Friday, September 11, 2026 at 12:15

JILA Foothills Room

Visal Sok & David Barker, CU Boulder

"A gas-tly tale: how metallicity reveals the role of gas in clump formation near cosmic noon & Physics Beyond the Standard Model: Constraining Dark Matter and New Physics Models with Low Frequency Radio Telescopes from the Moon using the 21 cm Dark Ages Global Signal"

Abstract:

Speaker: Visal Sok Title: "A gas-tly tale: how metallicity reveals the role of gas in clump formation near cosmic noon"

Abstract: Star-forming clumps are ubiquitous in galaxies during the epoch of peak mass assembly near cosmic noon. However, their origins remain poorly constrained by observations. The leading hypothesis suggests that clumps form within gas-rich disks fueled by near- pristine gas accretion from cosmological streams. If so, the gas disks of clumpy galaxies should have lower metallicity compared to non- clumpy galaxies. In this talk, I will present one of the first observational constraints on the gas-phase metallicity of clumpy and non-clumpy galaxies at z ~ 2. We find that clumpy galaxies typically exhibit lower metallicities than their non-clumpy counterparts, supporting a scenario in which inflowing gas plays a role in clump formation. Additionally, galaxies with lower metallicities typically host younger clumps with higher SFRs. I will also discuss work with JWST to measure resolved clump properties in galaxies up to z~5, and how measurements of the clump mass function can offer crucial insights into their origins and evolution.

Speaker: David Barker Title: Physics Beyond the Standard Model: Constraining Dark Matter and New Physics Models with Low Frequency Radio Telescopes from the Moon using the 21 cm Dark Ages Global Signal

Abstract: The global 21 cm signal from the cosmic Dark Ages provides a unique opportunity to probe fundamental physics during an epoch largely free from the astrophysical complexity introduced by the first stars and galaxies. Future low-frequency radio experiments on the lunar farside, such as LuSEE-Night, may therefore provide access to both the expected ΛCDM signal and departures produced by physics beyond the standard cosmological model. However, detecting these signals requires separating faint cosmological structure from a Galactic foreground that is orders of magnitude brighter. In this work, we use the pylinex signal-extraction pipeline to investigate how foreground uncertainty and radiometer noise affect the ability of an idealized lunar radio experiment to recover the global Dark Ages signal. We construct beam-weighted foreground models with varying levels of uncertainty and use Bayesian model comparison to determine when the expected ΛCDM signal can be distinguished from a foreground- only observation. We find that detectability depends strongly on foreground knowledge: for our fiducial two-antenna, 5,000-hour observation, constraining the foreground to approximately the percent level substantially improves the probability of detecting the ΛCDM signal, while further improvements in foreground knowledge or radiometer noise are required for robust detection. We then extend this framework to signals generated by seven representative models of non-standard physics—including dark matter interactions, exotic energy injection, excess radio backgrounds, early dark energy, primordial black holes, and primordial magnetic fields—to determine the regions of parameter space in which future lunar radio observations could identify departures from ΛCDM. These results characterize the interplay between foreground knowledge, instrumental sensitivity, and the discovery potential of future lunar Dark Ages experiments.

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