Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Equatorial Survey
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Megan B Gralla↗
Engineering topics
Edward J Wollack
Publications and source records attributed to Edward J Wollack.
Assembly and Integration Process of the High-Density Detector Array Readout Modules for the Simons Observatory
The Simons Observatory will measure the cosmic microwave background tempera-ture and polarization using a suite of new telescopes in the Atacama Desert in Chile. The Simons Observatory will use dichroic transition edge sensor (TES) bolometer arrays spanning six frequency bands from 27 to 280 GHz. The Simons Observa-tory will pioneer the use of a densely packed multiplexing architecture based on the microwave SQUID multiplexer ( 𝜇mux), housing ∼2000 microwave resonators, each coupled to a TES. The Simons Observatory aims to multiplex each array of ∼2000 detectors with a single pair of coaxial cables and requires a multiplexing factor of ∼1000 . The Simons Observatory cryogenic readout system is called the universal microwave multiplexing module (UMM). The UMM couples to both horn and lenslet-coupled detector arrays and is integrated into the universal focal-plane module (UFM) after being independently characterized. We present processes we have developed for highly repeatable and automated integration methods of UMMs, which will be needed for the production of the 49 UFMs required for the first stage of the Simons Observatory.
CMB↗
SOFIA/HAWC plus Traces the Magnetic Fields in NGC 1068
We report the first detection of galactic spiral structure by means of thermal emission from magnetically aligned dust grains. Our 89μm polarimetric imaging of NGC 1068 with the High-resolution Airborne Wideband Camera/Polarimeter(HAWC+)on NASAs Stratospheric Observatory for Infrared Astronomy(SOFIA)also sheds light on magnetic field structure in the vicinity of the galaxyʼs inner-bar and active galactic nucleus(AGN).We find correlations between the 89μm magnetic field vectors and other tracers of spiral arms, and a symmetric polarization pattern as a function of the azimuthal angle arising from the projection and inclination of the disk field component in the plane of the sky. The observations can befit with a logarithmic spiral model with pitch angle of-+16.92.82.7and a disk inclination of 48°±2°. We infer that the bulk of the interstellar medium from which the polarized dust emission originates is threaded by a magnetic field that closely follows the spiral arms. Inside the central starburst disk(<1.6 kpc), the degree of polarization is found to be lower than for far-infrared sources in the Milky Way, and has minima at the locations of most intense star formation near the outer ends of the inner-bar. Inside the starburst ring, the field direction deviates from the model, becoming more radial along the leading edges of the inner-bar. The polarized flux and dust temperature peak∼3′′–6′′NE of the AGN at the location of a bow shock between the AGN outflow and the surrounding interstellar medium, but the AGN itself is weakly polarized(<1%)at both 53 and 89μm.
Active galactic nuclei↗
The Bidirectional Reflectance of Black Silicon Used in Space and Earth Remote Sensing Applications
Space-based astrophysical and remote sensing observations often require the detection and measurement of light originating from distant and relatively faint objects. These observations are highly susceptible to scattered light which may introduce imaging artifacts, obscure object details, and increase measurement noise. This paper describes the initial work of characterizing representative black materials used in coronagraph instruments and other spaceborne instruments. Measurements of “blackness” and the achieved reflectance of black silicon are provided in the spectral range from 400nm to 2500nm using 8o directional hemispherical measurements. The bidirectional reflectance of black silicon was also measured at discrete wavelengths, 633nm, and 1064nm, using the optical scatterometer located at NASA Goddard Space Flight Center’s Diffuser Calibration Laboratory (DCL). A 100mm diameter black silicon sample was fabricated and optically characterized. The BRDF of other well-known black materials such as Z306 and Fractal Black are also presented and discussed.
BRDF↗
Machine Learning, Markov Chain Monte Carlo, and Optimal Algorithms to Characterize the AdvACT Kilopixel Transition-Edge Sensor Arrays
Next-generation focal planes comprising dozens of kilopixel transition-edge sensor (TES) arrays require new methods to rapidly screen candidate arrays, evaluate array non-idealities in the field, identify outlier devices for removal, and optimize the array performance in the field. We demonstrate robust methods to estimate TES parameters (critical temperatures and thermal conductivity parameters) and their uncertainties using a custom Markov Chain Monte Carlo (MCMC) algorithm. We also constrain systematic effects in estimating the TES parameters from non-isothermal current-voltage curves (IVs) at approximately a ~3% level. Additionally, for the first time, we have applied Machine Learning (ML) algorithms to tune detector arrays and optimize their performance.
Maria Salatino↗
A 3D-printed Broadband Millimeter Wave Absorber
We present the design, manufacturing technique, and characterization of a 3D-printed broadband graded index millimeter wave absorber. The absorber is additively manufactured using a fused filament fabrication (FFF) 3D printer out of a carbon-loaded high impact polystyrene (HIPS) filament and is designed using a space-filling curve to optimize manufacturability using said process. The absorber's reflectivity is measured from 63 GHz to 115 GHz and from 150 GHz to 215 GHz and is compared to electromagnetic simulations. The intended application is for terminating stray light in Cosmic Microwave Background (CMB) telescopes, and the absorber has been shown to survive cryogenic thermal cycling.
Matthew Petroff↗
SOFIA Far-infrared Imaging Polarimetry of M82 and NGC 253: Exploring the Supergalactic Wind
We present far-infrared polarimetry observations of M82 at 53 and 154μm and NGC 253 at 89μm, which were taken with High-resolution Airborne Wideband Camera-plus(HAWC+)in polarimetry mode on the Stratospheric Observatory for Infrared Astronomy. The polarization of M82 at 53μm clearly shows a magnetic field geometry perpendicular to the disk in the hot dust emission. For M82 the polarization at 154μm shows a combination of field geometry perpendicular to the disk in the nuclear region, but closer to parallel to the disk away from the nucleus. The fractional polarization at 53μm(154μm)ranges from 7%(3%)off nucleus to 0.5%(0.3%)near the nucleus. A simple interpretation of the observations of M82 invokes a massive polar outflow, dragging the field along, from a region∼700pc in diameter that has entrained some of the gas and dust, creating a vertical field geometry seen mostly in the hotter(53μm)dust emission. This outflow sits within a larger disk with a more typical planar geometry that more strongly contributes to the cooler(154μm)dust emission. For NGC 253, the polarization at 89μm is dominated by a planar geometry in the tilted disk, with weak indication of a vertical geometry above and below the plane from the nucleus. The polarization observations of NGC 253 at 53μm were of a insufficient signal-to-noise ratio for a detailed analysis.
Galaxies↗
The Atacama Cosmology Telescope: Two-Season ACTPol Extragalactic Point Sources and Their Polarization Properties
We report on measurements of the polarization of extragalactic sources at 148 GHz made during the first two seasons of the Atacama Cosmology Telescope Polarization (ACTPol) survey. The survey covered 680 deg 2 of the sky on the celestial equator. Polarization measurements of 169 intensity-selected sources brighter than 30 mJy, that are predominantly active galactic nuclei, are presented. Above a total flux of 215 mJy where the noise bias removal in the polarization measurement is reliable, we detect 26 sources, 14 of which have a detection of linear polarization at greater than 3σ significance. The distribution of the fractional polarization as a function of total source intensity is analysed.
Rahul Datta↗
A Four-Pole Power-Combiner Design for Far-Infrared and Submillimeter Spectroscopy
The far-infrared and submillimeter portions of the electromagnetic spectrum provide a unique view of the astrophysical processes present in the early universe. Micro-Spec (μ-Spec), a high-efficiency direct-detection spectrometer concept working in the 450–1000-micron wavelength range, will enable a wide range of spaceflight missions that would otherwise be challenging due to the large size of current instruments and the required spectral resolution and sensitivity. This paper focuses on the μ-Spec two-dimensional multimode region, where the light of different wavelengths diffracts and converges onto a set of detectors. A two-step optimization process is used to generate geometrical configurations given specific requirements on spectrometer size, operating spectral range, and performance. The canonically employed focal-plane constraints for the power combiner were removed to probe the design space in its entirety. A new four-stigmatic-point optical design solution is identified and explored for use in far-infrared and submillimeter spectroscopy.
electromagnetic spectrum↗
Precision Epoch of Reionization Studies with Next-Generation CMB Experiments
Future arcminute resolution polarization data from ground-based Cosmic Microwave Background (CMB) observations can be used to estimate the contribution to the temperature power spectrum from the primary anisotropies and to uncover the signature of reionization near l = 1500 in the small angular-scale temperature measurements. Our projections are based on combining expected small-scale E-mode polarization measurements from Advanced ACTPol in the range 300 < l < 3000 with simulated temperature data from the full Planck mission in the low and intermediate l region, 2 < l < 2000. We show that the six basic cosmological parameters determined from this combination of data will predict the underlying primordial temperature spectrum at high multipoles to better than 1% accuracy. Assuming an efficient cleaning from multi-frequency channels of most foregrounds in the temperature data, we investigate the sensitivity to the only residual secondary component, the kinematic Sunyaev-Zel'dovich (kSZ) term. The CMB polarization is used to break degeneracies between primordial and secondary terms present in temperature and, in effect, to remove from the temperature data all but the residual kSZ term. We estimate a 15 sigma detection of the di use homogeneous kSZ signal from expected AdvACT temperature data at l > 1500, leading to a measurement of the amplitude of matter density fluctuations, sigma 8, at 1% precision.
Precision↗
High-Resolution µ-Spec Spectrometers for EXCLAIM
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Instrumentation and Photography↗
u-Spec Spectrometers for the EXCLAIM Instrument
The EXperiment for Cryogenic Large-aperture Intensity Mapping (EXCLAIM) is a cryogenic balloon-borne instrument that will map carbon monoxide and singly-ionized carbon emission lines across redshifts from 0to 3.5, using an intensity mapping approach. EXCLAIM will broaden our understanding of these elemental and molecular gases, and the role they play in star formation processes across cosmic time scales. The focal plane of EXCLAIM’s cryogenic telescope features sixμ-Spec spectrometers.μ-Spec is a compact, integrated grating-analog spectrometer, which uses meandered superconducting niobium microstrip transmission lines on a single-crystal silicon dielectric to synthesize the grating. It features superconducting aluminum microwave kinetic inductance detectors (MKIDs), also in a microstrip architecture. The spectrometers for EXCLAIM couple to the telescope optics via a hybrid planar antenna coupled to a silicon lenslet. The spectrometers operate from420−540 GHz with a resolving power R=λ/∆λ= 512, and employ an array of 355 MKIDs on each spectrometer. The spectrometer design targets a noise equivalent power (NEP) of 2×10−18W/√Hz (defined at the input to the main lobe of the spectrometer lenslet beam, within a 9◦half width), enabled by the cryogenic telescope environment, the sensitive MKID detectors, and the low dielectric loss of single-crystal silicon. We report on these spectrometers under development for EXCLAIM, providing an overview of the spectrometer and component designs, the spectrometer fabrication process, fabrication developments since previous prototype demonstrations, and the current status of their development for the EXCLAIM mission.
EXCLAIM Instrument↗
The Experiment for Cryogenic Large-aperture Intensity Mapping (EXCLAIM)
Submillimeter and far-IR spectroscopy provides insight into galaxy evolution through measurement of atomic and molecular line emission. The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a cryogenic balloon-borne instrument designed to carry out intensity mapping to measure the cumulative redshifted line emission from carbon monoxide and singly-ionized carbon to probe star formation in windows from the present to z=3.5. During this time, the rate of star formation dropped dramatically, while dark matter continued to cluster. Intensity mapping permits a blind and complete survey of emitting gas through statistics of cumulative brightness fluctuations. EXCLAIM achieves high sensitivity using a cryogenic telescope coupled to six integrated spectrometers with spectral resolving power R=512 and employing microwave kinetic inductance detectors. Here we summarize the status of the mission.
Maryam Rahmani↗
The Experiment for Cryogenic Large-aperture Intensity Mapping (EXCLAIM)
Submillimeter and far-IR spectroscopy provides insight into galaxy evolution through atomic and molecular line emission. The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a cryogenic balloon-borne instrument designed to carry out an intensity mapping to measure the cumulative redshifted line emission from carbon monoxide and singly-ionized carbon to probe star formation in windows from the present to z=3.5. During this time, the rate of star formation dropped dramatically, while dark matter continued to cluster. Intensity mapping permits a blind and complete survey of emitting gas through statistics of cumulative brightness fluctuations. EXCLAIM achieves high sensitivity using a cryogenic telescope coupled to six integrated spectrometers with spectral resolving power R = 512 and employing kinetic inductance detectors. Here we summarize the status of the mission.
Maryam Rahmani↗
Characterization of Aerogel Scattering Filters for Astronomical Telescopes
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Optics↗
Novel Infrared-blocking Aerogel Scattering Filters and Their Applications in Astrophysical and Planetary Science Observations
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Kyle R Helson↗
Novel Infrared-blocking Aerogel Scattering Filters and Their Applications in Astrophysical and Planetary Science Observations
Infrared-blocking scattering aerogel filters have a broad range of potential applications in astrophysics and planetary science observations in the far-infrared, sub-millimeter, and microwave regimes. Successful dielectric modeling of aerogel filters allowed the fabrication of samples to meet the mechanical and science instrument requirements for several experiments, including the Sub-millimeter Solar Observation Lunar Volatiles Experiment (SSOLVE), the Cosmology Large Angular Scale Surveyor (CLASS), and the Experiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM). Thermal multi-physics simulations of the filters predict their performance when integrated into a cryogenic receiver. Prototype filters have survived cryogenic cycling to 4 K with no degradation in mechanical properties.
Kyle R Helson↗
Design and Characterization of New 90 GHz Detectors for the Cosmology Large Angular Scale Surveyor (CLASS)
The Cosmology Large Angular Scale Surveyor (CLASS) is a polarization-sensitive telescope array located at an altitude of 5,200 m in the Chilean Atacama Desert. CLASS is designed to measure “E-mode” (even parity) and “B-mode” (odd parity) polarization patterns in the Cosmic Microwave Background (CMB) over large angular scales with the aim of improving our understanding of inflation, reionization, and dark matter. CLASS is currently observing with three telescopes covering four frequency bands: one at 40 GHz (Q); one at 90 GHz (W1); and one dichroic system at 150/220 GHz (G). In these proceedings, we discuss the updated design and in-lab characterization of new 90 GHz detectors. The new detectors include design changes to the transition-edge sensor (TES) bolometer architecture, which aim to improve stability and optical efficiency. We assembled and tested four new detector wafers, to replace four modules of the W1 focal plane. These detectors were installed into the W1 telescope, and will achieve first light in the austral winter of 2022. We present electrothermal parameters and bandpass measurements from in-lab dark and optical testing. From in-lab dark tests, we also measure a median NEP of 12.3 aW √ s across all four wafers about the CLASS signal band, which is below the expected photon NEP of 32 aW √ s from the field. We therefore expect the new detectors to be photon noise limited."
Carolina Nunez↗