Search

A collision-induced magnetic reconnection (CMR) mechanism was recently proposed to explain the formation of a filament in the Orion A molecular cloud. In this mechanism, a collision between two clouds with antiparallel magnetic fields produces a dense filament due to the magnetic tension of the reconnected fields. The filament contains fiber-like sub-structures and is confined by a helical magnetic field. To show whether the dense filament is capable of forming stars, we use the \textsc{Arepo} code with sink particles to model star formation following the formation of the CMR-filament. First, the CMR-filament formation is confirmed with \textsc{Arepo}. Second, the filament is able to form a star cluster after it collapses along its main axis. Compared to the control model without magnetic fields, the CMR model shows two distinctive features. First, the CMR-cluster is confined to a factor of $\sim4$ smaller volume. The confinement is due to the combination of the helical field and gravity. Second, the CMR model has a factor of $\sim2$ lower star formation rate. The slower star formation is again due to the surface helical field that hinders gas inflow from larger scales. Mass is only supplied to the accreting cluster through streamers., Comment: 18 pages, 13 figures, 1 table, accepted by MNRAS

Aspera is an extreme-UV (EUV) Astrophysics small satellite telescope designed to map the warm-hot phase coronal gas around nearby galaxy halos. Theory suggests that this gas is a significant fraction of a galaxy’s halo mass and plays a critical role in its evolution, but its exact role is poorly understood. Aspera observes this warm-hot phase gas via Ovi emission at 1032 °A using four parallel Rowland-Circle-like spectrograph channels in a single payload. Aspera’s robust-and-simple design is inspired by the FUSE spectrograph, but with smaller, four 6.2 cm × 3.7 cm, off-axis parabolic primary mirrors. Aspera is expected to achieve a sensitivity of 4.3×10⁻¹⁹ erg/s/cm²/arcsec² for diffuse Ovi line emission. This superb sensitivity is enabled by technological advancements over the last decade in UV coatings, gratings, and detectors. Here we present the overall payload design of the Aspera telescope and its expected performance. Aspera is funded by the inaugural 2020 NASA Astrophysics Pioneers program, with a projected launch in late 2024.

Molecular clouds are a crucial stage in the lifecycle of a star, and the far ultraviolet (FUV) spectral range is a prime observation band. Hyperion is an FUV space telescope that investigates the birth clouds of stars using a high-resolution spectrometer. To meet the scientific requirements, we developed and evaluated a spectrometer that covers the 140.5 to 164.5 nm wavelength range with a spectral resolution higher than 30,000. We employed on-axis and on-plane dispersive optic layouts to control the aberration from a large aspect ratio slit (10 arcmin × 2.5 arcsec, aspect ratio R = 240). The cross-dispersion isolates three orders from the echelle grating (n = − 19, −18, and −17), and the subsequent two-mirror freeform imaging optics form a two-dimensional spectral distribution on a 50 mm × 50 mm detector array. The geometrical and spectral performances of this innovative design are evaluated.

Understanding the origin of accretion and dispersal of protoplanetary disks is fundamental for investigating planet formation. Recent numerical simulations show that launching winds are unavoidable when disks undergo magnetically driven accretion and/or are exposed to external UV radiation. Observations also hint that disk winds are common. We explore how the resulting wind mass loss rate can be used as a probe of both disk accretion and dispersal. As a proof-of-concept study, we focus on magnetocentrifugal winds, MRI (magnetorotational instability) turbulence, and external photoevapotaion. By developing a simple, yet physically motivated disk model and coupling it with simulation results available in the literature, we compute the mass loss rate as a function of external UV flux for each mechanism. We find that different mechanisms lead to different levels of mass loss rate, indicating that the origin of disk accretion and dispersal can be determined, by observing the wind mass loss rate resulting from each mechanism. This determination provides important implications for planet formation. This work thus shows that the ongoing and future observations of the wind mass loss rate for protoplanetary disks are paramount to reliably constrain how protoplanetary disks evolve with time and how planet formation takes place in the disks., Comment: 16 pages; 7 figures, 5 tables, accepted for publication in ApJL; no change in the conclusions; the additional Monte-Carlo based, parameter study was conducted, following the referee's comment

The Faint Intergalactic Medium Redshifted Emission Balloon (FIREBall-2) is a UV multi-object spectrograph exploring the CGM of galaxies at low redshifts (0.3 < z < 1.0). The science detector is a EMCCD cooled by a Sunpower cryocooler to minimize the noise contributions from dark current. To efficiently remove the heat generated by the cryocooler and other critical hardware, we built a custom water cooling circuit which uses a water/alcohol/ice mixture to regulate temperatures during flight. We report the ground and flight performances of the thermal system during the 2018 campaign and the lessons learned since then. We will discuss the model predictions of the potential impacts of several major upgrades as well as modifications to adapt to those impacts, and the ground performance of the thermal system during the rebuild of FIREBall-2, compared with the model predictions, for the next launch of FIREBall-2 in Fort Sumner in 2020.

The payload of the Faint Intergalactic Redshifted Emission Balloon (FIREBall-2), the second generation of the FIREBall instrument (PI: C. Martin, Caltech), has been calibrated and launched from the NASA Columbia Scientific Balloon Facility (CSBF) in Fort Sumner, NM. FIREBall-2 was launched for the first time on the 22nd September 2018, and the payload performed the very first multi-object acquisition from space using a multi-object slit spectrograph (MOS). This performance-oriented paper presents the calibration and last ground adjustments of FIREBall-2, the in-flight performance assessed based on the flight data, and the predicted instrument's ultimate sensitivity. This analysis predicts that future flights of FIREBall-2 should be able to detect the HI Ly\alpha resonance line in galaxies at z~0.67, but will find it challenging to spatially resolve the circumgalactic medium (CGM)., Comment: PUBLISHED IN JATIS: 20 pages, 8 figures

Hyperion is a far-UV mission that investigates the birth clouds of stars using a 40 cm aperture telescope feeding an imaging long-slit spectrometer. The science requirements of the mission dictate that the spectrometer covers 140.5- 164.5 nm spectral range with resolution greater than 30,000. We employ smart and efficient design to create a longslit, cross dispersed, echelle spectrometer that utilizes a two-mirror freeform imaging optics. Echelle spectra for n = - 19, -18, and -17 over a 10 arcmin × 2.5 arcsec (length × width) FFOV are imaged onto the focal plane. We simulate the optical performance and the expected spectral efficiency.

The Faint Intergalactic Medium Redshifted Emission Balloon (FIREBall) is a mission designed to observe faint emission from the circumgalactic medium of moderate redshift (z~0.7) galaxies for the first time. FIREBall observes a component of galaxies that plays a key role in how galaxies form and evolve, likely contains a significant amount of baryons, and has only recently been observed at higher redshifts in the visible. Here we report on the 2018 flight of the FIREBall-2 Balloon telescope, which occurred on September 22nd, 2018 from Fort Sumner, New Mexico. The flight was the culmination of a complete redesign of the spectrograph from the original FIREBall fiber-fed IFU to a wide-field multi-object spectrograph. The flight was terminated early due to a hole in the balloon, and our original science objectives were not achieved. The overall sensitivity of the instrument and telescope was 90,000 LU, due primarily to increased noise from stray light. We discuss the design of the FIREBall-2 spectrograph, modifications from the original FIREBall payload, and provide an overview of the performance of all systems. We were able to successfully flight test a new pointing control system, a UV-optimized, delta-doped and coated EMCCD, and an aspheric grating. The FIREBall-2 team is rebuilding the payload for another flight attempt in the Fall of 2021, delayed from 2020 due to COVID-19., 23 Pages, 14 Figures, Accepted for Publication in ApJ

We present the status of on-going detector development efforts for our joint NASA/CNES balloon-borne UV multi-object spectrograph, the Faint Intergalactic Redshifted Emission Balloon (FIREBall-2; FB-2). FB-2 demonstrates a new UV detector technology, the delta-doped Electron Multiplying CCD (EMCCD), in a low risk suborbital environment, to prove the performance of EMCCDs for future space missions and Technology Readiness Level (TRL) advancement. EMCCDs can be used in photon counting (PC) mode to achieve extremely low readout noise ($, Comment: 36 pages, 9 figures

A significant fraction of baryons in galaxies are in the form of diffuse gas of the circumgalactic medium (CGM). One critical component of the multi-phases of CGM, the so-called "coronal" warm-hot phase gas ($\rm 10^{5}-10^{6}$ K) traced by O VI 1031.93, 1037.62 \r{A} resonance lines, has rarely been detected in emission from galaxy halos other than Milky Way. Here we report four additional detections of O VI emission gas in the halos of nearby edge-on galaxies, NGC 4631 and NGC 891, using archival Far Ultraviolet Spectroscopic Explorer data and an updated data pipeline. We find the most intense O VI emission to be from fields forming a vertical line near the center of NGC 4631, despite the close proximity to the disk of two other fields. The detected O VI emission surface brightness are about 1.1$\pm 0.3$ $\times$ $10^{-18}$ to 3.9$\pm0.8$ $\times$ $10^{-18}$ ergs s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$. The spatial distribution of the five 30" $\times$ 30" O VI detection fields in NGC 4631 can be interpreted as the existence of filamentary structures of more intense O VI emission superimposed within a diffuse and faint O VI halo in star-forming galaxies. Volume-filled O VI emission mapping is greatly needed to determine the structure and prevalence of warm-hot gas and the role it plays in the cycling of gas between the galaxy disk and the halo. Finally, we present the sensitivity of future funded and proposed UV missions (LUVOIR-A, LUVOIR-B, CETUS, and Aspera) to the detection of diffuse and faint O VI emission in nearby galaxy halos., Comment: 12 pages, 5 figures, accepted for publication in ApJ

We simulate the flux emitted from galaxy halos in order to quantify the brightness of the circumgalactic medium (CGM). We use dedicated zoom-in cosmological simulations with the hydrodynamical Adaptive Mesh Refinement code RAMSES, which are evolved down to z=0 and reach a maximum spatial resolution of 380 $h^{-1}$pc and a gas mass resolution up to 1.8$\times 10^{5} h^{-1} \rm{M}_{\odot}$ in the densest regions. We compute the expected emission from the gas in the CGM using CLOUDY emissivity models for different lines (e.g. Ly$\alpha$, CIV, OVI, CVI, OVIII) considering UV background fluorescence, gravitational cooling and continuum emission. In the case of Ly$\alpha$ we additionally consider the scattering of continuum photons. We compare our predictions to current observations and find them to be in good agreement at any redshift after adjusting the Ly$\alpha$ escape fraction. We combine our mock observations with instrument models for FIREBall-2 (UV balloon spectrograph) and HARMONI (visible and NIR IFU on the ELT) to predict CGM observations with either instrument and optimise target selections and observing strategies. Our results show that Ly$\alpha$ emission from the CGM at a redshift of 0.7 will be observable with FIREBall-2 for bright galaxies (NUV$\sim$18 mag), while metal lines like OVI and CIV will remain challenging to detect. HARMONI is found to be well suited to study the CGM at different redshifts with various tracers., Comment: accepted for publication in MNRAS

The Faint Intergalactic-medium Redshifted Emission Balloon (FIREBall-2, FB-2) is designed to discover and map faint UV emission from the circumgalactic medium around low redshift galaxies (z ~ 0.3 (C IV); z ~ 0.7 (Lyα); z ~ 1.0 (O VI)). FIREBall-2's first launch, on September 22nd 2018 out of Ft. Sumner, NM, was abruptly cut short due to a hole that developed in the balloon. FIREBall-2 was unable to observe above its minimum require altitude (25 km; nominal: 32 km) for its shortest required time (2 hours; nominal: 8+ hours). The shape of the deflated balloon, as well as a concurrent full moon close to our observed target field, revealed a severe, off-axis scattered light path directly to the UV science detector. Additional damage to FB-2 added complications to the ongoing effort to prepare FB-2 for a quick re-flight. Upon landing, several mirrors in the optical chain, including the two large telescope mirrors, were damaged, resulting in chunks of material broken off the sides and reflecting surfaces. The magnifying optical element, called the focal corrector, was discovered to be misaligned beyond tolerance after the 2018 flight, with one of its two mirrors damaged from the landing impact. We describe the steps taken thus far to mitigate the damage to the optics, as well as procedures and results from the ongoing efforts to re-align the focal corrector and spectrograph optics. We report the throughput of the spectrograph before and after the 2018 flight and plans for improving it. Finally, we describe several methods by which we address the scattered light issues seen from FIREBall-2's 2018 campaign and present the current status of FB-2 to fly during the summer campaign in Palestine, TX in 2020.

In this talk, I will describe briefly the telescope, instrument, and flight of the Faint Intergalactic medium Redshifted Emission Balloon (FIREBall-2). FIREBall-2 is a UV multi-object spectrograph fed by a 1 meter parabola mirror. The instrument was designed to observe 4 pre-selected fields and uses a UV optimized delta-doped EMCCD. The telescope flew on September 22, 2018 from Fort Sumner, NM, as part of the fall CSBF balloon campaign. The telescope collected data for several night hours before being cut down. I will describe the testing, flight, and hardware performance with an emphasis on the in flight performance of the instrument, including resolution, throughput, and the overall operation of the UV optimized EMCCD. Additional talks will be presented on other aspects of the flight and data.

I will present on-going detector developments in our joint NASA/CNES balloon-borne UV multi-object spectrograph, FIREBall-2, the Faint Intergalactic Redshifted Emission Balloon. FIREBall-2 is a path finding mission to test new technology (EMCCDs) and make new constraints on the temperature and density of this gas. This instrument has been designed to detect faint emission from the circumgalactic medium (CGM) around low redshift galaxies (z ~ 0.7). One major change from FIREBall-1 has been the use of a delta-doped Electron Multiplying CCD (EMCCD). EMCCDs can be used in photon-counting (PC) mode to achieve extremely low readout noise (< 1 electron). Our testing initially focused on reducing clock-induced-charge (CIC) through wave shaping and well depth optimisation with a NuVu CCD Controller for Counting Photons (CCCP). This optimisation also includes methods for reducing dark current, via cooling, and exploring substrate voltage levels. I will present some of our dark current results from laboratory testing. We recently launched FIREBall-2 from Fort Sumner, New Mexico on September 22nd, 2018. This was the first time an EMCCD has been used for UV/optical observations in flight! I will present performance data from the flight including cosmic ray rate measurements, and some of our preliminary on-sky UV results using our data reduction.

Here we discuss advances in UV technology over the last decade, with an emphasis on photon counting, low noise, high efficiency detectors in sub-orbital programs. We focus on the use of innovative UV detectors in a NASA astrophysics balloon telescope, FIREBall-2, which successfully flew in the Fall of 2018. The FIREBall-2 telescope is designed to make observations of distant galaxies to understand more about how they evolve by looking for diffuse hydrogen in the galactic halo. The payload utilizes a 1.0-meter class telescope with an ultraviolet multi-object spectrograph and is a joint collaboration between Caltech, JPL, LAM, CNES, Columbia, the University of Arizona, and NASA. The improved detector technology that was tested on FIREBall-2 can be applied to any UV mission. We discuss the results of the flight and detector performance. We will also discuss the utility of sub-orbital platforms (both balloon payloads and rockets) for testing new technologies and proof-of-concept scientific ideas, Submitted to the Proceedings of SPIE, Defense + Commercial Sensing (SI19)

We present Searches After Gravitational-waves Using ARizona Observatories (SAGUARO), a comprehensive effort dedicated to the discovery and characterization of optical counterparts to gravitational wave (GW) events. SAGUARO utilizes ground-based facilities ranging from 1.5m to 10m in diameter, located primarily in the Northern Hemisphere. We provide an overview of SAGUARO's telescopic resources, pipeline for transient detection, and database for candidate visualization. We describe SAGUARO's discovery component, which utilizes the $5$~deg$^2$ field-of-view optical imager on the Mt. Lemmon 1.5m telescope, reaching limits of $\approx 21.3$~AB mag while rapidly tiling large areas. We also describe the follow-up component of SAGUARO, used for rapid vetting and monitoring of optical candidates. With the onset of Advanced LIGO/Virgo's third observing run, we present results from the first three SAGUARO searches following the GW events S190408an, S190425z and S190426c, which serve as a valuable proof-of-concept of SAGUARO. We triggered and searched 15, 60 and 60 deg$^{2}$ respectively, 17.6, 1.4 and 41.8 hrs after the initial GW alerts. We covered 7.8, 3.0 and 5.1\% of the total probability within the GW event localizations, reaching 3$\sigma$ limits of 19.8, 21.3 and 20.8 AB mag, respectively. Although no viable counterparts associated with these events were found, we recovered 6 known transients and ruled out 5 potential candidates. We also present Large Binocular Telescope spectroscopy of PS19eq/SN2019ebq, a promising kilonova candidate that was later determined to be a supernova. With the ability to tile large areas and conduct detailed follow-up, SAGUARO represents a significant addition to GW counterpart searches., Comment: 16 pages, 7 figures, 1 table. Accepted to ApJL

Theory suggests that there are two primary modes of accretion through which dark-matter halos acquire the gas to form and fuel galaxies: hot- and cold-flow accretion. In cold-flow accretion, gas streams along cosmic web filaments to the centre of the halo, allowing for the efficient delivery of star-forming fuel. Recently, two quasar-illuminated H i Lyman ɑ (Lyα)-emitting objects were reported to have properties of cold, rotating structures1,2. However, the spatial and spectral resolution available was insufficient to constrain the radial flows associated with connecting filaments. With the Keck Cosmic Web Imager (KCWI)3, we now have eight times the spatial resolution, permitting the detection of these inspiralling flows. To detect these inflows, we introduce a suite of models that incorporate zonal radial flows, demonstrate their performance on a numerical simulation that exhibits cold-flow accretion, and show that they are an excellent match to KCWI velocity maps of two Lyα emitters observed around high-redshift quasars. These multi-filament inflow models kinematically isolate zones of radial inflow that correspond to extended filamentary emission. The derived gas flux and inflow path is sufficient to fuel the inferred central galaxy star-formation rate and angular momentum. Thus, our kinematic emission maps provide strong evidence that the inflow of gas from the cosmic web is building galaxies at the peak of star formation.

We present the pilot study component of the Fluorescent Lyman-Alpha Structures in High-z Environments (FLASHES) Survey; the largest integral-field spectroscopy survey to date of the circumgalactic medium at $z=2.3-3.1$. We observed 48 quasar fields between 2015 and 2018 with the Palomar Cosmic Web Imager (Matuszewski et al. 2010). Extended HI Lyman-$\mathrm{\alpha}$ emission is discovered around 42/48 of the observed quasars, ranging in projected, flux-weighted radius from 21-71 proper kiloparsecs (pkpc), with 26 nebulae exceeding $100\mathrm{~pkpc}$ in effective diameter. The circularly averaged surface brightness radial profile peaks at a maximum of $\mathrm{1\times 10^{-17}~erg~s^{-1}~cm^{-2}~arcsec^{-2}}$ ($2\times10^{-15}~\mathrm{erg~s^{-1}~cm^{-2}~arcsec^{-2}}$ adjusted for cosmological dimming) and luminosities range from $1.9\times10^{43}~\mathrm{erg~s^{-1}}$ to $-14.1\times10^{43}~\mathrm{erg~s^{-1}}$. The emission appears to have a highly eccentric morphology and a maximum covering factor of $50\%$ ($60\%$ for giant nebulae). On average, the nebular spectra are red-shifted with respect to both the systemic redshift and Ly$\alpha$ peak of the quasar spectrum. The integrated spectra of the nebulae mostly have single or double-peaked line shapes with global dispersions ranging from $167~\mathrm{km~s^{-1}}$ to $690~\mathrm{km~s^{-1}}$, though the individual (Gaussian) components of lines with complex shapes mostly appear to have dispersions $\leq 400$ $\mathrm{km~s^{-1}}$, and the flux-weighted velocity centroids of the lines vary by thousands of $ \mathrm{km~s^{-1}}$ with respect to the systemic QSO redshifts. Finally, the root-mean-square velocities of the nebulae are found to be consistent with gravitational motions expected in dark matter halos of mass $\mathrm{M_h \simeq10^{12.5} M_\odot}$. We compare these results to existing surveys at both higher and lower redshift.

This guest editorial summarizes the Special Section on Detectors for Astronomy and Cosmology.

The faint signature of gas filaments in the intergalactic medium is finally detected

We report on multilayer high efficiency antireflection coating (ARC) design and development for use at UV wavelengths on CCDs and other Si-based detectors. We have previously demonstrated a set of single-layer coatings, which achieve >50% quantum efficiency (QE) in four bands from 130 to 300 nm. We now present multilayer coating designs that significantly outperform our previous work between 195 and 215 nm. Using up to 11 layers, we present several model designs to reach QE above 80%. We also demonstrate the successful performance of 5 and 11 layer ARCs on silicon and fused silica substrates. Finally, we present a five-layer coat- ing deposited onto a thinned, delta-doped CCD and demonstrate external QE greater than 60% between 202 and 208 nm, with a peak of 67.6% at 206 nm., 11 pages, 8 figures. Published by JATIS

The Faint Intergalactic medium Redshifted Emission Balloon (FIREBall-2) is an ultraviolet multi-object spectrograph mission designed to observe the faint gas surrounding z ≈ 0.7 galaxies from the very top of the Earth’s stratosphere, explains Project Scientist Erika Hamden.

We present the latest developments in our joint NASA/CNES suborbital project. This project is a balloon-borne UV multi-object spectrograph, which has been designed to detect faint emission from the circumgalactic medium (CGM) around low redshift galaxies. One major change from FIREBall-1 has been the use of a delta-doped Electron Multiplying CCD (EMCCD). EMCCDs can be used in photon-counting (PC) mode to achieve extremely low readout noise (¡ 1e-). Our testing initially focused on reducing clock-induced-charge (CIC) through wave shaping and well depth optimisation with the CCD Controller for Counting Photons (CCCP) from Nüvü. This optimisation also includes methods for reducing dark current, via cooling and substrate voltage adjustment. We present result of laboratory noise measurements including dark current. Furthermore, we will briefly present some initial results from our first set of on-sky observations using a delta-doped EMCCD on the 200 inch telescope at Palomar using the Palomar Cosmic Web Imager (PCWI).

Fireball (Faint Intergalactic Redshifted Emission Balloon) is a NASA/CNES balloon-borne experiment to study the faint diffuse circumgalactic medium from the line emissions in the ultraviolet (200 nm) above 37 km flight altitude. Fireball relies on a Multi Object Spectrograph (MOS) that takes full advantage of the new high QE, low noise 13 μm pixels UV EMCCD. The MOS is fed by a 1 meter diameter parabola with an extended field (1000 arcmin2) using a highly aspherized two mirror corrector. All the optical train is working at F/2.5 to maintain a high signal to noise ratio. The spectrograph (R~ 2200 and 1.5 arcsec FWHM) is based on two identical Schmidt systems acting as collimator and camera sharing a 2400 g/mm aspherized reflective Schmidt grating. This grating is manufactured from active optics methods by double replication technique of a metal deformable matrix whose active clear aperture is built-in to a rigid elliptical contour. The payload and gondola are presently under integration at LAM. We will present the alignment procedure and the as-built optic performances of the Fireball instrument.

Future UV, X-ray, and sub-millimeter telescopes and spectrometers have the potential to revolutionize our understanding of the formation and habitability of the modern universe.[1-4] Star formation, dark energy, and the composition of the intergalactic medium are only some of the key scientific topics that can be addressed by UV astronomy and astrophysics. Sub-millimeter astronomy can probe the fine structure of the cosmic microwave background, giving glimpses into the early universe immediately following the Big Bang.[5] Various surface engineering techniques including molecular beam epitaxy and atomic layer deposition have been utilized here to significantly boost the performance of key components of instruments for astronomy and astrophysics investigation, taking advantage of the atomic level precision that these techniques provide.

Enormous Lyα nebulae (ELANe) represent the extrema of Lyα nebulosities. They have detected extents of >200 kpc in Lyα and Lyα luminosities >10^(44) erg s^(−1). The ELAN population is an ideal laboratory to study the interactions between galaxies and the intergalactic/circumgalactic medium (IGM/CGM) given their brightness and sizes. The current sample size of ELANe is still very small, and the few z ≈ 2 ELANe discovered to date are all associated with local overdensities of active galactic nuclei (AGNs). Inspired by these results, we have initiated a survey of ELANe associated with quasi-stellar object (QSO) pairs using the Palomar and Keck Cosmic Web Imagers (PCWI/KCWI). In this Letter, we present our first result: the discovery of ELAN0101+0201 associated with a QSO pair at z = 2.45. Our PCWI discovery data shows that, above a 2σ surface brightness of 1.2 × 10^(−17) erg s^(−1) cm^(−2) arcsec^(−2), the end-to-end size of ELAN0101+0201 is ≳ 232 kpc. We have conducted follow-up observations using KCWI, resolving multiple Lyα emitting sources within the rectangular field of view of ≈ 130 × 165 projected kpc^2, and obtaining their emission line profiles at high signal-to-noise ratios (S/Ns). Combining both KCWI and PCWI, our observations confirm that ELAN0101+0201 resides in an extremely overdense environment. Our observations further support that a large amount of cool (T ~ 10^4 K) gas could exist in massive halos (M ≳ 10^(13) M_⊙) at z ≈ 2. Future observations on a larger sample of similar systems will provide statistics of how cool gas is distributed in massive overdensities at high redshift and strongly constrain the evolution of the intracluster medium.

The Faint Intergalactic-medium Redshifted Emission Balloon (FIREBall-2) is an experiment designed to observe low density emission from HI, CIV, and OVI in the circum-galactic medium around low-redshift galaxies. To detect this diffuse emission, we use a high-efficiency photon-counting EMCCD as part of FIREBall-2's detector. The flight camera system includes a custom printed circuit board, a mechanical cryo-cooler, zeolite and charcoal getters, and a Nüvü controller, for fast read-out speeds and waveform shaping. Here we report on overall detector system performance, including pressure and temperature stability. We describe dark current and CIC measurements at several temperatures and substrate voltages, with the flight set-up.

We present an overview of the detector for the upcoming Faint Intergalactic Red-shifted Emission Balloon (FIREBall-2) experiment, with a particular focus on the development of device-integrated optical coatings and detector quantum efficiency (QE). FIREBall-2 is designed to measure emission from the strong resonance lines of HI, OVI, and CIV, all red-shifted to 195-225 nm window; its detector is a delta-doped electron multiplying charge coupled device (EM-CCD). Delta-doped arrays, invented at JPL, achieve 100% internal QE from the UV through the visible. External losses due to reflection (~70% in some UV regions) can be mitigated with antireflection coatings (ARCs). Using atomic layer deposition (ALD), thin-film optical filters are incorporated with existing detector technologies. ALD offers nanometer-scale control over film thickness and interface quality, allowing for precision growth of multilayer films. Several AR coatings, including single and multi-layer designs, were tested for FIREBall-2. QE measurements match modeled transmittance behavior remarkably well, showing improved performance in the target wavelength range. Also under development are ALD coatings to enhance QE for a variety of spectral regions throughout the UV (90-320 nm) and visible (320-1000 nm) range both for space-based imaging and spectroscopy as well as for ground-based telescopes.

Enormous Ly$\alpha$ Nebulae (ELANe), unique tracers of galaxy density peaks, are predicted to lie at the nodes and intersections of cosmic filamentary structures. Previous successful searches for ELANe have focused on wide-field narrowband surveys, or have targeted known sources such as ultraluminous quasi-stellar-objects (QSOs) or radio galaxies. Utilizing groups of coherently strong Ly$\alpha$ absorptions (CoSLAs), we have developed a new method to identify high-redshift galaxy overdensities and have identified an extremely massive overdensity, BOSS1441, at $z=2-3$ (Cai et al. 2016a). In its density peak, we discover an ELAN that is associated with a relatively faint continuum. To date, this object has the highest diffuse Ly$\alpha$ nebular luminosity of $L_{\rm{nebula}}=5.1\pm0.1\times10^{44}$ erg s$^{-1}$. Above the 2$\sigma$ surface brightness limit of SB$_{\rm{Ly\alpha}}= 4.8\times10^{-18}$ erg s$^{-1}$ cm$^{-2}$ arcsec$^{-2}$, this nebula has an end-to-end spatial extent of 442 kpc. This radio-quiet source also has extended \civ\ $\lambda1549$ and \heii\ $\lambda1640$ emission on $\gtrsim30$ kpc scales. Note that the Ly$\alpha$, \heii\ and \civ\ emission all have double-peaked line profiles. Each velocity component has a full-width-half-maximum (FWHM) of $\approx700 - 1000$ km s$^{-1}$. We argue that this Ly$\alpha$ nebula could be powered by shocks due to an AGN-driven outflow or/and photoionization by a strongly obscured source., Comment: corrected a typo of a coordinate in the last published version; and also updated Fig.2

The Faint Intergalactic Redshifted Emission Balloon (FIREBall) is a NASA/CNES balloon-borne ultraviolet multi-object spectrograph designed to observe the diffuse gas around galaxies (the circumgalactic medium) via line emission redshifted to ~ 205 nm. FIREBall uses a ultraviolet-optimized delta doped e2v CCD201 with a custom designed high efficiency five layer anti-re ection coating. This combination achieves very high quantum efficiency (QE) and photon-counting capability, a first for a CCD detector in this wavelength range. We also present new work on red blocking mirror coatings to reduce red leak.

We present an all sky map of the diffuse Galactic far ultraviolet (1344-1786 Angstroms) background using GALEX data, covering 65% of the sky with 11.79 arcmin square pixels. We investigate the dependence of the background on Galactic coordinates, finding that a standard cosecant model of intensity is not a valid fit. Furthermore, we compare our map to Galactic all sky maps of 100 micron emission, N_HI column, and H-alpha intensity. We measure a consistent low level FUV intensity at zero-points for other Galactic quantities, indicating a 300 CU non-scattered isotropic component to the diffuse FUV. There is also a linear relationship between FUV and 100 micron emission below 100 micron values of 8 MJy/sr. We find a similar linear relationship between FUV and NHI below 10^21 square cm. The relationship between FUV and H-alpha intensity has no such constant cutoff. For all Galactic quantities, the slope of the linear portion of the relationship decreases with Galactic latitude. A modified cosecant model, taking into account dust scattering asymmetry and albedo, is able to accurately fit the diffuse FUV at latitudes above 20 degrees. The best fit model indicates an albedo, a, of 0.62 +- 0.04 and a scattering asymmetry function, g, of 0.78 +- 0.05. Deviations from the model fit may indicate regions of excess FUV emission from fluorescence or shock fronts, while low latitude regions with depressed FUV emission are likely the result of self-shielding dusty clouds., 15 pages, 19 Figures, Accepted for publication by ApJ

The authors report here on a new technique, combining the atomic precision of molecular beam epitaxy and atomic layer deposition, to fabricate back illuminated silicon CCD detectors that demonstrate world record detector quantum efficiency (>50%) in the near and far ultraviolet (155–300 nm). This report describes in detail the unique surface engineering approaches used and demonstrates the robustness of detector performance that is obtained by achieving atomic level precision at key steps in the fabrication process. The characterization, materials, and devices produced in this effort will be presented along with comparison to other approaches.

Antireflection coatings are grown directly onto detector surfaces by atomic layer deposition. Through careful design of single- and multi-layer coatings, optical performance can be optimized for specific applications.

Ultraviolet (UV) studies in astronomy, cosmology, planetary studies, biological and medical applications often require precision detection of faint objects and in many cases require photon-counting detection. We present an overview of two approaches for achieving photon counting in the UV. The first approach involves UV enhancement of photon-counting silicon detectors, including electron multiplying charge-coupled devices and avalanche photodiodes. The approach used here employs molecular beam epitaxy for delta doping and superlattice doping for surface passivation and high UV quantum efficiency. Additional UV enhancements include antireflection (AR) and solar-blind UV bandpass coatings prepared by atomic layer deposition. Quantum efficiency (QE) measurements show QE > 50% in the 100–300 nm range for detectors with simple AR coatings, and QE ≅ 80% at ~206 nm has been shown when more complex AR coatings are used. The second approach is based on avalanche photodiodes in III-nitride materials with high QE and intrinsic solar blindness.

We describe recent progress in the development of anti-reflection coatings for use at UV wavelengths on CCDs and other Si-based detectors. We have previously demonstrated a set of coatings which are able to achieve greater than 50% QE in 4 bands from 130nm to greater than 300nm. We now present new refinements of these AR-coatings which will improve performance in a narrower bandpass by 50% over previous work. Successful test films have been made to optimize transmission at 190nm, reaching 80% potential transmission.

We present a catalog of 1964 isolated, compact neutral hydrogen clouds from the Galactic Arecibo L-Band Feed Array Survey Data Release One (GALFA-HI DR1). The clouds were identified by a custom machine-vision algorithm utilizing Difference of Gaussian kernels to search for clouds smaller than 20'. The clouds have velocities typically between |VLSR| = 20-400 km/s, linewidths of 2.5-35 km/s, and column densities ranging from 1 - 35 x 10^18 cm^-2. The distances to the clouds in this catalog may cover several orders of magnitude, so the masses may range from less than a Solar mass for clouds within the Galactic disc, to greater than 10^4 Solar Masses for HVCs at the tip of the Magellanic Stream. To search for trends, we separate the catalog into five populations based on position, velocity, and linewidth: high velocity clouds (HVCs); galaxy candidates; cold low velocity clouds (LVCs); warm, low positive-velocity clouds in the third Galactic Quadrant; and the remaining warm LVCs. The observed HVCs are found to be associated with previously-identified HVC complexes. We do not observe a large population of isolated clouds at high velocities as some models predict. We see evidence for distinct histories at low velocities in detecting populations of clouds corotating with the Galactic disc and a set of clouds that is not corotating., 34 Pages, 9 Figures, published in ApJ (2012, ApJ, 758, 44), this version has the corrected fluxes and corresponding flux histogram and masses

We have used molecular beam epitaxy (MBE) based delta-doping technology to demonstrate nearly 100% internal quantum efficiency (QE) on silicon electron-multiplied charge-coupled devices (EMCCDs) for single photon counting detection applications. We used atomic layer deposition (ALD) for antireflection (AR) coatings and achieved atomic-scale control over the interfaces and thin film materials parameters. By combining the precision control of MBE and ALD, we have demonstrated more than 50% external QE in the far and near ultraviolet in megapixel arrays. We have demonstrated that other important device performance parameters such as dark current are unchanged after these processes. In this paper, we briefly review ultraviolet detection, report on these results, and briefly discuss the techniques and processes employed.

We report on development of antireflective coatings optimized for a telescope detector in a UV spectrograph. We discuss progress in the development of a CCD with theoretical QE greater than 60% from 100 to 300nm.