Next Colloquia

TBC

• Speaker: Stefano Facchini (Milan)
• Thursday 17 October 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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TBC

• Speaker: Stefano Facchini (Milan)
• Thursday 17 October 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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I will present surprising observational results on the 3D shapes and large-scale alignments of high-redshift galaxies from JWST . I will show that there are many more linear, elongated dwarf galaxies than there are round, circular dwarf galaxies seen in projection at high redshift (z>1). This puzzle was first hinted at with HST 30 years ago but has defied a clear explanation since. After ruling out a detection bias against faint, face-on disks with JWST , I will explore a variety of solutions. One reasonable interpretation is that, unlike in the local Universe, the majority of high-redshift dwarf galaxies (including Milky Way progenitors at z3) may be significantly flattened along two axes like prolate (cigar-shaped) or triaxial (surfboard-shaped) ellipsoids. This preferential elongation is naturally expected from the tidal field of the filamentary cosmic web, in which case we should also see strong intrinsic alignments. I will present evidence for such alignments when averaging over the orientations of background galaxies in a “blank” JWST deep field. We cannot yet rule out a lensing origin for the alignments and I will discuss implications for upcoming weak lensing searches with Roman and Euclid. If confirmed, this new dominant class of early elongated protogalaxies may hold unique clues about the origin of the Hubble Sequence and the emergence of early cosmic web filaments. Finally, I will also summarize how this seemingly niche puzzle bridges together many different areas of astrophysics and cosmology (including Galactic archaeology, dynamics and dark matter phenomenology), unlocks fresh science cases for the upcoming era of Extremely Large Telescopes, and requires a mixture of theory, observations, statistics and AI/ML to fully understand.

• Speaker: Viraj Pandya (Columbia University)
• Thursday 10 October 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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The Condor Array Telescope comprises six refracting telescopes and six large-format CMOS cameras on a common mount. The telescope is optimized for very low surface-brightness sensitivity, rapid time resolution, and a very wide field of view. The telescope has been operating autonomously on dark site in New Mexico since 2021. Condor has obtained sensitive broad- and narrow-band images of a variety of objects, including extended regions surrounding dwarf novae, extended regions surrounding nearby galaxies and galaxy groups; hundreds of thousands of source hours of rapid-cadence broad-band photometry of white dwarfs; narrow-band images of redshifted Lyman-alpha emission, to detect the high-redshift circum- and inter-galactic media, providing the first hints of the direct detection of the low redshift cosmic web. This illustrated talk will describe all these discoveries and outline plans for the construction of Condor phase 2, a new facility in the Atacama desert at an altitude of 5200m.

• Speaker: Prof. Ken Lanzetta (Stony Brook University)
• Thursday 27 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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The Condor Array Telescope comprises six refracting telescopes and six large-format CMOS cameras on a common mount. The telescope is optimized for very low surface-brightness sensitivity, rapid time resolution, and a very wide field of view. The telescope has been operating autonomously on dark site in New Mexico since 2021. Condor has obtained sensitive broad- and narrow-band images of a variety of objects, including extended regions surrounding dwarf novae, extended regions surrounding nearby galaxies and galaxy groups; hundreds of thousands of source hours of rapid-cadence broad-band photometry of white dwarfs; narrow-band images of redshifted Lyman-alpha emission, to detect the high-redshift circum- and inter-galactic media, providing the first hints of the direct detection of the low redshift cosmic web. This illustrated talk will describe all these discoveries and outline plans for the construction of Condor phase 2, a new facility in the Atacama desert at an altitude of 5200m.

• Speaker: Prof. Ken Lanzetta (Stony Brook University)
• Thursday 27 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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The first stellar generations in the Universe were sources of ionizing radiation and of newly synthesized elements. They played a key role in the reionization process as well as initiating the chemical evolution of the Universe. The talk will begin recalling the expected main physical properties of the first stellar generations that likely make them to evolve significantly differently from stars in the present-day Universe. We will then focus on aspects dealing with the chemical enrichments by the first stellar generations. Comparisons between predictions of models with the observed surface composition of halo stars will be presented. The special case of the Carbon-Enhanced Metal poor stars (CEMP), especially the most iron-poor ones, provide very precious and interesting clues about the very early chemical enrichment processes. The talk will end by discussing the extremely interesting cases of nitrogen-rich regions in high redshift galaxies.

• Speaker: Georges Meynet (Geneva)
• Thursday 13 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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The first stellar generations in the Universe were sources of ionizing radiation and of newly synthesized elements. They played a key role in the reionization process as well as initiating the chemical evolution of the Universe. The talk will begin recalling the expected main physical properties of the first stellar generations that likely make them to evolve significantly differently from stars in the present-day Universe. We will then focus on aspects dealing with the chemical enrichments by the first stellar generations. Comparisons between predictions of models with the observed surface composition of halo stars will be presented. The special case of the Carbon-Enhanced Metal poor stars (CEMP), especially the most iron-poor ones, provide very precious and interesting clues about the very early chemical enrichment processes. The talk will end by discussing the extremely interesting cases of nitrogen-rich regions in high redshift galaxies.

• Speaker: Georges Maynet (Geneva)
• Thursday 13 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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Planetary systems are shaped as much by destructive processes— N-body instabilities, catastrophic impacts, and atmospheric loss— as by accretionary ones. We examine the histories of violence written in: (a) the orbital architectures of super-Earths and sub-Neptunes; (b) the scattered light morphologies of debris disks; (c) chondritic meteorites and high-temperature minerals in comets; and (d) the chaotically variable light curves of disintegrating planets.

• Speaker: Eugene Chiang, Professor of Astronomy and Earth & Planetary Science, University of California, Berkeley
• Thursday 23 May 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: .

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Clusters of galaxies serve as excellent laboratories for exploring the physics of black hole feedback, illustrating how AGN -driven jets can deliver substantial energy to their surroundings via shock fronts, sound waves, and turbulence. These jets can also drive powerful molecular outflows and expel metals from galaxies. In this talk, I will review the current state of the field, focusing on how these powerful AGN -driven jets influence the properties of galaxy clusters over cosmic time. Additionally, I will present new observations of the giant multiphase nebula within the Perseus galaxy cluster and share insights into the pivotal role machine learning can—and will—play in advancing our understanding of galaxy clusters.

• Speaker: Julie Hlavacek-Larrondo, Université de Montréal
• Thursday 30 May 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: .

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Abstract not available

• Speaker: Georges Maynet (Geneva)
• Thursday 13 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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Abstract not available

• Speaker: Siyi Xu (NOIRlab, USA)
• Thursday 13 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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Abstract not available

• Speaker: Siyi Xu (NOIRlab, USA)
• Thursday 13 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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I will discuss the GMGalaxies programme, which is pursuing a new ‘hybrid’ approach to cosmological galaxy formation simulations combining the best of cosmological zooms and idealised approaches of the past. By customising (‘genetically modifying’) our initial conditions, we can construct controlled tests of structure formation within a fully cosmological environment. This approach has allowed us to obtain new and unique insights into ultra-faint dwarf galaxy formation, AGN -driven galaxy quenching, large scale structure formation and — in soon-to-be-released ultra-high-resolution simulations — the Milky Way fossil record seen by Gaia. In this talk, I will summarise some of these results but focus especially on recent insights into dwarf galaxy formation.

• Speaker: Andrew Pontzen (UCL)
• Thursday 09 May 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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Most of the power from an Active Galactic Nucleus is released close to the black hole, and thus studying accretion at event horizon scales—at the intersection of inflow and outflow—is essential for understanding how much matter accretes and grows the black hole vs. how much matter is ejected, thus effecting the black hole’s large-scale environments. In the past decade, we have had a breakthrough in how we probe the inner accretion flow, through the discovery of X-ray Reverberation Mapping, where X-rays produced close to the black hole reverberate off inflowing gas. By measuring reverberation time delays, we can quantify the effects of strongly curved space time and measure black hole spin, which is key for understanding how efficiently energy can be tapped from the accretion process. In this talk, I will give an overview of this field, and will show how extending these spectral-timing techniques to extreme, transient (and possibly multi-messenger) accretion events like Tidal Disruption Events and Quasi Periodic Eruptions can help us understand the growth and impact of black holes in galactic centers.

• Speaker: Erin Kara (MIT)
• Thursday 06 June 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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More than a century ago, Albert Einstein presented his general theory of gravitation. One of the predictions of this theory is that not only particles and objects with mass, but also the quanta of light, photons, are tied to the curvature of space-time, and thus to gravity. There must be a critical mass density, above which photons cannot escape. These are black holes. It took fifty years before possible candidate objects were identified by observational astronomy. Another fifty years have passed, until we finally can present detailed and credible experimental evidence that black holes of 10 to 10^10 times the mass of the Sun exist in the Universe. Three very different experimental techniques have enabled these critical experimental breakthroughs. It has become possible to investigate the space-time structure in the vicinity of the event horizons of black holes. I will summarize these interferometric techniques, and discuss the spectacular recent improvements achieved with all three techniques. In conclusion, I will sketch where the path of exploration and inquiry may lead to in the next decades.

• Speaker: Reinhard Genzel (Max Planck Institute for Extraterrestrial Physics)
• Thursday 02 May 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy (and online - details to be sent by e-mail).
• Series: The Kavli Lectures; organiser: Alison Wilson.

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I will use a real-time general relativistic Black Hole Flight Similator to show what really happens inside astronomically realistic black holes. The inner horizon of a rotating black hole is the most violent place in the Universe, easily reaching and surpassing energy densities attained in the Big Bang. What does Nature do at this extraordinary place?

• Speaker: Prof. Andrew Hamilton (University of Colorado Boulder)
• Thursday 16 May 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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More than a century ago, Albert Einstein presented his general theory of gravitation. One of the predictions of this theory is that not only particles and objects with mass, but also the quanta of light, photons, are tied to the curvature of space-time, and thus to gravity. There must be a critical mass density, above which photons cannot escape. These are black holes. It took fifty years before possible candidate objects were identified by observational astronomy. Another fifty years have passed, until we finally can present detailed and credible experimental evidence that black holes of 10 to 1010 times the mass of the Sun exist in the Universe. Three very different experimental techniques have enabled these critical experimental breakthroughs. It has become possible to investigate the space-time structure in the vicinity of the event horizons of black holes. I will summarize these interferometric techniques, and discuss the spectacular recent improvements achieved with all three techniques. In conclusion, I will sketch where the path of exploration and inquiry may lead to in the next decades.

• Speaker: Reinhard Genzel (Max Planck Institute for Extraterrestrial Physics)
• Thursday 02 May 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy (and online - details to be sent by e-mail).
• Series: The Kavli Lectures; organiser: Alison Wilson.

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Abstract not available

• Speaker: Reinhard Genzel (Max Planck Institute for Extraterrestrial Physics)
• Thursday 02 May 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy (and online - details to be sent by e-mail).
• Series: The Kavli Lectures; organiser: Alison Wilson.

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For more than 15 years, NANO Grav and other pulsar-timing array collaborations have been carefully monitoring networks of pulsars across the Milky Way. The goal was to find a tell-tale correlation signature amid the data from all those pulsars that would signal the presence of an all-sky background of nanohertz-frequency gravitational waves, washing through the Galaxy. At the end of June 2023, the global pulsar-timing array community finally announced its evidence for this gravitational-wave background, along with a series of studies that interpreted this signal as either originating from a population of supermassive black-hole binary systems, or as relics from cosmological processes in the very early Universe. I will describe the journey up to this point (including the integral role that the IoA played), what led to the ultimate breakthrough, how this affects our knowledge of supermassive black holes and the early Universe, and what lies next for gravitational-wave astronomy at light-year wavelengths.

• Speaker: Dr Stephen Taylor, Vanderbilt University, Nashville, Tennessee, USA
• Thursday 07 March 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, Institute of Astronomy.
• Series: Institute of Astronomy Colloquia; organiser: eb694.

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For more than 15 years, NANO Grav and other pulsar-timing array collaborations have been carefully monitoring networks of pulsars across the Milky Way. The goal was to find a tell-tale correlation signature amid the data from all those pulsars that would signal the presence of an all-sky background of nanohertz-frequency gravitational waves, washing through the Galaxy. At the end of June 2023, the global pulsar-timing array community finally announced its evidence for this gravitational-wave background, along with a series of studies that interpreted this signal as either originating from a population of supermassive black-hole binary systems, or as relics from cosmological processes in the very early Universe. I will describe the journey up to this point (including the integral role that the IoA played), what led to the ultimate breakthrough, how this affects our knowledge of supermassive black holes and the early Universe, and what lies next for gravitational-wave astronomy at light-year wavelengths.

• Speaker: Stephen Taylor, Vanderbilt University
• Thursday 07 March 2024, 16:00-17:00
• Venue: Hoyle Lecture Theatre, IoA (tea at 3:30 pm).
• Series: The Eddington Lectures ; organiser: .

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