The summer 2023 CMB-S4 workshop will focus on continuing the development of the broadest possible CMB-S4 science case, including in conjunction with other experiments and observatories. One key goal of the meeting will be to outline the second edition of the CMB-S4 Science Book. The meeting will be in person and remote, open to CMB-S4 members and non-members alike.
The meeting will include plenary science sessions on the following topics:
The workshop will include:
A discussion with our Equity, Diversity & Inclusion committee
A closed Junior member lunch and two JSAC plenary sessions (organized by Lindsey Bleem and the JSAC committee, jsac@cmb-s4.org)
Parallel work sessions on the second edition of the Science Book
A poster session
An evening EPO event
A tour of the CMB labs at SLAC & Stanford
Please familiarize yourself with the meeting code of conduct (https://sites.google.com/cmb-s4.org/cmb-s4/code-of-conduct) and respect it in all venues. On zoom, please set your name to "First Last (preferred pronouns)", and mute your microphone. To ask a question please raise your hand or post it to the chat.
For in-person attendees, the registration fee is 99 USD for senior members and 60 USD junior members. Links for registration can be found here: https://sites.google.com/cmb-s4.org/cmb-s4-summer2023/registration.
The registration fee includes venue costs, morning and afternoon coffee breaks, lunch, a reception, and other miscellaneous costs.
Rooms & Zooms:
Zoom lines for plenary, parallel 1, parallel 2, parallel 3, parallel 4.
Sign up sheet for (1) LSST camera tours, (2) SLAC lab tour, and (3) Stanford campus lab tours: Lab tours sign up
Link to meeting notes for plenary sessions.
LOC announcements for the day.
Welcome / Code of Conduct / Goals of Meeting.
Convener: Sara Simon (Fermilab)
Synthetic datasets generated from large-volume gravity-only simulations are an important tool in the calibration of cosmological analyses. Their creation often requires accurate inference of baryonic observables from the dark matter field. I will present an investigation on the effectiveness of a baryon pasting algorithm in providing precise estimations of three-dimensional gas thermodynamic properties based on gravity-only simulations. This analysis is performed using the Borg Cube, a pair of simulations originating from identical initial conditions, with one run evolved as a gravity-only simulation, and the other incorporating non-radiative hydrodynamics. Matching halos in both simulations enables comparisons of gas properties on an individual halo basis. This comparative analysis allows us to fit for the model parameters that yield the closest agreement between the gas properties in both runs. We find that the investigated algorithm, utilizing information solely from the gravity-only simulation, achieves few-percent accuracy in reproducing the median intracluster gas pressure and density, with a scatter of approximately 20%, for cluster-scale objects up to z=2. These results constitute a first step towards the implementation of a systematic baryon pasting pipeline for gravity-only simulations produced using the HACC solver, which will help provide state of the art multi-wavelength synthetic datasets for cluster cosmology.
Weak gravitational lensing of the Cosmic Microwave Background (CMB) and galaxies is a clean probe of the total matter in the universe as it probes the baryonic and dark matter. The matter that gravitationally lenses galaxies, which are at lower redshifts than the CMB, also contributes to the lensing of the CMB, but with different weighing. Resultant cross-correlation between the CMB weak lensing and weak lensing of galaxies offers a way to put robust constraints on the cosmological and astrophysical parameters that are immune to certain systematics affecting either survey. We measure the angular power spectrum between the weak lensing convergence map provided by the Atacama Cosmology Telescope (Data Release-4 data) and the weak lensing shear map by Dark Energy Survey (Year-3 data). We use the angular power spectrum measurement, which passes specific null tests, to constrain the density of the matter and the amplitude of the fluctuations in the matter distribution. In the modelling, we consider and marginalise over nuisance parameters of the photometric uncertainty, multiplicative shear bias and intrinsic alignment of galaxies.
Kavli 3rd floor auditorium & Parallel #4 zoom line
Three talks and discussion of the new inflation chapter of the science book.
Convener: Simone Ferraro (LBNL). Three talks and discussion of the new LSS chapter of the science book.
Review of the collaboration values and an overview of next steps
Overview of the scientific values draft and panel discussion
There are two 30-minute tours (5-5:30p and 5:30-6p). We will depart Kavli 51 at 4:40p and 5:10p for each tour. It is a 15-20 minute walk from Kavli 51 to IR2.
Sign up sheet: https://docs.google.com/spreadsheets/d/1wCNRpDa04yKX7BOcd_PepcD1xPH6lvHcMmVdp01zI7s/edit#gid=0
Both public and CMB-S4 participants should register at the link below.
relativistic SZ; Joint ymap + cluster; kSZ 2pt and 4pt; rotational kSZ; ultra high-z clusters/proto clusters; ymap cross-correlations (partly covered in Fiona McCarthy's talk)
Sign up sheet: https://docs.google.com/spreadsheets/d/1wCNRpDa04yKX7BOcd_PepcD1xPH6lvHcMmVdp01zI7s/edit#gid=0
Convener: Marius Millea (UC Davis)
The ΛCDM cosmological model has been very successful, but cosmological data makes it clear that extensions are still highly motivated. As the quality of CMB and LSS survey data increases, higher-dimensional model parameter spaces are necessary to make these extensions beyond the concordance model. Performing parameter inference in high dimensions is extremely challenging and is often only feasible when gradient information is available. Einstein-Boltzmann (E-B) solvers are the backbone of cosmological models of the CMB and LSS, and state-of-the-art codes do not provide gradient information. We present Bolt.jl, the first differentiable E-B solver. Bolt automatically supplies gradients with respect to cosmological parameters when the Boltzmann equations are solved. Bolt's use of Julia also lowers the barrier between equations and source code, assisting model builders to make changes fast. We compare Bolt to the standard Boltzmann codes CLASS and CAMB at the level of the matter power spectrum and perturbations. Bolt also makes it possible to account for more flexible model extensions with deep neural networks and can account for unknown physics at the level of differential equation models.
Convenor: Darcy Barron (New Mexico)
I present the low ell BB groups r estimate pipeline on the South Pole Deep Patch, and discuss the map-level iterative lensing reconstruction software on the curved sky, delensalot.
The thermal Sunyaev-Zel'dovich (tSZ) effect is a spectral distortion of the cosmic microwave background (CMB) resulting from inverse Compton scattering of CMB photons with electrons in the medium of galaxy clusters. The spectrum of the tSZ effect is typically calculated assuming the spectrum of the CMB is a blackbody. However, energy or photon number injection at any epoch after photon creation processes become inefficient will distort the blackbody, potentially leading to a chemical potential or μ-distortion for early injection. These primordial spectral distortions will therefore introduce a change in the tSZ effect, effectively a distortion of a distortion. While this effect is small for an individual cluster's spectrum, upcoming and proposed CMB surveys expect to detect tens of thousands of clusters with the tSZ effect. We forecast constraints on the μ-distortion monopole from the distortion of the tSZ spectrum of clusters measured by CMB surveys.
CMB-S4 will be able to detect or reject the unique pattern of rotation of the polarisation of the CMB radiation induced by string-like topological defects in ultralight axion fields. If detected by CMB-S4, future concepts such as CMB-HD will be able to extract the non-Gaussian information in this rotation pattern to measure the axion-photon coupling, which carries crucial information about the smallest unit of charge in the theory beyond the Standard Model.
The patchiness in the free-electron distribution during reionization affects the statistics of CMB, leading to patchy B-mode polarization and the kSZ temperature anisotropies. As Stage-4 CMB experiments like CMB-S4 aim to detect the primordial B-mode polarization at large scales and small-scale kSZ temperature anisotropies, this necessitates accurate modelling of patchy reionization. To address this, we have developed a CMB anisotropy evaluation framework, using the photon conserving semi-numerical reionization scheme SCRIPT, that can self-consistently predict CMB observables related to reionization. Our analysis indicates that neglecting the contribution from patchy reionization while modelling the CMB B-mode can bias the tensor-to-scalar power spectrum ratio r by up to 0.56σ. However, employing an EB minimum variance estimator, CMB-S4 might be able to detect the patchy B-mode signal with ≥ 2.3σ confidence level, which can reach ~5.7σ for extreme reionization scenarios, which is an essential step towards unbiased measurement of r. The reionization can also be constrained using kSZ spectrum shape over a range of multipoles which, in turn, can be enabled via techniques like Cross-ILC. We show that using CMB-S4’s kSZ and LiteBIRD's 𝜏 measurements, we can unprecedentedly constrain the reionization duration within a range ∼ 0.21 and the patchy reionization B-mode signal at multipole of 200 within ∼1nK2. These results highlight CMB-S4's potential in unravelling the details of reionization era and as a consequence improving our knowledge of the early universe
In this talk, I will present how atomic dark matter (ADM) can bring concordance to the cosmological parameters measured by different observations. In the ADM model, a fraction of the dark matter is dark protons and dark electrons, that interact with dark photons. If the dark photon temperature today is ~ 0.6 K (about what one expects for light relics that decouple at a very early time), we find that the current data allow 10% or more of the dark matter to be ADM. At such a low temperature, the dark photons only provide weak pressure support to the dark baryons, leading to consequences compatible with the current CMB data but that still slightly suppress the matter power at small scales, easing the S8 tension. If this is the cause for the S8 tension, future CMB experiments, like CMB-S4, will be able to detect the amount of ADM, mostly via the CMB lensing effect.
Meet outside Kavli building before/at 11:10a to walk over to Marguerite bus stop to take the shuttle to Stanford campus.
Sign up sheet: https://docs.google.com/spreadsheets/d/1wCNRpDa04yKX7BOcd_PepcD1xPH6lvHcMmVdp01zI7s/edit#gid=0