[Astro] [CAPT] CAPT Weekly Bulletin (w/c 23-02-26)

[Ella Batchelor (staff)]

Monday 23rd February at 1.30pm, A113 CAPT – Theoretical Physics Student Seminar

Rayff de Souza

Dark Sector Interactions in Cosmology

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Tuesdays at 11am, CAPT Foyer – Astro Coffee

Tuesdays at 11.30am, A113 CAPT – Astronomy Journal Club



Tuesday 24th February at 1pm, A113 CAPT – Particle Cosmology and Gravity Seminar

George Efstathiou (Cambridge)

The Evidence for Dynamical Dark Energy


The Dark Energy Spectroscopic Instrument (DESI) collaboration has measured baryon acoustic oscillation (BAO) features over a wide range of redshifts with unprecedented precision. They argue that the data provide evidence for evolving dark energy, quoting 'significance' levels of 2.5-4.5 sigma depending on which additional data (CMB anisotropies and supernovae) are added to the BAO data. The favoured model of dynamical dark energy is unusual, requiring phantom-like behaviour at high redshift. I will present a different way of looking at the DESI data that provides simple and robust tests of consistency with the LCDM cosmology. I find no evidence for a deviation from LCDM and my analysis explains the degeneracy direction in the w_0-w_a plane found by the DESI collaborations. I will summarize some recent work on type Ia Supernova (SN) that supports my earlier claims that SN catalogues are not yet accurate enough to constrain models of dynamical dark energy.



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 25th February at 3pm, B1 Physics – EDI Colloquium
Jenni Dyer (Royal Society)

Taking an intersectional approach in STEM: Moving beyond the boxes



In the current political climate—where public conversations about equality and diversity are increasingly polarised—adopting an intersectional approach within STEM is more critical than ever. Intersectionality offers a powerful lens for understanding how overlapping identities – such as sex, ethnicity, gender identity, class, disability, and sexual orientation - shape experiences within science education and employment and how they then overlap with “science identity”.   This talk will highlight some of the structural barriers that persist in understanding how to take an intersectional approach and will look at how embedding intersectional thinking can be transformative when it comes to practices, policies, decision-making and culture.

Refreshments are available in C10 following the colloquium.

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Thursday 26th February at 1pm, A113 CAPT – Astronomy Lunch Talk

Rhys Jordan

Infalling groups revealed by machine learning


Galaxy evolution is strongly influenced by its environment, as evidenced by the prevalence of blue, star-forming galaxies in the field compared to the red, quiescent populations that dominate galaxy clusters. Increasing evidence suggests that a significant fraction of this transformation occurs prior to cluster accretion, through so-called pre-processing in galaxy groups and filaments. Understanding where and when this pre-processing occurs is therefore essential for disentangling the environmental influence on galaxy evolution.

In this talk, I present the current development of a new group-identification framework designed to detect galaxy groups in cluster infall regions. Our approach combines machine learning with an adapted Friends-of-Friends algorithm, optimised for application to spectroscopic surveys of galaxy clusters. Using mock observations from simulated data, we recover approximately 80% of the true groups across the infall region. When identifying galaxies belonging to specific groups, we achieve an average completeness of 60% and purity of 75%. This balance between completeness and purity enables robust identification of infalling groups along with their members. Importantly, the framework does not bias the stellar mass functions of either the group central or member populations. It therefore provides a powerful foundation for studying how galaxies in infalling groups transition into the cluster population.



Thursday 26th February at 2.45pm, A113 CAPT – Particle Cosmology Journal Club

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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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