22, 2004. For version with full resolution images go to: http://edoc.mpg.de/204700.0

We use the Galaxy Evolution Explorer (GALEX) Medium Imaging Survey (MIS) and All-sky Imaging Survey (AIS) data available in the first internal release, matched to the Sloan Digital Sky Survey (SDSS) catalogs in the overlapping regions, to classify objects by comparing the multiband photometry to model colors. We show an example of the advantage of such broad wavelength coverage (GALEX far-UV and near-UV, SDSS ugriz) in classifying objects and augmenting the existing samples and catalogs. From the MIS (AIS) sample over an area of 75 (92) deg2, we select a total of 1736 (222) QSO candidates at redshifts less than 2, significantly extending the number of fainter candidates and moderately increasing the number of bright objects in the SDSS list of spectroscopically confirmed QSOs. Numerous hot stellar objects are also revealed by the UV colors, as expected.

We present measurements of the FUV (1530A) and NUV (2310A) galaxy luminosity functions (LF) at low redshift (z, This paper will be published as part of the Galaxy Evolution Explorer (GALEX) Astrophysical Journal Letters Special Issue. Links to the full set of papers will be available at : http://www.galex.caltech.edu/PUBLICATIONS/ after November 22, 2004

Mission requirements, the baseline design, and optical systems budgets for the SuperNova/Acceleration Probe (SNAP) telescope are presented. SNAP is a proposed space-based experiment designed to study dark energy and alternate explanations of the acceleration of the universe’s expansion by performing a series of complementary systematics-controlled astrophysical measurements. The goals of the mission are a Type Ia supernova Hubble diagram and a wide-field weak gravitational lensing survey. A 2m widefield three-mirror telescope feeds a focal plane consisting of 36 CCDs and 36 HgCdTe detectors and a high-efficiency, low resolution integral field spectrograph. Details of the maturing optical system, with emphasis on structural stability during terrestrial testing as well as expected environments during operations at L2 are discussed. The overall stray light mitigation system, including illuminated surfaces and visible objects are also presented.

A well-adapted visible and infrared spectrograph has been developed for the SNAP (SuperNova/Acceleration Probe) experiment proposed for JDEM. The primary goal of this instrument is to ensure the control of Type Ia supernovae. The spectrograph is also a key element for calibration and is able to measure redshift of some thousands of galaxy spectra both in visible and IR. An instrument based on an integral field method with the powerful concept of imager slicing has been designed and is presented. We present the current design and expected performances. We show that with the current optimization and the proposed technology, we expect the most sensitive instrument proposed on this kind of mission. We recall the readiness of the concept and of the slicer technology thanks to large prototyping efforts performed in France which validate the proposition

We describe the Galaxy Evolution Explorer (GALEX) satellite that was launched in April 2003 specifically to accomplish far ultraviolet (FUV) and near ultraviolet (NUV) imaging and spectroscopic sky-surveys. GALEX is currently providing new and significant information on how galaxies form and evolve over a period that encompasses 80% of the history of the Universe. This is being accomplished by the precise measurement of the UV brightness of galaxies which is a direct measurement of their rate of star formation. We briefly describe the design of the GALEX mission followed by an overview of the instrumentation that comprises the science payload. We then focus on a description of the development of the UV sealed tube micro-channel plate detectors and provide data that describe their on-orbit performance. Finally, we provide a short overview of some of the science highlights obtained with GALEX.

We have used the first matched set of GALEX and SDSS data to investigate the properties of a sample of 74 nearby galaxies with far-ultraviolet luminosities chosen to overlap the luminosity range of typical high-z Lyman Break Galaxies (LBGs). GALEX deep surveys have shown that ultraviolet-luminous galaxies (UVLGs) similar to these are the fastest evolving component of the UV galaxy population. Model fits to the combined GALEX and SDSS photometry yield typical FUV extinctions similar to LBGs. The implied star formation rates are SFR ~ 3 to 30 solar mass per year. This overlaps the range of SFRs for LBGs. We find a strong inverse correlation between galaxy mass and far-ultraviolet surface brightness, and on this basis divide the sample into ``large\'\' and ``compact\'\' UVLGs. The compact UVLGs have half-light radii of a few kpc or less (similar to LBGs). They are relatively low mass galaxies (~10 billion solar masses) with typical velocity dispersions of 60 to 150 km/s. They span a range in metallicity from 0.3 to 1 times solar, have blue optical-UV colors, and are forming stars at a rate sufficient to build the present galaxy in ~a Gigayear. In all these respects they appear similar to the LBG population. These ``living fossils\'\' may therefore provide an opportunity for detailed investigation of the physical processes occurring in typical star forming galaxies in the early universe.