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DTSTART;TZID=Australia/Sydney:20230301T150000
DTEND;TZID=Australia/Sydney:20230301T160000
DTSTAMP:20260516T231423
CREATED:20250819T061710Z
LAST-MODIFIED:20250819T061711Z
UID:14884-1677682800-1677686400@www.atnf.csiro.au
SUMMARY:S&A Colloquium: Robert Main (MPIfR)
DESCRIPTION:Scintillation Arcs: Scattering Screens and Surprises\n\nAbstract\n\nRadio emission from pulsars scintillates in time and frequency – an interference pattern arising from small-scale inhomogeneities in electron density in the interstellar medium. The discovery of “scintillation arcs” showed that scintillation is often remarkably ordered\, well described by scattering in highly anisotropic thin screens. Scintillation arcs are a powerful probe of small-scale structures in the ionized interstellar medium\, and can be used to determine the location of screens\, measure the variable time delays from scattering\, and measure pulsar orbits on the plane of the sky. In this talk\, I will show the first scintillation results from the Thousand Pulsar Array at MeerKAT\, with scintillation arcs seen in upwards of 100 pulsars. I will then describe a long-term multi-frequency study of the high-velocity pulsar B1508+55 with LOFAR and Effelsberg\, solving the observed scintillation from two interacting screens\, and where low frequency `echoes’ preceded a change in scintillation by ~3 years. Motivated by this study\, I will describe ongoing efforts to connect scintillation across many scales in frequency\, and the most promising future avenues. \n\n The image above shows scintillation arcs towards >100 pulsars observed as part of the MeerKAT Thousand Pulsar Array. \nWatch recording\nEvent details\nDownload iCal\nCategory\nColloquia
URL:https://www.atnf.csiro.au/event/sa-colloquium-robert-main-mpifr/
LOCATION:NSW
CATEGORIES:Colloquia
ATTACH;FMTTYPE=image/png:https://www.atnf.csiro.au/wp-content/uploads/2024/12/Colloq-01032023.png
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Australia/Sydney:20230308T150000
DTEND;TZID=Australia/Sydney:20230308T160000
DTSTAMP:20260516T231423
CREATED:20250819T061627Z
LAST-MODIFIED:20250819T061628Z
UID:14885-1678287600-1678291200@www.atnf.csiro.au
SUMMARY:S&A Colloquium: Trey Wenger (University of Wisconsin-Madison)
DESCRIPTION:Galactic HII regions\, diffuse ionised gas\, and structure in the Milky Way\n\nAbstract\n\nRadio recombination lines (RRLs) are an unobscured tracer of ionized gas in both the diffuse interstellar medium (ISM) as well as high-mass star-forming regions. The HII Region Discovery Surveys (HRDS) have nearly tripled the number of known high-mass star-forming regions in the Milky Way by detecting RRL emission toward infrared-identified HII region candidates. HII regions are the classic tracer of structure in galaxies\, and their physical conditions (e.g.\, metallicity\, internal kinematics) inform models of high-mass star formation and Galactic chemodynamical evolution. I will give a brief overview of our latest Australia Telescope Compact Array project\, the Southern HII Region Discovery Survey\, and some preliminary results with the first Galaxy-wide flux-limited HII region sample\, including a novel technique to constrain the Milky Way morphological structure. We serendipitously discovered (1) a population of HII regions with ionized gas velocity gradients and (2) RRL emission from diffuse ionized gas. I will discuss these discoveries\, their implications\, and our follow-up work\, which will inform both models of high-mass star formation as well as our understanding of the ISM and Galactic structure. \n\n As part of a large Australia Telescope Compact Array (ATCA) project\, the Southern HII Region Discovery Survey (SHRDS) serendipitously discovered ionized gas velocity gradients in a population of massive star forming regions. The figure above shows one such nebula\, the HII region known as G297.651–00.973. The background color is a WISE three-color infrared image (22 micron in red\, 12 micron in green\, and 3.4 micron in blue)\, the black contours represent the SHRDS radio continuum brightness\, and the colored contours represent the ionized gas velocity field. What is the origin and nature of these ionized gas velocity gradients? Follow-up work with the ATCA and the Very Large Array will hopefully answer these questions. \nWatch recording\nEvent details\nDownload iCal\nCategory\nColloquia
URL:https://www.atnf.csiro.au/event/sa-colloquium-trey-wenger-university-of-wisconsin-madison/
LOCATION:NSW
CATEGORIES:Colloquia
ATTACH;FMTTYPE=image/jpeg:https://www.atnf.csiro.au/wp-content/uploads/2024/12/Colloq-08032023.jpg
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BEGIN:VEVENT
DTSTART;TZID=Australia/Sydney:20230315T150000
DTEND;TZID=Australia/Sydney:20230315T160000
DTSTAMP:20260516T231423
CREATED:20250819T061554Z
LAST-MODIFIED:20250819T061555Z
UID:14886-1678892400-1678896000@www.atnf.csiro.au
SUMMARY:S&A Colloquium: Douglas Scott (University of British Columbia)
DESCRIPTION:The Standard Cosmological Model\n\nAbstract\n\nAll empirical data relating to our Universe are currently well fit by a basic model that contains only a few key ingredients: the background is described by homogeneous and isotropic solutions within General Relativity\, in which there is domination by vacuum energy and cold dark matter in a roughly flat expanding geometry; the density fluctuations appear to be nearly scale-invariant\, adiabatic and Gaussian (close to the simplest thing we could imagine); and all of today’s structure grew through gravitational instability. Within this picture the Universe is described by just a handful of numbers\, which are now known to quite high precision. So what is left to do in cosmology? How many digits of precision do we need? Where did these values come from? Are there more numbers that we haven’t thought of yet? Is this model anything like the Standard Model of Particle Physics? Are there signs that we need “physics beyond the standard model”? Did someone say “anomalies” and “tensions”? \nWatch recording\nEvent details\nDownload iCal\nCategory\nColloquia
URL:https://www.atnf.csiro.au/event/sa-colloquium-douglas-scott-university-of-british-columbia/
LOCATION:NSW
CATEGORIES:Colloquia
ATTACH;FMTTYPE=image/png:https://www.atnf.csiro.au/wp-content/uploads/2024/12/Colloq-15032023.png
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BEGIN:VEVENT
DTSTART;TZID=Australia/Sydney:20230322T150000
DTEND;TZID=Australia/Sydney:20230322T160000
DTSTAMP:20260516T231423
CREATED:20250819T061527Z
LAST-MODIFIED:20250819T061527Z
UID:14887-1679497200-1679500800@www.atnf.csiro.au
SUMMARY:S&A Colloquium: Natasha Hurley Walker (ICRAR/Curtin)
DESCRIPTION:Long-period radio transients\n\nAbstract\n\nSKA pathfinder instruments are probing the radio sky in new ways\, probing the sky on timescales hitherto poorly-explored. Sensitive image-plane surveys are discovering new kinds of radio transients\, with unusual temporal\, spectral\, and polarisation properties. Two intriguing periodic transients were published last year: a pulsar-like object repeating every 76s that is growing fainter with time (Caleb et al. 2022)\, and a short-lived radio transient repeating every 18 minutes (Hurley-Walker et al. 2022a). Both are potential examples of “ultra-long period” (ULP) magnetars\, and their radio emission might be explained by a temporary twisting and/or reorganisation of their intense magnetic fields. \n\n These discoveries are spurring new searches for similar long-period sources. Last year we conducted a transient imaging survey of the Galactic plane with the MWA at 200 MHz. We were successful in detecting a further long-period transient\, which compared to previous examples shows different pulse morphology\, polarisation behaviour\, and a staggeringly different activity window. Timing estimates place the source below the conventional “death lines” of emission mechanisms that explain radio emission in neutron stars. These sources are just the tip of the iceberg of a new population\, the exploration of which will illuminate the behaviour of neutron stars and therefore physics in extreme environments. I will conclude the talk with future survey plans across a range of telescopes. \nWatch recording\nEvent details\nDownload iCal\nCategory\nColloquia
URL:https://www.atnf.csiro.au/event/sa-colloquium-natasha-hurley-walker-icrar-curtin/
LOCATION:NSW
CATEGORIES:Colloquia
ATTACH;FMTTYPE=image/jpeg:https://www.atnf.csiro.au/wp-content/uploads/2024/12/Colloq-22032023-scaled.jpg
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BEGIN:VEVENT
DTSTART;TZID=Australia/Sydney:20230331T150000
DTEND;TZID=Australia/Sydney:20230331T160000
DTSTAMP:20260516T231423
CREATED:20250819T061501Z
LAST-MODIFIED:20250819T061501Z
UID:14888-1680274800-1680278400@www.atnf.csiro.au
SUMMARY:S&A Colloquium: Michael Kramer (MPIfR\, Bonn)
DESCRIPTION:Probing relativistic gravity with radio astronomy\n\nAbstract\n\nWe experience a golden era in testing and exploring relativistic gravity. Whether it is results from gravitational wave detectors\, satellite or lab experiments\, radio astronomy plays an important complementary role. Here one can mention the cosmic microwave background\, black hole imaging and\, obviously\, binary pulsars. This talk will provide an overview how these methods relate to each other\, and will in particular focus on new results from the study of binary pulsars\, where we can test the behaviour of strongly self-gravitating bodies with unrivalled precision. The talk will also give an outlook of what we can expect from new experiments\, such as with MeerKAT or the SKA. \nWatch recording\nEvent details\nDownload iCal\nCategory\nColloquia
URL:https://www.atnf.csiro.au/event/sa-colloquium-michael-kramer-mpifr-bonn-2/
LOCATION:NSW
CATEGORIES:Colloquia
ATTACH;FMTTYPE=image/jpeg:https://www.atnf.csiro.au/wp-content/uploads/2024/12/Colloq-31032023.jpg
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