UChicago-2020: JuniorScientistTalks

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Junior Scientist Talks Organized by the CMB-S4 Junior Scientist Advancement Committee
These talks are highlighting the recent work of graduate students and postdocs in cosmology.

Connection Details

Zoom: https://fnal.zoom.us/j/97391022720?pwd=QTE4ZzBzcml4MmlZQ1crWjZib0R1dz09 One-tap: +13126266799,,97391022720#,,,,,,0#,,695564# US (Chicago)

Time/Date: 8:00am - 12:15pm Pacific Time / Friday August 14, 2020

Organizers: Darcy Barron for the CMB-S4 Junior Scientist Advancement Committee


Session 1: 8:00am - 10:15am PDT

  • Yuto Minami - Simultaneous determination of the cosmic birefringence and miscalibrated polarization angles
  • Dongwon 'DW' Han - The Atacama Cosmology Telescope: Delensed Power Spectra and Parameters File:Han CMB-S4 JRT.pdf
  • Suvodip Mukherjee - Peering into patchy reionization using kSZ and B-mode polarization
  • Omar Darwish - ACTPol lensing maps and foreground-cleaned galaxy correlations
  • Heather McCarrick - The Simons Observatory uMux detector modules
  • Benjamin Beringue - Cosmology with Rayleigh scattering
  • Max Abitbol - Robust B-mode foreground analysis for ground-based experiments
  • Jahmour J. Givans - Lyman-alpha forest perturbative modeling and improved CMB constraining power
  • Lindsay Ng Lowry - Development and Characterization of the POLARBEAR-2b Receiver for the Simons Array
  • Shouvik Roy Choudhury - Neutrino Mass and Mass Hierarchy from Cosmology
  • Ruby Byrne - Enabling Precision EoR Calibration
BREAK 10:15am - 10:30am PDT

Session 2: 10:30am - 12:15pm

  • Anna Ho - The Landscape of Relativistic Stellar Explosions
  • Charles Hill - A cryogenic half-wave plate for POLARBEAR-2b
  • Tucker Elleflot - DfMux Readout for CMB Experiments
  • Kirit Karkare - Cosmology with Next-Generation Millimeter-Wave Spectrometers
  • Theodore Macioce - Realistic Mock kSZ Observations to Forecast Constraints on Structure Formation and Cosmic Acceleration
  • John Groh - Development and deployment of the Simons Array CMB polarization experiment
  • Tyler St Germaine - Beam Systematics in BICEP3 and the Keck Array CMB Polarimeters
  • Tashalee Billings - Extracting Optical Depth from Simulated 21cm Data

Speaker Information (in order of talks)

Name Short Bio Talk Title Abstract
Yuto Minami I'm postdoc fellow of High Energy Accelerator Research Organization (KEK) in Japan. I'm members of LiteBIRD and Simons Array. My research history is here: https://inspirehep.net/authors/1238534. Simultaneous determination of the cosmic birefringence and miscalibrated polarization angles We show that the cosmic birefringence and miscalibrated polarization angles can be determined simultaneously by cosmic microwave background (CMB) experiments using the cross-correlation between E- and B-mode polarization data. This is possible because the polarization angles of the CMB are rotated by both the cosmic birefringence and miscalibration effects, whereas those of the Galactic foreground emission are rotated only by the latter. Our method does not require prior knowledge of the E- and B-mode power spectra of the foreground emission, but uses only the knowledge of the CMB polarization spectra. Specifically, we relate the observed EB correlation to the difference between the observed E- and B-mode spectra in the sky, and use different multipole dependences of the CMB (given by theory) and foreground spectra (given by data) to derive the likelihood for the miscalibration angle α and the birefringence angle β⁠. We show that a future satellite mission similar to LiteBIRD can determine β with a precision of 6 arcmin.
Dongwon 'DW' Han A PhD student at Stony Brook University studying CMB data analysis with Dr. Neelima Sehgal The Atacama Cosmology Telescope: Delensed Power Spectra and Parameters We present LCDM cosmological parameter constraints obtained from delensed microwave background power spectra. Lensing maps from a subset of DR4 data from the Atacama Cosmology Telescope (ACT) are used to undo the lensing effect in ACT spectra observed at 150 and 98 GHz. At 150 GHz, we remove the lensing

distortion with an effective efficiency of 30% (TT), 30% (EE), 26% (TE) and 20% (BB); this results in detections of the delensing effect at 8.7 sigma (TT), 5.1 sigma (EE), 2.6 sigma (TE), and 2.4 sigma (BB) significance. The combination of 150 and 98 GHz TT, EE, and TE delensed spectra is well fit by a standard LCDM model. We also measure the shift in best-fit parameters when fitting delensed versus lensed spectra; while this shift does not inform our ability to measure cosmological parameters, it does provide a three-way consistency check among the lensing inferred from the best-fit parameters, the lensing in the CMB power spectrum, and the reconstructed lensing map. This shift is predicted to be zero when fitting with the correct model since both lensed and delensed spectra originate from the same region of sky. Fitting with a LCDM model and marginalizing over foregrounds, we find that the shift in cosmological parameters is consistent with zero. Our results show that gravitational lensing of the microwave background is internally consistent within the framework of the standard cosmological model.

Suvodip Mukherjee University of Amsterdam, GRAPPA postdoctoral fellow, https://staff.fnwi.uva.nl/s.mukherjee/ Peering into patchy reionization using kSZ and B-mode polarization The epoch of cosmic reionization can be probed using the secondary anisotropies induced in the cosmic microwave background (CMB) temperature and polarization field. I will discuss the impact of patchy reionization on CMB temperature and polarization anisotropies using the results obtained from semi-numerical simulations. I will introduce two new scaling relations to connect the kSZ power spectrum and secondary B-mode power spectrum with the scenarios of patchy reionization and is going to discuss its utility for the ongoing/upcoming CMB experiments. By using a physically motivated model of reionization, I will show the first constraints on patchiness during reionization from the current kSZ measurement and will present the corresponding upper bound on the amplitude of secondary B-mode polarization. I will also discuss the advantage of a joint study of the kSZ signal and secondary B-mode polarization from the upcoming CMB experiments to unveil the reionization history.
Omar Darwish University of Cambridge, Blake Sherwin, PhD, CMB Lensing cross correlations, LSS reconstruction, https://www.maths.cam.ac.uk/person/od261 ACTPol lensing maps and foreground-cleaned galaxy correlations We construct cosmic microwave background lensing mass maps using data from the 2014 and 2015 seasons of observations with the Atacama Cosmology Telescope (ACT). These maps cover 2100 square degrees of sky and overlap with a wide variety of optical surveys. The maps are signal dominated on large scales and have fidelity such that their correlation with the cosmic infrared background is clearly visible by eye. We also create lensing maps with thermal Sunyaev-Zel’dovich contamination removed using a novel cleaning procedure that only slightly degrades the lensing signal-to-noise ratio. The cross-spectrum between the cleaned lensing map and the BOSS CMASS galaxy sample is detected at 10-σ significance, with an amplitude of A = 1.02±0.10 relative to the Planck best-fit LCDM cosmological model with fiducial linear galaxy bias. Our measurement lays the foundation for lensing cross-correlation science with current ACT data and beyond.
Heather McCarrick I am a postdoc at Princeton, advised by Suzanne Staggs. I primarily work on the Simons Observatory with a focus on the readout, detectors, and focal plane module design. The Simons Observatory uMux detector modules The Simons Observatory (SO) will be a cosmic microwave background (CMB) survey experiment with four small-aperture telescopes and one large-aperture telescope, which will observe from the Atacama Desert. In total, SO will field over 60,000 transition-edge sensor (TES) bolometers in six spectral bands centered between 27 and 280 GHz in order to achieve the sensitivity necessary to measure or constrain numerous cosmological quantities, as outlined in The Simons Observatory Collaboration et al. (2019). SO will use a microwave SQUID multiplexing (uMux) readout with an initial multiplexing factor of 1000. Comparatively, current CMB experiments use a multiplexing factor of ~64. The focal plane modules contain the uMUX readout, TES bias circuitry and detectors. The focal plane module design is both critical to the readout performance and allows for close-packing of the modules within the focal plane. In this talk, I will discuss the evolved SO focal plane module design and status.
Benjamin Beringue My name is Benjamin Beringue, I am a third year PhD student at the University of Cambridge under the supervision of Dr Daan Meerburg. I have been working on several aspects of CMB data analysis from forecasting detectability of Rayleigh scattering of the CMB to implementing component separation methods for SO. Cosmology with Rayleigh scattering "The cosmic microwave background (CMB) has been a treasure trove for cosmology. Over the next decade, current and planned CMB experiments are expected to exhaust nearly all primary CMB information. However, CMB photons can be affected after recombination, which can be a nuisance in extracting the primary modes, but will also provide valuable cosmological information. Well-studied examples include deflection of CMB photons by gravitational lensing and the Sunyaev-Zel'dovich effects describing scattering by free electrons in collapsed objects. Several of these effects have been detected and have been, or will be, used for cosmological inference.

Among these secondaries, Rayleigh scattering of the CMB is a less studied yet potentially powerful probe of the recombination history. Scattering of CMB photons off neutral species right after recombination presents a distinctive $\nu^4$ scaling with frequency as well as a strong correlation with the primary CMB. These unique features should guarantee its detection by the next generation of CMB experiments. We will present detectability forecasts combining the Simons Observatory and CCAT-prime telescopes as well as more futuristic space missions. Finally, we will present potential cosmological implications of the detection of this signal by studying improvement of parameter constrains."

Max Abitbol I am a postdoc at University of Oxford working with David Alonso on CMB B-mode foregrounds and systematics for Simons Observatory. Robust B-mode foreground analysis for ground-based experiments In this talk I will discuss foreground and instrument systematic modeling for upcoming ground-based B-mode searches. I will begin by introducing a moment-expansion method, which aims to address the problem of spatially varying foreground SEDs by adding physically motivated parameters to the SEDs. Next I will summarize the power-spectrum domain foreground and systematic cleaning pipeline for the Simons Obsevatory. Using this framework we have quantified calibration requirements on bandpass and polarization angle systematics for the SO target of $\sigma_r\approx 10^{-3}$. We show that we can explicitly model and marginalize over systematic parameters without a large penalty on $\sigma_r$. The pipeline was validated on simulations and BICEP data. We also propagated these systematic requirements into instrument design choices. Finally, I will present preliminary results from a new power-spectrum domain moment-expansion based foreground modeling procedure. This method combines the practicality of power-spectrum domain cleaning with the expressiveness of additional foreground moment parameters to allow for robust foreground subtraction and CMB B-mode identification.
Jahmour J. Givans I am a fifth-year graduate student at The Ohio State University working under Chris Hirata. I am a member of the DESI Lyman-alpha forest working group and the Roman Space Telescope image simulation group. My previous and current projects are related to Lyman-alpha forest perturbation theory, the relative velocity effect on the H I power spectrum, and modeling detector effects as a source of weak lensing systematics. You can read more about me at https://u.osu.edu/givans.2/ Lyman-alpha forest perturbative modeling and improved CMB constraining power Efforts to improve the constraining power of CMB measurements by incorporating probes of large-scale structure have primarily focused on synergies between the CMB and galaxies or clusters. Over redshifts 2<z<6 where galaxies are more difficult to resolve, the Lyman-alpha forest is an excellent probe of structure. In this talk I will present my work on using perturbation theory beyond leading order to model Lyman-alpha forest flux fluctuations. This improved model is a first step toward obtaining a nonlinear Lyman-alpha forest power spectrum model without using any fitting functions. I then discuss how measurements of this power spectrum by DESI can be combined with future CMB data to place tighter constraints on the sum of neutrino masses and test for primordial non-Gaussianity.
Lindsay Ng Lowry My name is Lindsay Ng Lowry and I am currently a grad student at UC San Diego working on the Simons Array with Professor Brian Keating as my advisor. I joined the group in 2014 and have been focused on hardware development and testing for the POLARBEAR-2b receiver as well as site preparation for the Simons Array's three telescopes. Aside from research, I love participating in physics outreach and mentoring programs such as giving shows with UCSD's portable planetarium and leading the graduate Women in Physics group. Development and Characterization of the POLARBEAR-2b Receiver for the Simons Array POLARBEAR-2b (PB-2b) is the receiver to be installed in the second telescope of the Simons Array. The cryogenic receiver was developed and characterized at UC San Diego where it was also integrated with its detectors (7,588 transition edge sensor bolometers with lenslet-coupled sinuous antennas), readout system (frequency-division multiplexing utilizing LC resonators and SQUID series array amplifiers), and optical elements (reimaging lenses and cryogenic, continuously rotating half-wave plate). I will describe the results of this lab work along with the current status and future plans for PB-2b.
Shouvik Roy Choudhury I am currently a Postdoctoral fellow (Feb 2020 - present) at the Indian Institute of Technology Bombay (IIT B), India, where my current advisor is Prof. Vikram Rentala. I did my PhD (defended: Feb 2020) from Harish-Chandra Research Institute (HRI), Allahabad, India with Prof. Sandhya Choubey as my supervisor. My research work involves cosmological parameter estimation with a strong focus on neutrino cosmology. Currently, my research interests also include dark energy, dark matter, the Hubble tension, etc. Link to my publications list: http://old.inspirehep.net/author/profile/Shouvik.Roy.Choudhury.1 Neutrino Mass and Mass Hierarchy from Cosmology In this talk I shall discuss results from my paper (arXiv: 1907.12598, published in JCAP) where we update the bounds on the sum of neutrino masses, $\sum m_{\nu}$ from latest publicly available cosmological data and likelihoods using Bayesian analysis, while explicitly considering particular neutrino mass hierarchies. In the minimal $\Lambda\textrm{CDM}+\sum m_{\nu}$ model with most recent CMB data from Planck 2018 TT,TE,EE, lowE, and lensing; and BAO data from BOSS DR12, MGS, and 6dFGS, we find that at 95\% C.L. the bounds are: $\sum m_{\nu}<0.12$ eV (degenerate), $\sum m_{\nu}<0.15$ eV (normal), $\sum m_{\nu}<0.17$ eV (inverted). The bounds vary across the different mass orderings due to different priors on $\sum m_{\nu}$. Also, we find that the normal hierarchy is very mildly preferred relative to the inverted, using both minimum $\chi^2$ values and Bayesian Evidence ratios. We also provide bounds on $\sum m_{\nu}$ considering different neutrino mass hierarchies in various extended cosmological models: $\Lambda\textrm{CDM}+\sum m_{\nu}+r$, $w\textrm{CDM}+\sum m_{\nu}$, $w_0 w_a \textrm{CDM}+\sum m_{\nu}$, $w_0 w_a \textrm{CDM}+\sum m_{\nu}$ with $w(z)\geq -1$, $\Lambda \textrm{CDM} + \sum m_{\nu} + \Omega_k$, and $\Lambda \textrm{CDM} + \sum m_{\nu} + A_{\textrm{Lens}}$. We do not find any strong evidence of normal hierarchy over inverted hierarchy in the extended models either.
Ruby Byrne I am currently in the last year of my Ph.D. at the University of Washington, where I am advised by Prof. Miguel Morales and Dr. Bryna Hazelton. My work focuses on enabling measurement of the 21 cm power spectrum from the Epoch of Reionization (EoR) with the Murchison Widefield Array (MWA) and the Hydrogen EoR Array (HERA). In particular, I specialize in polarimetry and next-generation calibration approaches. My recent projects include polarized diffuse foreground mapping, characterizing redundant calibration errors, and using Bayesian statistics to develop novel calibration algorithms that mitigate calibration error. Enabling Precision EoR Calibration "Calibration errors are a dominant systematic in 21 cm cosmology experiments. Measurement of the 21 cm power spectrum from the Epoch of Reionization (EoR) relies on the separability of the faint cosmological signal from the bright astrophysical foreground emission. Frequency-dependent calibration errors limit this separability and can preclude a detection of the cosmological signal.

We discuss two complimentary approaches for mitigating calibration error. Foreground model incompleteness - particularly related to diffuse foreground structure - is a major source of frequency-dependent calibration error for both redundant and non-redundant arrays. To that end, we present a fully-polarized diffuse map of the southern sky (-1.6 to 7 hours RA, -50 to 0 degrees Dec) and discuss its applications for improved calibration. The map is produced with data from the Murchison Widefield Array (MWA) Phase I configuration and processed with the Fast Holographic Deconvolution (FHD) software package. It includes diffuse structure of 1- to 10-degree scales on the sky.

Next, we discuss next-generation calibration approaches that can mitigate calibration errors. Traditional interferometric calibration approaches can be generally characterized as either sky-based or redundant. Novel calibration approaches unify these disparate frameworks to produce calibration models that are highly general, physically motivated, and statistically rigorous. We present simulation results illustrating that these approaches improve calibration performance. Combining with improved foreground emission models, these new techniques could enable the detection of the faint 21 cm cosmological signal."

Anna Ho I recently obtained my PhD from Caltech under the supervision of Shri Kulkarni. Beginning in Sept 2020, I will be a Miller Fellow at UC Berkeley. The focus of my thesis was relativistic stellar explosions, using the Zwicky Transient Facility. My website is at this link: annayqho.github.io The Landscape of Relativistic Stellar Explosions "For the last half-century, relativistic outflows accompanying the final collapse of

massive stars have predominantly been detected via high-energy emission, as long-duration gamma-ray bursts (GRBs). For my thesis, I used the Zwicky Transient Facility (ZTF) to conduct the first large-scale optical survey dedicated to finding relativistic stellar explosions. I successfully detected a suite of GRB-related phenomena without relying on a GRB trigger, and followed them up with facilities across the electromagnetic spectrum, including the Atacama Large Millimeter/submillimeter Array (ALMA). The emerging zoo includes relativistic afterglows at cosmological distances, broad-lined Ic (Ic-BL) supernovae with X-ray and radio emission, and fast-luminous transients powered by circumstellar interaction. Based on the rate of fast (intra-night) optical transients, I showed that a ""clean"" jet seems central to the phenomenon of collimated energetic outflows, i.e., there is no evidence for afterglow-like optical transients whose area (sky) rate greatly exceed the classical GRB rate. With a radio and millimeter-wave investigation of AT2018cow (""The Cow""), and the discovery of a similar event in ZTF (""The Koala""), I helped to establish a new class of engine-driven stellar explosions that arise from different progenitors to GRBs and explode embedded in dense circumstellar material. I showed that ""death omens"" (late-stage eruptive mass-loss) are prevalent across a greater variety of stars than was previously thought, and that this complicates searches for choked and off-axis jets in Ic-BL SNe. My work helps set the stage for discovering and characterizing relativistic stellar explosions and their death omens during the era of ZTF Phase II, the Large Synoptic Survey Telescope (LSST), and millimeter-band facilities like ALMA and the NOrthern Extended Millimeter Array (NOEMA)."

Charles Hill I am a graduate student at UC Berkeley and LBNL working under Adrian Lee and Akito Kusaka on Simons Array (SA) and Simons Observatory (SO). My primary research areas are ambient and cryogenic half-wave plate polarization modulators for SA and SO, NET forecasting for SO, and anti-reflection coatings for alumina and sapphire optics. I am entering the final year of my PhD and am looking for new opportunities in 2021! A cryogenic half-wave plate for POLARBEAR-2b I will present the design and laboratory evaluation of a cryogenic continuously rotating half-wave plate (CHWP) for POLARBEAR-2b (PB-2b), the second installment of the Simons Array. In order to suppress 1/f noise and improve large-angular-scale sensitivity, it employs a CHWP rotating at 2 Hz to modulate linear sky polarization and reject unpolarized atmospheric fluctuations. The CHWP has a 440 mm clear aperture diameter and is cooled to ~50 K in the PB-2b receiver cryostat. It consists of a low-friction superconducting magnetic bearing (SMB) and a low-torque synchronous electromagnetic motor, which together dissipate < 2 W. During cooldown, a grip-and-release mechanism centers the rotor to < 0.5 mm, and during continuous rotation, an incremental optical encoder measures the rotor angle with a noise level of ~0.1 urad/Hz. The PB-2b CHWP has been deployed to Chile and is expected to see first light in 2020-21.
Tucker Elleflot I received my PhD from UCSD where I worked with Brian Keating and Kam Arnold on the Simons Array. I moved to LBNL in January to work with Toki Suzuki on improving MHz frequency multiplexing of TESs for CMB experiments. DfMux Readout for CMB Experiments Digital Frequency Multiplexing (DfMux) is a technique that uses AC tones in the 1-5 MHz range to bias and readout sets of TES sensors. POLARBEAR-2 (PB-2), a CMB polarization experiment in northern Chile, observes with nearly 8,000 TES sensors (per cryogenic receiver) multiplexed using DfMux. Before PB-2 was deployed, measurements of detector parameters were performed and calibrated using a simplified model of stray impedances in the DfMux circuit. Future iterations of DfMux can be improved by employing low dynamic impedance SQUIDs operated at the detector bath temperature. In this talk, I will present details of the characterization of the TES sensors and DfMux circuit used by PB-2 as well as recent progress on DfMux for future CMB experiments.
Zachary Martinot I am a 4th year graduate student in Physics & Astronomy at the University of Pennsylvania working under James Aguirre and as a member of the HERA collaboration. Interferometric Visibililty Simulations for HERA Data Analysis The measurement/detection of the power spectrum of redshifted 21-cm emission is made challenging by the faintness of the cosmological signal compared to local sources of emission. While spectral structure should provide the lever with which to seperate the signal, the data reduction process required to exploit this lever is still in development, and a reliable detection will involve understanding and rejecting many possible contaminants. A robust measurement will thus involve rigourous modeling of the data and in this talk I will describe some of my work simulating interferometric visibilities in order to ensure that data reduction in the HERA experiment is validated against realistic known inputs, and to better understand possible systematics.
Kirit Karkare I'm a Grainger/KICP Fellow at the University of Chicago. I primarily work on:

- Developing on-chip spectrometers and the science case for mm-wave line intensity mapping (SuperSpec) - Instrumental systematics in degree-scale B-mode searches (BICEP/Keck, CMB-S4) https://scholar.harvard.edu/kkarkare

Cosmology with Next-Generation Millimeter-Wave Spectrometers Line intensity mapping (LIM) is a promising technique for efficiently measuring large-scale structure in 3D, without resolving individual sources. Future large-scale LIM experiments will push well beyond the redshift reach of planned galaxy surveys, providing a unique handle on key cosmological questions. I will discuss my work developing LIM at millimeter wavelengths - both on the instrumentation front with the SuperSpec on-chip spectrometer, and on forecasting the science reach of next-generation instruments.
Theodore Macioce I am a fifth-year graduate student in Sunil Golwala's group at Caltech. The first of my two ongoing projects is to develop realistic mock Sunyaev-Zel'dovich observations to forecast constraints on the motion of massive clusters; the other is to design a broadband antireflective coating for silicon vacuum windows as part of my NASA Space Technology Research Fellowship. Realistic Mock kSZ Observations to Forecast Constraints on Structure Formation and Cosmic Acceleration As millimeter and submillimeter-wavelength instrumentation improves, detections of the kinetic Sunyaev-Zel'dovich (kSZ) effect in massive galaxy clusters will become increasingly feasible. Measurements of the velocity field of the intracluster medium (ICM) via multi-band kSZ imaging will give a better understanding of clusters' energy budgets, testing, for example, hydrodynamical simulations that predict incomplete thermalization of infalling matter by accretion shocks. In addition, measurements of cluster peculiar velocities via the kSZ effect can be used constrain dark energy and deviations from general relativity on large scales, complementing constraints from upcoming surveys of large-scale structure. However, efforts to measure the ICM velocity with kSZ are complicated by the presence of the typically dominant thermal SZ signal and by other contaminants such as primary CMB anisotropies and emission from dusty star-forming galaxies. Predictions of the constraints attainable with kSZ measurements typically rely on Fisher matrix analyses, but these cannot give a fully accurate description of the degeneracies among the physical parameters describing the ICM. In this talk, I will discuss the software package I am developing to make realistic mock observations of the kSZ signal in clusters, complete with all relevant contaminants. Analysis of these mock observations will yield forecasts of constraints on ICM velocity together with other parameters, and the analysis tools developed will also be usable on real data. Finally, I will share some preliminary results from the analyses I have done thus far.
John Groh I'm a rising 7th year graduate student advised by Adrian Lee at UC Berkeley. I've focused mainly on bringing the Simons Array, and in particular its first telescope, to cosmology readiness. This has primarily involved development of the detector and readout systems and instrument field commissioning, but I've also contributed to the cryogenic design, optics testing, telescope mechanics, data acquisition, and offline analysis infrastructure. I'm targeting a graduation date at the end of the academic year, and am pursuing postdoctoral opportunities in experimental cosmology. Development and deployment of the Simons Array CMB polarization experiment As the field of ground-based CMB measurements moves toward CMB-S4, a handful of "Stage 3" experiments have arisen to both push the science forward and develop instrumentation and measurement techniques needed for the future. Among these is the Simons Array, which consists of three 2.5 meter offset Gregorian telescopes in the Chilean Atacama desert with observing bands centered at 90, 150, 220, and 280 GHz and is currently coming online. The Simons Array extends the heritage of the POLARBEAR experiment, and targets simultaneous sensitivity to inflation science from recombination B-modes and lensing science from CMB polarization. It will incorporate over 22,000 transition edge sensor bolometer detectors across three cryogenic receivers, and as such, has undertaken a technically ambitious program of instrumentation development which will help bridge the gap between published sensitivities and those required for CMB-S4. In this talk, I will discuss developments in the detector cryomechanical packaging and multiplexed readout which have enabled these large detector counts. I will also describe the integration of the first Simons Array telescope and its commissioning in Chile.
Tyler St Germaine I am a sixth-year graduate student at Harvard University, working with John Kovac and the BICEP/Keck CMB experiment. The bulk of my work with B/K focuses on direct measurements and end-to-end analysis of various systematics impacting our measurement of the tensor-to-scalar ratio, including temperature-to-polarization leakage from far-field beam mismatch. Beam Systematics in BICEP3 and the Keck Array CMB Polarimeters The BICEP/Keck (BK) experiment is a series of small-aperture refracting telescopes observing degree-scale Cosmic Microwave Background (CMB) polarization from the South Pole in search of a primordial B-mode signature. As a pair differencing experiment, an important systematic is the differential beam response between the co-located, orthogonally polarized detectors. We use high-fidelity, in-situ measurements of the beam response to estimate the temperature-to-polarization (T—>P) leakage in our latest data including all observations from 2010 through 2018 (BK18). In this talk, I present measured per-detector far-field beam maps and differential beam mismatch, and preliminary maps of the T—>P leakage present in the BK18 data set. I also discuss recent effort in linking together physical optics simulations and real beam measurements, in the context of validating the design simulated performance of the CMB-S4 Small Aperture Telescopes.
Tashalee Billings I am a 5th year PhD candidate at the University of Pennsylvania in the Department of Physics and Astronomy. My thesis advisor is Dr. James Aguirre. My projects include calibration and imaging techniques using CASA and using machine learning techniques to extract reionization parameters. Extracting Optical Depth from Simulated 21cm Data Upcoming measurements of the high-redshift 21 cm signal from the Epoch of Reionization (EoR) is a promising probe of cosmological information and parameters. One parameter in particular is the optical depth to the cosmic microwave background (CMB). Previous proposals for extracting this parameter from future 21 cm datasets used semi-numerical models to compare to power spectra and reconstruct the reionization history. A robust measurement of the optical depth would help eliminate it as a nuisance parameter from CMB data analysis, and provide tighter constraints on other cosmological parameters. We present here an application of convolution neural networks (CNNs) to mock images of the 21 cm signal from the EoR. We show that well-trained CNNs are able to recover optical depth values with typical error values of 3% or better. Furthermore, we show that this level of accuracy is achievable even when removing Fourier modes that are expected to be corrupted by bright foreground contamination of the 21 cm signal. We also perform automated hyperparameter optimization of the CNNs used in this analysis, and demonstrate that the accuracy of the results are not very sensitive to the precise architecture chosen.