Repository of works by Caltech published authors.
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IGM Emission Observations with the Cosmic Web Imager: I. The Circum-QSO Medium of QSO 1549+19, and Evidence for a Filamentary Gas Inflow - Martin, D. Christopher; Chang, Daphne; Matuszewski, Matt; Morrisey, Patrick; Rahman, Shahin; Moore, Anna; Steidel, Charles C.
The Palomar Cosmic Web Imager (PCWI), an integral field spectrograph designed to detect and map low surface brightness emission, has obtained imaging spectroscopic maps of Lyα from the circum-QSO medium (CQM) of QSO HS1549+19 at redshift z=2.843. Extensive extended emission is detected from the CQM, consistent with fluorescent and pumped Lyα produced by the ionizing and Lyα continuum of the QSO. Many features present in PCWI spectral images match those detected in narrow-band images. Filamentary structures with narrow line profiles are detected in several cases as long as 250-400 kpc. One of these is centered at a velocity redshifted with...
IGM Emission Observations with the Cosmic Web Imager:
II. Discovery of Extended, Kinematically-Linked Emission around SSA22 Lyα Blob 2 - Martin, D. Christopher; Chang, Daphne; Matuszewski, Matt; Morrisey, Patrick; Rahman, Shahin; Moore, Anna; Steidel, Charles C.; Matsuda, Yuichi
The intergalactic medium (IGM) is the dominant reservoir of baryons, delineates the large scale structure of the universe at low to moderate overdensities, and provides gas from which galaxies form and evolve. Simulations of a Cold Dark Matter (CDM) dominated universe predict that the
IGM is distributed in a cosmic web of filaments, and that galaxies should form along and at the intersections of these filaments (Bond, Kofman, & Pogosyan 1994; Miralda-Escude et al. 1996). While observations of QSO absorption lines and the large-scale distribution of galaxies have
confirmed the CDM paradigm, the cosmic web of IGM has never been confirmed by...
Giant Sparks at Cosmological Distances? - Kulkarni, S. R.; Ofek, E. O.; Neill, J. D.; Zheng, Z.; Juric, M.
Millisecond duration bright radio pulses in the 1.4-GHz band and with inferred dispersion measures (DM)
well in excess of Galactic values have been reported by Lorimer et al. and Thornton et al. The all-sky rate
of these events is large, ≈ 10^4 per day above ~1 Jy. To add to the mystery there now exists “Perytons” – also
pulsed and dispersed sources but most certainly of local (artificial or atmospheric) origin. The suggested models
now range from sources originating in the Earth’s atmosphere, in stellar coronae, in other galaxies and at even cosmological distances. Using a series of physically motivated assumptions combined with the...
Near-IR Direct Detection of Water Vapor in Tau Boötis B - Lockwood, Alexandra C.; Johnson, John A.; Bender, Chad F.; Carr, John S.; Barman, Travis; Richert, Alexander J. W.; Blake, Geoffrey A.
We use high dynamic range, high-resolution L-band spectroscopy to measure the radial velocity variations of the hot Jupiter in the τ Boötis planetary system. The detection of an exoplanet by the shift in the stellar spectrum alone provides a measure of the planet's minimum mass, with the true mass degenerate with the unknown orbital inclination. Treating the τ Boo system as a high flux ratio double-lined spectroscopic binary permits the direct measurement of the planet's true mass as well as its atmospheric properties. After removing telluric absorption and cross-correlating with a model planetary spectrum dominated by water opacity, we measure...
Self-Interacting Dark Matter from a Non-Abelian Hidden Sector - Boddy, Kimberly K.; Feng, Jonathan L.; Kaplinghat, Manoj; Tait, Tim M. P.
There is strong evidence in favor of the idea that dark matter is self-interacting, with cross section-to-mass
ratio σ/m ~ 1 cm^2/g ~ 1 barn=GeV. We show that viable models of dark matter with this large cross
section are straightforwardly realized with non-Abelian hidden sectors. In the simplest of such models, the
hidden sector is a pure gauge theory, and the dark matter is hidden glueballs with mass around 100 MeV.
Alternatively, the hidden sector may be a supersymmetric pure gauge theory with a ~ 10 TeV gluino thermal
relic. In this case, the dark matter is largely composed of glueballinos that strongly self-interact through
Naturalness and the Weak Gravity Conjecture - Cheung, Clifford; Remmen, Grant N.
The weak gravity conjecture (WGC) asserts a powerful consistency condition on gauge theories
coupled to quantum gravity: an Abelian, long-range force requires a state of charge q and mass m
such that q > m/mPl. Failure of this condition implies the existence of stable black hole remnants
and is in tension with no-hair theorems. In this paper, we argue that the WGC creates a nonperturbative
obstruction to naturalness, which is the notion that dimensionless coefficients should
take on O(1) values in the absence of enhanced symmetry. As an illustration, we show that for
scalar quantum electrodynamics, a natural spectrum can actually be forbidden by the WGC,...
Multiple Lac-mediated loops revealed by Bayesian statistics and tethered particle motion - Johnson, Stephanie; van de Meent, Jan-Willem; Phillips, Rob; Wiggins, Chris H.; Lindén, Martin
The bacterial transcription factor LacI loops DNA by binding to two separate locations on the DNA simultaneously. Despite being one of the best-studied model
systems for transcriptional regulation, the number and conformations of loop structures accessible to LacI remain unclear, though the importance of multiple coexisting loops has been implicated in interactions between LacI and other cellular regulators of gene expression. To probe this issue, we have developed a new analysis method for tethered particle motion (TPM), a versatile and commonly-used in vitro single-molecule technique. Our method, vbTPM, is based on a variational Bayes treatment of hidden Markov
models. It learns the...
Spectroscopic Confirmation of Young Planetary-Mass Companions on Wide Orbits - Bowler, Brendan P.; Liu, Michael C.; Kraus, Adam L.; Mann, Andrew W.
We present moderate-resolution (R~4000–5000) near-infrared integral field spectroscopy of the young (1–5 Myr) 6–14 M_(Jup) companions ROXs 42B b and FW Tau b obtained with Keck/OSIRIS and Gemini-North/NIFS. The spectrum of ROXs 42B b exhibits clear signs of low surface gravity common to young L dwarfs, confirming its extreme youth, cool temperature, and low mass. Overall, it closely resembles the free-floating 4–7 M_(Jup) L-type Taurus member 2MASS J04373705+2331080. The companion to FW Tau AB is more enigmatic. Our optical and near-infrared spectra show strong
evidence of outflow activity and disk accretion in the form of line emission from [S II], [O...
CSI 2264: Characterizing Accretion-Burst Dominated Light Curves for Young Stars in NGC 2264 - Stauffer, John; Cody, Ann Marie; Rebull, Luisa; Carey, Sean; Hillenbrand, Lynne A.; Carpenter, John; Findeisen, Krzysztof; Plavchan, Peter
Based on more than four weeks of continuous high cadence photometric monitoring of several hundred members of the young cluster NGC 2264 with two space telescopes, NASA’s Spitzer and the CNES CoRoT (Convection, Rotation, and planetary Transits), we provide high quality, multi-wavelength light curves for young stellar objects (YSOs) whose optical variability is dominated by short duration
flux bursts, which we infer are due to enhanced mass accretion rates. These light curves show many
brief – several hour to one day – brightenings at optical and near-infrared (IR) wavelengths with
amplitudes generally in the range 5-50% of the quiescent value. Typically, a dozen...
CSI 2264: Simultaneous optical and infrared light curves of young disk-bearing stars in NGC 2264 with CoRoT and Spitzer-- evidence for multiple origins of variability - Cody, Ann Marie; Stauffer, John; Rebull, Luisa M.; Carey, Sean; Hillenbrand, Lynne A.; Carpenter, John; Findeisen, Krzysztof; Plavchan, Peter
We present the Coordinated Synoptic Investigation of NGC 2264, a continuous 30-day multi-
wavelength photometric monitoring campaign on more than 1000 young cluster members using 16
telescopes. The unprecedented combination of multi-wavelength, high-precision, high-cadence, and
long-duration data opens a new window into the time domain behavior of young stellar objects. Here
we provide an overview of the observations, focusing on results from Spitzer and CoRoT. The high-
light of this work is detailed analysis of 162 classical T Tauri stars for which we can probe optical and
mid-infrared flux variations to 1% amplitudes and sub-hour timescales. We present a morphological
variability census and then use metrics of...
Performance of the Caltech Submillimeter Observatory Dual-Color 180-720 GHz Balanced SIS Receivers - Kooi, J. W.; Chamberlin, R. A.; Monje, R.; Kovács, A.; Rice, F.; Yoshida, H.; Force, B.; Cooper, K.; Miller, D.; Gould, M.; Lis, D.; Bumble, B.; LeDuc, R.; Stern, J. A.; Phillips, T. G.
We report on balanced SIS receivers covering the astronomical important 180-720 GHz submillimeter atmospheric window. To facilitate remote observations and automated spectral line surveys, fully synthesized local oscillators are employed. High-current-density Nb-AlN-Nb superconducting-insulating-superconducting (SIS) tunnel junctions are used as the mixing element. The measured double-sideband (DSB) 230 GHz receiver noise temperature, uncorrected for optics loss, ranges from 50K at 185 GHz, 33K at 246 GHz, to 51K at 280 GHz. In this frequency range the mixer has a DSB conversion gain of 0 +- 1.5 dB. The measured 460 GHz double-sideband receiver noise temperature, uncorrected for optics loss, is 32K...
Nanowire photonic crystal waveguides for single-atom trapping and strong light-matter interactions - Yu, S.-P.; Hood, J. D.; Muniz, J. A.; Martin, M. J.; Norte, Richard; Hung, C.-L.; Meenehan, Seán M.; Cohen, Justin D.; Painter, Oskar; Kimble, H. J.
We present a comprehensive study of dispersion-engineered nanowire photonic crystal waveguides suitable for experiments in quantum optics and atomic physics with optically trapped atoms. Detailed design methodology and specifications are provided, as are the processing steps used to create silicon nitride waveguides of low optical loss in the near-IR. Measurements of the waveguide optical properties and power-handling capability are also presented.
Radial Quasiballistic Transport in Time-Domain Thermoreflectance Studied Using Monte Carlo Simulations - Ding, D.; Minnich, A. J.
Recently, a pump beam size dependence of thermal conductivity was observed in Si at cryogenic temperatures using time-domain thermal reflectance (TDTR). These observations were attributed to quasiballistic phonon transport, but the interpretation of the measurements has been semi-empirical. Here we present a numerical study of the heat conduction that occurs in the full 3D geometry of a TDTR experiment, including an interface, using the Boltzmann Transport Equation. We identify the radial suppression function that describes the suppression in heat flux, compared to Fourier's law, that occurs due to quasiballistic transport and demonstrate good agreement with experimental data.
Quasiballistc Heat Conduction in Transient Grating Spectroscopy - Hua, Chengyun; Minnich, Austin J.
Transient grating (TG) spectroscopy is an important experimental technique to measure mean free path (MFP) spectra using observations of quasiballistic heat conduction. To obtain MFP spectra, the measurements must be interpreted within the framework of the frequency-dependent Boltzmann transport equation (BTE), but previous solutions have restricted validity due to simplifying assumptions. Here, we analyze heat conduction in TG using a new analytical solution of the frequency-dependent BTE that accurately describes thermal transport from the diffusive to ballistic regimes. We demonstrate that our result enables a more accurate measurement of MFP spectra and thus will lead to an improved understanding of...
Investigation of the Young’s modulus and thermal expansion of
amorphous titania-doped tantala films - Abernathy, Matthew R.; Hough, James; Martin, Iain W.; Rowan, Sheila; Oyen, Michelle; Linn, Courtney; Faller, James E.
The current generation of advanced gravitational wave detectors utilize titania-doped tantala/silica multilayer stacks for their mirror coatings. The properties of the low-refractive-index silica are well known; however, in the absence of detailed direct measurements, the material parameters of Young’s modulus and coefficient of thermal expansion (CTE) of the high refractive index material, titania-doped tantala, have been assumed to be equal to values measured for pure tantala coatings. In order to ascertain the true values necessary for thermal noise calculations, we have undertaken measurements of Young’s modulus and CTE through the use of nanoindentation and thermal-bending measurements. The measurements were designed...