arXiv subjects

Edward J. Wollack

Publications and source records attributed to Edward J. Wollack.

At least 19 recordsLinked to original sources

arXiv2026

The Atacama Cosmology Telescope: Release of A databaSe of millimeTeR ObservatioNs of Asteroids Using acT ($\mathtt{ASTRONAUT}$)

We present A databaSe of millimeTeR ObservatioNs of Asteroids Using acT ($\mathtt{ASTRONAUT}$) hosted on Amazon Web Services, Inc. (AWS) in the form of a public Amazon Simple Storage Service (S3) bucket. This bucket is an Amazon cloud storage database containing flux measurements for a group of asteroids at millimeter (mm) wavelengths. These measurements were collected by the Atacama Cosmology Telescope (ACT) from 2017 to 2021 in frequency bands centered near 90, 150, and 220 GHz. The $\mathtt{ASTRONAUT}$ database contains observation times, normalized flux values, and associated error bars for 170 asteroids above a signal-to-noise ratio of 5 for a single frequency band over the stacked co-added maps. We provide an example in generating light curves with this database. We also present a Jupyter notebook to serve as a reference guide when using the S3 bucket. The container and notebook are publicly available in a GitHub repository.

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arXiv2026

The Atacama Cosmology Telescope: DR6 Constraints on Isotropic Time-Dependent Cosmic Birefringence from Axion-like Particles

Axion-like particles (ALPs) with sufficiently low masses are dark matter candidates because they could account for much or all of the observed dark matter energy density and help explain observations of galactic substructure. Such pseudoscalar fields could couple to photons, causing a time-dependent rotation of the polarization of the light with an oscillation frequency equal to the ALP mass. We use measurements of the polarization of the cosmic microwave background (CMB) by the Atacama Cosmology Telescope (ACT) between 2017 and 2022 to search for this effect using an EB power spectrum estimator. By probing oscillation periods from days to years, the data constrain the coupling between ALPs and photons for ALP masses between $2.5\times 10^{-23}$ eV and $4.8\times 10^{-20}$ eV. We find no evidence for such a signal and set a 95% upper bound on the axion-photon coupling constant, $g_{ϕγ} < 1.1\times10^{-11}\left({m_ϕ}/{10^{-21}\,\mathrm{eV}}\right)\,\mathrm{GeV}^{-1} .$ This limit assumes that ALPs make up all of the dark matter and that the ALP field amplitude is stochastically distributed, which leads to more conservative bounds than the deterministic-field assumption used in some previous CMB polarization analyses. Among searches for ALP-photon coupling using CMB polarization, we set the strongest bounds to date under the stochastic-field assumption. This work develops a methodology to analyze over 10,000 time-sliced "depth-1" polarization maps from ACT, a data product that will be standard for time-domain astrophysics with the Simons Observatory, enabling searches with a higher sensitivity and observing span.

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arXiv2026

The Simons Observatory: Frequency-resolved beam calibration for the SO SATs with POLOCALC

We present a far-field beam calibration of the Simons Observatory (SO) Small Aperture Telescopes (SATs) using scanned single-frequency measurements of a drone-mounted source emitting in the 90 GHz band, where the SATs have an angular resolution of $\sim$30$'$. We then compare the results from two campaigns in April and December 2025 to the band-averaged beams from planet observations by the SATs. Measuring the telescope beam response at different frequencies across the observing bands enables modeling the system's frequency-dependent behavior. This helps track optical non-idealities. The comparison with planet beams informs the frequency resolution necessary to accurately reconstruct the band-averaged beams in this way; it uses only the average drone and planet products, as it is intended to demonstrate the feasibility of the frequency-resolved calibration scheme rather than to set the precise beam covariance and instrument requirements. We find that the beams of the two SATs near 90 GHz follow the frequency scaling expected for diffraction-limited optics, with only modest deviations observed in the nearest lobes of one telescope. We establish consistency between the real band-averaged planet beams and the synthesized drone band-averaged beams for the center wafers of both telescopes, with an average deviation smaller than 4% for multipoles $\ell < 500$.

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arXiv2026

The Nancy Grace Roman Space Telescope Wide Field Instrument: Characterization of the Brighter-Fatter Effect in a Roman H4RG-10 Detector using the Talbot Effect

The Nancy Grace Roman Space Telescope will conduct several community-driven surveys using its Wide Field Instrument (WFI), which contains 18 Teledyne H4RG-10 near-infrared detectors in the focal plane. Roman's wide area survey to measure weak gravitational lensing places particularly stringent requirements on point spread function (PSF) precision for the WFI. The brighter-fatter effect (BFE) is a nonlinear detector effect caused by the deflection of new charge away from pixels with previously accumulated charge during an exposure. As a result, the PSF measured at the detector depends on the charge contrast between pixels, and therefore the effective PSF for astronomical sources is a function of flux contrast and integration time. We present characterization of the BFE observed in a non-flight H4RG by projecting a grid of bright point sources onto the detector using the Talbot Illuminator at the NASA Goddard Space Flight Center Detector Characterization Lab. We find that the effective area of a pixel decreases by $(-2.18\pm0.04) \times 10^{-6}$ per electron of charge contrast with its neighbors, corresponding to a measurable increase in the effective PSF size over the course of an exposure. Despite charge migration, the total signal detected in the vicinity of a bright source is roughly conserved. We also analyze flat field statistics for the same detector to measure the total inter-pixel nonlinearity (IPNL), which is dominated by BFE. We present a method to correct BFE in H4RG images using the flat field IPNL results, adapted from an extant optical correction technique. The correction reduces the observed BFE by about a factor of 25 as measured by the effective pixel area change, but there is remaining nonlinearity in the corrected data. We discuss possible sources of residual nonlinearity and suggest avenues to investigate optimal BFE correction in Roman survey images.

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arXiv2026

The Simons Observatory: Design and Initial Performance of the Detector Readout System for the Large-Aperture Telescope

We present the design, implementation, and initial performance of a highly multiplexed cryogenic superconducting detector readout system in the context of its deployment to the Simons Observatory large-aperture telescope (LAT). The Simons Observatory is a cosmic microwave background experiment located at 5,200 m in Chile's Atacama Desert. In addition to its 6 m LAT, whose broad range of science goals spans probing large-scale structure to searching for new Solar System objects, the observatory also currently includes three 0.42 m small-aperture telescopes, which search for signatures of primordial gravitational waves. Nearly 100,000 optically-coupled transition-edge sensor bolometers have been deployed across the observatory's four telescopes to enable these science goals. The readout systems for these telescopes use microwave frequency multiplexing to simultaneously read out 860 optically-coupled bolometers per transmission line. This is enabled by the large-scale fabrication of multiplexing chips which house radio-frequency superconducting quantum interference devices for each detector, and the development of room-temperature electronics to read out these bolometers. This has enabled the largest deployment of superconducting sensors for astronomical observations to date. This paper focuses on the design and implementation of the readout system for the 63,000 detectors in the LAT's cryogenic receiver. We present performance results from an early phase in the telescope's operation. We show that the readout system's performance enables the instrument to meet key benchmarks, including successful readout of 81.4% of its optically-coupled bolometers, which exceeds projections, and readout noise-equivalent current consistent with pre-deployment specifications.

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arXiv2026

Improved Constraints on Cosmic Microwave Background Circular Polarization with CLASS

We present improved constraints on circular polarization in the cosmic microwave background (CMB) from the Cosmology Large Angular Scale Surveyor (CLASS) experiment using data at 90, 150, and 220 GHz to complement previous results based on 40 GHz data alone. We extend constraints on circular polarization from the atmosphere to all CLASS frequencies and compare with a model of the atmospheric circular polarization spectrum. The inclusion of data at all CLASS frequencies improves upper limits on circular polarization, Stokes $V$, in the CMB by a factor of $\sim 5$ at the largest angular scales ($10 < \ell < 30$) and extends the constraints to smaller angular scales, $\ell = 700$. In combination with Planck temperature data, we provide the first limits on the temperature-circular-polarization ($TV$) power spectrum to date. Both circular polarization ($VV$) and $TV$ power spectra are consistent with zero, and CLASS places upper limits of $5.4 \times 10^{-3}$ $μ$K$_{\text{CMB}}^2$ on $VV$ at large angular scale ($10 < \ell < 30$) and $5.8 \times 10^{-1}$ $μ$K$_{\text{CMB}}^2$ on $TV$ at 95% confidence at $30 < \ell < 50$.

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arXiv2026

The Atacama Cosmology Telescope: A demonstration of CMB lensing measurement from daytime data

We present a cosmic microwave background (CMB) lensing power spectrum analysis using daytime data (11am-11pm UTC) gathered by the Atacama Cosmology Telescope (ACT) over the period 2017-2022 (ACT Data Release 6). This dataset is challenging to analyze because the Sun heats and deforms the telescope mirror, complicating the characterization of the telescope. We perform more than one hundred null and consistency checks to ensure the robustness of our measurement and its compatibility with nighttime observations. We detect the CMB lensing power spectrum at 18$σ$ significance, with an amplitude $A_\textrm{lens} = 1.071 \pm 0.060$ with respect to the prediction from the best-fit Planck-ACT CMB power spectrum $Λ$CDM cosmology. In combination with the Dark Energy Spectroscopic Instrument (DESI) Baryon Acoustic Oscillation (BAO) data, this corresponds to a constraint on the amplitude of matter fluctuations $σ_8 = 0.842 \pm 0.026$. The analysis presented here is especially relevant for ground-based millimeter-wave CMB experiments at the Atacama site, paving the way for future analyses making use of both nighttime and daytime data to place tight constraints on cosmological parameters.

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arXiv2026

The Canadian Galactic Emission Mapper (CGEM): A Cosmic Microwave Foreground Experiment

The Canadian Galactic Emission Mapper (CGEM) is a 4-meter single-dish radio telescope located at the Dominion Radio Astrophysical Observatory (DRAO) in Penticton, Canada. CGEM is designed to map polarized Galactic synchrotron emission across the entire northern sky at 8-10 GHz with 1 MHz frequency resolution and 0.5 degree angular resolution. Its goal is to obtain high-fidelity, low-noise maps of polarized Galactic synchrotron radiation, at frequencies where synchrotron dominates, in order to provide a reliable template for CMB B-mode foreground cleaning. We will show on sky performance of CGEM's single-pixel azimuthally-symmetric telescope, its coherent, dual-polarized radiometer, and show maps made from commissioning data from the first few months of operation.

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arXiv2026

The Canadian Galactic Emission Mapper: A New 8-10 GHz Telescope to Map the Polarization of the Northern Sky

The Canadian Galactic Emission Mapper (CGEM) radio telescope is mapping polarized Galactic foregrounds from 8-10 GHz to aid in the search for B-modes in the Cosmic Microwave Background (CMB). Here we describe the design and early on-sky characterization of the CGEM optics. CGEM employs an on-axis, hat feed optical design that is a body of revolution (BOR) and exhibits excellent intrinsic polarization purity. We describe how we have optimized the optics with a novel framework that can directly minimize simulated intensity to polarized intensity ($T\rightarrow P$) leakage in angular power spectrum space. The optimized optics exhibit simulated $T\rightarrow P$ leakage that is orders of magnitude below anticipated $C_\ell^{BB}$ for $r = 10^{-3}$ when scaled from 8-10 GHz to the CMB observing window near 95 GHz. We go on to describe the mechanical design of the optics, including a novel secondary mirror support made from Astroquartz composite that has low loss, low dielectric constant, and preserves the BOR symmetry of the optics. We then showcase the early on-sky performance of the optics with observations of the Sun and satellites, which probe the beam to 40 dB down from the peak. A beam model for the deployed CGEM optics based on electromagnetic simulations is in excellent agreement with the on-sky data.

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arXiv2026

The Atacama Cosmology Telescope: Passband Measurements with an Analysis of Systematic Errors

We present measurements of the spectral response of the four Advanced ACTPol (AdvACT) multichroic detector arrays, which observed in frequency bands centered near 30, 40, 90, 150, and 220 GHz. The passbands were measured with a Fourier transform spectrometer (FTS) combined with coupling optics that direct and match the output of the FTS to the AdvACT receiver. We perform optical simulations of the FTS and coupling optics in order to model frequency-dependent systematic effects in this system. We use these simulations to apply corrections to the measurements and evaluate the remaining systematic uncertainty. We combine these systematic estimates with statistical errors to determine the measured passbands and their uncertainties from our FTS measurement, which are typically 0.75 to 1.5% per detector array. We present the passband characteristics for all measurements made by ACT in a common framework. Additionally, we discuss the performance achieved as well as ways to improve passband measurements in the future.

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arXiv2026

In-Band Scattering and Absorption of Infrared Blocking Foam Filters for Millimeter-wave Cameras

Expanded closed-cell polymer foams are widely used as thermal infrared (IR) blocking filters in millimeter-wave cameras, particularly for Cosmic Microwave Background observations. Precise knowledge of their millimeter-wave properties is essential for optimizing sensitivity. We present broadband (150 GHz - 2 THz) transmittance spectroscopy of Styroace-II and several Zotefoam filters, fitting their spectra with a radiative transfer model incorporating dielectric absorption and Rayleigh, Mie, and higher-order scattering. For a typical 5~cm thick filter stack at 280~GHz, Styroace-II exhibits ${\sim}10\%$ scattering with absorption estimated as ${\lesssim}5\%$ by effective-medium theory, while Zotefoam HD30 offers superior performance at ${\sim}3\%$ scattering and absorption likewise bounded to ${{\lesssim}0.3\%}$. Each model component is constrained at the ${\sim}0.1\%$ transmittance level for millimeter wavelengths. We observe batch-to-batch scattering variability of up to 2 percentage points in foams with multiple tested batches. Less commonly used Zotefoam formulations (LD15 and LD24) can further reduce in-band scattering to ${<}1\%$ while maintaining negligible in-band absorption and likely comparable IR blocking due to shared polyethylene absorption features and similar cell sizes. Based on this work, a filter constructed from the best measured LD24 batch has replaced the Styroace-II filter in a Simons Observatory 220/280 GHz Small Aperture Telescope.

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arXiv2026

Optimization of lenslet arrays for PRIMA Kinetic Inductance Detectors

The PRobe far-Infrared Mission for Astrophysics (PRIMA) is a cryogenically cooled 1.8-m space telescope designed to address fundamental questions about the evolution of galactic ecosystems, the origins of planetary atmospheres, and the buildup of dust and metals over cosmic time. PRIMA will achieve unprecedented sensitivity in the 24 - 261 $μ$m wavelength range, enabled by background-limited kinetic inductance detectors (KIDs) cooled to 120 mK. For PRIMA's Far-InfraRed Enhanced Survey Spectrometer (FIRESS) instrument, we have developed monolithic kilopixel silicon lenslet arrays to efficiently couple incident radiation from the telescope's fore-optics onto the KID absorber elements. These three-dimensional lenslet arrays are fabricated using grayscale lithography, followed by deep reactive ion etching (DRIE), and are anti-reflection (AR) coated with a quarter-wavelength thick deposition of Parylene-C. The lenslet arrays are aligned and bonded to the KID arrays using a thin layer of epoxy through a flip-chip bonder. In this work, we report on the optimized fabrication, lens design, AR coating, and bonding processes developed for the FIRESS lenslet arrays. We characterize brassboard lenslet arrays fabricated to meet the specifications of the FIRESS low and high spectral bands, demonstrate stepped-thickness AR-coatings to achieve high efficiency across broad wavelength ranges, and present spectral transmission measurements of the AR coating and the epoxy bonding layers.

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arXiv2026

Detectors for CLASS-W2: The second 90 GHz telescope of the Cosmology Large Angular Scale Surveyor

The Cosmology Large Angular Scale Surveyor (CLASS) is measuring the Cosmic Microwave Background (CMB) polarization anisotropy on the largest angular scales (>1 degree) to probe the epochs of inflation and reionization. To enhance the CMB mapping speed, we have built, tested, and commissioned in August 2025 a second 90 GHz receiver (CLASS-W2) with a detector focal plane composed of feedhorn-coupled Transition Edge Sensor (TES) bolometers fabricated at NIST-Boulder. The focal plane consists of four modules, each containing 37 feedhorns coupling orthogonal polarizations onto two TES bolometers, for a total of 296 optically sensitive detectors. Laboratory tests show highly uniform TES properties with an array average critical temperature of 184+-3 mK, a thermal conductance of 460+-47 pW/K, and a normal resistance of 7.8+-0.3 mOhms. The detector array has an average band center frequency of 95.2 GHz with 28.3 GHz bandwidth, and achieves a detector yield of 94%. On-sky measurements indicate a mean detector optical load of 3.3 pW, corresponding to an antenna temperature of ~23 K. The array's average beam solid angle is 124 $μ$sr, with a full width at half maximum of 0.592 degrees, and the end-to-end average optical efficiency is 0.37. We find that high-frequency 'blue-leak' radiation couples directly to the TES bolometer islands; adding a metal-mesh low-pass filter with cutoff frequency of 157 GHz in front of the focal plane suppresses the 'blue-leak' power by 0.9 pW. The four-module array achieves a noise-equivalent temperature of NET= 16 uKrtS. Adding this array has boosted the CLASS 90 GHz mapping speed by 41%.

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arXiv2026

The Atacama Cosmology Telescope: stellar mass growth in massive galaxy clusters from DR5 over the past 7 billion years

We probe the stellar mass growth in a sample of 568 Sunyaev-Zel'dovich (SZ) selected galaxy clusters with masses greater than $2.9 \times 10^{14} \mathrm{M_{\odot}}$ and redshifts in the range $0.2 < z < 0.8$, drawn from the fifth data release of the Atacama Cosmology Telescope (ACT DR5). By utilising deep photometry from the tenth data release of the Dark Energy Camera Legacy Survey (DECaLS DR10), we construct redshift- and cluster mass-binned composite cluster stellar mass functions (SMFs), down to $M_* = 10^{9.5} \mathrm{M_{\odot}}$. This work presents the first analysis of the cluster SMF for this cluster sample at this epoch. We find that the characteristic stellar mass ($M^*$) of the cluster SMF evolves marginally from $0.55 \leq z < 0.8$, with most of the measurable growth occurring at $ 0.2 < z < 0.55$. This suggests that most of the massive galaxy population in clusters ($M_* \gtrsim 10^{10.75} \mathrm{M_{\odot}}$) is largely established by $z \sim 0.8$, with subsequent evolution driven by late-time assembly processes. The low-mass slope ($α$) of the composite cluster SMF is flat at high-$z$ ($z \sim 0.8$) but steepens at $z < 0.55$, suggesting an abundance of massive galaxies in high-$z$ clusters compared to low-$z$ clusters. We measure the evolution of cluster stellar mass fractions contained within galaxies with $M_* > 10^{9.5} \mathrm{M_{\odot}}$ between $ 0.2 < z < 0.8$, and find evidence of significant growth, by a factor of $2.5$, after accounting for the growth in cluster halo mass over this epoch.

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arXiv2026

The Atacama Cosmology Telescope: A Test of the Gravitational Force Law on Cosmological Scales Using the Kinematic Sunyaev-Zeldovich Effect

The mean pairwise velocity of massive halos reflects the gravitational force law on cosmic scales. We combine cosmic microwave background intensity maps from the Atacama Cosmology Telescope and a galaxy catalog from the Sloan Digital Sky Survey to estimate the mean pairwise velocity using the kinematic Sunyaev-Zeldovich (kSZ) effect. On scales from 30 -- 230 megaparsecs, we constrain the gravitational acceleration between pairs of halos at separation $r$ to be $g\propto 1/r^n$ with $n=2.1\pm 0.3$, which is consistent with Newtonian gravity in an expanding spacetime (\textit{i.e.}, the standard $Λ$CDM model). This constraint shows agreement with an inverse quadratic radial dependence over the large distances separating galaxy halos, as expected in standard cosmology. Upcoming surveys have the potential to rule out $n = 1$ at $10σ$ significance. Our results establish the kSZ effect as a powerful tool for testing gravity on cosmological scales.

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arXiv2026

Diamond-loaded polyimide aerogel scattering filters and their applications in astrophysical and planetary science observations

Infrared-blocking, aerogel-based scattering filters have a broad range of potential applications in astrophysics and planetary science instruments in the far-infrared, sub-millimeter, and microwave regimes. This paper demonstrates the ability of conductively-loaded, polyimide aerogel filters to meet the mechanical and science instrument requirements for several experiments, including the Cosmology Large Angular Scale Surveyor (CLASS), the Experiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM), and the Sub-millimeter Solar Observation Lunar Volatiles Experiment (SSOLVE). 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. Measurement of total hemispherical reflectance and transmittance, as well as cryogenic tests of the aerogel filters in a full receiver context, allow estimates of the integrated infrared emissivity of the filters. Knowledge of the emissivity will help instrument designers incorporate the filters into future experiments in planetary science, astrophysics, and cosmology.

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arXiv2026

The Simons Observatory: Quantifying the impact of beam chromaticity on large-scale B-mode science

The Simons Observatory (SO) Small Aperture Telescopes (SATs) will observe the Cosmic Microwave Background (CMB) temperature and polarization at six frequency bands. Within these bands, the angular response of the telescope (beam) is convolved with the instrument's spectral response (commonly called bandpass) and the signal from the sky, which leads to the band-averaged telescope beam response, which is sampled and digitized. The spectral properties of the band-averaged beam depend on the natural variation of the beam within the band, referred to as beam chromaticity. In this paper, we quantify the impact of the interplay of beam chromaticity and intrinsic frequency scaling from the various components that dominate the polarized sky emission on the tensor-to-scalar ratio, $r$, and foreground parameters. We do so by employing a parametric power-spectrum-based foreground component separation algorithm, namely BBPower, to which we provide beam-convolved time domain simulations performed with the beamconv software while assuming an idealized version of the SO SAT optics. We find a small, $0.02σ$, bias on $r$, due to beam chromaticity, which seems to mostly impact the dust spatial parameters, causing a maximum $0.77 σ$ bias on the dust $B$-mode spectra amplitude, $A_{d}$, when employing Gaussian foreground simulations. However, we find all parameter biases to be smaller than $1σ$ at all times, independently of the foreground model. This includes the case where we introduce additional uncertainty on the bandpass shape, which accounts for approximately half of the total allowed gain uncertainty, as estimated in previous work for the SO SATs.

astro-ph.CO↗

arXiv2026

Measurements of the Thermal Sunyaev-Zel'dovich Effect with ACT and DESI Luminous Red Galaxies

Cosmic Microwave Background (CMB) photons scatter off the free-electron gas in galaxies and clusters, allowing us to use the CMB as a backlight to probe the gas in and around low-redshift galaxies. The thermal Sunyaev-Zel'dovich effect, sourced by hot electrons in high-density environments, measures the thermal pressure of the target objects, shedding light on halo thermodynamics and galaxy formation and providing a path toward understanding the baryon distribution around cosmic structures. We use a combination of high-resolution CMB maps from the Atacama Cosmology Telescope (ACT) and photometric luminous red galaxy (LRG) catalogues from the Dark Energy Spectroscopic Instrument (DESI) to measure the thermal Sunyaev-Zel'dovich signal in four redshift bins from $z=0.4$ to $z=1.2$, with a combined detection significance of 19$σ$ when stacking on the fiducial CMB Compton-$y$ map. We discuss possible sources of contamination, finding that residual dust emission associated with the target galaxies is important and limits current analyses. We discuss several mitigation strategies and quantify the residual modelling uncertainty. This work complements closely related measurements of the kinematic Sunyaev-Zel'dovich and weak lensing of the same galaxies.

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