
Cambridge Astrophysics Joint Colloquia
Thu 27 Feb 16:00: Prof
Title to be confirmed
- Speaker: Ravit Helled
- Thursday 27 February 2025, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.
Thu 20 Feb 16:00: Prof
Title to be confirmed
- Speaker: Hagai Perets
- Thursday 20 February 2025, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.
Thu 06 Feb 16:00: Dr
Title to be confirmed
- Speaker: Natascha M. Foerster Schreiber
- Thursday 06 February 2025, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Jan Scholtz.
Thu 30 Jan 16:00: Dr
Title to be confirmed
- Speaker: Esra Bulbul
- Thursday 30 January 2025, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.
Thu 23 Jan 16:00: Dr
Title to be Confirmed
- 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.
Thu 05 Dec 16:00: Should we observe spirals in young planet-forming discs?
We live in exciting times where new observations are hinting to us that planets may form early on in planet-forming discs. Young discs are expected to exhibit spiral structures, yet only few observations actually show spirals that are indicative of young discs. In this colloquium I will explore some of the possible reasons why this might be, and in particular I will look at processes that occur in discs which might act to erase the spiral structures.
- Speaker: Farzana Meru University of Warwick
- Thursday 05 December 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: eb694.
Thu 05 Dec 16:00: Should we observe spirals in young planet-forming discs?
Abstract not available
- Speaker: Farzana Meru University of Warwick
- Thursday 05 December 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: eb694.
Thu 05 Dec 16:00: TBC
Abstract not available
- Speaker: Farzana Meru University of Warwick
- Thursday 05 December 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: eb694.
Thu 28 Nov 16:00: Small-scale structure in cold dark matter: from ultra-faint dwarfs to prompt cusps
In our present paradigm of galaxy formation, the onset of structure is brought about via the gravitational collapse of (cold) dark matter, which subsequently acts as the scaffolding for the visible universe. A vigorous programme of numerical simulations has established several features of the dark matter model: the formation of haloes, and how their structure and abundance is influenced by the particle physics of the underlying model. The smallest visible galaxies—so-called “ultra-faint dwarfs”—are fossil records of an early phase of galaxy formation in the Universe and their assembly provides strong clues into the Epoch of Reionisation, galactic feedback, and the nature of the dark matter particle. Yet, the cold dark matter model predicts the formation of structure many orders-of-magnitude below the scale where galaxy formation ends, where individual dark matter haloes have masses comparable to that of the Earth. In this talk, I will discuss some of the progress we have made in understanding this regime using numerical simulations, and what their implications are for understanding the physics of galaxy formation, the nature of dark matter, and our prospects for detecting dark matter in the future.
- Speaker: Sownak Bose Durham University
- Thursday 28 November 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Jan Scholtz.
Thu 21 Nov 16:00: Ways of Probing the Assembly Mechanism of Individual Black Hole Binary Mergers
I will illustrate how different binary black hole (BBH) merger formation channels give rise to phase shifts, or modulations, in the GW signal that can be used to infer the origin of individual BBH mergers. I will in particular describe the case of GW phase shifts arising from chaotic triple BH scatterings that are known to take place in stellar clusters. New ideas on GW phase shifts in strong lensing events will also be presented. Modeling, quantifying and looking for GW modulations will start to play a key-role in the coming years when the GW sensitivity goes up and might be the only way of determining the origin of GW events case-by-case.
- Speaker: Prof. Johan Samsing
- Thursday 21 November 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Mor Rozner.
Thu 07 Nov 16:00: The origin and nature of spiral features in galactic disks
In this talk I will discuss a new view of structure formation in galactic disks mediated by gravity and rotation in the regime beyond where the Toomre criterion applies. The description is an extension of the Lin-Shu framework to the regime of ‘open spiral’ waves, well outside the conventional ‘tight-winding’ limit. In this regime, structures grow readily but at specific `critical’ orientations (pitch angles) that help, given local conditions, the growing wave capitalize on azimuthal gravitational forcing. From this perspective the ‘swing amplification’ of shearing material patterns results from the spiral pattern’s swing through the critical pitch angle. The same physical process also stimulates the growth of wave modes at corotation. In both cases, the spiral structures that go on to dominate a disk’s appearance are predicted to appear on scales nearer to the Jeans length than the Toomre length. In gas disks, this makes them consistent with the highly regular, remarkably long filamentary features newly revealed by JWST across the neutral gas disks of nearby galaxies.
- Speaker: Sharon Meidt van der Wel Ghent University
- Thursday 07 November 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Jan Scholtz.
Thu 07 Nov 16:00: The origin and nature of spiral features in galactic disks
Abstract not available
- Speaker: Sharon Meidt van der Wel Ghent University
- Thursday 07 November 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Jan Scholtz.
Thu 31 Oct 16:00: The long-term evolution of turbulent discs in high-redshift galaxies
Most disc galaxies go through an early epoch of being “gas rich,” an era that is being actively explored today through ALMA and JWST observations. This high gas-fraction phase got going much sooner (z > 3) than anticipated by cosmological N-body simulations. A new class of controlled (Nexus) simulations of these early times reveals that these turbulent discs have extraordinary properties. Unexpectedly, spiral arms, stellar and gaseous bars, even bulges, all form under these conditions. Moreover, baryon sloshing in 3D driven by strong feedback gives rise to thick stellar discs. We argue this is the most likely origin of alpha-enriched thick stellar discs observed today. The sloshing gives rise to specific signatures that may already be observable in ALMA data. We discuss the implications of the new work on galaxy studies.
- Speaker: Joss Bland-Hawthorn (Sydney)
- Thursday 31 October 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: eb694.
Thu 14 Nov 16:00: The growth of supermassive black holes is dominated by galaxy merger-free processes
The strong correlations that are found between supermassive black hole (SMBH) mass and velocity dispersion, stellar mass and bulge mass have long been interpreted as co-evolution of galaxies and their SMB Hs through galaxy mergers. However, a flurry of new results, both observational and theoretical, have suggested that galaxy mergers may not be the dominant mechanism powering this co-evolution. I shall review these findings before presenting results showing that merger-free galaxies have SMB Hs up to a billion solar masses and have substantial energetic outflows powered by the active galactic nuclei (AGN). In addition I will present work in collaboration with the Horizon-AGN simulation team showing that merger-free evolutionary processes also lead to co-evolution of galaxies and their SMB Hs. This has interesting implications: if both galaxy-merger-driven and galaxy-merger-free SMBH growth leads to co-evolution, this suggests that co-evolution is regulated by AGN feedback in both scenarios. AGN feedback is thought to be a key regulator of co-evolution and considered necessary in cosmological volume simulations employing ΛCDM, yet the role of AGN feedback in the absence of mergers is currently unknown. I will therefore discuss the future observations needed to understand the role of this understudied merger-free co-evolution pathway.
- Speaker: Rebecca Smethurst University of Oxford
- Thursday 14 November 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Jan Scholtz.
Thu 31 Oct 16:00: The long-term evolution of turbulent discs in high-redshift galaxies
Most disc galaxies go through an early epoch of being “gas rich,” an era that is being actively explored today through ALMA and JWST observations. This high gas-fraction phase got going much sooner (z > 3) than anticipated by cosmological N-body simulations. A new class of controlled (Nexus) simulations of these early times reveals that these turbulent discs have extraordinary properties. Unexpectedly, spiral arms, stellar and gaseous bars, even bulges, all form under these conditions. Moreover, baryon sloshing in 3D driven by strong feedback gives rise to thick stellar discs. We argue this is the most likely origin of alpha-enriched thick stellar discs observed today. The sloshing gives rise to specific signatures that may already be observable in ALMA data. We discuss the implications of the new work on galaxy studies.
- Speaker: Jonathan Bland-Hawthorn University Sydney
- Thursday 31 October 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Ebreedt.
Thu 24 Oct 16:00: Towards the LISA Global Fit
The Laser Interferometer Space Antenna (LISA), one of ESA ’s upcoming large-class missions, is designed to detect gravitational waves (GWs) at millihertz frequencies. This frequency band containing an abundance of galactic, extragalactic, and cosmological sources. The large number of sources, together with the fact that sources will be overlapping in both time and frequency, requires the development of a new global approach to LISA data analysis where all the sources and instrument are characterised simultaneously. In this talk, I will discuss the key data analysis challenges associated with the LISA global fit, recent advances toward addressing them, and how these efforts align with LISA ’s major scientific objectives.
- Speaker: Christopher Moore (Cambridge)
- Thursday 24 October 2024, 16:00-17:00
- Venue: Hoyle Lecture Theatre, Institute of Astronomy.
- Series: Institute of Astronomy Colloquia; organiser: Matthew Grayling.
Thu 17 Oct 16:00: Unveiling the physico-chemical conditions of planet formation environments
The large variety of observed planetary systems is rooted in the complex physical and chemical processes that lead to their formation. Spatially and spectrally resolved observations of molecular lines of planet nurseries – protoplanetary disks – can be leveraged to characterise simultaneously the dynamical state of the planet formation environments, and their chemical inventory. In this talk, I will show a new exquisite characterisation of disk kinematics by the exoALMA Large Program, a large effort that has involved more than 50 scientists for the last three years. These observations provide a novel methodology to determine the physical structure of disks, constrain their masses, reveal physical mechanisms yielding annular dust concentrations, and potentially unveil embedded planets. In jointure with direct imaging searches of such planets, and a chemical inventory of disk gas abundances, these observations yield the most accurate characterisation of protoplanetary disks to date. I will end the talk by discussing the future of this exciting research field, and potential new efforts to extend these studies to a much larger and more representative sample of disks.
- 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.
Thu 17 Oct 16:00: Unveiling the physico-chemical conditions of planet formation environments
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.
Thu 17 Oct 16:00: TBC
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.
Thu 10 Oct 16:00: New Puzzles in Galaxy Formation: From the Cosmic Web to the Origin of the Hubble Sequence
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.