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There is still a great deal to be learnt from CMB measurements. I will give an overview of science that the community hope to do with new data, from testing initial conditions of the universe to probing the dark sector and better understanding cosmic reionization and galaxy evolution. I will also describe some of the rich millimeter-wave science that can be done with these datasets, including time-domain astrophysics.
The measurement of cosmic microwave background (CMB) from space is ideal for the entire sky access and broad observational frequency coverage. The past CMB satellite missions, COBE, WMAP, and Planck, play crucial roles in establishing modern cosmology. Now next-generation satellite missions will aim for even more demanding scientific goals, and the various corresponding requirements on the mission become stringent. In this talk, we will review the achievements and lessons learned from the past CMB space missions. With these heritages in the community, I will try projecting the upcoming challenges and make a bridge to the rest of the talks in this workshop.
The temperature and polarisation anisotropies of the CMB offer our most direct view of the early universe and their observation has, and continues to be, critical in constraining early-universe models. In this talk, I will review the key ways that the CMB constrains the properties of the primordial fluctuations, which were likely produced during an early period of cosmological inflation, and the implications of current constraints for models of inflation. I will also discuss some of the challenges faced in these measurements and review the prospects of forthcoming CMB experiments to advance our understanding of inflation.
The cosmic microwave background (CMB) has played a foundational role in the establishment of the standard model of cosmology. Driven by significant technological advances, future CMB experiments aim to make dramatic strides in our understanding of the universe. Some of our most ambitious efforts, however, run the risk of being hamstrung by poorly-understood instrument effects, systematics. A commonly-discussed class of systematic effects relate to our optical systems in one way or another. In this talk, I will review some of the challenges that past CMB missions have faced and highlight lessons learned. I will present algorithms that have been developed to help us understand the impact of optical non-idealities and summarize key results from the applications of those. I will conclude by reviewing some of the challenging calibration requirements for upcoming missions and discuss how the community can work towards meeting those.
The tantalizing science reach of CMB observations has driven remarkable innovation in superconducting detectors. Roughly two decades ago, CMB focal planes consisted of a few individually assembled detection channels. By use of modern micro-fabrication equipment and improved microwave design tools, today’s imaging focal planes consist of multiple-tiled, large-format wafers. A wafer may contain hundreds of spatial pixels, each an integrated superconducting circuit capable of polarization diplexing and power sensing in multiple frequency channels. In this talk I will present the current CMB focal plane landscape, including the various optical coupling, sensing, and multiplexing techniques in use. Attention will be given to the formidable scaling challenge of near-term ground-based observations. Lastly, I will offer my opinion on what future focal plane developments would be most impactful for future ground and space-based CMB instruments.
Planck set new standards for calibration of CMB experiments. That was hard. Calibration of future experiments, which will require map noise levels of nanokelvin or better, will be much harder. I will discuss lessons learned in calibrating Planck for future experiments.
Observations of the cosmic microwave background provide us with a unique window on the early Universe, and great new insights are expected from the next generation of dedicated ground and space telescopes. While probing the elusive inflationary epoch may be the most sought-after objective of those missions, they will also shed some light on another poorly-known era of the early Universe: the reionisation era. In this talk, after recalling the essentials of the reionisation epoch, I will review the methodologies used and state-of-the-art constraints derived from current data. I will then focus on the future of reionisation studies, detailing forecasts and new probes remaining to be exploited.
The interaction between cosmology and particle physics has always been very fruitful. Cosmological observations provide a powerful mean to test particle physics theories, and to measure the properties of existing particles like neutrinos. At the same time, the solution to two long-standing mysteries in cosmology - the origin of dark matter and dark energy - might lie in physics beyond the standard model of particles. In my talk I will review what we have learned from cosmological observations of the recent past, especially Planck's, on light relics (including neutrinos) and dark matter, and discuss prospects for future experiments.
In the recent years it has become clear how the contamination coming from Galactic and extra-Galactic emissions represents one of the main limiting factor for any new science achievable with Cosmic Microwave Background observations. Having a thorough understanding of the foreground properties is therefore fundamental in order to achieve a reliable reconstruction of the clean CMB signal and to constrain its cosmological properties. In this talk I will review the current status of knowledge and characterization of foregrounds, focusing in particular Galactic polarized emission. I will summarize the main results from the latest analysis of available multi-frequency data, highlighting which are the main limitations in our current models and how we can overcome them in view of future CMB experiments.
Beyond the significant legacy of the ESA's Planck mission, the cosmic microwave background (CMB) radiation carries much more information that remains to be exploited in the coming decades. Next-generation CMB experiments of unprecedented sensitivity are being planned to extract and interpret new cosmological observables out of future CMB data. Among these new, yet undetected, cosmological observables is the primary CMB B-mode polarization signal, but also secondary distortions to CMB anisotropies caused by the cosmic web, such as the relativistic SZ effect. A common aspect of these new cosmological signals is their very faint signature, furthermore obscured by intense astrophysical foreground emissions, which makes their recovery much more sensitive to foreground mismodeling, while the exact spectral properties of the foregrounds are also poorly known at the sensitivity levels required for these signals. I will discuss the problem of foregrounds and component separation for the search for such faint cosmological signals, and emphasize specific challenges in this context: foreground mismodeling, foreground spectral distortions, and spectral degeneracies versus frequency coverage. I will also present some recent developments in component separation which rely on statistical moment expansion of the foreground emission, and show how this offers an interesting avenue to overcome these new challenges.
All data analysis for an experiment is, at least implicitly, integrated. It all aims to distill scientific knowledge from a common data set. Whether the architects of the data reduction pipelines make the integration explicit is influenced by external constraints (processing power, availability of accurate models) and design strategy (highly modular or tightly coupled). Regardless of the case, need for faithful simulations of the deliverable data set often lead to end-to-end simulations that end up integrating all of the analysis modules together. In my talk I will review the data reduction and end-to-end simulation strategies employed in the production of Planck public data releases, discuss the importance of integrating simulations into early development work and make connections with the next generation CMB experiments that are right now designing their data analysis pipelines.
We are expecting high-precision observations from upcoming CMB surveys, such as the Simons Observatory, CMB-S4, and LiteBIRD, as well as from future surveys of the large-scale structure, such as Euclid, Rubin LSST, SPHEREx, PSF, and Roman Space Telescope. Most of the observables from these independent surveys will be correlated due to their large overlaps in sky and redshift coverage. Joint analysis of CMB and LSS surveys will allow us to increase the overall signal, break degeneracies, mitigate systematics, and potentially probe new science. In this talk, I will discuss the possible paths to simulate correlated CMB and LSS observables to achieve these scientific goals.
CMB spectral distortion measurements are going to be challenging and multiple groups are considering experimental approaches that might allow us to target these small signals in the near and distant future. In my talk I will give a brief overview of all the ongoing and planned CMB spectrometer concepts and initiatives trying in particular to highlight synergies and individual strengths. I will then address the question about what is still needed for us to take major steps forward and how we might start to get organized with this ambitious goal.
Ground-based CMB experiments are evolving from fielding thousands of detectors on telescope(s) of a single size at a single observing site in the last decade (eg. the Atacama Cosmology Telescope, BICEP/Keck, Polarbear/Simons Array, and South Pole Telescope), through tens of thousands of detectors on telescopes of multiple sizes at a single observing site in this decade (the South Pole Observatory and Simons Observatory), culminating in hundreds of thousands of detectors on telescopes of multiple apertures at multiple observing sites in the next decade (CMB-S4). In this talk I will describe the scientific, technical, and organizational drivers and challenges in this evolution.