Denys Wilkinson Building, Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH
1. Dr Steve Prabu
A Random Walk Through Radio Astronomy: From Near-Field Imaging and Bent Black Hole Jets to the Lunar Farside
The breadth of radio astronomy becomes apparent even after only a few years of exposure to the field. In this talk, I will present a brief tour of several science topics that I have had the opportunity to work on as an early-career researcher, all unified by radio observational techniques. These range from unconventional uses of radio telescopes to image objects in the near-field of the radio telescope, to a serendipitous discovery of black hole jets bent by interactions with stellar winds. I will conclude by discussing an ongoing project focused on the design of a radio telescope on the lunar farside, aimed at technosignature searches and transient studies.
2. Luke Parker
A new mid-infrared window on the clouds and chemistry of exoplanet atmospheres
High resolution spectroscopy with 8m-class ground-based telescopes has been enormously successful in advancing our knowledge of exoplanet atmospheres, including their chemistry, rotation speed, and atmospheric dynamics. This powerful technique now underpins major science cases for the Extremely Large Telescope (ELT), including the search for biosignatures (e.g. CO2, H2O, CH4) in the atmospheres of the nearest rocky exoplanets with the METIS instrument. METIS, which aims to see first light by the end of the decade, will operate in the mid-infrared between 3-5 microns. This wavelength range faces challenges from background noise and extreme telluric contamination and represents a previously untested frontier for exoplanet characterisation. Here, I will demonstrate the first use of high-resolution spectroscopy beyond 3.5 microns to characterise an exoplanet atmosphere, paving the way for ELT first-light science. Observing the directly imaged exoplanet beta Pic b with CRIRES+/VLT, we detect spectral signatures of H2O, CO, and, unexpectedly, signs of gas phase SiO, never before detected in an exoplanet atmosphere, revealing the discovery power of this novel wavelength regime. Building on this pathfinding study, I will present the first results from my PI survey of directly imaged planets from 3.5-5 microns with CRIRES+/VLT, exploring the behaviour of silicon chemistry across the giant planet population. Measuring precise abundances of SiO across this population provides a new avenue for determining the exact composition of the cloud species forming on giant exoplanets.
3. Aris Amvrosiadis
Searching for dark-matter subhalos with strong gravitational lensing
Understanding the nature of dark matter requires probing its structure on the smallest scales, where different models, such as cold and warm dark matter, predict markedly different halo abundances. Strong gravitational lensing offers one of the most powerful ways to detect these low-mass halos, which are otherwise invisible because they do not form stars. In this talk, I will present new results from ALMA observations of the strongly lensed dusty star-forming galaxy PJ011646. Using high-resolution continuum data and a flexible lens-modelling framework, we test whether the lensed emission contains evidence for a dark-matter subhalo. We find strong support for a subhalo within the lens potential, detected at nearly 6σ significance, with an inferred mass of approximately 3×10⁹ M⊙ within a radius of about 2 kpc. These results demonstrate the power of high-resolution ALMA lensing data for mapping dark-matter substructure, and pave the way for the first systematic subhalo census using the growing sample of ALMA strong lenses.