Mon 26 Feb 14:00: Dynamics in gas is different
Gaseous environments are abundant in the Universe and include AGN disks, star-forming regions, protoplanetary disks and regions of late star formation in globular clusters. While the dynamics of binaries in gas-free environments have been studied extensively, gas-rich environments are fertile ground for phenomena that are still largely unexplored, and in this talk, we will discuss some of the unique phenomena of dynamics in gas. Binaries tend statistically to get softer as they encounter other stars, according to Heggie’s law. However, in gaseous environments, this law should be modified as gas-hardening could lead to a significant energy dissipation that could dominate over stellar softening. Here we explore the effect of gas hardening on the softening rate of binaries and its implications. We will also discuss gas-assisted binary formation. In gaseous media, interactions between two initially unbound objects could result in gas-assisted binary formation, induced by a loss of kinetic energy to the ambient gas medium. Here, we derive analytically the criteria for gas-assisted binary capture through gas dynamical friction dissipation. In some environments, these captures could occur more than once per object, leading to multicaptures. We will discuss that and further implications.
- Speaker: Mor Rozner (Technion-Israel Institute of Technology)
- Monday 26 February 2024, 14:00-15:00
- Venue: MR14 DAMTP and online.
- Series: DAMTP Astrophysics Seminars; organiser: Thomas Jannaud.
Tue 05 Mar 11:15: New Space & the CubeSat Revolution
CubeSats stand at the forefront of the New Space revolution, a paradigm shift in space exploration characterised by reduced launch costs and increased accessibility to space. These miniature satellites, defined by their standardised dimensions and modular design, have emerged as a pivotal technology with some implications of research in astronomy. With their standardised dimensions and modular design, these small satellites enable a wide range of experiments that were previously the domain of larger, more costly missions. In my talk, I aim to introduce you to valuable opportunities that can emerge by leading a CubeSat project with special interest in payloads dedicated to astrophysics research. As a cost-effective space instrument, CubeSats unlock observational windows across the ultraviolet, far-infrared, and low-frequency radio spectra, which are inaccessible from Earth’s surface. Beyond their technical capabilities, these satellites enable sustained observations of celestial bodies over extended periods, free from the scheduling constraints of larger telescopes.
- Speaker: Dolev Bashi
- Tuesday 05 March 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Dolev Bashi.
Tue 27 Feb 13:00: Protoplanetary disc: what can we learn by combining theory and observations?
Protoplanetary discs serve as the cradle for planetary formation and evolution. It is then fundamental to study their evolution to gain a comprehensive understanding of exoplanetary system formation. These discs can be studied using two distinct approaches.
On one side, they can be analysed as a set of single sources, allowing for a detailed analysis of the mechanisms behind the diversity of observed morphologies using gas and dust tracers such as rings, gaps and asymmetries.
On the other side, it is crucial to study star-forming regions, understanding which physical processes are governing the global disc evolution.
In this talk, I will firstly describe results from the modelling of single sources, underlining the information we can obtain by comparing multi-wavelengths observations with results from the hydrodynamical models of specific sources (e.g., HD169142 , PDS70, GG Tau A). In particular, I will focus on how simulations can help in constraining the mass and position of the candidate proto-planets that may be responsible for the ALMA and SPHERE observational results, as well as how they can support future observational strategies.
I will then summarize some of the results obtained by testing disc evolution models by comparing them with the Lupus star forming region. In these works, we tested the secular evolution of the observed dust and gas radius of disc populations and their ratio, to test the efficiency of radial drift and the viscous evolution theory.
- Speaker: Claudia Toci (ESO)
- Tuesday 27 February 2024, 13:00-14:00
- Venue: Ryle seminar room + ONLINE - Details to be sent by email.
- Series: Exoplanet Seminars; organiser: Dr Emily Sandford.
Tue 27 Feb 11:15: Real-time pipelines for SKA — Progress and challenges
The Square Kilometre Array (SKA) will be the largest interferometric radio telescope to date, with unprecedented resolution and sensitivity to study various phenomena of the universe. In data processing pipelines for radio telescopes, real time calibration, such as beam former and pointing offset calibration, are crucial for obtaining high-quality interferometric data from the observations. As an example, I will discuss the design and ongoing implementation of the pointing offset calibration pipeline within SKA ’s data processing software, describing the steps carried out to integrate the pipeline into telescope execution control and data queue system, as well as outlining challenges and greater implications on the data processing algorithm and software within the radio astronomy community.
- Speaker: Dr. Ying-He Celeste Lü (Cavendish Astrophysics)
- Tuesday 27 February 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Charles Walker.
Tue 05 Mar 11:15: New Space & the CubeSat Revolution
CubeSats stand at the forefront of the New Space revolution, a paradigm shift in space exploration characterised by reduced launch costs and increased accessibility to space. These miniature satellites, defined by their standardised dimensions and modular design, have emerged as a pivotal technology with some implications of research in astronomy. With their standardised dimensions and modular design, these small satellites enable a wide range of experiments that were previously the domain of larger, more costly missions. In my talk, I aim to introduce you to valuable opportunities that can emerge by leading a CubeSat project with special interest in payloads dedicated to astrophysics research. As a cost-effective space instrument, CubeSats unlock observational windows across the ultraviolet, far-infrared, and low-frequency radio spectra, which are inaccessible from Earth’s surface. Beyond their technical capabilities, these satellites enable sustained observations of celestial bodies over extended periods, free from the scheduling constraints of larger telescopes.
- Speaker: Dolev Bashi
- Tuesday 05 March 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Dolev Bashi.
JADES: The production and escape of ionizing photons from faint Lyman-alpha emitters in the epoch of reionization
Mon 13 May 13:00: Title to be confirmed
Abstract not available
- Speaker: Jean-Luc Lehners (MPI for Gravitational Physics, Potsdam)
- Monday 13 May 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Thomas Colas.
Tue 27 Feb 11:15: Real-time pipelines for SKA — Progress and challenges
The Square Kilometre Array (SKA) will be the largest interferometric radio telescope to date, with unprecedented resolution and sensitivity to study various phenomena of the universe. In data processing pipelines for radio telescopes, real time calibration, such as beam former and pointing offset calibration, are crucial for obtaining high-quality interferometric data from the observations. As an example, I will discuss the design and ongoing implementation of the pointing offset calibration pipeline within SKA ’s data processing software, describing the steps carried out to integrate the pipeline into telescope execution control and data queue system, as well as outlining challenges and greater implications on the data processing algorithm and software within the radio astronomy community.
- Speaker: Celeste Lu (Cavendish Astrophysics)
- Tuesday 27 February 2024, 11:15-12:00
- Venue: Coffee area, Battcock Centre.
- Series: Hills Coffee Talks; organiser: Charles Walker.
Data-Space Validation of High-Dimensional Models by Comparing Sample Quantiles
Simulations of spin-driven AGN jets in gas-rich galaxy mergers
Dark Energy Survey: Galaxy Sample for the Baryonic Acoustic Oscillation Measurement from the Final Dataset
Dark Energy Survey: A 2.1% measurement of the angular Baryonic Acoustic Oscillation scale at redshift $z_{\rm eff}$=0.85 from the final dataset
Mon 26 Feb 13:00: On the physical spectra of primordial perturbations from inflation
It has been suggested that the effects of renormalization significantly reduce the amplitude of the inflationary spectra at scales measurable in the cosmic microwave background. Via a gauge-invariant analysis, we compute the renormalized scalar and tensor power spectra and follow their evolution in an inflating universe that undergoes a transition to an FRW phase with a growing horizon. For perturbations originating from Minkowski vacuum fluctuations, we show that the standard prediction for the spectrum on superhorizon scales is a late-time attractor, while it is UV finite at all times. Our result is independent of the equation of state after inflation, showing that the standard prediction is fully robust.
- Speaker: Silvia Pla Garcia (King's College London)
- Monday 26 February 2024, 13:00-14:00
- Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
- Series: Cosmology Lunch; organiser: Thomas Colas.
Wed 21 Feb 14:00: Emergent gauge fields, fractionalised quasiparticles and dynamical fractals
Field theoretic descriptions are a powerful tool to capture the emergent, collective behaviour of strongly correlated many body systems on large scales. Gauge field theories in particular are of special interest in modern physics, due to their connection to topological behaviour and fractionalisation. Through this modelling, the original dense system of strongly interacting degrees of freedom can be interpreted as an emergent vacuum with quasiparticle excitations whose properties are closely related to the nature of the emergent gauge fields. This change in perspective affords us an unprecedented insight into the properties of these systems and in predicting new behaviour. We will review some of these concepts in a model and material that has become a paradigmatic case in point: spin ice. We shall further discuss how microscopic details can lead to surprisingly important effects in the cooperative dynamics of these systems, which becomes underpinned by near-fractal structures.
- Speaker: Claudio Castelnovo (Cavendish)
- Wednesday 21 February 2024, 14:00-15:00
- Venue: MR2.
- Series: Theoretical Physics Colloquium; organiser: Hannah Banks.
On the Constraints on Superconducting Cosmic Strings from 21-cm Cosmology
Unveiling Dark Matter free-streaming at the smallest scales with high redshift Lyman-alpha forest
Building the First Galaxies -- Chapter 2. Starbursts Dominate The Star Formation Histories of 6 < z <12 Galaxies
Wed 21 Feb 13:40: Stellar Mass Assembly of Galaxy Populations up to z = 4 with pop-cosmos
In a recent paper we presented pop-cosmos, a state-of-the-art stellar population synthesis (SPS) framework. We described the details of how we fitted this framework to a large, deep, flux-limited (r < 25) sample of galaxies from the Cosmic Evolution Survey (COSMOS), enabling investigation of the full web of dependencies between different galaxy properties for the first time. In this talk I will present my recent work investigating the star formation histories (SFHs) of galaxy populations up to z=4 utilising the pop-cosmos model. I will begin by summarizing the details of our model and the SFH prescription employed in it. I will then present key galaxy evolution results such as the mean stellar mass assembly histories of galaxy populations through cosmic time. Further, by defining star-forming and quiescent subpopulations based on recent star formation activity (i.e. last 100 Myr), these relations will highlight how these subpopulations build up their stellar mass.
- Speaker: Sinan Deger
- Wednesday 21 February 2024, 13:40-14:05
- Venue: The Hoyle Lecture Theatre + Zoom .
- Series: Institute of Astronomy Seminars; organiser: Hannah Uebler.