Fri 03 May 11:30: Title to be confirmed
Abstract not available
- Speaker: Tsevi Mazeh (Tel Aviv)
- Friday 03 May 2024, 11:30-12:30
- Venue: Ryle seminar room + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.
Thu 02 May 16:00: Experimental Studies of Black Holes: Status & Prospects
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.
Fri 07 Jun 11:30: Modelling supermassive black holes: accretion, spin evolution, jets and winds
Abstract not available
- Speaker: Martin Bourne (IoA)
- Friday 07 June 2024, 11:30-12:30
- Venue: Ryle seminar room + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.
Mon 22 Apr 13:00: Title to be confirmed
Abstract not available
- Speaker: Licia Verde (University of Barcelona)
- Monday 22 April 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Fiona McCarthy.
Mon 25 Mar 13:00: The FLAMINGO project: revisiting the S8 tension and the role of baryonic physics
A number of recent studies have found evidence for a tension between observations of large-scale structure (LSS) and the predictions of the standard model of cosmology with the cosmological parameters fit to the cosmic microwave background (CMB). The origin of this ‘S8 tension’ remains unclear, but possibilities include new physics beyond the standard model, unaccounted for systematic errors in the observational measurements and/or uncertainties in the role that baryons play. In this talk, I will examine the latter possibility using the new FLAMINGO suite of large-volume cosmological hydrodynamical simulations. I will discuss how important ‘feedback’ processes that affect the baryons are implemented and calibrated in the simulations and how the simulations are projected onto observable space for comparisons with observational measurements of cosmic shear, CMB lensing, and the thermal Sunyaev-Zel’dovich (tSZ) effect. I will then focus on the dependence of the predictions on the efficiency and nature of baryonic feedback and whether or not it can plausibly resolve the S8 tension. Finally, I will discuss some independent tests that the simulations can be subjected to in order to build confidence (or undermine it!) in our cosmological conclusions.
- Speaker: Ian McCarthy (Liverpool John Moores University)
- Monday 25 March 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Fiona McCarthy.
Fri 03 May 11:30: Modelling supermassive black holes: accretion, spin evolution, jets and winds
Abstract not available
- Speaker: Martin Bourne (IoA)
- Friday 03 May 2024, 11:30-12:30
- Venue: Ryle seminar room + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.
Wed 15 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Michael Cates, University of Cambridge
- Wednesday 15 May 2024, 14:00-15:00
- Venue: MR2.
- Series: Theoretical Physics Colloquium; organiser: Ronak M Soni.
Wed 08 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Vyacheslav Rychkov, Institut des Hautes Études Scientifiques
- Wednesday 08 May 2024, 14:00-15:00
- Venue: MR2.
- Series: Theoretical Physics Colloquium; organiser: Ronak M Soni.
Wed 01 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Eric Perlmutter, IPhT
- Wednesday 01 May 2024, 14:00-15:00
- Venue: MR2.
- Series: Theoretical Physics Colloquium; organiser: Ronak M Soni.
Mon 20 May 13:00: Title to be confirmed
Abstract not available
- Speaker: Silvia Galli (Institut Astrophysique de Paris)
- Monday 20 May 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Fiona McCarthy.
Tue 19 Mar 14:00: Primordial black holes in the dark matter halo of our Galaxy
If there are primordial black holes in the dark matter halo, they must collide with the Galactic neutron stars (NSs) and produce light black holes (LBHs), with masses below 1.4 M_Sun. This has observational consequences that may be checked by microlensing, by LIGO -Virgo-Kagra interferometers detecting gravitational waves from collisions of LBHs with NSs and BHs, and (possibly) by detecting LBHs in X-ray binaries and from pulsars statistics.
- Speaker: Prof. Marek Abramowicz
- Tuesday 19 March 2024, 14:00-15:00
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: .
Fri 22 Mar 11:30: Modelling supermassive black holes: accretion, spin evolution, jets and winds
Abstract not available
- Speaker: Martin Bourne (IoA)
- Friday 22 March 2024, 11:30-12:30
- Venue: Ryle seminar room + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.
Thu 02 May 16:00: Experimental Studies of Black Holes: Status & Prospects
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.
Tue 19 Mar 11:15: Source dynamics and evolution of low-luminosity FRII radio galaxies
I will present new VLA observations that reveal the structure of a new population of low-luminosity FRII radio galaxies discovered in LoTSS. Fanaroff and Riley (1974) identified a luminosity break between their two morphological classes. FRIs are defined to be low-luminosity, centre bright jets and the higher luminosity FRI Is have jets that are edge brightened and terminate in hotspots. Using LoTSS DR1 , Mingo et al (2019) demonstrated an overlap in luminosity between FRI and FRII morphology rather than a clear divide, discovering a sub-sample of FRI Is with luminosities up to 3 magnitudes lower than the typical FR break. A population of low-luminosity FRI Is raises questions about their origins; are they older, fading FRI Is, or hosted by lower mass galaxies? Our new VLA observations of a sample of LoTSS-selected low-luminosity FRI Is allow us to make comparisons between the two FRII luminosity populations on the prevalence of hotspots, as well as morphological and spectral differences.
- Speaker: Dr. Bonny Barkus (University of Hertfordshire)
- Tuesday 19 March 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Charles Walker.
Fri 15 Mar 13:00: Fully general Cauchy evolution of asymptotically AdS spacetimes: the non-linear instability of Kerr-AdS
In addition to being at the core of the widely employed AdS/CFT correspondence, asymptotically anti-de Sitter (AdS) spacetimes with reflective boundary conditions can serve as the arena for a range of strong gravity effects: arbitrarily small perturbations are bound to remain in the bulk, where they continue to interact and typically become sizeable. Initially, I will review a numerical scheme that enables the Cauchy evolution of these spacetimes to be performed in full generality. Then, I will present the first simulations of the trapping mechanism occurring in the exterior of a Kerr-AdS black hole. This mechanism has been conjectured to cause a non-linear instability, the existence of which remains a topic of debate. The simulations offer insights into this debate, providing new perspectives on the non-linear instability of Kerr-AdS.
- Speaker: Lorenzo Rossi, Queen Mary University of London
- Friday 15 March 2024, 13:00-14:00
- Venue: Potter room/Zoom.
- Series: DAMTP Friday GR Seminar; organiser: Xi Tong.
Wed 13 Mar 13:15: A new convection scheme for exoplanet atmospheres
Convection is an essential process for transporting heat and moisture in planetary atmospheres. The standard Earth picture of moist convection rising from the surface is only one of a number of modes of convection. Notably, convection in atmospheres with a high condensible mass fraction (non-dilute atmospheres), or with a lighter background gas than the condensible species (e.g. water convection in a hydrogen dominated atmosphere) – acts very differently and can be much weaker or even shut down entirely in the latter case. Here I present a new mass-flux scheme which can capture these variations and simulate convection in a wide range of parameter space for use in 3D climate models. A validation using the case of Trappist-1 e is presented.
- Speaker: Edouard Barrier (University of Cambridge)
- Wednesday 13 March 2024, 13:15-13:40
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: Hannah Uebler.
Fri 15 Mar 11:30: Effects of primordial black holes on early star formation
Primordial black holes (PBHs) have long been considered a promising candidate or an important component of dark matter (DM). Recent gravitational wave (GW) observations of binary black hole (BH) mergers have triggered renewed interest in PBHs in the stellar-mass (∼ 10 − 100 Msun) and supermassive regimes (∼ 107 − 1011 Msun). Although only a small fraction (≲ 1%) of dark matter in the form of PBHs is required to explain observations, these PBHs may play important roles in early structure/star formation. We use cosmological zoom-in simulations and semi-analytical models to explore the possible impact of stellar-mass PBHs on first star formation, taking into account two effects of PBHs: acceleration of structure formation and gas heating by BH accretion feedback. We find that the standard picture of first star formation is not changed by stellar-mass PBHs (allowed by existing observational constraints), and their global impact on the cosmic star formation history is likely minor. However, PBHs do alter the properties of the first star-forming halos and can potentially trigger the formation of direct-collapse BHs in atomic cooling halos. On the other hand, supermassive PBHs may play more important roles as seeds of massive structures that can explain the apparent overabundance of massive galaxies in recent JWST observations. Our tentative models and results call for future studies with improved modelling of the interactions between PBHs, particle DM, and baryons to better understand the effects of PBHs on early structure/star formation and their imprints in high-redshift observations.
- Speaker: Boyuan Liu (IoA)
- Friday 15 March 2024, 11:30-12:30
- Venue: Ryle seminar room + online.
- Series: Galaxies Discussion Group; organiser: Sandro Tacchella.
Wed 13 Mar 13:40: Constraining physics and astrophysics with multifrequency CMB data
The CMB anisotropies are measured in several microwave frequency bands. Having this frequency information allows us to separate signals that are due to different sources. We can easily make maps that are sensitive to specific frequency combinations, and in this way isolate the contribution from the primary CMB (early-Universe) and various other CMB interactions such as the Sunyaev—Zel’dovich (SZ) effect (the scattering of the CMB from electrons in the late Universe). I will talk about constraints on the SZ effect from Planck data using a new frequency-separation code, pyilc, which we use to isolate the signal while removing other late-Universe biases, in particular the infrared emission from star-forming galaxies. I will also show an application to beyond standard model interactions between the CMB and a non-trivial dark sector, and how we can use the CMB to constrain beyond-standard-model particle physics.
- Speaker: Fiona McCarthy (DAMTP)
- Wednesday 13 March 2024, 13:40-14:05
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: Hannah Uebler.
Thu 07 Mar 16:00: Eddington lecture 2024: The Dawn of Galaxy-scale Gravitational Wave Astronomy
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.
Tue 07 May 14:00: Title to be confirmed
Abstract not available
- Speaker: Alvaro Ribas (IOA Cambridge)
- Tuesday 07 May 2024, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Roger Dufresne.