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Advances in optical testing are as important as advances in fabrication because one can make only what one can measure. A high-precision metrology capability is utilized to close the gap between interferometric testing and lower precision metrology, laser radar, or contact-probe-based coordinate measuring machines (CMM) to accurately measure surfaces with large form error. This nearly universal optical testing method employs a precision CMM equipped with a non-contact, confocal probe. This technique was developed to characterize and align a broad spectrum of optical surfaces including ones with high slopes that are nearly impossible to measure using traditional interferometric testing without custom-made optics. Optical components covering a wide range of prescriptions, such as large convex conics, high-sloped aspherics, grazing-incidence x-ray optics, and highly deformed flats, were successfully measured. The resulting data were processed using custom-developed routines to determine the optic’s alignment, the departure from design surface, and the as-built prescription parameters. This information was used to verify and guide the development and fabrication of novel optics.

The desirability of making deployable mirrors for space telescopes has been known for years. Yet, once the wave lengths are longer than the short wave radio, progress has been slow. Therefore, we are exploring a new technology based on using a magnetic smart material film deposited on a shape-memory alloy (SMA) sheet. Our preliminary result is that when we apply an about 0.1-0.35 T in-plane magnetic field, we can produce greater than micron deflections in the SMA. Furthermore, we have shown the SMA can return to shape to within 1 micron. We will present an update on how long these deflections can be maintained and our progress toward making the SMA surface smooth enough to produce specular reflection. In addition, we assess the brightness and shininess of the NiTi piece before and after heating that is needed to produce a return to shape.

Photodetectors with internal gain are of great interest for imaging applications, since internal gain reduces the effective noise of readout electronics. High-gain photodetectors have been demonstrated, but only individually rather than as a full array in a camera. Consequently, there has been little investigation of the interaction between camera complementary metal oxide semiconductor (CMOS) electronics and the slow response time that high-gain photodetectors often exhibit. Here we show that this interaction filters shot noise and causes noise statistics to differ from the common Poisson distribution. As an example, we investigate a 320 × 256 array of InGaAs/InP high-gain phototransistors bonded to a CMOS readout chip. We demonstrate the filtering effects and discuss their consequences, including new (to the best of our knowledge) methods for extracting gain and increasing dynamic range.

We analyzed 17 galaxy clusters, and investigated, for the first time, the dependence of the SFR and sSFR as a function of projected distance (as a proxy for environment) and stellar mass for cluster galaxies in an intermediate-to-high redshift range ($0.4 < z < 0.9$). We used up to nine flux points (BVRIZYJHKs magnitudes), its errors and redshifts to compute M$_{\rm{star}}$, SFR and sSFR through spectral energy distribution fitting technique. We use a z-dependent sSFR value to distinguish star-forming (SF) from quiescent galaxies. To analyse the SFR and sSFR history we split our sample in two redshift bins: galaxies at $0.4 < z < 0.6$ and $0.6 < z < 0.9$. We separate the effects of environment and stellar mass on galaxies by comparing the properties of star-forming and quiescent galaxies at fixed environment (projected radius) and fixed stellar mass. For the selected spectroscopic sample of more than 500 galaxies, the well-known correlation between SFR and $M_{\rm star}$ is already in place at $z \sim 0.9$, for both SF and quenched galaxies. Our results are consistent with no evidence that SFR (or sSFR) depends on environment, suggesting that for cluster galaxies at an intermediate-to-high redshift range, mass is the primary characteristic that drives SFR., 10 pages, 5 figures

Larger mirrors are needed to satisfy the requirements of the next generation of UV–Vis space telescopes. Our study attempts to meet this requirement by demonstrating a technology that would deploy a large, continuous, high figure accuracy membrane mirror. The figure of the membrane mirror is corrected after deployment using a contiguous coating of a magnetic smart material (MSM) and a magnetic field. The MSM is a magnetostrictive material that is operable by magnetic write head(s), locally imposed on the nonreflective side of the membrane mirror. We report preparation, figure accuracy, stress analysis, and stability of the MSM coated CP1 polyimide substrate membrane mirror. The figure accuracy and magnetostrictive performance of the MSM coated membrane mirror are measured; furthermore, stability of the CP1 membrane for 48 h is observed and the results are found to be promising. In addition to membrane coating and the experimental procedure, the results of the surface profiling experiments are introduced and discussed.

The only way to increase the sensitivity of X-ray telescopes without significantly increasing their size (compared to existing telescopes) is to use thinner mirror shells. However, to maintain the figure of thin mirror shells, their shape will need to be adjusted after they are mounted and/or actively controlled during flight. Here we describe progress toward developing a method that can be used to do both. The core of the concept is to coat thin (

Larger mirrors are needed to satisfy the requirements of the next generation of UV-Vis space telescopes. Our NASA-NIAC funded project, titled A Precise Extremely large Reflective Telescope Using Reconfigurable Elements (APERTURE), attempts to meet this requirement. The aim of the project is to demonstrate technology that would deploy a large, continuous, high figure accuracy membrane mirror. The figure of the membrane mirror is corrected after deployment using a contiguous coating of a Magnetic Smart Material (MSM) and a magnetic field. The MSM is a magnetostrictive material which is driven by magnetic write head(s) (MWH), locally imposed on the non-reflective side of the membrane mirror. In this proceeding we report the figure accuracy of the MSM coated membrane mirror under various conditions using a Shack-Hartmann surface profiler. The figure accuracy and magnetostrictive performance of the membrane mirror is found to be significantly dependent on ambient temperature fluctuations, the tension load on the membrane, time, magnetic writing head orientation and magnetic field strength. The results and reproducibility of the surface profiling experiments under various conditions are introduced and discussed.

One of the pressing needs for the UV-Vis is an affordable design that allows larger mirrors than the JWST primary. In this publication we report the results of the first year of a NASA Innovative Advanced Concepts Phase II study. Our project is called A Precise Extremely large Reflective Telescope Using Reconfigurable Elements (APERTURE). The concept is to deploy a continuous membrane-like mirror. The mirror figure will be corrected after deployment, causing the figure error to decrease below λ/20. While the basic concept is not new, our innovation lies in a different approach to correcting the residual figure errors from the classical piezoelectricpatch technology. Instead, our concept is based on a contiguous coating of a magnetic smart material (MSM). After deployment, a magnetic write head will move along the non-reflecting side of the mirror. The magnetic field will produce a stress in the MSM which then corrects the mirror shape. This publication summarizes the results of minimizing the MSM deposition stress as well as the size and stability of the deformation, which is maintained by a magnetically hard material.

Highly sensitive and fast imaging at short-wavelength infrared (SWIR) is one of the key enabling technologies for the direct-imaging of habitable exoplanets. SWIR imaging systems currently available in the market are dominated by imagers based on InGaAs PIN photodiodes. The sensitivity of these cameras is limited by their read-out noise (RON) level. Sensors with internal gain can suppress the RON and achieve lower noise imaging. In this paper, we demonstrate a SWIR camera based on 3D-engineered InP/InGaAs heterojunction phototransistors with responsivities around 2000 A/W which provides a shot-noise limited imaging sensitivity at a very low light level. We present the details of the semiconductor structure, the microfabrication, and the heterogeneous integration of this camera. The low capacitance pixels of the imager achieve 36 electron effective RON at frame rates around 5 kilo-frames per second at an operating temperature of 220 K and a bias voltage of 1.1 V. This is a significant step toward achieving highly sensitive imaging at SWIR at high frame rates and noncryogenic operating temperatures. Based on the proposed modeling and experimental results, a clear path to reach the RON less than 10 electrons is presented.

Here we report progress toward the fabrication of adaptive or active Si X-ray mirrors via a two step process. The first step is to curve a Si flat and then coat it with Terfenol-D that will allow the shape control via the application of a magnetic field. The goal is to create a mirror whose local (a few mm-length scale) slope can be changed and left for several hours or more. The current work described here was done in on Si to demonstrate the ability to produce the initial curvature, and in parallel, work to on magnetically hard NiCo 5 cm x 5 cm square plus on a glass sample. The glass sample was used a proto-type to model making changes in two different locations on a mirror. The NiCo sample was used to show that a magnetic field can be retained in a magnetically hard substrate such that the magnetically induced stress in the Terfenol-D was able to maintain a deformation for as long as time permitted to make the measurement which was 71 hours.

This article reports the progress on the development of a novel detector with the promise of addressing the needs of extreme AO (ExAO) in the near-IR band (NIR), 0.9-1.7 μm. The camera is based on the electron injection mechanism which resembles how the human eye processes light. The camera design allows high sensitivity operation at TEC reachable temperatures for ExAO at 1-4 kHz frame rates, and at the same time the concept produces sufficient gain to overcome the read noise of the device. Here we present the overall design, test results on Gen-1 (outdated but operable) camera, along with early results of our next generation of detectors.

One of the pressing needs for the UV-Vis is a design to allow even larger mirrors than the JWST primary at an affordable cost. We report here the results of a NASA Innovative Advanced Concepts phase 1 study. Our project is called A Precise Extremely large Reflective Telescope Using Reconfigurable Elements (APERTURE). The idea is to deploy a continuous membrane-like mirror. The mirror figure will be corrected after deployment to bring it into better or equal lambda/20 deviations from the prescribed mirror shape. The basic concept is not new. What is new is to use a different approach from the classical piezoelectric-patch technology. Instead, our concept is based on a contiguous coating of a so called magnetic smart material (MSM). After deployment a magnetic write head will move on the non-reflecting side of the mirror and will generate a magnetic field that will produce a stress in the MSM that will correct the mirror deviations from the prescribed shape.

Context. Clusters of galaxies are located at the intersection of cosmic filaments and are still accreting galaxies and groups along these preferential directions. However, because of their relatively low contrast on the sky, filaments are difficult to detect (unless a large amount of spectroscopic data are available), and unambiguous detections have been limited until now to relatively low redshifts (z< ∼ 0.3). Aims. This project is aimed at searching for extensions and filaments around clusters, traced by galaxies selected to be at the cluster redshift based on the red sequence. In the 0.4, F.D. acknowledges long-term support from CNES. I.M. acknowledges financial support from the Spanish Ministry of Economy and Competitiveness through the grant AYA2013-42227P.

The galaxy cluster RXJ1257$+$4738 at $z=0.866$ is one of the highest redshift clusters with a richness of multi-wavelength data, and thus a good target to study the star formation-density relation at early epochs. Using a sample of spectroscopically-confirmed cluster members, we derive the star formation rates of our galaxies using two methods, (I) the relation between SFR and total infrared luminosity extrapolated from the observed \textit{Spitzer} MIPS 24$\mu$m imaging data, and (II) spectral energy distribution (SED) fitting using the MAGPHYS code, including eight different bands. We show that, for this cluster, the SFR-density relation is very weak and seems to be dominated by the two central galaxies and the SFR presents a mild dependence on stellar mass, with more massive galaxies having higher SFR. However, the specific SFR (SSFR) decreases with stellar mass, meaning that more massive galaxies are forming less stars per unit of mass, and thus suggesting that the increase in star-forming members is driven by cluster assembly and infall. If the environment is somehow driving the SF, one would expect a relation between the SSFR and the cluster centric distance, but that is not the case. A possible scenario to explain this lack of correlation is the contamination by infalling galaxies in the inner part of the cluster which may be on their initial pass through the cluster center. As these galaxies have higher SFRs for their stellar mass, they enhance the mean SSFR in the center of the cluster., Comment: Accepted for publication in ApJ. 12 pages, 6 figures

In order to advance significantly scientific objectives, future x-ray astronomy missions will likely call for x-ray telescopes with large aperture areas (≍ 3 m2) and fine angular resolution (≍ 12). Achieving such performance is programmatically and technologically challenging due to the mass and envelope constraints of space-borne telescopes and to the need for densely nested grazing-incidence optics. Such an x-ray telescope will require precision fabrication, alignment, mounting, and assembly of large areas (≍ 600 m2) of lightweight (≍ 2 kg/m2 areal density) high-quality mirrors, at an acceptable cost (≍ 1 M$/m2 of mirror surface area). This paper reviews relevant programmatic and technological issues, as well as possible approaches for addressing these issues-including direct fabrication of monocrystalline silicon mirrors, active (in-space adjustable) figure correction of replicated mirrors, static post-fabrication correction using ion implantation, differential erosion or deposition, and coating-stress manipulation of thin substrates....

Our goal is to improve initially fabricated X-ray optics figures by applying a magnetic field to drive a magnetic smart material (MSM) coating on the non-reflecting side of the mirror. The consequent deformation of the surface should be three-dimensional. Here we will report on the results of working with a glass sample of 50x50x0.2 mm that has been coated with MSMs. The coated glass can be deformed in 3 dimensions and its surface profile was measured under our Zygo NewView white light interferometer (WLI). The driving magnetic field was produced via a pseudo-magnetic write head made up of two permanent magnet posts. The magnet posts were moved about the bottom of the glass sample with a 3-d computer controlled translation stage. The system allowed four degrees of freedom of motion, i.e., up and down, side to side, back and forth, and rotation of the posts (3.175 mm diameter) about the vertical axis to allow us to change the orientation of the magnetic field in the (horizontal) plane of the sample. We established a finite element analysis (FEA) model to predict deformations and compare with the observed results in order to guide the application of the magnetically controlled MSMs to improve the future X-ray optics figures.

We compute optical galaxy luminosity functions (GLFs) in the B, V, R, and I rest-frame bands for one of the largest medium-to-high-redshift (0.4 < z < 0.9) cluster samples to date in order to probe the abundance of faint galaxies in clusters. We also study how the GLFs depend on cluster redshift, mass, and substructure, and compare the GLFs of clusters with those of the field. We separately investigate the GLFs of blue and red-sequence (RS) galaxies to understand the evolution of different cluster populations. We find that the shapes of our GLFs are similar for the B, V, R, and I bands with a drop at the red GLF faint end that is more pronounced at high-redshift: alpha(red) ~ -0.5 at 0.40 < z < 0.65 and alpha(red) > 0.1 at 0.65 < z < 0.90. The blue GLFs have a steeper faint end (alpha(blue) ~ -1.6) than the red GLFs, that appears to be independent of redshift. For the full cluster sample, blue and red GLFs intersect at M(V) = -20, M(R) = -20.5, and M(I) = -20.3. A study of how galaxy types evolve with redshift shows that late type galaxies appear to become early types between z ~ 0.9 and today. Finally, the faint ends of the red GLFs of more massive clusters appear to be richer than less massive clusters, which is more typical of the lower redshift behaviour. Our results indicate that our clusters form at redshifts higher than z = 0.9 from galaxy structures that already have an established red sequence. Late type galaxies then appear to evolve into early types, enriching the red-sequence between this redshift and today. This effect is consistent with the evolution of the faint end slope of the red-sequence and the galaxy type evolution that we find. Finally, faint galaxies accreted from the field environment at all redshifts might have replaced the blue late type galaxies that converted into early types, explaining the lack of evolution in the faint end slopes of the blue GLFs., accepted for publication in A&A

© ESO 2015. Context. The discovery of new galaxy clusters is important for two reasons. First, clusters are interesting per se, since their detailed analysis allows us to understand how galaxies form and evolve in various environments and second, they play an important part in cosmology because their number as a function of redshift gives constraints on cosmological parameters. Aims. We have searched for galaxy clusters in the Stripe 82 region of the Sloan Digital Sky Survey, and analysed various properties of the cluster galaxies. Methods. Based on a recent photometric redshift (hereafter photo-z) galaxy catalogue, we built a cluster catalogue by applying the Adami & MAzure Cluster FInder (AMACFI). Extensive tests were made to fine-tune the AMACFI parameters and make the cluster detection as reliable as possible. The same method was applied to the Millennium simulation to estimate our detection efficiency and the approximate masses of the detected clusters. Considering all the cluster galaxies (i.e. within a 1 Mpc radius of the cluster to which they belong and with a photo-z diering by less than ±0.05 from that of the cluster), we stacked clusters in various redshift bins to derive colour-magnitude diagrams and galaxy luminosity functions (GLFs). For each galaxy brighter than Mr < - 19.0, we computed the disk and spheroid components by applying SExtractor, and by stacking clusters we determined how the disk-to-spheroid flux ratio varies with cluster redshift and mass. Results. We detected 3663 clusters in the redshift range 0.15 ≤ z ≤ 0.70, with estimated mean masses between ∼1013 and a few 1014 M⊙. We cross-matched our catalogue of candidate clusters with various catalogues extracted from optical and/or X-ray data. The percentages of redetected clusters are at most 40% because in all cases we detect relatively massive clusters, while other authors detect less massive structures. By stacking the cluster galaxies in various redshift bins, we find a clear red sequence in the (ǵ - ŕ) versus ŕ colour-magnitude diagrams, and the GLFs are typical of clusters, though with a possible contamination from field galaxies. The morphological analysis of the cluster galaxies shows that the fraction of late-type to early-type galaxies shows an increase with redshift (particularly in 9σ clusters) and a decrease with detection level, i.e. cluster mass. Conclusions. From the properties of the cluster galaxies, the majority of the candidate clusters detected here seem to be real clusters with typical cluster properties., F.D. acknowledges long-term support from CNES. I.M. acknowledges financial support from the Spanish grants AYA2010-15169 and AYA2013-42227-P and from the Junta de Andalucia through TIC-114 and the Excellence Project P08-TIC-03531. A.T. acknowledges the support and the hospitality of IAP/CNRS for two one month visits. We are grateful to Andrea Biviano for giving us his IDL program to fit GLFs with a Schechter function and to Alberto Cappi for discussions. We thank the six high school students M.A. Garcia Valverde, B. Hernandez Ramos, J. Leon Lovell, L. Martinez Sanchez de Lara, J. Rodriguez Zamorano and L. Vallecillos Azor for their careful eye classification of about 1000 galaxies. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the US Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org/. SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.

We have made substantial progress in the development of GaN photocathodes, including crystalline and polycrystalline GaN and InGaN coatings grown by chemical vapor deposition or molecular beam epitaxy on sapphire substrates. GaN and InGaN photocathodes have been developed with efficiencies up to 70% and cutoffs at ∼380 nm with low out of band response, and high stability and longevity. Samples have been processed and tested at ultra high vacuum to establish cathode process parameters, and some have been integrated into sealed tubes for long-term evaluation.

We report on a search for faint (R total magnitude fainter than 21) and low surface brightness galaxies (R central surface brightness fainter than ~24) (fLSBs) in a 0.72x0.82 deg2 area centered on the Coma cluster. We analyzed deep B and R band CCD imaging obtained using the CFH12K camera at CFHT and found 735 fLSBs. The total B magnitudes, at the Coma cluster redshift, range from -13 to -9 with B central surface brightness as faint as 27 mag/arcsec2. Using empty field comparisons, we show that most of these fLSBs are probably inside the Coma cluster. We present the results of comparing the projected fLSB distributions with the distributions of normal galaxies and with known X-ray over densities. We also investigate their projected distribution relative to their location in the color magnitude relation. Colors of fLSBs vary between B-R~0.8 and ~1.4 for 2/3 of the sample and this part is consistent with the known CMR red-sequence for bright (R, To be published in A&A, 3 jpeg figures, data and full resolution article can be retrieved from http://cencosw.oamp.fr/. Updated CFHT ackowledgements

We have been working on 3 separate projects that together will give us the ability to make 1 arc second, light weight Wolter I optics that work above 40 keV. The three separate tasks are: (a) plasma spraying of metal-coated micro-balloons; (b) coating of the inside of Wolter I mirrors, (c) actuator designs for improving figure quality. We give a progress report on our work on all three areas.

Deep level luminescence in In0.07Ga0.93N:Mg was examined. A strong photoluminescence (PL) band at 2.45 eV was observed with a well-resolved fine structure that was attributed to phonon-assisted donor-acceptor pair (DAP) recombination. Analysis of the fine structure reveals a large Huang-Rhys parameter of 6.5 for this DAP band, indicating strong localization of carriers at DAP centers. From the phonon replicas, the longitudinal-optical (LO) phonon energy was determined to be 105 meV. The large, measured phonon energy was attributed to the large compressive strain caused by compositional fluctuations in the films.

We investigated the detection of dielectric nanoparticles using static light scattering spectroscopy (LSS) in the UV range (from 250 to 390 nm). The light scattered by the polystyrene nanospheres in the backward direction were collected by means of an optical fiber probe and a charge-coupled device (CCD) spectrograph. The size distributions of the nanoparticles were obtained by a discrete inverse on the backscattering spectra using a theoretical model based on Mie theory. Our results show that UV LSS can be used to measure the sizes of nanoparticles with an accuracy far exceeding the diffraction limit and to study subwavelength structures at nanometer scale. This technique may find potential scientific and industrial applications including the study of macromolecular complexes at nanoscale, detection and identification of viral particles, non-invasive probing of nanoscale surface structures, and monitoring the processing of pharmaceutical nanoparticles.

The desire for continuously gaining new knowledge in astronomy has pushed the frontier of engineering methods to deliver lighter, thinner, higher quality mirrors at an affordable cost for use in an x-ray observatory. To address these needs, we have been investigating the application of magnetic smart materials (MSMs) deposited as a thin film on mirror substrates. MSMs have some interesting properties that make the application of MSMs to mirror substrates a promising solution for making the next generation of x-ray telescopes. Due to the ability to hold a shape with an impressed permanent magnetic field, MSMs have the potential to be the method used to make light weight, affordable x-ray telescope mirrors. This paper presents the experimental setup for measuring the deformation of the magnetostrictive bimorph specimens under an applied magnetic field, and the analytical and numerical analysis of the deformation. As a first step in the development of tools to predict deflections, we deposited Terfenol-D on the glass substrates. We then made measurements that were compared with the results from the analytical and numerical analysis. The surface profiles of thin-film specimens were measured under an external magnetic field with white light interferometry (WLI). The analytical model provides good predictions of film deformation behavior under various magnetic field strengths. This work establishes a solid foundation for further research to analyze the full three-dimensional deformation behavior of magnetostrictive thin films.

A likely tidal disruption of a star by the intermediate-mass black hole (IMBH) of a dwarf galaxy was recently identified in association with Abell 1795. Without deep spectroscopy for this very faint object, however, the possibility of a more massive background galaxy or even a disk-instability flare from a weak AGN could not be dismissed. We have now obtained 8 hours of Gemini spectroscopy which unambiguously demonstrate that the host galaxy is indeed an extremely low-mass $(M_\ast\sim 3\times 10^8\; {\rm M}_{\odot})$ galaxy in Abell 1795, comparable to the least-massive galaxies determined to host IMBHs via other studies. We find that the spectrum is consistent with the X-ray flare being due to a tidal disruption event rather than an AGN flare. We also set improved limits on the black hole mass $({\rm log}[M_{\bullet}/{\rm M}_{\odot}] \sim 5.3 - 5.7)$ and infer a 15-year X-ray variability of a factor of $> 10^4$. The confirmation of this galaxy-black hole system provides a glimpse into a population of galaxies that is otherwise difficult to study, due to the galaxies' low masses and intrinsic faintness, but which may be important contributors to the tidal disruption rate., 9 pages, 4 figures. Accepted by MNRAS

The future of x-ray astronomy depends upon development of x-ray telescopes with larger aperture areas (approx. = 3 square meters) and fine angular resolution (approx. = 1 inch). Combined with the special requirements of nested grazing-incidence optics, the mass and envelope constraints of space-borne telescopes render such advances technologically and programmatically challenging. Achieving this goal will require precision fabrication, alignment, mounting, and assembly of large areas (approx. = 600 square meters) of lightweight (approx. = 1 kilogram/square meter areal density) high-quality mirrors at an acceptable cost (approx. = 1 million dollars/square meter of mirror surface area). This paper reviews relevant technological and programmatic issues, as well as possible approaches for addressing these issues-including active (in-space adjustable) alignment and figure correction.

This report begins with a review of the basic concept of deformable X-ray optics, and the need for this approach for future X-ray astronomy missions that have ~1” resolution. We then report on our advances made on using magnetic smart materials (MSMs) to adjust the shape of thin (~100-200 µm thickness) electroformed replicated optics or glass optics. We show that we can well model deflections in 5 mm x 20 mm glass pieces and we provide preliminary evidence that the concept will work that involves imposing a magnetic field on the hard magnetic substrate (NiCo) to maintain the change in mirror shape.

We analyse the structures of all the clusters in the DAFT/FADA survey for which XMM-Newton and/or a sufficient number of galaxy redshifts in the cluster range is available, with the aim of detecting substructures and evidence for merging events. These properties are discussed in the framework of standard cold dark matter cosmology.XMM-Newton data were available for 32 clusters, for which we derive the X-ray luminosity and a global X-ray temperature for 25 of them. For 23 clusters we were able to fit the X-ray emissivity with a beta-model and subtract it to detect substructures in the X-ray gas. A dynamical analysis based on the SG method was applied to the clusters having at least 15 spectroscopic galaxy redshifts in the cluster range: 18 X-ray clusters and 11 clusters with no X-ray data. Only major substructures will be detected. Ten substructures were detected both in X-rays and by the SG method. Most of the substructures detected both in X-rays and with the SG method are probably at their first cluster pericentre approach and are relatively recent infalls. We also find hints of a decreasing X-ray gas density profile core radius with redshift. The percentage of mass included in substructures was found to be roughly constant with redshift with values of 5-15%, in agreement both with the general CDM framework and with the results of numerical simulations. Galaxies in substructures show the same general behaviour as regular cluster galaxies; however, in substructures, there is a deficiency of both late type and old stellar population galaxies. Late type galaxies with recent bursts of star formation seem to be missing in the substructures close to the bottom of the host cluster potential well. However, our sample would need to be increased to allow a more robust analysis., Comment: Acknowledgements and thanks updated. Accepted in A&A, english improved by A&A office, 1 figure in jpeg format, shortened abstract

This paper presents and gives the COP (COP: CFHT Optical PDCS; CFHT: Canada-France-Hawaii Telescope; PDCS: Palomar Distant Cluster Survey) survey data. We describe our photometric and spectroscopic observations with the MOS multi-slit spectrograph at the CFH telescope. A comparison of the photometry from the PDCS (Postman et al. 1996) catalogs and from the new images we have obtained at the CFH telescope shows that the different magnitude systems can be cross-calibrated. After identification between the PDCS catalogues and our new images, we built catalogues with redshift, coordinates and V, I and Rmagnitudes. We have classified the galaxies along the lines of sight into field and structure galaxies using a gap technique (Katgert et al. 1996). In total we have observed 18 significant structures along the 10 lines of sight.

We present the first dynamical study of the optically selected Palomar Distant Cluster Survey (PDCS). We have measured redshifts for 17 clusters of galaxies in the PDCS and velocity dispersions for a subset of 11. Using our new cluster redshifts, we redetermine the X-ray luminosities and upper limits. We show that 11 of 12 PDCS clusters we observed are real overdensities of galaxies. Most clusters have velocity dispersions appropriate for clusters of galaxies. However, we find a fraction (about one-third) of objects in the PDCS that have velocity dispersions in the range of groups of galaxies (200 ± 100 km s-1) but have richnesses appropriate for clusters of galaxies. Within our survey volume of 31.7 × 104 h-3 Mpc3 (q0 = 0.1) for richness class 2 and greater clusters, we measure the richness function, X-ray luminosity function (using both the detections and upper limits), and the mass function derived from our velocity dispersions. We confirm that the space density, as a function of richness, of clusters of galaxies in the PDCS is ~5 times that of the Abell catalog. Excluding the above fraction of one-third of objects with low velocity dispersions, we measure a space density ~3 times that of the Abell catalog for equivalent mass clusters of galaxies, raising the possibility that the Abell catalog is incomplete. However, our space density estimates are in agreement with other low-redshift, optically selected cluster surveys such as the EDCC, APM, and EDCC2. Our X-ray luminosity function agrees with other measurements based on both X-ray and optically selected samples, so we find that the PDCS does not miss clusters of galaxies that would be found in an X-ray selected survey. Our resulting mass function, centered on 1014 M☉ h-1, agrees with the expectations from such surveys as the Canadian Network for Observational Cosmology cluster survey, though errors on our mass measurements are too large to constrain cosmological parameters. We do show that future machine-based, optically selected surveys can be used to constrain cosmological parameters.

The broad photoluminescence band with a maximum at about 2.9 eV widely observed in undoped epitaxial GaN is studied as a function of temperature and excitation intensity. We attribute the band to transitions from a shallow donor to a deep localized acceptor. The zero-phonon transition for this band is at 3.098 eV as determined from the fine structure at low temperatures. A local vibrational mode in the ground state with an energy of 36 meV is found.

Broad photoluminescence bands with maxima at 2.2, 2.5 and 2.9 eV in undoped GaN are studied. The bands are related to three deep acceptors, which are characterized by strong electron–phonon coupling. Vibrational properties of the defects are reported.

We have conducted a redshift survey of sixteen cluster candidates from the Palomar Distant Cluster Survey (PDCS) to determine both the density of PDCS clusters and the accuracy of the estimated redshifts presented in the PDCS catalog (Postman et. al. 1996). We find that the matched-filter redshift estimate presented in the PDCS has an error sigma_z = 0.06 in the redshift range 0.1 < z < 0.35 based on eight cluster candidates with three or more concordant galaxy redshifts. We measure the low redshift (0.1 < z < 0.35) space density of PDCS clusters to be 31.3^{+30.5}_{-17.1} * E-06 h^3 Mpc^-3 (68% confidence limits for a Poisson distribution) for Richness Class 1 systems. We find a tentative space density of 10.4^{+23.4}_{-8.4}* E-06 h^3 Mpc^-3 for Richness Class 2 clusters. These densities compare favorably with those found for the whole of the PDCS and support the finding that the space density of clusters in the PDCS is a factor of ~5 above that of clusters in the Abell catalog (Abell 1958; Abell, Corwin, and Olowin 1989). These new space density measurements were derived as independently as possible from the original PDCS analysis and therefore, demonstrate the robustness of the original work. Based on our survey, we conclude that the PDCS matched-filter algorithm is successful in detecting real clusters and in estimating their true redshifts in the redshift range we surveyed., 23 pages with 4 figures and 3 seperate tables. To be published in the November Issue of the Astronomical Journal

We report the analysis of 1 hour's worth of RXTE data in which it was possible to detect individual pulses from the Crab pulsar. These data demonstrate that the Crab pulsar X-ray pulses are steady at the level of 7%, and we suggest that the emitting region is likely to come from a region where the magnetic field is "stiff."

We present here initial results on the X-ray Cluster Luminosity Function (XCLF) from the Bright SHARC sample of distant X-ray clusters of galaxies. This sample is 97% complete in its optical identifications and contains 12 X-ray luminous clusters in the range 0.3 < z < 0.83 (median z = 0.42) and 1.1 < Lx(44) < 8.5 erg/s [0.5-2.0 keV]. We present a preliminary selection function for the Bright SHARC based on Monte Carlo simulations. Using this selection function, we have computed the Bright SHARC XCLF and find it to be fully consistent with a non-evolving XCLF to Lx(44) = 5 erg/s and z = 0.7. At Lx(44) > 5 erg/s, we find evidence for a deficit of clusters compared to that expected from a non-evolving XCLF. We detect only one such cluster in the redshift range 0.3 < z < 0.7 when we would expect 4.9 clusters based on the local XCLF of De Grandi et al. (1999). The statistical significance of this deficit is 96%. To increase the statistical significance of this possible deficit, we have combined the Bright SHARC and the 160 sq. deg. survey of Vikhlinin et al (1998a). This joint survey covers 260 sq. degs. and contains only one confirmed 0.3 < z < 0.7, Lx(44) > 5 erg/s cluster, while we would expect 7.6 such clusters based on the local XCLF (De Grandi et al. 1999). The statistical significance of the deficit in this joint survey increases to 99.5%. These results remain preliminary because of incompletenesses in the optical follow-up and uncertainties in the local XCLF., 9 pages, 2 figures, accepted for publication in the Letters of the Astrophysical Journal. Companion data paper (Romer et al.) will follow. Corrected several typographical errors

We have investigated the planarizing effects of multilayered superconducting thin films. Atomic force microscopy measurements indicate that coating a standard niobium base electrode with alternating layers of aluminum and niobium significantly reduces the film’s overall surface roughness. Planarized films such as these were used as the base electrodes of superconducting tunnel junctions that show vastly improved leakage characteristics over conventional junctions fabricated under the same conditions.

We review recent results from the SHARC Survey for distant X-ray clusters of galaxies. We first discuss the SHARC South project which finds no evidence for evolution in the faint end of the X-ray cluster luminosity function out to a redshift of z ≲ 0.7. We then give an overview of the Bright SHARC project; this project will provide an independent measurement of the evolution of bright (Lx[0.5 - 2keV] > 3 × 1044 erg s−1) X-ray clusters and allow us to put strong constraints on the value of ω0.

Based on ROSAT PSPC pointed observations, we have determined the aggregate X-ray shapes of 10 distant (z = 0.17-0.54) rich clusters: A2397, A222, A520, A1689, A223B, A1758, A2218, A2111, A2125, and CL0016+16. Four of the clusters have global X-ray ellipticities greater than 0.2, as measured on a scale of diameter 3 h_{50}^{-1} Mpc. These strongly elongated clusters tend to show substantial amounts of substructure, indicating that they are dynamically young systems. Most interestingly, the global X-ray ellipticities of the clusters correlate well with their blue galaxy fractions; the correlation coefficient is 0.75 with a 90% confidence range of 0.44-0.92. This correlation suggests that blue cluster galaxies originate in the process of cluster formation, and that the blue galaxy proportion of a cluster decreases as the intracluster medium relaxes onto equipotential surfaces.

A sputtering deposition system has been developed to grow high-quality superconductor/insulator multilayers specifically for use in fabricating vertically stacked Josephson junctions. A unique feature of the design is the computer control of all parameters involved in the repetitive deposition of multilayers. The computer is interfaced with stepper motors that position the substrate, and shutter wheels. Additional computer controlled stepper motors allow in situ changing of up to five contact masks. The computer is also interfaced to a gas flowmeter that controls the partial pressure of the inert and reactive sputtering gases. High-quality, reproducible multilayer films have been produced and are described. Stacked Josephson junctions have been patterned with the multilayer films and some of their electrical characteristics are presented.

Spatially and spectrally resolved X-ray observations of the Perseus cluster in the 1-10 keV band were made by the Spartan 1 instrument. Analysis of the data reveals that the dark matter comprises 60% of the total mass and is concentrated toward the cluster center. This concentration may be caused by a baryonic component of the dark matter, consisting of cluster gas which has cooled. The average luminous baryon fraction within the cluster is consistent with big bang nucleosynthesis only if the cosmic mass density lies in the range 0.12 < Ω < 0.26 (H0 = 50 km s-1 Mpc-1). The total mass derived from the X-ray data is 40% of that obtained from analysis of the galaxy spatial and velocity distributions.

As part of our ongoing archival X-ray survey of galaxy clusters for tidal flares, we present evidence of an X-ray transient source within 1 arcmin of the core of Abell 1795. The extreme variability (a factor of nearly 50), luminosity (> 2 x 10^42 erg s^{-1}), long duration (> 5 years) and supersoft X-ray spectrum (< 0.1 keV) are characteristic signatures of a stellar tidal disruption event according to theoretical predictions and to existing X-ray observations, implying a massive >~10^5 M_sun black hole at the centre of that galaxy. The large number of X-ray source counts (~700) and long temporal baseline (~12 years with Chandra and XMM-Newton) make this one of the best-sampled examples of any tidal flare candidate to date. The transient may be the same EUV source originally found contaminating the diffuse ICM observations of Bowyer et al. (1999), which would make it the only tidal flare candidate with reported EUV observations and implies an early source luminosity 1-2 orders of magnitude greater. If the host galaxy is a cluster member then it must be a dwarf galaxy, an order of magnitude less massive than the quiescent galaxy Henize 2-10 which hosts a massive black hole that is difficult to reconcile with its low mass. The unusual faintness of the host galaxy may be explained by tidal stripping in the cluster core., Accepted by MNRAS 2013 July 23. 27 pages, 10 figures

We describe a technique of shape modification that can be applied to thin walled (∼100-400 μm thickness) electroformed replicated optics or glass optics to improve the near net shape of the mirror as well as the midfrequency (∼2-10 mm length scales) ripple. The process involves sputter deposition of a magnetic smart material (MSM) film onto a magnetically hard material (i.e., one that retains a magnetic field, e.g., the material in hard disk drives). Since the previous report, we have made extensive measurements of the deflection versus magnetic field strength and direction. Here we report those results along with detailed finite element analysis modeling.

We have studied the static I–V characteristics and cavity modes in stacked double Nb/AlOx/Nb Josephson junctions. In junction stacks consisting of two junctions with identical critical currents Ic, the Ic vs H characteristics have been observed to deviate from the usual Fraunhofer pattern in the small junction limit; the data are consistent with a model involving a structural phase transformation to a triangular vortex lattice with increasing H. In a finite voltage state interlayer coupling leads to splitting of the Swihart mode, which manifests itself as Fiske steps with different voltage spacings. The results provide clear evidence that the two junctions in the stack do phase lock.

When subjected to microwave radiation, the I - V characteristics of stacked Josephson junctions should exhibit interesting new features which are absent in a single junction. Evidence for collectively phase-locked Shapiro steps and coherent phase-locking of fluxon motion to the external microwave field has been found in observations on stacked Nb/AlAlO x /Nb Josephson junctions.