[Astro] [CAPT] CAPT Weekly Bulletin (w/c 05-05-25)

[Ella Batchelor]

Tuesdays at 11am, CAPT Foyer – Astro Coffee



Tuesday 6th May at 11.30am, A113 CAPT – Astronomy Journal Club



Tuesday 6th May at 1pm, A113 CAPT – Particle Cosmology and Gravity Seminar
Ameek Malhotra (Swansea)

Bayesian Optimisation for efficient cosmological model selection



Cosmological model selection, in the framework of Bayesian inference requires the calculation of the Bayesian evidence. This can often be quite challenging, especially if the underlying likelihood function is expensive to evaluate. I will show how a technique called Bayesian Optimisation, based on Gaussian Process regression, can be used to calculate this evidence in far fewer likelihood evaluations, offering a much more efficient approach compared to traditional methods. If time permits, I will also discuss another ongoing project related to the reconstruction of the primordial curvature power spectrum and the equation of state from scalar induced gravitational waves.


Link to join: https://teams.microsoft.com/l/meetup-join/19%3ameeting_OGM3OTk5NzQtZWEwZS00ZmUyLTk3MGUtZjFhY2M5OTU2MjI1%40thread.v2/0?context=%7b%22Tid%22%3a%2267bda7ee-fd80-41ef-ac91-358418290a1e%22%2c%22Oid%22%3a%22f3250584-4b5f-48fa-a897-08e77f2246b7%22%7d
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Wednesday 7th May at 3.45pm, C4 Physics – Astronomy Weekly Seminar

Prof Jim Dunlop (Edinburgh)

Charting early galaxy formation and growth with JWST and ALMA


The James Webb Space Telescope (JWST) is transforming our view of galaxy formation and evolution in the young Universe. I will provide an overview of the latest results from the PRIMER survey, the largest JWST Cycle-1 “Galaxies” programme which, in combination with other public JWST imaging, is now enabling us to chart the emergence of the galaxy population back to within ~300 million years of the Big Bang. Specifically, I will present and discuss the first robust determination of the evolving UV galaxy luminosity function extending out to redshifts z~13, as well as new measurements of the galaxy stellar mass function reaching out to z~9. I will then interpret these results in the context of our current understanding of the evolving dark matter halo mass function and the efficiency with which galaxies are able to convert their baryons into stars. Finally, I will discuss new results on the early growth of dust-enshrouded star formation, and the prospects for future progress exploiting the combined power of JWST and the Atacama Large Millimeter Array (ALMA).
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Thursday 8th May at 1pm, C14 Physics – Astronomy Lunch Talk

Rhys Jordan

Identifying group galaxies merging with massive clusters using machine learning


The environment plays a critical role in shaping galaxy evolution. Galaxy clusters and their surroundings offer diverse conditions that influence galaxies before they reach the dense cluster core, known as “pre-processing”. However, robustly identifying environmental substructures, particularly galaxy groups in the infall regions, remains a significant challenge. Traditional phase space clustering methods struggle in these transitional zones due to severe projection effects and finger-of-god (FoG) distortions, precisely where distinguishing between local and global environments is most important. In this talk, I will present a supervised machine-learning framework for identifying group galaxies in and around clusters using projected positions and radial velocities. Our model trains on mock observations derived from cosmological simulations tailored to match survey conditions. It classifies galaxies into three environmental categories: main cluster, group, and neither (field). The model achieves an overall accuracy of 75% and a class-weighted precision of 81%. The main cluster class is most successfully recovered with a recall of 84%, followed by the group (77%) and neither (70%) classes. Model performance for group classification is notably suppressed within 1xR200. However, resampling strategies allow users to tune the model for precision or recall, depending on their scientific goals. The model remains unbiased across various cluster masses and dynamical states. Our method is flexible, observationally motivated, and well-suited for upcoming spectroscopic surveys. It provides a promising avenue for disentangling environmental influences on galaxy evolution across large-scale structures.


Thursday 8th May at 3pm, A113 CAPT – Particle Cosmology Journal Club

Fridays at 4pm, CAPT Foyer – CAPT Cakes
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If you have any events/visitors you would like included in next week’s bulletin, please let me know.



Best wishes

Ella

Ella Batchelor (she/her)
Administrator

School of Physics & Astronomy

University of Nottingham
A112a Centre for Astronomy & Particle Theory
University Park
Nottingham, NG7 2RD

+44 (0) 115 74 86778 |  nottingham.ac.uk<http://nottingham.ac.uk/>

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