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DTSTART;TZID=Australia/Perth:20260401T120000
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DTSTAMP:20260518T182446
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UID:18536-1775044800-1775048400@www.atnf.csiro.au
SUMMARY:S&A Colloquium: Yuxiang Qin (Australian National University)
DESCRIPTION:Inferring properties of the first galaxies and intergalactic medium with 21-cm cosmology\n\nAbstract: \n\nThe redshifted 21-cm signal provides a unique probe of the first galaxies and their imprint on the thermal and ionization state of the intergalactic medium (IGM) during the Cosmic Dawn and Epoch of Reionization. In this talk\, I present a unified inference framework that jointly interprets constraints from low-frequency interferometers (e.g.\, HERA and MWA) and global-signal experiments such as EDGES\, in combination with complementary galaxy and CMB observations. \n\nBy jointly modelling these datasets\, we find converging evidence that the IGM was heated early\, ruling out a broad class of cold reionization scenarios and placing new constraints on the X-ray emissivity of the first galaxies. Within a galaxy-driven framework\, these results imply enhanced high-redshift X-ray production relative to local scaling relations\, potentially driven by metal-poor stellar populations and their remnants. In parallel\, global-signal analyses provide independent constraints on the timing and amplitude of the cosmic dawn signal\, and serve as a critical test of its astrophysical interpretation. \n\nAs these early sources are likely beyond the reach of direct detection\, even for facilities such as JWST\, the 21-cm signal remains a uniquely powerful probe of their collective impact. Looking ahead\, I will show how the Square Kilometre Array (SKA) will transform this field\, enabling precision constraints on the thermal history of the IGM and the properties of the first galaxies. \n\nPlease note that the event timezone is AWST (UTC+8 hrs) \nJoin Event on Microsoft Teams\nLocation\n\nOrganiser\n\nEvent details\nDownload iCal\nCategory\nColloquia
URL:https://www.atnf.csiro.au/event/sa-colloquium-yuxiang-qin-australian-national-university/
LOCATION:CSIRO – Kensington\, Australian Resources Research Centre (ARRC)\, 26 Dick Perry Ave\, Kensington\, WA\, 6101\, Australia
CATEGORIES:Colloquia
ATTACH;FMTTYPE=image/jpeg:https://www.atnf.csiro.au/wp-content/uploads/2026/03/yuxiang_qin_apad-1.jpg
ORGANIZER;CN="Gemma Anderson":MAILTO:gemma.anderson@csiro.au
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DTSTART;TZID=Australia/Sydney:20260408T150000
DTEND;TZID=Australia/Sydney:20260408T160000
DTSTAMP:20260518T182446
CREATED:20260330T022844Z
LAST-MODIFIED:20260330T023210Z
UID:18562-1775660400-1775664000@www.atnf.csiro.au
SUMMARY:S&A Colloquium: Georgia Stewart (University of Tasmania)
DESCRIPTION:Echoes of the Dying Light: The Evolution and Spectral Signatures of Simulated Remnant Radio Galaxies\n\nAbstract: \n\nRadio galaxy remnants are the quiescent phase of radio-loud active galactic nuclei (RLAGN) and provide key insight into AGN duty cycles and feedback. Observationally\, remnants are challenging to identify\, as their spectral and morphological properties often overlap with active sources\, necessitating multi-frequency data. \n\nIn my PhD\, I worked on the largest suite (to-date) of three-dimensional hydrodynamic simulations of active and remnant RLAGN evolving in realistic environments. Using synthetic radio emission generated from these simulations\, I investigated how jet power\, environment\, and active-phase duration shape the dynamics\, spectral evolution\, and observability of remnants. I showed that low-density environments delay the transition to buoyancy\, and high-powered sources sustain forward shocks that continue heating their surroundings. I also find several trends in the spectral evolution of remnants that are dependent on environment properties. \n\nI further explore remnant identification using machine learning on simulated radio data\, finding that even simple models can distinguish active and remnant sources\, though younger remnants are harder to classify. Finally\, I introduce a new method to calculate radio and X-ray observables directly from simulations\, enabling detailed\, high-resolution studies of lobe emission and its interaction with the environment. \n\nThese results provide a theoretical framework to interpret current and upcoming low-frequency surveys and improve our understanding of the lifecycle and impact of RLAGN. \n\n \nJoin Event on Microsoft Teams\nLocation\n\nOrganiser\n\nEvent details\nDownload iCal\nCategory\nColloquia
URL:https://www.atnf.csiro.au/event/sa-colloquium-georgia-stewart-university-of-tasmania/
LOCATION:Marsfield Lecture Theatre\, 26 Pembroke Road\, Marsfield\, NSW\, 2122\, Australia
CATEGORIES:Colloquia
ATTACH;FMTTYPE=image/png:https://www.atnf.csiro.au/wp-content/uploads/2026/03/talk_graphic_G_Stewart-scaled.png
ORGANIZER;CN="Jishnu Thekkeppattu":MAILTO:Jishnunambissan.Thekkeppattu@csiro.au
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