Global End-to-End Analysis at All Frequencies

31 Aug 2026, 09:00 → 18 Sept 2026, 19:00 Europe/Stockholm

Albano Building 3

Katrine Alice Glasscock (University of Oslo), Mathew Galloway (University of Oslo)

 

Venue

Nordita, Stockholm, Sweden

Albano Building 3

Hannes Alfvéns väg 12, 10691 Stockholm, Sweden

 Go to map

---

Scope

Current and future astronomical experiments face unprecedented challenges in their calibration, systematics and modelling, as well as the interplay between them. The Cosmoglobe initiative aims to tackle these challenges head on, using the power of Bayesian end-to-end iterative analysis. By combining datasets from the radio, millimeter, infrared, visible, and all the way to the UV and X-ray ranges of the electromagnetic spectrum, we can jointly constrain cosmological parameters such as the tensor-to-scalar ratio, the optical depth to reionization, cosmic birefringence, the Cosmic Infrared Background and the structure of emissions from our own Galaxy. The meeting will focus on bringing together researchers working across modelling, simulation, and data analysis at all levels. It aims to foster discussion and collaboration within the community.

---

Themes and preliminary program schedule

NEWS: A detailed schedule for week three has been released here.

-------

Week 1 | Aug 31 - Sep 4 | CMB anisotropies workshop

[Detailed schedule week 1

• Tensor-to-scalar ratio /  The microwave sky / Systematics mitigation 
• E.g. HFI, LiteBIRD, SO, and related experiments
• Around 2 hours of presentations per day with lots of time allocated for discussions and active work sessions
• Lunch and coffee will be provided

 

Week 2 | Sep 7 - Sep 11 | Cosmoglobe conference 2026 

[Detailed schedule week 2] 

The topic of the conference is large scale science and data analysis across the entire spectrum. We therefore welcome and encourage conference contributions from anyone whose work fits into this broad category, regardless of whether you are already working directly with the Cosmoglobe team.

• Global end-to-end analysis at all frequencies from radio to UV and X-ray
• E.g. SKA and precursors, HFI, LiteBIRD, SO, C-BASS, QUIJOTE, DIRBE, AKARI, FIRAS, IRAS, Fermi, eROSITA, etc. 
• Submitted and invited talks on all things related to global sky modelling 
• Lunch and coffee and a conference dinner (tentatively Sept. 8th) will be provided
• We welcome contributions from early career researchers!

 

Week 3 | Sep 14 - Sep 18 | Global sky modelling workshop 

[Detailed schedule week 3]

• Infrared dust modelling / CMB spectral distortions 
• E.g. DIRBE, AKARI, FIRAS, IRAS, and related experiments
• Around 2 hours of presentations per day with lots of time allocated for discussions and active work sessions
• Lunch and coffee will be provided

 

---

Speakers

The current list of confirmed participants can be found here. 

NEWS: The speaker list can be found here.

---

Accommodation / Housing support

[Registration closed] There is limited housing available through Biz Apartments, which will be given preferentially to early career researchers who would not be able to attend otherwise. Please indicate in the registration form if you would like to be considered for housing support or whether you will arrange your own accommodation.

It is also possible to book rooms yourself directly via Biz Apartments website if you prefer to stay at the conference housing. Note, Biz Apartments is ~40 minutes in public transport away from Nordita, there are other hotels closer to Nordita e.g. Best Western at 108. 

---

Travel support

[Registration closed] There is a limited amount of travel support available, which will be given preferentially to early career researchers who would not be able to attend otherwise. If this applies to you, please fill out that section of the registration form.

---

Application/Registration

[Registration closed] Registration to be considered for on-site participation will close May 17! Registrants will receive a participation confirmation from the organizers after this date.

Note, you will receive an email with confirmation of completion of the application form after submission. If you don't receive this email please try again from a different browser or contact Nordita via event@nordita.org. 

---

VISA / Certificate of Attendance

To check whether you need a VISA please access the Schengen Visa Info site as soon as possible, note that VISAs can take >1 month to obtain. 

If you require an invitation letter for the conference/workshop, please send an email to cosmoglobe-contact [at] astro.uio.no with your

• Name, surname, and date of birth
• Passport number, country of issue, and expiration date

 

---

Sponsored by:

OpenHFI  - RCN Young Research Talents agreement no. 360024 - PI M. Galloway - 2026-2030

LiteBIRD-Norway - RCN FRIPRO agreement No. 351037 – PI U. Fuskeland - 2025-2033

Origins - EU ERC-StG agreement No. 101165647 – PI D. Watts - 2025-2030

Commander - EU ERC-AdG agreement No. 101141621 – PI H. K. Eriksen - 2024-2029

CosmoglobeHD - RCN Young Research Talents agreement no. 344934 – PI D. Watts - 2024-2027

Monday 31 August

09:00 Registration

Participant registration on the 6th floor of the Nordita building

09:30 Fika (Coffee and buns)

Join us for a morning "fika" on the 6th floor of the Nordita building

Welcome: Welcome and logistics

Conveners: Katrine Alice Glasscock (University of Oslo), Mathew Galloway (University of Oslo)

Welcome + Logistics

Welcome week 2

Welcome week 3

1 Cosmoglobe overview

Speaker: Ingunn Kathrine Wehus (University of Oslo)

11:00 Coffee

2 OpenHFI

OpenHFI is a new initiative within Cosmoglobe to implement an end-to-end Bayesian re-analysis pipeline for Planck HFI. Building on our successful experience with LFI, WMAP and DIRBE, we aim to construct a complete data model for the HFI sky and instrument, and then implement steps within commander to sample them. In this talk, I will discuss the status of this work, currently known issues and what the next steps will be. It will serve as a basic introduction for those who are interested in getting involved during the subsequent workshop sessions.

Speaker: Mathew Galloway (University of Oslo)

OpenHFI

3 Commander4: Status and future

The Cosmoglobe collaboration has over the last decade developed and utilized the Commander3 Fortran codebase for global Bayesian CMB analysis. Commander4 is a ground-up rewrite of this algorithm with the necessary performance and scalability to analyze modern (>10TB) CMB datasets. While less mature than Commander3, it has now matured to the state of being able to perform preliminary analysis of datasets like SO and LiteBIRD simulations.

Speaker: Jonas Lunde (University of Oslo)

WG: Commander4

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

WG: Planck HFI

Conveners: Mathew Galloway (University of Oslo), Raelyn Sullivan (University of Oslo)

13:00 Lunch

4 Challenges in Planck HFI data analysis

Accurate measurements of the Cosmic Microwave Background (CMB) with Planck’s High Frequency Instrument (HFI) required unprecedented control of systematic effects arising from the instrument and its environment. Several effects—including analogue-to-digital converter (ADC) nonlinearities, detector time constants, and signals induced by cosmic rays—were not anticipated before launch. Addressing them required intensive modelling based on flight data and the development of innovative data-processing techniques. These lessons are relevant to future satellite missions such as LiteBIRD, which aims to detect the faint B-mode polarisation signal. I will present the main challenges encountered in the Planck data analysis and the methods developed to address them.

Speaker: Guillaume Patanchon (U. Paris La Cite)

WG: Planck HFI

Conveners: Mathew Galloway (University of Oslo), Raelyn Sullivan (University of Oslo)

WG: Simons Observatory

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

16:00 Coffee

WG: Planck HFI

Conveners: Mathew Galloway (University of Oslo), Raelyn Sullivan (University of Oslo)

WG: Simons Observatory

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

17:30 Socialising at arcade and bar (self-funded)

We will go to this arcade-bar https://heysthlm.se/ for a social afternoon

Tuesday 1 September

09:30 Coffee

5 Tutorial: Gibbs sampling (Part A)

Speaker: Hans Kristian Eriksen (University of Oslo)

11:00 Coffee

6 Challenges in Planck HFI data analysis

Accurate measurements of the Cosmic Microwave Background (CMB) with Planck’s High Frequency Instrument (HFI) required unprecedented control of systematic effects arising from the instrument and its environment. Several effects—including analogue-to-digital converter (ADC) nonlinearities, detector time constants, and signals induced by cosmic rays—were not anticipated before launch. Addressing them required intensive modelling based on flight data and the development of innovative data-processing techniques. These lessons are relevant to future satellite missions such as LiteBIRD, which aims to detect the faint B-mode polarisation signal. I will present the main challenges encountered in the Planck data analysis and the methods developed to address them.

Speaker: Guillaume Patanchon (U. Paris La Cite)

WG: Commander4

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

7 Challenges in Planck HFI data analysis

Accurate measurements of the Cosmic Microwave Background (CMB) with Planck’s High Frequency Instrument (HFI) required unprecedented control of systematic effects arising from the instrument and its environment. Several effects—including analogue-to-digital converter (ADC) nonlinearities, detector time constants, and signals induced by cosmic rays—were not anticipated before launch. Addressing them required intensive modelling based on flight data and the development of innovative data-processing techniques. These lessons are relevant to future satellite missions such as LiteBIRD, which aims to detect the faint B-mode polarisation signal. I will present the main challenges encountered in the Planck data analysis and the methods developed to address them.

Speaker: Guillaume Patanchon (U. Paris La Cite)

WG: Planck HFI

Conveners: Mathew Galloway (University of Oslo), Raelyn Sullivan (University of Oslo)

13:00 Lunch

8 An efficient method to compute beam convolution at the map level

We present a map-based method for beam convolution using spin-mapmaking, enabling efficient simulation and propagation of systematics from non-ideal beams. Validated against litebird_sim TOD 4π convolution, our approach is significantly faster while retaining numerical precision.

Speaker: Camille Demay (University of Trento, University of Ferrara)

9 Millimeter and submillimeter characterization of polymers used for infrared filters in high sensitivity microwave telescopes

Speaker: Rustam Balafandiev (University of Iceland)

WG: Planck HFI

Conveners: Mathew Galloway (University of Oslo), Raelyn Sullivan (University of Oslo)

WG: Simons Observatory

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

16:00 Coffee

WG: Planck HFI

Conveners: Mathew Galloway (University of Oslo), Raelyn Sullivan (University of Oslo)

WG: Simons Observatory

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

Wednesday 2 September

09:30 Coffee

10 Tutorial: Gibbs sampling (Part B)

Speaker: Hans Kristian Eriksen (University of Oslo)

10:45 Coffee

WG: Commander4

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

WG: LiteBIRD

Conveners: Ingunn Kathrine Wehus (University of Oslo), Reijo Keskitalo (University of Oslo), Unni Fuskeland (University of Oslo)

13:00 Lunch

WG: Planck HFI

Conveners: Mathew Galloway (University of Oslo), Raelyn Sullivan (University of Oslo)

WG: Simons Observatory

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

16:00 Workshop picture!

16:30 Reception (Fingerfood and drinks)

Thursday 3 September

09:30 Coffee

11 Studying the optical systematics of CMB Telescopes using MeepSAT FDTD code

In a CMB Telescope, no single optical modeling technique captures all of the systematics (such as stray lights from scattering/reflection/thermal emission, inclusion of complex absorbers/ARCs structures in full scale telescope simulation etc). Geometrical Optics (GO), Physical Optics (PO), and Method of Moments (MoM) each rely on approximations that leave parts of the problem inaccessible. I will present MeepSAT (MEEP Simulation and Analysis for Telescopes), a open source full-wave, time-domain 2D simulation framework for CMB Telescopes and an addition to the existing set of techniques that will help us closing the gaps in understanding some of these systematics.

Speaker: Ashesh Abhisek Khatua (University of Iceland)

WG: Commander4

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

WG: LiteBIRD

Conveners: Ingunn Kathrine Wehus (University of Oslo), Reijo Keskitalo (University of Oslo), Unni Fuskeland (University of Oslo)

11:00 Coffee

WG: Commander4

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

WG: LiteBIRD

Conveners: Ingunn Kathrine Wehus (University of Oslo), Reijo Keskitalo (University of Oslo), Unni Fuskeland (University of Oslo)

13:00 Lunch

Informal parallels

16:00 Coffee

Informal parallels

16:30 Coffee

Friday 4 September

09:30 Coffee

WG: Commander4: and SO

Conveners: Jonas Lunde (University of Oslo), Leo Bianchi (University of Oslo)

WG: Planck HFI

Conveners: Mathew Galloway (University of Oslo), Raelyn Sullivan (University of Oslo)

11:00 Coffee

WG: Commander4: and SO

WG: Planck HFI

Summaries/presentations from the working groups: Sub-project aims, progress and future work

12:45 Closing statements

13:00 Lunch

Monday 7 September

09:00 Registration and fika (coffee and buns)

Participant registration on the 6th floor of the Nordita building (same place as the coffee)

Welcome

Conveners: Katrine Alice Glasscock (University of Oslo), Mathew Galloway (University of Oslo)

Welcome + Logistics

Welcome week 2

Welcome week 3

12 Cosmoglobe - mapping the sky from the Milky Way to the Big Bang

Speaker: Ingunn Kathrine Wehus (University of Oslo)

13 Cosmoglobe DIRBE DR2 results

In this talk, I will give an overview of the Cosmoglobe DR2 analysis, in particular the application of global end-to-end processing to COBE/DIRBE data. As an absolutely calibrated instrument, DIRBE is uniquely sensitive to the cosmic infrared background monopole from 1 micron to 240 microns. I will give an overview of the improved time-ordered data processing that results in maps with significantly reduced zodiacal dust contamination, as well as improved CIB monopole values consistent with theoretical predictions from integrated galactic light models.

Speaker: Duncan Watts

14 Zodiacal light modelling in Cosmoglobe DR2

I will present an improved zodiacal light (ZL) model for COBE-DIRBE derived through global Bayesian analysis within the Cosmoglobe Data Release 2 framework. The parametric form of the ZL model is inspired by the original DIRBE model by Kelsall et al. (K98), but the specific best-fit parameter values are re-derived using the combination of DIRBE Calibrated Individual Observations, Planck HFI sky maps, and WISE and Gaia compact object catalogs.

Speaker: Angela Bonato (University of Oslo)

11:00 Coffee

15 The Simons Observatory: Early Data from the Small Aperture Telescopes

The Simons Observatory (SO) is a cosmic microwave background survey experiment located in the Atacama Desert in Chile. SO consists of multiple small-aperture telescopes (SATs) carrying out a focused small-area survey, as well as a large-aperture telescope (LAT) conducting a wide-field, high-resolution survey. The SATs are specifically designed to target primordial B-mode polarization sourced by tensor perturbations in the early Universe. The SO mid-frequency SATs saw first light in late 2023, and have since been conducting initial science observations. I will present the current status of and early data from the SATs and the SAT data processing pipeline.

Speaker: Erik Rosenberg (University of Manchester)

16 Polarization from Planck 857GHz data

Planck survey may have completed in 2013 but the data analysis continues. I will give an overview of a recent analysis of the 857GHz channel making use of the slight residual polarization sensitivity of the nominally unpolarized spiderweb bolometers.

Speaker: Reijo Keskitalo (University of Oslo)

17 New State-of-the-Art Constraints on Cosmic Birefringence from OpenHFI Maps

Cosmic birefringence ($\text{CB}$)—the in-vacuum rotation of the linear polarization plane of photons—presents a compelling hint of parity-violating physics beyond the Standard Model. Recent analyses have brought this effect to the forefront of $\text{CMB}$ cosmology: Planck PR4 data yielded an estimate of $\beta = 0.3^\circ \pm 0.05^\circ \text{ (stat)} \pm 0.28^\circ \text{ (sys)}$, while the Atacama Cosmology Telescope ($\text{ACT}$) DR6 independently found $\beta = 0.2^\circ \pm 0.07^\circ$. Together, their combined significance stands at $4.6\sigma$, hovering just below the definitive discovery threshold.The primary bottleneck in confirming or ruling out this signal lies in the meticulous control of instrumental systematic effects, particularly polarization angle calibrations. In this talk, we discuss how to leverage the OpenHFI end-to-end $\text{CMB}$ maps, which benefit from the comprehensive systematic mitigation framework of the Cosmoglobe endeavor. By applying different $TB$ and $EB$ power spectra-based estimators to these freshly processed Planck HFI products, we demonstrate how to tightly constrain the cosmic birefringence angle. Finally, we show how this enhanced control over systematic contaminants impacts the total error budget and explore the potential of these maps to push the current detection significance past the $5\sigma$ threshold.

Speaker: Simone Paradiso (INAF-OAS)

18 Avenues for improving dust foreground modeling with stellar polarization

The alignment of dust grains with the Galactic magnetic field gives rise to polarized dust emission and polarization of starlight in the optical/NIR. This results in a tight correlation between the polarization angles of distant stars and that of dust emission. I will give an overview of recent works that use stellar polarimetry and stellar distances to inform foreground modeling, including disentangling different emitting regions along the line of sight, and quantifying the effects of frequency decorrelation. I will discuss how the tight correlation between the Stokes parameters of dust emission and starlight polarization found by Planck can be used to construct higher angular resolution polarized emission templates than are presently available. Finallly, I will present new results that suggest that the optical-FIR polarization correlation varies over the sky and discuss implications for foreground models and for deducing the microphysical properties of dust in the diffuse ISM.

Speaker: Gina Panopoulou (Chalmers University of Technology)

13:00 Lunch

19 Constraining Low-Frequency Foregrounds with CHIPASS

One of the greatest challenges faced by CMB experiments is the detailed modeling and subtraction of Galactic foregrounds. Observations across multiple frequencies are necessary to constrain the synchrotron SED as well as to disentangle it from other foregrounds such as free-free emission. CHIPASS, a continuum reprocessing of the HI Parkes All Sky Survey (HIPASS) with an angular resolution of 14.4 arcmin, offers a unique window on the synchrotron foreground with the potential to constrain spectral index variations and curvature as well as to reveal small-scale structures. The Cosmoglobe collaboration has begun integrating in raw time-ordered data from CHIPASS in combination with other low-frequency datasets such as Haslam, S-PASS, and others. Here we present a preliminary look at the re-analyzed CHIPASS data.

Speaker: Danielle Sponseller (Chalmers University of Technology)

20 All-Sky Modelling of Galactic Emission at Radio-Microwave Frequencies

I will begin by introducing the C-BASS survey and its role as a key low-frequency radio dataset for Galactic foreground studies, before presenting a new all-sky model of low-frequency diffuse Galactic emission describing the regime where synchrotron, free-free, and spinning dust emission dominate. The model extends the Planck 2015 diffuse component-separation by incorporating more recent radio and microwave surveys. We fit 35 full- and partial-sky maps, at 1 degree resolution, including S-PASS (2.30 GHz), C-BASS (4.76 GHz), and QUIJOTE (10-20 GHz), together with reprocessed WMAP and Planck LFI data from the Cosmoglobe collaboration and Planck HFI channels. Using a Bayesian parametric approach with Commander, we derive spatially varying amplitude and spectral parameter maps for the dominant low-frequency foreground components in total intensity. The main products of this work are: (i) a new full-sky synchrotron amplitude and spectral index solution, (ii) an all-sky characterisation of spinning dust emission based on a single-component log-normal spectral model, including peak frequency and width, and (iii) a new all-sky reconstruction at 4.76 GHz providing a tracer of diffuse synchrotron emission with reduced systematics relative to the Haslam map (408 MHz). These products describe the transition between radio and microwave emission and provide a new reference for foreground modelling and sky-simulation applications.

Speaker: Gabriel Hoerning (University of Manchester)

21 Diffuse Polarised Synchrotron Reconstruction with GNILC On Latest Planck Data

Primordial gravitational waves from inflation imprint a faint B-mode polarisation in the Cosmic Microwave Background (CMB), but this signal is strongly obscured by Galactic foregrounds. Detecting CMB B-modes therefore requires accurate characterisation of foreground polarisation, dominated by synchrotron emission at low frequencies. To address this, we apply the Generalised Needlet Internal Linear Combination (GNILC) method to Planck PR4 data (30–353 GHz), producing clean, low-noise synchrotron polarisation maps at low frequencies without relying on prior models. GNILC employs needlets for localised processing in both pixel and harmonic space, a principal component analysis to retain modes above noise, and a multi-frequency weighting scheme orthogonal to the CMB spectrum to deproject the CMB. Radio source inpainting prior to GNILC processing further reduces contamination in the resulting maps. The method is validated on Planck NPIPE simulations, and PR4-derived GNILC weights are applied to NPIPE noise, systematics and CMB realizations to provide robust residual error characterisation of the GNILC PR4 maps. The final GNILC PR4 maps at 30 and 44 GHz provide reliable full-sky diffuse polarised synchrotron templates at uniform 34' angular resolution, as demonstrated by map inspection, residual error estimates, power spectra, and low correlation with Planck cleaned CMB maps. Exploiting the frequency scaling between our 30 and 44 GHz GNILC PR4 maps, we derive a first-of-its-kind 48-pixel full sky synchrotron spectral index map from Planck-only data, with the associated uncertainty.

Speaker: Mohammad Ishaque Khan (Instituto de Fisica de Cantabria (IFCA, CSIC-UC))

22 The Canadian Galactic Emission Mapper: Overview and Early Observations

Gravitational waves from inflation may have left a detectable signature in the parity-odd, “B-mode” component of the polarization of the Cosmic Microwave Background (CMB). Detecting B-modes in the CMB would be “smoking gun” evidence for inflation and would probe some of the highest-energy physics in the known universe. However, current experiments have placed stringent upper limits on B-modes. If B-modes are present in the CMB, the signal is extremely faint and is dominated by polarized Galactic foregrounds at all frequencies. It is therefore essential to map polarized foregrounds with high precision to enable a detection of CMB B-modes. The Canadian Galactic Emission Mapper (CGEM) is a new 4m single-dish radio telescope at the Dominion Radio Astrophysical Observatory that is mapping polarized Galactic synchrotron emission from 8-10GHz over the Northern sky, with a planned counterpart in the Southern hemisphere. CGEM will greatly improve models of polarized CMB foregrounds and will hence be an important aid to current and future B-mode experiments. In this talk, I’ll give an overview of CGEM. I’ll then describe how we designed this purpose-built instrument to measure the sky with minimal polarization systematics, highlighting in particular the polarization purity of the optical design. I’ll also showcase early observations from a pathfinder version of CGEM, deployed in February 2025, which has been mapping the sky since. These data already show immense promise for future science with CGEM.

Speaker: Joshua MacEachern (National Research Council of Canada, Dominion Radio Astrophysical Observatory)

16:00 Coffee

23 From Few Simulations to Trustworthy Posteriors: Scattering-Covariance Latent Spaces for Simulation Augmentation and Interpretable SBI in CMB Cosmology

Modern CMB analyses face a statistical bottleneck: the data are high-dimensional, non-Gaussian, affected by complex systematics, and often have intractable likelihoods, while the end-to-end simulations needed for Monte Carlo validation or Simulation-Based Inference are prohibitively expensive. I will present a unified framework based on the Scattering Covariance: an interpretable, physics-informed analogue of a convolutional neural network, built from fixed oriented wavelets, nonlinearities, and cross-scale/cross-channel covariance statistics. In recent work ([Campeti et al., A&A, 2025][1]), we used this representation to construct a fast map-level generative emulator for CMB instrumental systematics simulations. Even when trained on as few as ten high-fidelity simulations, the emulator generates statistically independent approximate realizations that reproduce power spectra, scattering statistics, Minkowski functionals, and pixel-covariance structure, enabling orders-of-magnitude simulation augmentation at negligible cost compared with full end-to-end campaigns. I will then describe how the same scattering-covariance latent space can be used for transparent SBI pipelines for CMB polarization in Planck, LiteBIRD and Simons Observatory data, to infer parameters such as the optical depth to reionization and the tensor-to-scalar ratio while controlling non-stationary foreground and instrumental residuals. The goal is a simulation-efficient, interpretable alternative to ``black-box'' neural inference: using a few expensive simulations as anchors for large, calibrated, statistically-controlled inference pipelines. [1]: https://www.aanda.org/articles/aa/full_html/2025/08/aa54540-25/aa54540-25.html

Speaker: Paolo Campeti (University of Ferrara)

24 Non-Gaussian statistics and machine learning for cosmological inference with 21cm intensity mapping

Cosmology is currently experiencing a data-rich era, with even more data expected in the coming decade. Intensity mapping of 21 cm neutral hydrogen emission offers a promising avenue for mapping vast volumes of the Universe with high redshift resolution, aiding in the study of large-scale structure and cosmological parameter estimation. However, extracting cosmological information from these datasets poses challenges, including significant foreground contamination, instrumental effects, and the loss of information inherent in using two-point statistics in highly non-Gaussian fields. This ongoing PhD project aims to explore the potential of higher-order statistics—such as Minkowski functionals, peak counts, and probability distribution functions—combined with machine learning techniques for cosmological inference from 21 cm data. The research is organized into three main topics: (i) assessing the robustness of these statistics against foreground residuals and instrumental imperfections; (ii) quantifying their cosmological information content using N-body simulations through a simulation-based inference approach (SBI); and (iii) developing an emulator for higher-order statistics and comparing different cosmological inference methodologies. The results and tools generated from this project will significantly contribute to the scientific preparation for future 21 cm experiments, such as SKA, the largest experiment of its kind currently under construction, and BINGO, a radio telescope being developed in Brazil.

Speaker: Gabriel Silva Costa (National Institute for Space Research (INPE))

Summary of the day

Conveners: Katrine Alice Glasscock (University of Oslo), Mathew Galloway (University of Oslo)

17:30 Welcome reception

Tuesday 8 September

09:30 Fika (coffee and buns)

Welcome

Conveners: Katrine Alice Glasscock (University of Oslo), Mathew Galloway (University of Oslo)

Welcome + Logistics

Welcome week 2

Welcome week 3

25 Three decades of cosmological Gibbs sampling

I will give a historical overview of how the method of Gibbs sampling was developed and applied during (soon) almost three decades of continuous work by a large group of people.

Speaker: Hans Kristian Eriksen (University of Oslo)

26 The FOSSIL mission

Speaker: Nabila Aghanim (IAS)

11:00 Coffee

27 AKARI and the infrared sky

AKARI’s Far-Infrared Surveyor (FIS) produced high-angular-resolution all-sky observations in four bands spanning 65-160 μm, offering a valuable view of thermal emission from interstellar dust, zodiacal light, and the cosmic infrared background. This talk provides an overview of the instrument, survey, and its place among infrared and microwave observations, emphasising synergies with current and upcoming surveys and foreground modelling relevant for CMB analyses. I will close by presenting preliminary results from our ongoing AKARI reanalysis within Cosmoglobe.

Speaker: Katrine Alice Glasscock (University of Oslo)

28 Cosmoglobe re-analysis of AKARI-FIS

In this talk, I will introduce the re-analysis of AKARI-FIS currently underway within the Cosmoglobe collaboration. I will discuss the potential of the AKARI observations to shed light on the Cosmoglobe sky model, in particular with regards to interstellar and zodiacal dust modelling as well as observations of the CIB. I will also showcase some of the AKARI time-ordered data, its characteristics and features, and the various ways they were tackled by the original AKARI team, and the ways in which we aim to tackle them within the Cosmoglobe framework, which has the benefit of being able to use other data sets and an existing sky model to shed light on the various systematics within AKARI, while also being able to optimally extract new science from the AKARI data itself to update said sky model.

Speaker: Eirik Gjerløw (University of Oslo)

29 Mitigating correlated noise in map-making for CMB experiments with BrahMap

Low-frequency correlated noise is a critical systematic for next-generation CMB experiments targeting the primordial B-mode signal. 1/f noise residuals are known to contaminate large angular scales and bias the estimation of the tensor-to-scalar ratio if they are not mitigated properly. In this context, we present BrahMap, a scalable and modular map-making framework designed for large-scale data reduction for current and future CMB polarization experiments. It features a user-friendly Python interface backed by performance-optimized C++ extensions with MPI+OpenMP parallelization. BrahMap implements generalized least squares (GLS) map-making with a large suite of noise covariance operators - from diagonal and circulant approximations to full Toeplitz operators - all accessible through a unified linear operator algebra interface. We explore several strategies for mitigating 1/f noise at the map-making level. First, we perform a systematic comparison of different circulant approximations of the exact noise covariance and assess their noise mitigation performance. Next, we implement superfast Toeplitz solvers to enable computing the exact GLS estimate using the full Toeplitz noise covariance. With realistic LiteBIRD simulations across a wide range of 1/f noise regimes, we demonstrate that the exact Toeplitz approach reduces the large-scale noise residual power by up to two orders of magnitude compared to circulant approximations, translating to an approximately four-fold reduction in the bias on the tensor-to-scalar ratio.

Speaker: Avinash Anand (University of Rome "Tor Vergata")

30 CG mapmaking for AKARI in Commander4

The most straightforward way to construct a map from a set of time-ordered data (TOD) is through a classic inverse-variance bin mapmaker. However, certain experiments such as AKARI and Planck HFI require to take into account non-local effects, such as the bolometer transfer function or detector cross-talks. In such case, inverting the mapmaking equation analytically is not feasible and a conjugate gradient search is required for retrieving the map solution, i.e. CG mapmaking.

This talk aims to give an insight on the implementation of CG mapmaking in Commander4, in relation to AKARI TOD reanalysis.

Speaker: Leo Bianchi (University of Oslo)

12:50 Lunch

31 Challenges of 21cm Radio Data Analysis

The 21cm signal from neutral hydrogen traces cosmic large-scale structure in 3D over an exceptionally wide redshift range. It has proven difficult to disentangle from foreground contamination and instrumental effects however. I will explain how the large dynamic range between signal and foregrounds and stringent spectral calibration requirements make this a difficult data analysis problem. I will then review the Hydra Gibbs sampling framework, which can handle low-frequency radio data from different types of radio telescope.

Speaker: Phil Bull (University of Manchester)

32 Making Absolutely Calibrated Measurements with Gaussian Constrained Realisations for the RHINO Global 21-cm Signal Experiment

The Remote HI eNvironment Observer (RHINO), currently under construction at Jodrell Bank Observatory, is an experiment aiming to observe between 60-85 MHz to measure the sky-averaged 21-cm absorption feature redshifted from the Cosmic Dawn. This signal is obscured by galactic synchrotron foregrounds that are brighter by over four orders of magnitude. Additionally, instrumental systematics impart additional spectral structure that can hinder extraction of the cosmological signal if not sufficiently calibrated for. This talk will outline how RHINO employs a Bayesian approach to calibrating instrumental systematics using Gaussian Constrained Realisations and propagating uncertainties into absolutely calibrated measurements of the low-frequency sky.

Speaker: Jordan Norris (University of Manchester)

33 Beam Systematics and Absolute Calibration in Global 21 cm Measurements

Global 21 cm experiments measure the absolute sky temperature at low radio frequencies, offering a potential low-resolution reference for large-scale sky models. However, the measurement is strongly shaped by the antenna beam, whose imperfect calibration can mix spurious sky structure into the observed spectrum. I present simulations testing whether controlled antenna rotation can help separate beam effects from true sky signals. By comparing different rotation strategies with realistic beams and sky models, this work explores a practical route toward improved absolute calibration for global sky analysis.

Speaker: Rashi Srivastava (University of Manchester)

34 Observations of the full northern sky at 10-40 GHz with the QUIJOTE experiment

In this talk I will give an overview of the status and recent results of QUIJOTE, a CMB polarization experiment working in the frequency range 10-40 GHz from the Teide Observatory (Tenerife, Spain). The QUIJOTE MFI instrument produced maps covering the full northern hemisphere at 11, 13, 17 and 19 GHz that were publicly released in 2023. I will highlight the scientific results coming out of these maps, addressing the measurement of the synchrotron spectrum in polarisation, the determination of the level of polarisation of the AME, and the study of the correlations of the AME with dust emission and with different environmental parameters. I will also briefly comment on the status of new QUIJOTE instrumentation at 10-20, 30 and 40 GHz, and of other CMB experiments operative (or to become operative) from the Teide Observatory (GroundBIRD, LSPE/Strip, TMS).

Speaker: Ricardo T. Génova-Santos (Instituto de Astrofísica de Canarias)

15:40 Conference picture!

15:50 Coffee

35 Probing the AME and PAH Connection via Multi-Frequency PCA

Anomalous Microwave Emission (AME) remains a critical uncertainty in global sky modeling, with its widely hypothesized origin tied to spinning Polycyclic Aromatic Hydrocarbons (PAHs). Robustly separating AME from other diffuse Galactic foregrounds requires using multi-frequency data across the electromagnetic spectrum. In this work, we present a blind component separation approach using Principal Component Analysis (PCA) applied to a comprehensive dataset spanning radio to infrared wavelengths. Our dataset synthesizes observations from space-based missions (Planck, WMAP, DIRBE, Haslam) and incorporates critical ground-based surveys (e.g., C-BASS, QUIJOTE). To physically interpret the extracted PCA components, we introduce a novel framework bridging blind and parametric techniques. We construct a theoretical basis via a moment expansion of standard foreground Spectral Energy Distributions (SEDs). By orthonormalizing this model basis, we can predict the uncorrelated spatial maps expected from the underlying physics. If the parametric model accurately describes the sky, its basis will span the exact same subspace as the data-derived PCA eigenvectors. We have successfully validated this methodology on simulated skies, demonstrating a high spatial correlation between the model-predicted components and the blind PCA maps. Building on this success, we will present the application of our pipeline to observational datasets, with the ultimate goal of isolating the AME component and robustly testing its correlation with infrared PAH tracers.

Speaker: Elena de la Hoz (NASA Goddard Space Flight Center)

36 Small-scale Non-Gaussianity of Galactic Foreground Emissions

Small-scale non-Gaussianity in Galactic foregrounds is an important source of uncertainty for future CMB experiments. We investigate the statistical properties of diffuse Galactic foregrounds using Minkowski Functionals and generalized skewness–kurtosis statistics across a range of angular scales. We find a remarkably similar kurtosis-type non-Gaussian signature in synchrotron, free-free, anomalous microwave emission, and thermal dust. Focusing on thermal dust, we compare Planck GNILC and 545 GHz observations with PySM and DUSTFILAMENTS simulations and perform patch-based analyses to study the spatial distribution of the signal. While PySM reproduces the global statistical trends, it fails to capture the observed spatial variations, and DUSTFILAMENTS underestimates the measured non-Gaussianity. Using controlled toy models with different one-point PDFs and power spectra, we show that the observed behaviour naturally arises from the combination of a heavy-tailed one-point PDF and a steep dust-like power spectrum. Finally, I will discuss our ongoing efforts to improve dust simulations by incorporating observed filament structural and spectral properties.

Speaker: Fazlu Rahman Panam Parambil (Texas A&M University)

Summary of the day

18:00 Conference dinner

Wednesday 9 September

09:30 Fika (coffee and buns)

Welcome

Conveners: Katrine Alice Glasscock (University of Oslo), Mathew Galloway (University of Oslo)

Welcome + Logistics

Welcome week 2

Welcome week 3

37 High resolution dust analysis with DIRBE and AKARI

The Cosmoglobe collaboration has recently completed the second data release, the reanalysis of the COBE-DIRBE data, producing new starlight emission models, zodiacal light models, cosmic infrared background (CIB) detections and new Milky Way dust models. In this talk, I will focus on the new dust models. This new dust model simplifies previously used dust models, and improves the interpretation, by breaking the old single component dust model into four physically motivated dust components. This is further motivated by the fantastic fit the dust has to both the DIRBE and Planck HFI data. Dust represents a significant systematic noise contribution to cosmic microwave background observations, so this new dust model will be crucial for future detection of signals important for understanding the earliest moments of our Universe, cosmic inflation.

Speaker: Raelyn Sullivan (University of Oslo)

38 Improved foreground cleaning via polarization-aided cleaning and CIB deprojection in thermal SZ Compton-y maps

The thermal Sunyaev-Zeldovich effect Compton-y parameter map (y-map) is a redshift-independent tracer of the hot baryon density across the sky. The all-sky y-maps reconstructed from Planck data have been utilized for the study of Lambda-CDM cosmology and the astrophysics of galaxy clusters. The current best minimum variance, all-sky y-map was made public in our previous work, using Needlet ILC on the latest Planck data. I will describe our effort to develop the best strategies for reconstructing y-maps with the least possible contamination from galactic foregrounds using the Hybrid ILC approach, and with the least cosmic infrared background (CIB) contamination using optimal deprojection of moments of the CIB SED. I will also compare our CIB minimization with other contemporary works with the same aim.

Speaker: Jyothis Chandran (Instituto de Fisica de Cantabria (IFCA, CSIC-UC))

39 Untangling dust emission and CIB anisotropies with the Scattering Transform Statistics

Template-fit approach is often used to separate the Galactic dust emission and the cosmic infrared background (CIB) anisotropies at low HI column density regions with an underlying assumption that the gas and dust are tightly correlated. However, this method fails in regions where additional Galactic emission from the molecular hydrogen, diffuse ionized gas, and dark gas are present. We develop and test a statistical component separation to extract the dust signal from the contaminated Planck 353 GHz observations using the Scattering Transform (ST) statistics. We apply two sub-classes of ST statistics to regions with high and low signal-to-noise ratios, where the dust-HI correlation breaks down, and extract the dust emission from beneath the CIB anisotropies.

Speaker: Srijita Sinha (NISER Bhubaneswar, RRI, Bangalore)

Posters and coffee

40 Component Separation of Fermi-LAT Gamma-Ray Sky

Speaker: Simon Berg (University of Oslo)

41 Gibbs sampling and unbiased power spectrum estimation for COMAP

Speaker: Simon Silverstein (University of Oslo)

42 Joint Reionization constraint with CoCoRI$\tau$A

The imprint of the Epoch of Reionization is encoded in the large-scale E-mode polarization of the CMB, which provides a direct constraint on the Thomson optical depth, $\tau$. Despite the high quality of the Planck and WMAP datasets, a fully consistent framework that jointly exploits all available large-scale polarization information has so far been lacking.
To address this, we have developed ELiCA (E-mode Likelihood for Cross-Analysis), a unified and publicly available likelihood that consistently combines the Planck 100 and 143 GHz HFI channels, the 70 GHz LFI channel, and the WMAP Ka, Q, and V bands. In this poster, I will present the first application of ELiCA in combination with x_HII data derived from different observables and reconstruction methods, all implemented within the public Python package CoReCon. By jointly analyzing large-scale CMB polarization and astrophysical probes while exploring both parametric and non-parametric reionization histories, this ongoing work aims to improve our understanding of the timing and evolution of cosmic reionization.
The core of this project is the development of a new public Python package, CoCoRI$\tau$A (CoReCon for Cobaya Reionization Inference on $\tau$ Analysis), which provides a unified framework for joint CMB + x_HII analyses under a wide range of reionization models. More generally, this work highlights the power of combining all available large-scale CMB E-mode polarization information with complementary astrophysical datasets to build a more complete and robust picture of the Epoch of Reionization.

Speaker: Valentina Genesini

43 Scanning Strategy Optimisation for Next-Generation CMB Experiments

Speaker: Synne Jørgensen (University of Oslo)

44 Searching for the signature of galaxy cluster rotation using ACT data

The scattering of the CMB photons off of free electrons contained within the intracluster medium (ICM) of galaxy clusters gives rise to the Sunyaev-Zel’dovich (SZ) effect. Typically, this effect can be separated into two components: the thermal and the kinematic SZ effect. The latter arises from contributions from bulk and internal motion of the gas, including rotational motion. Recent studies have shown possible signatures of a rotation-induced kinematic SZ signal. In this work, we present a stacking analysis to investigate the rotational-kinematic SZ effect in a sample of cluster regions with reported significant rotation using data from the Atacama Cosmology Telescope (ACT).

Speaker: Diana Victoria Lopez Navarro (Bonn University)

45 The CCAT sky-surveys from the Fred Young Submillimeter Telescope

We present the latest updates from the CCAT scientific collaboration, which is finishing the construction of its state-of-the-art Fred Young Submillimeter Telescope (FYST), at an altitude of 5600 m in the Atacama plateau in Chile. The telescope construction is nearly complete and the installation of the first-light cameras are in progress. We specifically highlight the status and the science objectives of the Prime-Cam and EoR-Spec cameras, designed for wide-area continuum surveys and narrow-field Line Intensity Mapping (LIM) surveys, respectively.

Speaker: Kaustuv Basu (Bonn University)

46 Forecasted constraints on Reionization and Neutrino masses from LiteBIRD

LiteBIRD is an ISAS/JAXA strategic L-class mission to probe cosmic inflation and the cosmic history of the Universe through full-sky measurements of cosmic microwave background (CMB) polarization. Its design will allow an almost cosmic variance limited measurement of the E-mode power spectrum at large angular scales and a much tighter constraint on the optical depth of reionization $\tau$ compared to Planck. We forecast how LiteBIRD, in combination with Planck CMB data for the smaller angular scales, will improve the constraints on $\tau$ and the reionization history. We perform an MCMC analysis using two mock datasets with different reionization histories and assuming four different reionization models. We see that LiteBIRD can constrain $\sigma(\tau)$ approximately three times better than Planck, and constrain the parameters of more general reionization models. If the assumed reionization model does not fit well the mock data reionization history, the best-fit $\tau$ from LiteBIRD can be biased. Combining LiteBIRD with the Simons Observatory (SO) CMB small-scales, SO lensing and Baryon Acoustic Oscillations (BAO), we forecast how the tighter $\sigma(\tau)$ from LiteBIRD translates into an improved constraint on the sum of neutrino masses $\Sigma m_{\nu}$. We also see that assuming the wrong reionization model would bias not only $\tau$, but also $\Sigma m_{\nu}$.

Speaker: Serena Giardiello (Cardiff University)

47 Exploring Rayleigh Scattering in the Era of Precision CMB Polarisation Measurements

Measurements of the Cosmic Microwave Background (CMB) temperature anisotropies over the past three decades have transformed our understanding of the Universe, while polarisation measurements have begun to provide additional powerful cosmological insights. Upcoming CMB experiments such as LiteBIRD, the Simons Observatory, and future missions including PICO will measure CMB polarisation with unprecedented sensitivity across a wide range of frequencies. In the standard cosmological framework, recombination physics is typically modelled considering only Thomson scattering. However, an additional and unavoidable process — Rayleigh scattering of CMB photons by neutral hydrogen and helium formed during recombination — becomes significant at high observational frequencies (≳200GHz). This effect introduces a characteristic frequency dependence in the CMB anisotropies and provides a new avenue for improving cosmological parameter estimation by breaking existing parameter degeneracies. In this talk, I will discuss the prospects for detecting the Rayleigh scattering signal with future CMB missions such as LiteBIRD and PICO, and quantify its impact on cosmological constraints. I will further highlight how Rayleigh scattering can serve as a sensitive probe of recombination physics and explore its role in testing alternative recombination scenarios aimed at alleviating the Hubble tension.

Speaker: Debabrata Adak (Institute of Astrophysics of the Canary Islands)

48 Reionization Constraints from a combined Planck+WMAP Low-ℓ Analysis

Reionisation marks the epoch when the first luminous structures ionised the intergalactic medium after recombination, producing free electrons that Thomson-scatter CMB photons. This imprint is encoded in the large-scale E-mode polarisation of the CMB, which directly constrains the optical depth τ. Despite the high quality of Planck and WMAP data, a fully consistent framework that jointly exploits all low-ℓ polarisation information has been missing. To fill this gap, we present ELiCA (E-mode Likelihood for Cross-Analysis), an harmonic-based unified likelihood that consistently combines Planck (100 GHz and 143 GHz HFI channels and 70 GHz LFI channel) and WMAP (Ka, Q, and V bands) large-scale polarisation data. Validated on simulations, ELiCA delivers robust and precise constraints on the optical depth: τ = 0.0581^{+0.0048}_{-0.0059} (68% CL). This result strongly disfavors high-τ scenarios associated with early reionisation, reinforcing a low optical depth picture. The improved precision propagates to ΛCDM extensions, yielding a stringent upper bound on the summed neutrino mass: Σmν < 0.069 eV (95% CL). ELiCA sets a new benchmark for large-scale CMB polarisation analyses and provides a natural framework for next-generation missions such as LiteBIRD, where precision measurements of τ will be critical for reionisation physics and cosmological tensions. The ELiCA likelihood is publicly available.

Speaker: Valentina Genesini (University of Ferrara)

13:00 Lunch

49 Time-ordered and map-based simulations of beam systematics for CMB experiments

I will present work done with Magdy Morshed on a new, fast way of simulating the temperature to polarization leakage due to beam pointing errors and mismatched ellipticity in detector pairs at the map level, as well as how we validated it using the TOAST time-domain simulation pipeline. Those effects are important for instruments that aim to measure the small scales of the polarized CMB, like the SO LAT.

Speaker: Alexandre Adler (UC Berkeley/LBNL)

50 The Simons Observatory: A framework for efficient map-based simulations of instrumental systematics for CMB surveys

The current and future observations of the CMB are expected to reach unprecedented sensitivity to place stringent constraints on both cosmological parameters and fundamental physics. The ground-based Simons Observatory Large Aperture Telescope started observations last year, and will provide the most sensitive small-scale CMB measurements. A tight control over instrumental systematics is critical, through the assessment of their impact as well as their mitigation. In this talk, we propose a new generalized framework to efficiently simulate systematics at the map level, along with the Python package smarties optimized to handle high resolution simulations. As a first application, we demonstrate that our results are in agreement with significantly more numerically expensive end-to-end simulations for a set of beam-related systematics. The ability to efficiently produce large ensembles of such simulations will allow for more robust cosmological parameter estimation from the power spectra of the CMB and gravitational lensing potential.

Speaker: Magdy Morshed (INFN, Ferrara)

Cosmoglobe_2026.pdf

51 BayesLIM: End-to-end, differentiable, Bayesian forward models for joint 21cm signal, foreground, and instrumental parameter inference

Next-generation 21cm cosmology experiments promise to revolutionize our understanding of the high redshift universe; however, these experiments are overwhelmed by foregrounds many orders of magnitude brighter. This sets a precise specification on instrumental modeling requirements that have to date made direct detection of the 21cm at the EoR elusive. However, next-gen computing and inference paradigms such as auto-diff and GPU acceleration will make joint modeling of the 21cm signal, foregrounds, and systematics possible, even for large-scale interferometric datasets. I'll discuss the BayesLIM approach, the first end-to-end, differentiable Bayesian forward model for low-frequency LIM, and the path forward for cosmological end-to-end modeling at low frequencies. (Arxiv:2504.07090)

Speaker: Nicholas Kern (University of Michigan)

52 Mapping the Star-Forming Universe with the COMAP

Modern cosmology has revealed many secrets of the nature and evolution of the Universe. To date, most surveys have done this by mapping the early Universe with the Cosmic Microwave Background (CMB) or relatively recent times by mapping the large-scale distribution of galaxies. However, epochs in between, from the dark ages through the epoch of reionization (EoR) all the way to the Epoch of Galaxy Assembly (EoGA), are strongly data-starved. This is where line intensity mapping aims to fill the gap by providing direct 3D measurements of the aggregate emission from redshifted lines such as the 21 cm line, CO rotational lines, [CII], and other atomic and molecular lines. These will be highly complementary to CMB, galaxy surveys, and other cosmological probes. In this talk, I will present results from the Carbon monOxide Mapping Array Project (COMAP). COMAP aims to map the large-scale distribution of star-forming matter at redshifts $z = 2$--$3$ and $z = 6$--$8$, respectively constraining the physics of the EoGA and EoR using the CO(1–0) and CO(2–1) lines of CO. In recent years, COMAP has produced two successive world-leading upper limits (Season 1 and 2), and is the first to directly constrain, on the 3D large-scale clustering power spectrum of CO(1-0). The Season 2 constraints between $0.09 \mathrm{Mpc^{-1}} < k < 0.72\mathrm{Mpc^{-1}}$ constrain the CO power spectrum to $kP_\mathrm{CO}(k) < 2400$--$4900 \mathrm{\mu K^2 Mpc^2}$, and is around an order of magnitude improvement on COMAP Season 1. I will present an overview of the COMAP experiment, the state-of-the-art Season 2 analysis and results, as well as preliminary results from the Season 3 analysis.

Speaker: Nils-Ole Stutzer (University of Oslo)

16:00 Coffee

53 Forecasting the detection of AME through LiteBIRD

Anomalous Microwave Emission (AME) is a poorly understood Galactic foreground that becomes increasingly relevant for the precision targeted by next-generation CMB experiments, particularly in polarisation where current observations only place sub-percent upper limits on its polarisation fraction. LiteBIRD, with its broad frequency coverage and high sensitivity, offers a unique opportunity to characterise AME in both intensity and polarisation. In this talk I present forecasts of LiteBIRD's ability to detect the AME signal using a template-fitting approach based on cross-correlations between LiteBIRD frequency maps and spatial templates. We find that the recovered amplitude is significantly biased by leakage between spatially correlated foreground components — synchrotron, thermal dust, and AME itself — and I discuss the mitigation strategies under development to recover an unbiased estimate of LiteBIRD's intrinsic sensitivity to AME. I will conclude by outlining how this work will be extended through the inclusion of complementary low-frequency data from ground-based experiments such as QUIJOTE and C-BASS, which is essential to break degeneracies between correlated foregrounds

Speaker: Kumar Aryan (Institute of Astrophysics of Canary Islands)

54 Joint Bayesian estimation of the synchrotron sky and modulation kernel

Observations from MeerKLASS exhibit significantly higher chromaticity than standard simulations, requiring approximately much more PCA modes for effective foreground removal than the 4–5 modes typically predicted. To address this discrepancy, we present a Bayesian framework designed to measure and characterize chromatic modulating effects on intensity maps. Our model represents instrumental and environmental effects as a product or convolution of a modulation kernel with the underlying sky signal. By assuming a power-law frequency dependence for the synchrotron sky, while marginalizing over model uncertainties, we simultaneously infer the modulation kernel and its associated statistical uncertainties. We validate this method using simulations that incorporate realistic beam chromaticity and sidelobes. In this talk, I will present preliminary results from this proof-of-concept work, demonstrating the method’s potential for characterize systematics

Speaker: Bruno Bizarria (INPE - Instituto Nacional de Pesquisas Espaciais)

Summary of the day

Thursday 10 September

09:30 Fika (coffee and buns)

Welcome

Conveners: Katrine Alice Glasscock (University of Oslo), Mathew Galloway (University of Oslo)

Welcome + Logistics

Welcome week 2

Welcome week 3

55 Measuring the Coherence Scale of Ultralight Axion-like Particles with Galaxy Polarization

Ultralight axion-like particles (ALPs) generically induce cosmic birefringence through their coupling to photons, but existing measurements based on integrated polarization rotation are primarily sensitive to the overall amplitude of the effect and do not directly probe the spatial coherence of the underlying field. We show that wide-field measurements of galaxy polarization provide a direct probe of the three-dimensional coherence structure of ALPs in the late Universe by exploiting the two-point correlation of the polarization-rotation angle as a function of the physical pair separation $(r)$. If the ALP behaves as nonrelativistic dark matter or a subdominant ultralight component, spatial fluctuations in its oscillating phase generate a correlation signal characterized by a coherence length $(r_{\rm coh}\propto(m_a v)^{-1})$, corresponding to the de~Broglie wavelength of the field. This geometric observable enables a direct and model-independent determination of the ALP mass, effectively breaking the degeneracy between coupling strength and field amplitude inherent in one-point statistics. We construct a tomographic estimator based on three-dimensional pair separations and show that the coherence scale can be robustly extracted from wide-field data using an inverse-variance--weighted collapsed correlation function. For a survey with $(\sim10^6)$ polarized galaxies over a large sky fraction, a polarization rotation amplitude of order $(0.1^\circ)–(1^\circ)$ is detectable at $(5\sigma)$ over the mass range $(m_a\sim10^{-28})–(10^{-27}\,\mathrm{eV})$. The corresponding coherence scale can be measured with a precision $(\sigma(\log_{10} m_a)\lesssim 0.1)$ across a broader range $(m_a\sim10^{-28})–(10^{-26}\,\mathrm{eV})$, provided that the signal is detected. At higher masses $((m_a\sim10^{-26}\,\mathrm{eV}))$, detection becomes challenging for the fiducial survey assumptions, but would be enabled by larger galaxy samples or improved inference of the intrinsic polarization position angles of the sources (e.g., from galaxy morphology). This method provides a direct geometric probe of the coherence scale of ultralight fields, complementary to CMB birefringence and structure-formation constraints.

Speaker: Yasuo Doi (The University of Tokyo)

56 Critical Importance of Calibration

High sensitivity is routinely prioritized in observational cosmology, yet the output of precision experiments is ultimately bound by instrument calibration. Too often treated as a late-stage detail, un-optimized calibration strategies—specifically instrumental offsets and gain drifts—directly limit measurement accuracy. Drawing on my experiences with COBE/FIRAS and ARCADE 2, I show how calibration systematics, rather than raw noise, constrained our knowledge of the absolute CMB temperature and bounded the FIRAS spectral distortion limits ($y$). I will show what could have been done differently to address these limitations, tracing how these hard-learned lessons directly shaped the calibration-first design architecture of PIXIE—where absolute calibration is elevated from a secondary routine to the primary mission requirement.

Speaker: Dale Fixsen (University of Maryland/Goddard Space Flight Center)

57 Revisiting the CMB spectrum

I will present the current results of the reanalysis of the COBE-FIRAS data, including a new temperature of the CMB monopole and constraints on spectral distortions.

Speaker: Ana Isabel Silva Martins (University of Oslo)

11:00 Coffee

58 12 Gyr of CMB–LSS Tomography: From Galactic Dust, tSZ and CIB to CO and [CII]

CMB data are fundamentally projected, with intricate secondary anisotropies each revealing distinct chapters of cosmic evolution. In a series of 6 papers, we carry out a deeply data-intensive cross-correlation tomography of CMB secondaries, jointly analyzing billions of HEALPix pixels across dozens of diffuse sky maps (e.g., Planck, IRAS, Herschel) and spectroscopic galaxies tracing large-scale structure. This unified effort provides a census of the cosmic baryon inventory across 12 Gyr of history. Key results include: (1) measuring the cosmic thermal energy history Ω_th in hot gas through the SZ effect, with implications for gravitational energy release Ω_grav; (2) reconstructing the most precise cosmic star formation history to date via 11-band CIB tomography with fully constrained SEDs over 90% of cosmic time; (3) tracing the evolution of cosmic dust abundance Ω_dust; (4) revealing CIB leakage in Galactic dust maps and developing a new field-level, 3D component separation method, producing the clean “CSFD” dust map; and (5) the first detections of CO and [CII] line backgrounds, probing the molecular gas density Ω_H2 and the cosmic cooling budget. Together, these results point toward a future of end-to-end, multi-wavelength sky analysis in which diffuse backgrounds become precision probes of cosmic evolution.

Speaker: Yi-Kuan Chiang (ASIAA)

59 Beyond the BLUE: CRLB-Referenced Benchmarking of Neural vs. Linear Estimation in mm/submm Surveys

Convolutional Neural Networks (CNNs) are now widely deployed in astronomy, often claiming superior performance over classical linear estimators for an extensive range of data applications. Yet it remains unclear when a CNN can genuinely outperform the matched filter (MF) -- which attains the Cramér–Rao Lower Bound (CRLB) as the minimum-variance unbiased estimator (MVUE) under Gaussian noise, and remains the best linear unbiased estimator (BLUE) in general. We test a ResNet-based CNN against the MF using image noise properties as the sole performance discriminator, and ask: when does a CNN's advantage reflect genuine information beyond the MF, rather than the bias-variance tradeoff inherent in any trained regression model? We address this through a series of realistic noise scenarios encountered in mm/submm astronomy (e.g., CMB surveys), demonstrating the surprising robustness of matched filtering, and isolating two distinct regimes where a CNN offers genuine advantage. The first is the conditionally Gaussian regime: per-image covariance variation that opens a modest CNN edge through adaptive noise modeling. The second is the genuinely non-Gaussian case, where the CNN exploits higher-order noise statistics to achieve lower-variance estimation than any linear filter. We further show that the advantage is template-dependent: governed by the spectral overlap between the source profile and the noise departure from Gaussianity, with distinct scaling for compact versus extended sources.

Speaker: Kaustuv Basu (Bonn University)

60 Component Separation of the Microwave Sky using Information Field Theory

Speaker: Ananya Shankar (Max-Planck Institute for Astrophysics)

12:35 Lunch

13:35 Social afternoon (Details on slack)

Open afternoon for socials before the bowling. We have brought indoor and outdoor games with us, and its also possible to join some other social activities such as walkings tours/scavenger hunts. We will end the afternoon with bowling for everyone.

16:45 Bowling, nachos and drinks

All conference participants are invited to join for bowling and snacks at O'Learys. We have booked 10 lanes including nachos and a drink for everyone. The venue has many other games and food available as well.

Friday 11 September

09:30 Fika (coffee and buns)

Welcome

Conveners: Katrine Alice Glasscock (University of Oslo), Mathew Galloway (University of Oslo)

Welcome + Logistics

Welcome week 2

Welcome week 3

61 Modelling and Forecasting for the FOSSIL and BISOU Experiments

The only precise measurement of the cosmic microwave background (CMB) spectrum to date was achieved by COBE-FIRAS in the early 1990s, demonstrating that the CMB spectrum is extraordinarily close to a perfect blackbody emission. However, both standard and non-standard physical processes are expected to generate small deviations from this spectrum, known as CMB spectral distortions. These distortions provide a unique and largely unexplored probe of the thermal history of the Universe, offering complementary insights into early-Universe physics, particle interactions, and structure formation. The measurement of CMB spectral distortions has therefore become a major objective for future cosmology missions and is now recognised as one of the three key scientific goals of the ESA Voyage 2050 programme. Since 2011, several dedicated space missions have been proposed, FOSSIL being the latest one, having been submitted to the ESA M8 call. In addition, pathfinders projects such as the balloon-borne experiment BISOU (CNES Phase A) are being developed targeting the first CMB spectral distortion monopole detection. After a brief overview of the observational challenges associated with spectral distortion measurements, I will present the latest optimization and forecasting studies for the BISOU and FOSSIL) projects. For this purpose, a flexible spectro-photometric model based on key instrument design choices and subsystem parameters, and a sky emission model dedicated to CMB spectral distortions studies have been developed.

Speaker: Xavier Coulon (IAS-CNRS)

62 Spectral distortions beyond the monopole: new targets for CMB imagers

Speaker: Jens Chluba (University of Manchester)

10:55 Coffee

63 Achievements and the Current Status of MAXI

MAXI (the All-Sky X-ray Imager) is an all-sky X-ray monitor that has been in operation on the International Space Station (ISS) since 2009. I will provide an overview of MAXI’s achievements over the past 17 years, including the discovery of 17 X-ray novae, and its current status.

Speaker: Ken Ebisawa (ISAS/JAXA)

64 In Search of Gravitational Waves from Fast X-ray Transients

Fast X-ray Transients (FXTs) are brief, intense X-ray flashes unassociated with persistent X-ray sources or known stellar objects, typically lasting from seconds to hours. Previous studies have identified the origins of some FXTs, e.g., XRO 080109/SN2008D as supernova shock breakouts and EP240315a as longduration Gamma-Ray Bursts. In the past 4 decades, a portion of FXTs has been identified as Gamma-Ray Bursts (GRBs). However, the origins of the rest of the FXTs remain uncertain, prompting the development of theoretical models, including binary neutron star mergers, accretion-induced collapse of compact objects, and tidal disruption events. With the launch of Einstein Probe in January 2024, the study of FXTs has entered a new phase. Its large field of view significantly increases the discovery rate, enabling a more robust statistical analysis. As of April 2025, Einstein Probe has reported approximately 80 FXTs — about four times the 22 events identified by Chandra between 2000 and 2022. We propose a methodology to search for possible relations between Gravitational Waves and FXTs. To achieve this, we intend to utilize X-Pipeline, an unmodeled search algorithm to identify excess coherent signals in LIGO-Virgo-KAGRA (LVK) O4 observations. By applying minimal assumptions, the search aims to test the existence of any temporal and spatial correlation, which may provide new insights into the physical mechanisms driving these transient X-ray events.

Speaker: Po-Ya Wang (National Tsing Hua University)

65 The state of Commander4

The Cosmoglobe collaboration has over the last decade developed and utilized the Commander3 Fortran codebase for global Bayesian CMB analysis. Commander4 is a ground-up rewrite of this algorithm with the necessary performance and scalability to analyze modern (>10TB) CMB datasets. While less mature than Commander3, it has now matured to the state of being able to perform preliminary analysis of datasets like SO and LiteBIRD simulations.

Speaker: Jonas Lunde (University of Oslo)

66 Next steps: Cosmoglobe Xtreme

Speaker: Mathew Galloway (University of Oslo)

12:45 Closing statements

13:00 Lunch

Monday 14 September

09:00 Registration

Participant registration on the 6th floor of the Nordita building (same place as the coffee)

09:30 Fika (coffee and buns)

Welcome: Welcome and logistics

Convener: Katrine Alice Glasscock (University of Oslo)

Welcome + Logistics

Welcome week 2

Welcome week 3

67 CosmoglobeHD and Origins

Speaker: Duncan Watts

11:00 Coffee

68 Tutorial: Zodipy

Speaker: Duncan Watts

WG: CHIPASS

Convener: Danielle Sponseller (Chalmers University of Technology)

WG: Zodiacal Light

Conveners: Angela Bonato (University of Oslo), Duncan Watts

13:00 Lunch

69 ARCADE-3 and the Synchrotron Sky

Synchrotron radiation dominates the radio sky. It encodes information on the cosmic ray energy spectrum and Galactic magnetic field and is an important foreground for measurements of the cosmic microwave background. Despite its importance for astrophysics, significant uncertainties remain in both the intensity and spectral index of diffuse synchrotron emission, complicating efforts to develop accurate full-sky models of Galactic and extragalactic emission. I will discuss the proposed ARCADE-3 mission to map synchrotron emission at frequencies 3--15 GHz to connect the radio
to microwave regimes and offer new insight into the origin, distribution, and energy spectrum of diffuse synchrotron emission.

Speaker: Al Kogut (NASA GSFC)

WG: CHIPASS

Convener: Danielle Sponseller (Chalmers University of Technology)

WG: Monopole experiments and spectral distortions

FOSSIL, FIRAS, and ARCADE2

Conveners: Ana Isabel Silva Martins (University of Oslo), Duncan Watts, Katrine Alice Glasscock (University of Oslo)

16:00 Coffee

WG: CHIPASS

Convener: Danielle Sponseller (Chalmers University of Technology)

WG: Monopole experiments and spectral distortions

FOSSIL, FIRAS, and ARCADE2

Conveners: Ana Isabel Silva Martins (University of Oslo), Duncan Watts, Katrine Alice Glasscock (University of Oslo)

17:30 Socialising at O'Learys bar -- bowling alley, karaoke, etc! (self-funded)

We will go to O'Learys for a social afternoon https://maps.app.goo.gl/RRepeKkmVeupNX636

Tuesday 15 September

09:30 Coffee

70 Tutorial: Gibbs sampling (Part A)

Using ARCADE2 as an example case study.

Speaker: Hans Kristian Eriksen (University of Oslo)

11:00 Coffee

WG: AKARI

Conveners: Eirik Gjerløw (University of Oslo), Katrine Alice Glasscock (University of Oslo)

WG: CHIPASS

Convener: Danielle Sponseller (Chalmers University of Technology)

13:00 Lunch

71 SPHEREx Completes Its First Full Sky Survey

SPHEREx is NASA’s all-sky near-infrared survey, producing spectrophotometric measurements of the entire sky at 6 arcsecond resolution in 102 spectral channels spanning 0.75 to 5 microns. The mission launched on March 11, 2025, and by late 2025 the mission completed one full sky survey after 6 months of its 2-year mission. This talk will describe the SPHEREx science data and findings from observations in SPHEREx's 650km low-Earth orbit. The science team is well on its way to achieving its science goals, and the full sky coverage has enabled preliminary SPHEREx science in a broad range of fields, including galaxy redshifts, cosmological intensity mapping, mapping of galactic ices, the distribution of Galactic dust through PAH emission, and solar system science. The science data become available to the public within 60 days of acquiring it, and the talk will describe ways to access and interact with the data through the archive system.

Speaker: Brendan Crill (JPL / California Institute of Technology)

72 Dust Band Structures near the Ecliptic Plane in the AKARI Far-IR All-Sky Maps and Identification of Their Source Asteroid Families

This talk will fokus on dust in AKARI and IRAS as part of the zodiacal light discussion.

Speaker: Takafumi Ootsubo (University of Occupational and Environmental Health)

WG: Monopole experiments and spectral distortions

FOSSIL, FIRAS, and ARCADE2

Conveners: Ana Isabel Silva Martins (University of Oslo), Katrine Alice Glasscock (University of Oslo)

WG: Zodiacal Light

Conveners: Angela Bonato (University of Oslo), Duncan Watts

16:00 Coffee

WG: Monopole experiments and spectral distortions: FOSSIL focused session

FOSSIL, FIRAS, and ARCADE2

Conveners: Ana Isabel Silva Martins (University of Oslo), Katrine Alice Glasscock (University of Oslo)

WG: Planck HFI

Convener: Hans Kristian Eriksen (University of Oslo)

WG: Zodiacal Light

Conveners: Angela Bonato (University of Oslo), Duncan Watts

Wednesday 16 September

09:30 Coffee

73 Tutorial: Gibbs sampling (Part B)

Speaker: Hans Kristian Eriksen (University of Oslo)

WG: AKARI

Conveners: Eirik Gjerløw (University of Oslo), Katrine Alice Glasscock (University of Oslo)

WG: Zodiacal Light

Conveners: Angela Bonato (University of Oslo), Duncan Watts

11:00 Coffee

WG: AKARI

Conveners: Eirik Gjerløw (University of Oslo), Katrine Alice Glasscock (University of Oslo)

WG: Zodiacal Light

Conveners: Angela Bonato (University of Oslo), Duncan Watts

13:00 Lunch

74 Optical Design and Systematics studies of BISOU

Although the cosmic microwave background (CMB) is remarkably well described by a perfect blackbody at a temperature of 2.725 K, small deviations, referred to as CMB spectral distortions, are predicted by a wide range of physical processes in the early Universe. Detecting these signals, however, is pushing instruments to their sensitivity limits while requiring exquisite control of their systematic effects.
BISOU (Balloon Interferometer for Spectral Observations of the primordial Universe) is an astronomical balloon-borne pathfinder instrument developed as part of a preparatory study for a future space mission aimed at measuring spectral distortions of the CMB. The optical system is based on a differential polarising Fourier Transform Spectrometer (FTS) that receives inputs from both a sky-facing telescope and an internal calibration source. The FTS focal plane is equipped with bolometric detectors coupled to multimode feed horns, distributed across two distinct detection units dedicated to the low- and high-frequency bands, covering the 90-1500 GHz range. The goal of this work is to present the design of the BISOU optical system with an emphasis on identifying and characterising the main systematic effects likely to affect the instrument's performance.

Speaker: Morgane Loquet le Gall (Institut d'Astrophysique Spatiale)

75 Revised modelling for the extragalactic CO monopole in the era of spectral distortion missions

Future spectral distortion missions, such as the proposed ESA mission FOSSIL and concepts like BISOU, will achieve unprecedented sensitivity to the sky-averaged millimetre and sub-millimetre radiation, opening new opportunities to detect astrophysical foregrounds alongside primordial spectral distortions. Among these, the cumulative emission from extragalactic carbon monoxide (CO) rotational transitions constitutes a relevant component of the cosmic monopole signal and requires accurate modelling to assess its impact on future observations. In this talk, I will present a revised modelling framework for the extragalactic CO monopole. I will discuss the main modelling assumptions and compare the predictions obtained with different approaches. Finally, I will show the expected CO monopole signal in the context of upcoming spectral distortion experiments.

Speaker: Giorgia Zagatti (University of Ferrara)

WG: CHIPASS

Convener: Danielle Sponseller (Chalmers University of Technology)

WG: Monopole experiments and spectral distortions

FOSSIL, FIRAS, and ARCADE2

Conveners: Ana Isabel Silva Martins (University of Oslo), Duncan Watts, Katrine Alice Glasscock (University of Oslo)

16:00 Workshop picture!

16:30 Reception (Fingerfood and drinks)

Thursday 17 September

09:30 Coffee

76 From Salvaged Raw Data to New Maps: Reconstructing IRAS Beam Response Functions

We present an early-stage effort toward the first end-to-end reanalysis of IRAS (1983), the first space telscope to perform a survey of the entire sky at infrared wavelengths. Our re-analysis is built directly from the raw time-ordered data (TOD), aiming to produce new public maps for cosmological use. Currently, the raw uncalibrated IRAS data does not exist publicly, however, we now have access to custom-compressed backups made by members of the original team in Groningen, which we have recovered.
IRAS presents numerous difficulties, both in terms of the raw data we have access to, which is partly incomplete and lossy, and in terms of original design choices. I will highlight one key challenge: the asymmetric rectangular detector masks, for which standard beam-deconvolution don’t apply. I will show preliminary efforts at reconstructing response functions, along with deconvolved images from said response functions.

Speaker: Vetle Vikenes (University of Oslo)

77 Probing Circumstellar Dust Shells with AKARI: Toward a Census of Stellar Mass Loss in the Nearby Universe

I am interested in understanding how stellar mass loss contributes to the circulation of matter in the nearby Universe. Stars undergoing mass loss may produce circumstellar dust shells, which can be observed in the infrared wavelengths.

In this talk, I will introduce my planned research using AKARI all-sky maps. I plan to develop a model for circumstellar dust shells and use it to search for and characterize such structures around stars in the AKARI data.

I would also like to discuss the possibility of using Commander products for this search, and whether the Commander framework could be useful for the dust-shell modeling and analysis.

Speaker: Hiyo Toriumi (ISAS/JAXA)

WG: AKARI

Conveners: Eirik Gjerløw (University of Oslo), Katrine Alice Glasscock (University of Oslo)

WG: SPHEREx

Convener: Duncan Watts

11:00 Coffee

WG: AKARI

Conveners: Eirik Gjerløw (University of Oslo), Katrine Alice Glasscock (University of Oslo)

WG: SPHEREx

Convener: Duncan Watts

13:00 Lunch

78 Application of Bayesian Inference to disentangle dust and CIB emission

Galactic dust emission and Cosmic Infrared Background (CIB) anisotropies are the dominant foreground signals in CMB observations at frequencies above 217 GHz. Since Galactic dust and CIB exhibit a similar spectral energy distribution, separating the two components poses a significant challenge. A reliable estimate of the CIB map serves as an external tracer of the CMB lensing potential, which can aid in detecting the primordial scalar-to-tensor ratio (r) through the delensing process.

In our work, we employ a Bayesian inference framework to separate the dust and CIB emission, utilizing Galactic HI emission as an external tracer of the dust component. A key outcome of this study is the estimation of the zero offset levels of the Planck intensity maps, accounting for pixel-dependent dust emissivities. The offset values derived in this analysis are found to be in good agreement with the official Planck offset values up to 545 GHz, while showing notable discrepancies at the 857 GHz frequency band.

Speaker: Tuhin Ghosh (NISER Bhubaneswar)

79 The faint-end CIB number counts from extreme-value statistics of the P(D)

We present a new approach to constraining the shape of the CIB source counts below the confusion limit, using the information contained in the tail of the image P(D) distribution. Applying the peaks-over-threshold formalism of extreme-value theory, we model the exceedances with a Generalized Pareto Distribution (GPD), whose shape parameter ξ is formally invariant to the map's mean, gain and count normalization. The method therefore sidesteps much of the instrument-specific modelling that a conventional forward-modelled P(D) fit requires. We show that ξ(u) is a flux-resolved measure of the local logarithmic slope of dN/dS at the intrinsic flux selected by the threshold u, while its modulation under gravitational lensing — the shift Δξ(u) between matched lensed and unlensed fields — tracks the local curvature of the counts, cancels common-mode systematics, and, with an externally known magnification, supplies a calibrated ruler that reaches intrinsic fluxes below the unlensed faint limit. We give simple analytic expressions for these dependences, validate them with realistic simulations including instrument noise, beam smoothing and source blending, and present the current constraints from Planck and Herschel/SPIRE 350 μm data, where the lensing signature is not yet detected and we report upper limits. (Basu, Guerrero & Bertoldi 2026, to be submitted)

Speaker: Kaustuv Basu (Bonn University)

Informal parallels

16:00 Coffee

Informal parallels

Friday 18 September

09:30 Coffee

80 ARCADE2 Flight movies

Speaker: Al Kogut (NASA GSFC)

WG: AKARI

Conveners: Eirik Gjerløw (University of Oslo), Katrine Alice Glasscock (University of Oslo)

WG: SPHEREx

Convener: Duncan Watts

11:00 Coffee

WG: AKARI

Conveners: Eirik Gjerløw (University of Oslo), Katrine Alice Glasscock (University of Oslo)

WG: SPHEREx

Convener: Duncan Watts

Summaries/presentations from the working groups: Sub-project aims, progress and future work

12:45 Closing statements

13:00 Lunch