Description
Organiser: Patrick Leahy; co organisers: Clive Dickinson, Vasundhara Shaw
Galactic foreground emissions in the Milky Way below a few 10s of GHz are dominated by three mechanisms: synchrotron radiation from cosmic ray electrons interacting with magnetic fields, free-free emission from electron-ion interactions, and anomalous microwave emission (AME) from rotating dust grains. These emissions are observed through Stokes parameters: I (total intensity), Q and U (linear polarization). Large-scale polarized emission primarily comes from Galactic synchrotron emission and thermal dust at higher frequencies.
Understanding these foregrounds is critical for decoding Galactic magnetic field structures governing Galactic dynamics and ultra-high energy cosmic ray propagation, while being fundamental for CMB cosmology research, particularly in detecting B-modes and analyzing 21-cm cosmological signals.
Recent multi-band radio surveys have revolutionized our approach through key initiatives like C-Band All-Sky Survey (C-BASS) at 5 GHz, QUIJOTE Wide Survey (11-20 GHz), Simons Observatory (27-280 GHz), and the upcoming LiteBIRD satellite mission (40-400 GHz). These observations enable comprehensive examination of Galactic foregrounds across frequencies, advancing both CMB foreground separation and our understanding of Galactic magnetic fields.
This research field exemplifies the convergence of observational capabilities and theoretical advances, fostering collaboration between CMB cosmology, 21 cm intensity mapping, and ISM physics communities. This session will feature keynote presentations on survey status, Galactic magnetic field physics, and radio foregrounds' impact on CMB science. Subsequent focused presentations and poster sessions will showcase ongoing research, followed by structured group discussions. The hybrid format ensures global participation through focused presentations, poster sessions, and structured group discussions, reflecting the field's international significance.
We present results from the C-BASS Northern survey. The survey covers the whole northern sky above declination -15.6 degrees with data taken in both total intensity and linear polarization at 4.76 GHz and with an angular resolution of 44 arcmin. The primary aims of C-BASS are to support CMB studies by improving our understanding of contaminating foreground emission, especially in polarization,...
QUIJOTE (Q-U-I JOint TEnerife) is a pair of 2.25m telescopes observing from Teide Observatory, Tenerife, at 10-20GHz (Multi-Frequency Instrument, MFI) and 30 and 40GHz (Thirty and Forty Gigahertz Instrument, TFGI). The wide survey of MFI1 has recently been released, while TFGI and MFI2 observations continue, and a 90GHz camera is under development for the future.
I will summarise the...
LiteBIRD (the Lite (Light) spacecraft for the study of B-mode polarization and Inflation from cosmic background Radiation Detection) is a space-based mission dedicated to primordial cosmology. Its objective is to investigate cosmic inflation by targeting primordial B modes in the CMB polarization. Specifically, it will focus on both the reionization and recombination peaks to measure the...
The Simons Observatory Small Aperture Telescopes (SATs), located in Chileโs Atacama desert, are currently observing the polarised microwave sky at degree scales, on a quest to measure or constrain primordial gravitational waves, or B-modes, from the very early Universe. Disentangling this elusive signal from Galactic foregrounds, instrumental noise, and systematic effects requires robust...
Accurate separation of diffuse foreground components in temperature maps is crucial for cosmological and astrophysical studies. We use theย Commanderย code, which employs a Bayesian approach throughย Gibbs sampling, to perform a new decomposition of low-frequency foregrounds. This analysis builds upon the methodology used in Planck 2015, incorporating 31 maps, enabling a cleaner separation of...
The C-Band All-Sky Survey (C-BASS) is a 5 GHz radio survey at 45 arcminute resolution in total intensity and polarisation. C-BASS provides a unique view of the Galactic synchrotron emission, which will be crucial for the success of future CMB missions such as Litebird and Simons Observatory, as well as for understanding astrophysical phenomena such as the Galactic magnetic field. Due to its...
The cosmic dipole measured in surveys of cosmologically distant sources is generally in disagreement with the kinematic expectation of the Cosmic Microwave Background (CMB). This discrepancy represents severe tension with the Cosmological Principle and challenges the standard model of cosmology. We present a Bayesian analysis that quantifies the tension between datasets used to measure the...
Precision inference from 21 cm intensity mapping surveys requires robust separation of signal, noise, and foregrounds across frequency channels and redshift bins. In this work, I present a Gibbs sampling framework that operates mode-by-mode in harmonic space, enabling efficient inference of redshift-binned sky maps while rigorously propagating uncertainties into power spectrum estimation โ...
At Jodrell Bank we have built a special purpose instrument to make a low resolution (23 degrees), but absolutely calibrated, map of the sky at a wavelenth of around 21 cm. Why? Firstly, existing maps which are used as templates for synchrotron emission in CMB analyses are limited in their usefulness by systematic calibration errors. A well-calibrated map can be used to bootstrap these...
The Haslam 408 MHz all-sky map is widely used as a template to model the Galactic synchrotron emission across the radio and microwave regions of the electromagnetic spectrum. However, recent studies have suggested that there may be uncorrected gain factors -- in addition to systematic effects, spatial variations, and curvature -- in the map. We address the former by applying a Bayesian...
The Remote HI eNvironment Observer (RHINO) is a 21-cm global signal experiment currently under construction at Jodrell Bank Observatory. RHINO aims to follow up the 2018 EDGES result by using independent observing strategies and calibration methods to make absolutely calibrated measurements between 60 and 80 MHz. The instrument will be built around a large horn antenna. The rationale for using...
Radio cosmology today is driven by high-precision instruments like LOFAR, MeerKAT, and HERA, which are continually improving limits on the 21cm power spectrum. The next-generation instrument SKA will be the largest radio interferometric array, enabling high dynamic range radio maps. However, vast data volumes expand radio inference challenges, with foregrounds up to five orders brighter than...
The Simons Observatory is a new observatory in Chile consisting of multiple telescopes observing the Cosmic Microwave Background and millimetre sky at 27-280 GHz. Here, I will review the status of commissioning and early science activities for the Large Aperture Telescope and three Small Aperture Telescopes (SATs), all of which have now been deployed. In particular, I will highlight early data...
