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arXiv:2506.04757v1 Announce Type: new Abstract: Feedback from supernovae and AGN shapes galaxy formation and evolution, yet its impact remains unclear. Galaxy groups offer a crucial probe, as their binding energy is comparable to that available from their central AGN. The XMM-Newton Group AGN Project (X-GAP) is a sample of 49 groups selected in X-ray (ROSAT) and optical (SDSS) bands, providing a benchmark for hydrodynamical simulations. In sight of such a comparison, understanding selection effects is essential. We aim to model the selection function of X-GAP by forward modelling the detection process in the X-ray and optical bands. Using the Uchuu simulation, we build a halo light cone, predict X-ray group properties with a neural network trained on hydro simulations, and assign galaxies matching observed properties. We compare the selected sample to the parent population. Our method provides a sample that matches the observed distribution of X-ray luminosity and velocity dispersion. The 50% completeness is reached at a velocity dispersion of 450 km/s in the X-GAP redshift range. The selection is driven by X-ray flux, with secondary dependence on velocity dispersion and redshift. We estimate a 93% purity level in the X-GAP parent sample. We calibrate the velocity dispersion-halo mass relation. We find a normalisation and slope in agreement with the literature, and an intrinsic scatter of about 0.06 dex. The measured velocity dispersion is accurate within 10% only for rich systems with more than about 20 members, while the velocity dispersion for groups with less than 10 members is biased at more than 20%. The X-ray follow-up refines the optical selection, enhancing purity but reducing completeness. In an SDSS-like setup, velocity dispersion measurement errors dominate over intrinsic scatter. Our selection model will enable the comparisons of thermodynamic properties and gas fractions between X-GAP groups and hydro simulations.

arXiv:2506.04309v1 Announce Type: new Abstract: Type Ia supernovae (SNe Ia) are standardisable candles: their peak magnitudes can be corrected for correlations between light curve properties and their luminosities to precisely estimate distances. Understanding SN Ia standardisation across wavelength improves methods for correcting SN Ia magnitudes. Using 150 SNe Ia from the Foundation Supernova Survey and Young Supernova Experiment, we present the first study focusing on SN Ia standardisation properties in the z band. Straddling the optical and near-infrared, SN Ia light in the z band is less sensitive to dust extinction and can be collected alongside the optical on CCDs. Pre-standardisation, SNe Ia exhibit less residual scatter in z-band peak magnitudes than in the g and r bands. SNe Ia peak z-band magnitudes still exhibit a significant dependence on light-curve shape. Post-standardisation, the z-band Hubble diagram has a total scatter of RMS = 0.195 mag. We infer a z-band mass step of $\gamma_{z} = -0.105 \pm 0.031$ mag, which is consistent within 1$\sigma$ of that estimated from gri data, assuming Rv = 2.61. When assuming different Rv values for high and low mass host galaxies, the z-band and optical mass steps remain consistent within 1$\sigma$. Based on current statistical precision, these results suggest dust reddening cannot fully explain the mass step. SNe Ia in the z band exhibit complementary standardisability properties to the optical that can improve distance estimates. Understanding these properties is important for the upcoming Vera Rubin Observatory and Nancy G. Roman Space Telescope, which will probe the rest-frame z band to redshifts 0.1 and 1.8.

arXiv:2506.03245v1 Announce Type: new Abstract: Dwarf galaxies provide powerful laboratories for studying galaxy formation physics. Their early assembly, shallow gravitational potentials, and bursty, clustered star formation histories make them especially sensitive to the processes that regulate baryons through multi-phase outflows. Using high-resolution, cosmological zoom-in simulations of a dwarf galaxy from \textit{the Pandora suite}, we explore the impact of stellar radiation, magnetic fields, and cosmic ray feedback on star formation, outflows, and metal retention. We find that our purely hydrodynamical model without non-thermal physics - in which supernova feedback is boosted to reproduce realistic stellar mass assembly - drives violent, overly enriched outflows that suppress the metal content of the host galaxy. Including radiation reduces the clustering of star formation and weakens feedback. However, the additional incorporation of cosmic rays produces fast, mass-loaded, multi-phase outflows consisting of both ionized and neutral gas components, in better agreement with observations. These outflows, which entrain a denser, more temperate ISM, exhibit broad metallicity distributions while preserving metals within the galaxy. Furthermore, the star formation history becomes more bursty, in agreement with recent JWST findings. These results highlight the essential role of non-thermal physics in galaxy evolution and the need to incorporate it in future galaxy formation models.

arXiv:2504.14009v2 Announce Type: replace Abstract: Supernova (SN) 2014C is a rare transitional event that exploded as a hydrogen-poor, helium-rich Type Ib SN and subsequently interacted with a hydrogen-rich circumstellar medium (CSM) a few months post-explosion. This unique interacting object provides an opportunity to probe the mass-loss history of a stripped-envelope SN progenitor. Using the James Webb Space Telescope (JWST), we observed SN 2014C with the Mid-Infrared Instrument Medium Resolution Spectrometer at 3477 days post-explosion (rest frame), and the Near-Infrared Spectrograph Integral Field Unit at 3568 days post-explosion, covering 1.7 to 25 $\mu$m. The bolometric luminosity indicates that the SN is still interacting with the same CSM that was observed with the Spitzer Space Telescope 40--1920 days post-explosion. JWST spectra and near-contemporaneous optical and near-infrared spectra show strong [Ne II] 12.831 $\mu$m, He 1.083 $\mu$m, H$\alpha$, and forbidden oxygen ([O I] $\lambda$$\lambda$6300, 6364, [O II] $\lambda$$\lambda$7319, 7330, and [O III] $\lambda$$\lambda$4959, 5007) emission lines with asymmetric profiles, suggesting a highly asymmetric CSM. The mid-IR continuum can be explained by ~$0.036 \ M_\odot$ of carbonaceous dust at ~300 K and ~0.043 $M_\odot$ of silicate dust at ~200 K. The observed dust mass has increased tenfold since the last Spitzer observation 4 yr ago, with evidence suggesting that new grains have condensed in the cold dense shell between the forward and reverse shocks. This dust mass places SN 2014C among the dustiest SNe in the mid-IR and supports the emerging observational trend that SN explosions produce enough dust to explain the observed dust mass at high redshifts.

Nature, Published online: 04 June 2025; doi:10.1038/d41586-025-01699-4

A surprising pattern of spatial distribution was discovered in dwarf galaxies, whereby diffuse ones cluster more strongly than do compact ones — opposite to the trend seen in massive galaxies. This finding challenges standard models of the formation of galactic structures, calling for theories about the assembly of visible- and dark-matter structures to be revised.

arXiv:2506.02316v1 Announce Type: new Abstract: The COMPAS public rapid binary population synthesis code has undergone a number of key improvements since the original COMPAS methods paper (Team COMPAS: Riley et al., 2022) was published. These include more sophisticated and robust treatments of binary interactions: mass transfer physics, common-envelope events, tides and gravitational-wave radiation reaction; and updated prescriptions for stellar evolution, winds and supernovae. The code structure and outputs have also been updated, with a focus on improving resolution without sacrificing computational speed. This paper describes the substantive changes in the code between the previous methods paper and COMPAS v03.20.02.

The Hubble constant, a set number that connects a galaxy’s speed to its distance from Earth and tells us how fast the universe is expanding, was first described more than a hundred years ago – but astronomers have debated it ever since

The Response and Observability of Exo-Earth Climates to Cometary Impacts

Impacts by icy bodies likely played a key role in shaping the composition, and habitability, of Solar-System planets. We determine the role they may play in exoplanetary systems by coupling a cometary impact model with a 3D, Earth-analogue, climate model. I will discuss how both the impact-delivered water and thermal energy affects the global climate and composition, including: i) a modified cloud greenhouse effect and planetary albedo, ii) an enhancement in the abundance of most oxygen-bearing molecules (bar ozone), and iii) an enhancement in the escape rate of hydrogen from the exosphere. I will describe how these responses are shaped by atmospheric circulations driven by the planetary orbital configuration, including the role that impact location plays in setting the vertical transport and hence hydrogen escape rate. Finally, I will quantify the potential observability of individual massive impacts in future observations of exo-Earths.

• Speaker: Felix Sainsbury-Martinez (Leeds)
• Tuesday 10 June 2025, 13:00-14:00
• Venue: Ryle seminar room + ONLINE - Details to be sent by email.
• Series: Exoplanet Seminars; organiser: Dr Dolev Bashi.

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Intuitive knowledge systems for discovery

Join us for an exploration of how intuitive knowledge systems might complement current approaches in scientific discovery. Drawing from conversations during her fellowship at the Cavendish, artist Akeelah Bertram examines the acknowledged limits of current calculation systems and the role of intuition for receiving unknown phenomena. Through readings from her developing publication “Sacred Architecture,” she reflects on parallel knowledge systems, drawing from Caribbean congregational practices and embodied ways of knowing. This talk explores questions about the convergence of rigorous scientific inquiry with intuitive methodologies, considering what might emerge when different ways of knowing are held in dialogue.

• Speaker: Akeelah Bertram (Cavendish Arts Science Fellow)
• Tuesday 10 June 2025, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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Transient astrophysics with the Gravitational wave Optical Transient Observer (GOTO)

Gravitational-wave (GW) multi-messenger astronomy holds immense promise for our understanding of the Universe, impacting studies of cosmology, the production of elements, and the final fates of stars. To date, however, only a single credible source, GW170817 , caused by the merger of two neutron stars, has been detected both in GWs and electromagnetically. I will discuss the scientific potential and challenges of observing more multi-messenger events, as motivation for the GOTO project: a UK-led transient sky survey composed of a fleet of rapidly-responding telescope arrays. The primary science driver of GOTO is scanning the sky in response to GW alerts, to search for their electromagnetic counterparts. Alongside overviewing GOTO ’s capabilities and recent multi-messenger efforts, I will present highlights from various ancillary science enabled by the array. This includes rapid localisation and characterisation of gamma-ray bursts, and discoveries of infant and extreme supernovae beyond the traditional core-collapse and thermonuclear regimes. I will also present our efforts to automate and expedite the characterisation of transients via algorithmically scheduled follow-up and citizen scientists.

• Speaker: Joseph Lyman, University of Warwick
• Thursday 12 June 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.

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arXiv:2405.12955v2 Announce Type: replace Abstract: We present observations of the $z\sim5.7$ Lyman-break galaxy HZ10 with the JWST/NIRSpec IFU in high and low spectral resolution (G395H, spectral resolving power $R\sim2700$ and PRISM, $R\sim100$, respectively), as part of the GA-NIFS program. By spatially resolving the source (spatial resolution $\sim0.15''$ or $\sim0.9$kpc), we find three spatially and spectrally distinct regions of line emission along with one region of strong continuum emission, all within a projected distance of $<10$kpc. The R2700 data features strong detections in H$\beta$, [OIII]$\lambda\lambda4959{,}5007$, [NII]$\lambda\lambda6548{,}6584$, H$\alpha$, and [SII]$\lambda\lambda6716{,}6731$. The R100 data additionally contains a strong detection of the Ly$\alpha$ break, rest-frame UV and optical continuum, and [OII]$\lambda\lambda3726{,}3729$. None of the detected lines present strong evidence for AGN excitation from line diagnostic diagrams, and no high-ionisation lines are detected. Using the detected lines, we constrain the electron density $\left( \rm \log_{10}\left( n_e / cm^{-3}\right)\sim 3\right)$ and metallicity ($\sim0.5-0.7$ solar) in each component. Spaxel-by-spaxel fits reveal a strong east-west velocity gradient and significant line asymmetries (possibly indicating tidal features or outflows). The western component features a very red UV slope ($\beta_{\rm UV}\sim-0.9$) and significant H$\alpha$ emission, suggesting an evolved population and active star formation. A comparison to high resolution ($\sim0.3''$ or $\sim1.8$kpc) [CII]$158\mu$m imaging obtained with the Atacama Large Millimetre/submillimetre Array (ALMA) reveals areas of dust obscuration. Altogether, these data suggest that HZ10 represents an ongoing merger, with a complex distribution of stars, gas, and dust $<1$Gyr after the Big Bang.

The Formation and Co-Evolution of Galaxies and Supermassive Black Holes

Cosmological hydrodynamical simulations are becoming increasingly realistic by incorporating a wider range of physical processes, higher spatial resolution, and larger statistical samples. Despite ongoing trade-offs between resolution and volume, recent advances now allow for simulations that resolve the multiphase interstellar medium and capture the clumpy nature of star formation in galaxies. In this context, I will present how such simulations shed light on the coupled evolution of galaxies and their central supermassive black holes. At high redshift, galaxies tend to be gas-rich, turbulent, and star-bursting, often exhibiting irregular, compact, and disturbed morphologies. As internal turbulence subsides, many systems transition into stable, rotating disc galaxies, typically once they reach stellar masses around 1e10 Msun. Simultaneously, black hole growth is tightly linked to the dynamical state of the host galaxy. In low-mass, turbulent systems, stellar feedback can suppress nuclear gas inflows, delaying black hole growth. Only when galaxies become sufficiently massive and dynamically settled can gas efficiently reach galactic centers to fuel sustained accretion. These processes also have important implications for the spin evolution of black holes or how fast they coalesce, which can reflect the varying modes of accretion and feedback across cosmic time.

• Speaker: Yohan Dubois (Institut d’Astrophysique de Paris)
• Thursday 05 June 2025, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.

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Exploring the End of Reionization

Abstract not available

• Speaker: George Becker (UC Riverside)
• Friday 06 June 2025, 11:30-12:30
• Venue: Ryle Seminar Room, KICC + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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Neurodiversity and Communication Styles

Dr Maria Dias, Neurodiversity Adviser at the Accessibility and Disability Resource Centre (ADRC) and St Catharine’s College, will explore how people with different neurotypes communicate in unique ways, and why understanding these differences is important for creating more inclusive and supportive environments. Whether you’re neurodivergent yourself, work with neurodivergent people, or just want to learn more, this talk is for you. There will be time for questions and open discussion at the end.

• Speaker: Maria Dias, Neurodiversity Adviser at the Accessibility and Disability Resource Centre (ADRC) and St Catharine’s College
• Wednesday 11 June 2025, 13:15-14:05
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: Cristiano Longarini.

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arXiv:2505.24129v1 Announce Type: new Abstract: Together optical/near infrared integral field spectroscopy and resolved sub-millimetre interferometry data have mapped the ionised and molecular gas motions in nearly one thousand galaxies at redshifts $z>0.5$. While these measurements have revealed a number of key properties about the evolution of disc structure and kinematics, heterogenous techniques and samples have led to disparate findings - especially when comparing different dynamical tracers (e.g., H$\alpha$, [C$\scriptstyle\rm~II$], CO). In this paper we present a literature compilation of 237 disc galaxies with measurements of velocity dispersion and rotational velocity between $z=0.5-8$, a subset of 63 galaxies have measurements of molecular gas fractions. We explore the connection between disc velocity dispersion measurements over 8 Gyrs as traced by multiple phases with the expectations from Toomre stability models. When sample properties are taken into account (e.g., stellar mass, tracer) there is little evolution in disc dispersions between $z\sim1.5-8$, consistent with expectations from model assumptions. We find ionised gas dispersions are higher by $\sim2\times$ from molecular gas dispersions at a fixed gas mass. These results are sensitive to the molecular gas tracer with results from [C$\scriptstyle\rm~II$] showing mixed behaviour indicative of its multi-phase origin. The [C$\scriptstyle\rm~II$] kinematics can be reconciled with molecular and ionised gas tracers when star-formation rates are taken into account.

Pulsar Timing Arrays and Astrometry: Going Beyond the Hellings-Downs correlation

The detection of gravitational waves (GWs) by pulsar timing arrays (PTAs) opens new avenues for probing the physics of GW sources at nanohertz frequencies. In the same frequency band, astrometric observations may also enable future GW detections. It is therefore important to investigate the potential for cross-correlating these two complementary approaches. Accordingly, I will discuss three topics related to the characterization of the stochastic gravitational-wave background using pulsar timing arrays and astrometry. The potential detection of its kinematic dipole. The prospects for measuring its circular polarization. A new method for identifying the possible presence of scalar polarization in the GW background.

• Speaker: Gianmassimo Tasinato (Swansea University)
• Monday 09 June 2025, 13:00-14:00
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Thomas Colas.

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Cracks in the Standard Cosmological Model: Anomalies, Tensions, and Hints of New Physics

The ΛCDM model has long served as the standard paradigm in cosmology, offering a remarkably successful description of the Universe’s evolution. Yet, as observational precision continues to improve, persistent tensions have emerged across a range of probes, including the well-known Hubble constant discrepancy. While individual datasets may each align with ΛCDM, their collective interpretation reveals significant discordances that challenge the model’s internal consistency. In this talk, I will review the most prominent tensions in modern cosmology and assess their implications. I will present recent results pointing to hints of dynamical dark energy and interactions within the dark sector. I will also reflect on the growing influence of methodological choices, such as dataset selection and model assumptions, in shaping our cosmological conclusions.

• Speaker: Eleonora Di Valentino (University of Sheffield)
• Monday 02 June 2025, 13:00-14:00
• Venue: SPECIAL LOCATION - CMS, MR4, Pav A basement.
• Series: Cosmology Lunch; organiser: Thomas Colas.

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GPU Accelerated Sampling and Model Comparison

This talk introduces a natively vectorized implementation of the Nested Sampling algorithm, enabling deployment of the entire inference process onto GPUs for massive acceleration. I will start by reviewing the benefits, and necessity, of the paradigm shift towards vectorized compute in the physical sciences. After a brief review of the how (and why) of Bayesian inference in Astronomy and Cosmology, I will then explore the nuances and challenges of taking some of the widely used inference algorithms within this community, in particular nested sampling, to the GPU accelerated frontier. Lastly I’ll present some practical benefit that this speedup can bring and comment on how this technical development can help push the boundaries of what we can achieve in the physical sciences.

• Speaker: David Yallup / IoA
• Wednesday 04 June 2025, 13:40-14:05
• Venue: The Hoyle Lecture Theatre + Zoom .
• Series: Institute of Astronomy Seminars; organiser: .

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Title TBC

Abstract TBC

• Speaker: Dr. Weiyang Wang (University of Chinese Academy of Sciences)
• Tuesday 21 October 2025, 11:15-12:00
• Venue: TBC.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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arXiv:2502.03085v3 Announce Type: replace Abstract: The shape of the Ly-$\alpha$ transmission in the near zone of the redshift $z=5.9896$ quasar ULAS J0148$+$0600 (hereafter J0148) is consistent with a damping wing arising from an extended neutral hydrogen island in the diffuse intergalactic medium (IGM). Here we use simulations of late-ending reionisation from Sherwood-Relics to assess the expected incidence of quasars with Ly-$\alpha$ and Ly-$\beta$ absorption similar to the observed J0148 spectrum. We find a late end to reionisation at $z=5.3$ is a necessary requirement for reproducing a Ly-$\alpha$ damping wing consistent with J0148. This occurs in $\sim3$ per cent of our simulated spectra for an IGM neutral fraction $\langle x_{\rm HI}\rangle=0.14$ at $z=6$. However, using standard assumptions for the ionising photon output of J0148, the a priori probability of drawing a simulated quasar spectrum with a Ly-$\alpha$ damping wing profile \emph{and} Ly-$\alpha$ near zone size that simultaneously match J0148 is low, $p<10^{-2}$. This may indicate that the ionising emission from J0148 is variable on timescales $t<10^{5}\rm\,yr$, or alternatively that the Ly-$\alpha$ transmission in the J0148 near zone is impacted by the transverse proximity effect from nearby star-forming galaxies or undetected quasars. We also predict the IGM temperature should be $T\sim 4\times 10^{4}\rm\,K$ within a few proper Mpc of the Ly-$\alpha$ near zone edge due to recent H$\,\rm \scriptstyle I$ and He$\,\rm \scriptstyle II$ photo-heating. Evidence for enhanced thermal broadening in the Ly-$\alpha$ absorption near the damping wing edge would provide further evidence that the final stages of reionisation are occurring at $z<6$.