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Zwicky Transient Facility Cosmology Science Working Group: Results and Perspectives

I will present the second data release of the Zwicky Transient Facility (ZTF) Cosmology Science Working Group: the largest Type Ia Supernovae release to date (by far!). It contains more than 3000+ good light curves of Type Ia Supernovae. After a brief introduction of the ZTF survey, I will present the characteristics of this unique dataset and show key results of recently submitted papers as part of the ZTF SN Ia DR2 Astronomy and Astrophysics special issue. I will then present our working program to derive brand new cosmological parameter constraints from Type Ia Supernova distances and the perspective for the next ZTF Cosmology releases.

• Speaker: Mickael Rigault
• Thursday 23 January 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:2406.07030v2 Announce Type: replace Abstract: The direct observation of cold and temperate planets within 1 to 10 AU would be extremely valuable for uncovering their atmospheric compositions but remains a formidable challenge with current astronomical methods. Ground-based optical interferometry, capable of high angular-resolution imaging, offers a promising avenue for studying these exoplanets, complementing space-based observations. Our objective is to explore the fundamental limits of dual-field interferometry and assess its potential for characterizing exoplanets in reflected light using the Very Large Telescope Interferometer (VLTI). We developed analytical expressions to describe the performance of dual-field interferometry and integrated these with simulations of atmospheric wavefronts corrected by extreme Adaptive Optics. An analytical solution for optimal phase apodization was formulated to enhance starlight rejection when injected into a single-mode fibre. This framework was applied to determine the detectability of known exoplanets in reflected light across various wavelength bands for both the current VLTI and a proposed extended version. Our results indicate that employing shorter wavelengths improves detectability, enabling at least seven Jupiter-mass exoplanets to be observed in the J band with current VLTI's baselines. Adding new baselines with lengths beyond 200 meters significantly enhances VLTI's capabilities, increasing the number of detectable exoplanets and revealing potential habitable zone candidates such as $\tau$ Ceti e and Proxima Centauri b. To substantially improve the VLTI's exoplanet characterization capabilities, we recommend developing instrumentation at wavelengths shorter than 1$\,\mu$m, as well as the addition of a fifth Unit Telescope (UT5).

Physicists have created a 3D shape called the cosmohedron, which can be used to reconstruct the quantum wavefunction of the universe - and potentially do away with the idea of space-time as the underlying fabric of the universe

From Small Worlds to Giant Planets: Uncovering New Exoplanets with Ground-Based Observations

Discerning patterns and trends in the physical properties of exoplanets is now possible thanks to the growing number of planet discoveries. In particular, TESS has been instrumental in adding to the sample with the detection of over 7000 potential planets, of which nearly 600 have been confirmed in the last 7 years. The distinct subpopulations that have emerged from grouping planets in different parameter spaces are now being tested against formation and evolution theories. Linking the two is still proving challenging in some cases, highlighting the need either to revise the current theories or, for rare planets, to increase the statistical sample. In this talk, I will discuss the efforts to validate TESS planet candidates with the TRAPPIST , SPECULOOS, and ASTEP ground-based facilities, focusing on small and giant planets orbiting M dwarfs. I will then present some of our most impressive results, including the discovery and study of the TOI -4336 A system, and the first confirmed planets from the MANGOS programme.

• Speaker: Mathilde Timmermans (Birmingham)
• Tuesday 28 January 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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Abstract not available

• Speaker: Timothy Hallatt (MIT)
• Tuesday 17 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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• 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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• Speaker: Anibal Sierra (UCL)
• Tuesday 03 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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• Speaker: Lev Tal-Or (Ariel)
• Tuesday 20 May 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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• Speaker: Olja Panic (Leeds)
• Tuesday 13 May 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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• Speaker: Craig Walton (ETH)
• Tuesday 18 March 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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• Speaker: Paul Huet (Paris Observatory)
• Tuesday 11 March 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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• Speaker: Haiyang Wang (Copenhagen)
• Tuesday 04 March 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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• Speaker: Eva-Maria Ahrer (MPIA)
• Tuesday 25 February 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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• Speaker: Clàudia Jano Muñoz (Cavendish)
• Tuesday 18 February 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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• Speaker: Ed Bryant (UCL)
• Tuesday 04 February 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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arXiv:2410.13935v2 Announce Type: replace-cross Abstract: Quasinormal modes (QNMs) are usually characterized by their time dependence; oscillations at specific frequencies predicted by black hole (BH) perturbation theory. QNMs are routinely identified in the ringdown of numerical relativity waveforms, are widely used in waveform modeling, and underpin key tests of general relativity and of the nature of compact objects; a program sometimes called BH spectroscopy. Perturbation theory also predicts a specific spatial shape for each QNM perturbation. For the Kerr metric, these are the ($s=-2$) spheroidal harmonics. Spatial information can be extracted from numerical relativity by fitting a feature with known time dependence to all of the spherical harmonic modes, allowing the shape of the feature to be reconstructed; a program initiated here and that we call BH cartography. Accurate spatial reconstruction requires fitting to many spherical harmonics and is demonstrated using highly accurate Cauchy-characteristic numerical relativity waveforms. The loudest QNMs are mapped, and their reconstructed shapes are found to match the spheroidal harmonic predictions. The cartographic procedure is also applied to the quadratic QNMs -- nonlinear features in the ringdown -- and their reconstructed shapes are compared with expectations based on second-order perturbation theory. BH cartography allows us to determine the viewing angles that maximize the amplitude of the quadratic QNMs, an important guide for future searches, and is expected to lead to an improved understanding of nonlinearities in BH ringdown.

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• Speaker: Alex Vañó-Viñuales (IST Lisbon)
• Friday 21 February 2025, 13:00-14:00
• Venue: Potter room.
• Series: DAMTP Friday GR Seminar; organiser: Daniela Cors.

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Geometric Characterizations of Kerr-de Sitter and Related Metrics in All Dimensions

The Kerr-de Sitter metric, originally proposed by Carter in four dimensions and later extended by Gibbons, Lü, Page and Pope to all dimensions, is likely to play a relevant role among Lambda positive vacuum spacetimes. To better understand what makes it special, we calculate the asymptotic data characterizing the metric near conformal infinity. This requires a review of tools in conformal geometry, such as the Fefferman-Graham expansion, and its relation with the asymptotic initial value problem in arbitrary dimensions. The asymptotic data obtained for Kerr-de Sitter admits a straightforward generalization to a broader class of spacetimes that depends on a set of parameters, which we refer to as Kerr-de Sitter-like class. This class of metrics is obtained explicitly as limits or analytic extensions of Kerr-de Sitter and the space of parameters inherits a natural topological structure from the asymptotic data. Furthermore, we discuss additional characterizations within the Kerr-Schild type metrics and the algebraically special metrics that highlight the geometrical significance of the class.

• Speaker: Carlos Peón Nieto (UPM, Madrid)
• Friday 24 January 2025, 13:00-14:00
• Venue: Potter Room / Zoom link https://cam-ac-uk.zoom.us/j/87235967698.
• Series: DAMTP Friday GR Seminar; organiser: Daniela Cors.

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arXiv:2405.18462v3 Announce Type: replace Abstract: The James Webb Space Telescope (JWST) has spectroscopically confirmed numerous galaxies at $z > 10$. While weak rest-ultraviolet emission lines have only been seen in a handful of sources, the stronger rest-optical emission lines are highly diagnostic and accessible at mid-infrared wavelengths with the Mid-Infrared Instrument (MIRI) of JWST. We report the photometric detection of the distant spectroscopically confirmed galaxy JADES-GS-z14-0 at $z = 14.32^{+0.08}_{-0.20}$ with MIRI at $7.7\ \mu\mathrm{m}$. The most plausible solution for the stellar population properties is that this galaxy contains half a billion solar masses in stars with a strong burst of star formation in the most recent few million years. For this model, at least one-third of the flux at $7.7\ \mu\mathrm{m}$ comes from the rest-optical emission lines $\mathrm{H}\beta$ and/or $\mathrm{[OIII]}\lambda\lambda4959,5007$. The inferred properties of JADES-GS-z14-0 suggest rapid mass assembly and metal enrichment during the earliest phases of galaxy formation. This work demonstrates the unique power of mid-infrared observations in understanding galaxies at the redshift frontier.