A5043546364- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Radio Wave Propagation Studies
- Nanowire Synthesis and Applications
- Galaxies: Formation, Evolution, Phenomena
- Calibration and Measurement Techniques
- Particle Accelerators and Free-Electron Lasers
- Atmospheric and Environmental Gas Dynamics
- Carbon Nanotubes in Composites
- Gamma-ray bursts and supernovae
- Sensor Technology and Measurement Systems
- Astronomy and Astrophysical Research
- Diamond and Carbon-based Materials Research
- Methane Hydrates and Related Phenomena
- Coal Properties and Utilization
- Water Quality Monitoring and Analysis
- Astrophysical Phenomena and Observations
- Quantum Dots Synthesis And Properties
- Silicon Nanostructures and Photoluminescence
- Isotope Analysis in Ecology
- Scientific Research and Discoveries
- Advanced Fiber Optic Sensors
- Scientific Measurement and Uncertainty Evaluation
- Spacecraft and Cryogenic Technologies
- Infrastructure Maintenance and Monitoring
California Institute of Technology
2012-2019
Astronomy and Space
2017
Jet Propulsion Laboratory
2012-2015
Following the first two annual intensity mapping workshops at Stanford in March 2016 and Johns Hopkins June 2017, we report on recent advances theory, instrumentation observation that were presented these meetings some of opportunities challenges identified looking forward. With preliminary detections CO, [CII], Lya low-redshift 21cm, a host experiments set to go online next few years, field is rapidly progressing all fronts, with great anticipation for flood new exciting results. This...
The Large-aperture Experiment to Detect the Dark Age (LEDA) was designed detect predicted O(100) mK sky-averaged absorption of cosmic microwave background by hydrogen in neutral pre- and intergalactic medium just after cosmological Age. spectral signature would be associated with emergence a diffuse Lyα from starlight during 'Cosmic Dawn'. Recently, Bowman et al. have reported detection this feature, an unexpectedly large amplitude 530 mK, centred at 78 MHz. Verification result independent...
The 21\,cm transition of neutral hydrogen is opening an observational window into the cosmic dawn universe---the epoch first star formation. We use 28\,hr data from Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) to place upper limits on spatial power spectrum emission at $z \approx 18.4$ ($\Delta_{21} \lesssim 10^4\,\text{mK}$), and within absorption feature reported by EDGES experiment (Bowman et al. 2018). In process we demonstrate application double Karhunen-Lo\`{e}ve...
Abstract A host of new low-frequency radio telescopes seek to measure the 21 cm transition neutral hydrogen from early universe. These have potential directly probe star and galaxy formation at redshifts 20 ≳ z 7 but are limited by dynamic range they can achieve against foreground sources emission. Consequently, there is a growing demand for modern, high-fidelity maps sky frequencies below 200 MHz use in modeling removal. We describe wide-field imaging technique drift-scanning...
Abstract The optical absorption efficiencies of vertically aligned multi‐walled (MW)‐carbon nanotube (CNT) ensembles are characterized in the 350−7000 nm wavelength range where CNT site densities > 1 × 10 11 /cm 2 achieved directly on metallic substrates. density impacts characteristics, and while high‐density arrays CNTs electrically insulating non‐metallic substrates have been commonly reported, achieving high site‐densities metals has challenging remains an area active research. These...
Abstract We have conducted the most sensitive low-frequency (below 100 MHz) search to date for prompt, radio emission associated with short-duration gamma-ray bursts (GRBs), using Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA). The OVRO-LWA’s nearly full-hemisphere field of view (∼20,000 square degrees) allows us (sub-100 counterparts a large sample subset GRB events which prompt has been predicted. Following detection short 170112A by Swift , we used all-sky OVRO-LWA images...
Abstract We present the results of first transient survey from Owens Valley Radio Observatory Long Wavelength Array (OVRO–LWA) using 31 hr data, in which we place most constraining limits on instantaneous surface density at timescales 13 s to a few minutes and frequencies below 100 MHz. The OVRO–LWA is dipole array that images entire viewable hemisphere with 58 MHz bandwidth 27 84 cadence. No transients are detected above 6.5 σ flux limit 10.5 Jy, implying an upper 2.5 × 10 −8 deg −2...
Abstract 21-cm cosmology is a powerful new probe of the intergalactic medium at redshifts 20 ≳ z 6 corresponding to Cosmic Dawn and Epoch Reionization. Current observations highly-redshifted transition are limited by dynamic range they can achieve against foreground sources low-frequency (<200 MHz) radio emission. We used Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) generate series modern high-fidelity sky maps that capture emission on angular scales ranging from tens...
In this study we investigate the capability of planned expansion Owens Valley Long Wavelength Array (OVRO-LWA) to perform radio based composition studies cosmic-ray flux between ~50 PeV and ~1 EeV. We use ZHAireS simulations in conjunction with a method similar one developed by LOFAR experiment, but that only uses data 30 80 MHz, reconstruct depth shower maximum $X_{\mathrm{max}}$. found lower antenna densities away from central core array lead decrease effective area for quality...
Optical absorbers based on vertically aligned multi-walled carbon nanotubes (MWCNTs), synthesized using electric-field assisted growth, are described here that show an ultra-low reflectance, 100X lower compared to Au-black from wavelength λ ~ 350 nm - 2.5 μm. A bi-metallic Co/Ti layer was shown catalyze a high site density of MWCNTs metallic substrates and the optical properties were engineered by controlling bottom-up synthesis conditions dc plasma-enhanced chemical vapor deposition...
We present the successful radio frequency (30 - 80 MHz) self-triggered detection and identification of 10 high energy cosmic rays with Caltech's Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA). The core OVRO-LWA consists 256 dual-polarization antennas that are approximately evenly spaced in a 200 m diameter disk several outliers at longer distances. Based on this success we future plans for an array covering 2.5 km area measuring flux composition $3\times10^{16}$ eV $10^{18}$ band.
Optical devices with features exhibiting ultra low reflectivity on the order of 10-7 specular reflectance in visible spectrum are required for coronagraph instruments and some spectrometers employed space research. Nanofabrication technologies have been developed to produce such various shapes feature dimensions meet these requirements. Infrared reflection is also suppressed significantly chosen wafers processes. Particularly, very high (>0.9) (<10-7) adjacent areas fabricated characterized....