skip to content

Institute of Astronomy

 

Thu 05 Jun 16:00: The Formation and Co-Evolution of Galaxies and Supermassive Black Holes

IoA Institute of Astronomy Talk Lists - Tue, 03/06/2025 - 09:21
The Formation and Co-Evolution of Galaxies and Supermassive Black Holes

Cosmological hydrodynamical simulations are becoming increasingly realistic by incorporating a wider range of physical processes, higher spatial resolution, and larger statistical samples. Despite ongoing trade-offs between resolution and volume, recent advances now allow for simulations that resolve the multiphase interstellar medium and capture the clumpy nature of star formation in galaxies. In this context, I will present how such simulations shed light on the coupled evolution of galaxies and their central supermassive black holes. At high redshift, galaxies tend to be gas-rich, turbulent, and star-bursting, often exhibiting irregular, compact, and disturbed morphologies. As internal turbulence subsides, many systems transition into stable, rotating disc galaxies, typically once they reach stellar masses around 1e10 Msun. Simultaneously, black hole growth is tightly linked to the dynamical state of the host galaxy. In low-mass, turbulent systems, stellar feedback can suppress nuclear gas inflows, delaying black hole growth. Only when galaxies become sufficiently massive and dynamically settled can gas efficiently reach galactic centers to fuel sustained accretion. These processes also have important implications for the spin evolution of black holes or how fast they coalesce, which can reflect the varying modes of accretion and feedback across cosmic time.

Add to your calendar or Include in your list

Thu 05 Jun 16:00: The Formation and Co-Evolution of Galaxies and Supermassive Black Holes

Next Colloquia - Tue, 03/06/2025 - 09:21
The Formation and Co-Evolution of Galaxies and Supermassive Black Holes

Cosmological hydrodynamical simulations are becoming increasingly realistic by incorporating a wider range of physical processes, higher spatial resolution, and larger statistical samples. Despite ongoing trade-offs between resolution and volume, recent advances now allow for simulations that resolve the multiphase interstellar medium and capture the clumpy nature of star formation in galaxies. In this context, I will present how such simulations shed light on the coupled evolution of galaxies and their central supermassive black holes. At high redshift, galaxies tend to be gas-rich, turbulent, and star-bursting, often exhibiting irregular, compact, and disturbed morphologies. As internal turbulence subsides, many systems transition into stable, rotating disc galaxies, typically once they reach stellar masses around 1e10 Msun. Simultaneously, black hole growth is tightly linked to the dynamical state of the host galaxy. In low-mass, turbulent systems, stellar feedback can suppress nuclear gas inflows, delaying black hole growth. Only when galaxies become sufficiently massive and dynamically settled can gas efficiently reach galactic centers to fuel sustained accretion. These processes also have important implications for the spin evolution of black holes or how fast they coalesce, which can reflect the varying modes of accretion and feedback across cosmic time.

Add to your calendar or Include in your list

Categories: Talks

Fri 06 Jun 11:30: Exploring the End of Reionization

IoA Institute of Astronomy Talk Lists - Mon, 02/06/2025 - 15:22
Exploring the End of Reionization

Abstract not available

Add to your calendar or Include in your list

Wed 11 Jun 13:15: Neurodiversity and Communication Styles

IoA Institute of Astronomy Talk Lists - Mon, 02/06/2025 - 14:54
Neurodiversity and Communication Styles

Dr Maria Dias, Neurodiversity Adviser at the Accessibility and Disability Resource Centre (ADRC) and St Catharine’s College, will explore how people with different neurotypes communicate in unique ways, and why understanding these differences is important for creating more inclusive and supportive environments. Whether you’re neurodivergent yourself, work with neurodivergent people, or just want to learn more, this talk is for you. There will be time for questions and open discussion at the end.

Add to your calendar or Include in your list

Wed 11 Jun 13:15: Neurodiversity and Communication Styles

Next Wednesday Seminars - Mon, 02/06/2025 - 14:54
Neurodiversity and Communication Styles

Dr Maria Dias, Neurodiversity Adviser at the Accessibility and Disability Resource Centre (ADRC) and St Catharine’s College, will explore how people with different neurotypes communicate in unique ways, and why understanding these differences is important for creating more inclusive and supportive environments. Whether you’re neurodivergent yourself, work with neurodivergent people, or just want to learn more, this talk is for you. There will be time for questions and open discussion at the end.

Add to your calendar or Include in your list

Categories: Talks

Mon 02 Jun 16:00: Imaging and Design with Differentiable Physics Models

IoA Institute of Astronomy Talk Lists - Mon, 02/06/2025 - 10:51
Imaging and Design with Differentiable Physics Models

The technology that underpins machine learning – differentiable programming – is poised to revolutionise astronomy, making it possible for the first time to fit very high dimensional models: hierarchical models describing many objects; the sensitivity of millions of pixels in a detector; models of images or spectra with very many free parameters; or neural networks that represent physics we cannot easily solve in closed form. It also enables fundamental information-theoretic quantities like the Fisher information to be calculated, allowing for determination and optimization of the information content of an experiment. I will discuss how we apply this to the James Webb interferometer experiment, to provide a data-driven self-calibration of the telescope’s highest resolution mode and its difficult systematics; to design the Toliman Space Telescope to do high-precision, distortion-tolerant astrometry; and give an overview of related work on interferometry, transits and AGN reverberation mapping in our group.

Add to your calendar or Include in your list

Gas meets Kozai: the influence of a gas-rich accretion disc on hierarchical triples undergoing von Zeipel-Lidov-Kozai oscillations

Recent IoA Publications - Mon, 02/06/2025 - 10:26
arXiv:2505.23889v1 Announce Type: new Abstract: Active galactic nuclei (AGNs) consist of a central supermassive black hole (SMBH) embedded in a region with both high gas and stellar densities: the gas is present as a thin accretion disc that fuels the central SMBH, while the stars form a dense, roughly isotropic nuclear star cluster. The binaries present in such a cluster could be considered naturally as triples, with the SMBH as a third object, and their dynamics also depend on the interaction with the gas-rich disc. In this paper, we study the evolution of such a binary on an inclined orbit with respect to the disc. The binary experiences both eccentricity excitation via the von Zeipel-Lidov-Kozai (ZLK) effect and drag forces from each time it penetrates the disc. We find that, as the outer orbital inclination decreases, the evolution of inner orbital separation can transition from a regime of gradual hardening to a regime of rapid softening. As such binaries grow wider, their minimum pericentre distances (during ZLK oscillations) decrease. We show that a simple geometric condition, modulated by the complex ZLK evolution, dictates whether a binary expands or contracts due to the interactions with the AGN disc. Our results suggest that the interaction with gas-rich accretion disc could enhance the rate of stellar mergers and formation of gravitational wave sources, as well as other transients. The treatment introduced here is general and could apply, with the proper modifications, to hierarchical triples in other gas-rich systems.

Gas meets Kozai: the influence of a gas-rich accretion disc on hierarchical triples undergoing von Zeipel-Lidov-Kozai oscillations

Stars and stellar evolution - Mon, 02/06/2025 - 10:26
arXiv:2505.23889v1 Announce Type: new Abstract: Active galactic nuclei (AGNs) consist of a central supermassive black hole (SMBH) embedded in a region with both high gas and stellar densities: the gas is present as a thin accretion disc that fuels the central SMBH, while the stars form a dense, roughly isotropic nuclear star cluster. The binaries present in such a cluster could be considered naturally as triples, with the SMBH as a third object, and their dynamics also depend on the interaction with the gas-rich disc. In this paper, we study the evolution of such a binary on an inclined orbit with respect to the disc. The binary experiences both eccentricity excitation via the von Zeipel-Lidov-Kozai (ZLK) effect and drag forces from each time it penetrates the disc. We find that, as the outer orbital inclination decreases, the evolution of inner orbital separation can transition from a regime of gradual hardening to a regime of rapid softening. As such binaries grow wider, their minimum pericentre distances (during ZLK oscillations) decrease. We show that a simple geometric condition, modulated by the complex ZLK evolution, dictates whether a binary expands or contracts due to the interactions with the AGN disc. Our results suggest that the interaction with gas-rich accretion disc could enhance the rate of stellar mergers and formation of gravitational wave sources, as well as other transients. The treatment introduced here is general and could apply, with the proper modifications, to hierarchical triples in other gas-rich systems.

Mon 09 Jun 13:00: Pulsar Timing Arrays and Astrometry: Going Beyond the Hellings-Downs correlation

Next External Talks - Mon, 02/06/2025 - 09:14
Pulsar Timing Arrays and Astrometry: Going Beyond the Hellings-Downs correlation

The detection of gravitational waves (GWs) by pulsar timing arrays (PTAs) opens new avenues for probing the physics of GW sources at nanohertz frequencies. In the same frequency band, astrometric observations may also enable future GW detections. It is therefore important to investigate the potential for cross-correlating these two complementary approaches. Accordingly, I will discuss three topics related to the characterization of the stochastic gravitational-wave background using pulsar timing arrays and astrometry. The potential detection of its kinematic dipole. The prospects for measuring its circular polarization. A new method for identifying the possible presence of scalar polarization in the GW background.

Add to your calendar or Include in your list

Categories: Talks

Mon 02 Jun 13:00: Cracks in the Standard Cosmological Model: Anomalies, Tensions, and Hints of New Physics

Next External Talks - Mon, 02/06/2025 - 09:12
Cracks in the Standard Cosmological Model: Anomalies, Tensions, and Hints of New Physics

The ΛCDM model has long served as the standard paradigm in cosmology, offering a remarkably successful description of the Universe’s evolution. Yet, as observational precision continues to improve, persistent tensions have emerged across a range of probes, including the well-known Hubble constant discrepancy. While individual datasets may each align with ΛCDM, their collective interpretation reveals significant discordances that challenge the model’s internal consistency. In this talk, I will review the most prominent tensions in modern cosmology and assess their implications. I will present recent results pointing to hints of dynamical dark energy and interactions within the dark sector. I will also reflect on the growing influence of methodological choices, such as dataset selection and model assumptions, in shaping our cosmological conclusions.

Add to your calendar or Include in your list

Categories: Talks

Hubble Spies Paired Pinwheel on Its Own

Astronomy News - Sat, 31/05/2025 - 10:35
Explore Hubble

2 min read

Hubble Spies Paired Pinwheel on Its Own This NASA Hubble Space Telescope image features the beautiful barred spiral galaxy NGC 3507 ESA/Hubble & NASA, D. Thilker

A single member of a galaxy pair takes centerstage in this NASA/ESA Hubble Space Telescope image. This beautiful spiral galaxy is NGC 3507, which is situated about 46 million light-years away in the constellation Leo (the Lion). NGC 3507’s classification is a barred spiral because the galaxy’s sweeping spiral arms emerge from the ends of a central bar of stars rather than the central core of the galaxy.

Though pictured solo here, NGC 3507 actually travels the universe with a galactic partner named NGC 3501 that is located outside the frame. While NGC 3507 is a quintessential galactic pinwheel, its partner resembles a streak of quicksilver across the sky. Despite looking completely different, both are spiral galaxies, simply seen from different angles.

For galaxies that are just a few tens of millions of light-years away, like NGC 3507 and NGC 3501, features like spiral arms, dusty gas clouds, and brilliant star clusters are on full display. More distant galaxies appear less detailed. See if you can spot any faraway galaxies in this image: they tend to be orange or yellow and can be anywhere from circular and starlike to narrow and elongated, with hints of spiral arms. Astronomers use instruments called spectrometers to split the light from these distant galaxies to study the nature of these objects in the early universe.

In addition to these far-flung companions, a much nearer object joins NGC 3507. The object is marked by four spikes of light: a star within the Milky Way, a mere 436 light-years away from Earth.

Text Credit: ESA/Hubble

Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble

Media Contact:

Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight CenterGreenbelt, MD

Share Details Last Updated May 30, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms Keep Exploring Discover More Topics From Hubble Hubble Space Telescope

Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.


Hubble’s Galaxies


Science Behind the Discoveries


Hubble’s Night Sky Challenge

Tue 10 Jun 16:00: Title to be confirmed

IoA Institute of Astronomy Talk Lists - Sat, 31/05/2025 - 08:58
Title to be confirmed

Abstract not available

Add to your calendar or Include in your list

Wed 04 Jun 13:40: GPU Accelerated Sampling and Model Comparison

IoA Institute of Astronomy Talk Lists - Fri, 30/05/2025 - 11:43
GPU Accelerated Sampling and Model Comparison

This talk introduces a natively vectorized implementation of the Nested Sampling algorithm, enabling deployment of the entire inference process onto GPUs for massive acceleration. I will start by reviewing the benefits, and necessity, of the paradigm shift towards vectorized compute in the physical sciences. After a brief review of the how (and why) of Bayesian inference in Astronomy and Cosmology, I will then explore the nuances and challenges of taking some of the widely used inference algorithms within this community, in particular nested sampling, to the GPU accelerated frontier. Lastly I’ll present some practical benefit that this speedup can bring and comment on how this technical development can help push the boundaries of what we can achieve in the physical sciences.

Add to your calendar or Include in your list

Wed 04 Jun 13:40: GPU Accelerated Sampling and Model Comparison

Next Wednesday Seminars - Fri, 30/05/2025 - 11:43
GPU Accelerated Sampling and Model Comparison

This talk introduces a natively vectorized implementation of the Nested Sampling algorithm, enabling deployment of the entire inference process onto GPUs for massive acceleration. I will start by reviewing the benefits, and necessity, of the paradigm shift towards vectorized compute in the physical sciences. After a brief review of the how (and why) of Bayesian inference in Astronomy and Cosmology, I will then explore the nuances and challenges of taking some of the widely used inference algorithms within this community, in particular nested sampling, to the GPU accelerated frontier. Lastly I’ll present some practical benefit that this speedup can bring and comment on how this technical development can help push the boundaries of what we can achieve in the physical sciences.

Add to your calendar or Include in your list

Categories: Talks

Tue 21 Oct 11:15: Title TBC

Next External Talks - Fri, 30/05/2025 - 11:06
Title TBC

Abstract TBC

  • Speaker: Dr. Weiyang Wang (University of Chinese Academy of Sciences)
  • Tuesday 21 October 2025, 11:15-12:00
  • Venue: TBC.
  • Series: Hills Coffee Talks; organiser: Charles Walker.

Add to your calendar or Include in your list

Categories: Talks

How probable is the Lyman-$\alpha$ damping wing in the spectrum of the redshift z = 5.9896 quasar ULAS J0148+0600?

Galaxy Evolution and AGN - Fri, 30/05/2025 - 10:54
arXiv:2502.03085v3 Announce Type: replace Abstract: The shape of the Ly-$\alpha$ transmission in the near zone of the redshift $z=5.9896$ quasar ULAS J0148$+$0600 (hereafter J0148) is consistent with a damping wing arising from an extended neutral hydrogen island in the diffuse intergalactic medium (IGM). Here we use simulations of late-ending reionisation from Sherwood-Relics to assess the expected incidence of quasars with Ly-$\alpha$ and Ly-$\beta$ absorption similar to the observed J0148 spectrum. We find a late end to reionisation at $z=5.3$ is a necessary requirement for reproducing a Ly-$\alpha$ damping wing consistent with J0148. This occurs in $\sim3$ per cent of our simulated spectra for an IGM neutral fraction $\langle x_{\rm HI}\rangle=0.14$ at $z=6$. However, using standard assumptions for the ionising photon output of J0148, the a priori probability of drawing a simulated quasar spectrum with a Ly-$\alpha$ damping wing profile \emph{and} Ly-$\alpha$ near zone size that simultaneously match J0148 is low, $p<10^{-2}$. This may indicate that the ionising emission from J0148 is variable on timescales $t<10^{5}\rm\,yr$, or alternatively that the Ly-$\alpha$ transmission in the J0148 near zone is impacted by the transverse proximity effect from nearby star-forming galaxies or undetected quasars. We also predict the IGM temperature should be $T\sim 4\times 10^{4}\rm\,K$ within a few proper Mpc of the Ly-$\alpha$ near zone edge due to recent H$\,\rm \scriptstyle I$ and He$\,\rm \scriptstyle II$ photo-heating. Evidence for enhanced thermal broadening in the Ly-$\alpha$ absorption near the damping wing edge would provide further evidence that the final stages of reionisation are occurring at $z<6$.

How probable is the Lyman-$\alpha$ damping wing in the spectrum of the redshift z = 5.9896 quasar ULAS J0148+0600?

Recent IoA Publications - Fri, 30/05/2025 - 10:54
arXiv:2502.03085v3 Announce Type: replace Abstract: The shape of the Ly-$\alpha$ transmission in the near zone of the redshift $z=5.9896$ quasar ULAS J0148$+$0600 (hereafter J0148) is consistent with a damping wing arising from an extended neutral hydrogen island in the diffuse intergalactic medium (IGM). Here we use simulations of late-ending reionisation from Sherwood-Relics to assess the expected incidence of quasars with Ly-$\alpha$ and Ly-$\beta$ absorption similar to the observed J0148 spectrum. We find a late end to reionisation at $z=5.3$ is a necessary requirement for reproducing a Ly-$\alpha$ damping wing consistent with J0148. This occurs in $\sim3$ per cent of our simulated spectra for an IGM neutral fraction $\langle x_{\rm HI}\rangle=0.14$ at $z=6$. However, using standard assumptions for the ionising photon output of J0148, the a priori probability of drawing a simulated quasar spectrum with a Ly-$\alpha$ damping wing profile \emph{and} Ly-$\alpha$ near zone size that simultaneously match J0148 is low, $p<10^{-2}$. This may indicate that the ionising emission from J0148 is variable on timescales $t<10^{5}\rm\,yr$, or alternatively that the Ly-$\alpha$ transmission in the J0148 near zone is impacted by the transverse proximity effect from nearby star-forming galaxies or undetected quasars. We also predict the IGM temperature should be $T\sim 4\times 10^{4}\rm\,K$ within a few proper Mpc of the Ly-$\alpha$ near zone edge due to recent H$\,\rm \scriptstyle I$ and He$\,\rm \scriptstyle II$ photo-heating. Evidence for enhanced thermal broadening in the Ly-$\alpha$ absorption near the damping wing edge would provide further evidence that the final stages of reionisation are occurring at $z<6$.

A black hole in a near-pristine galaxy 700 million years after the Big Bang

Cosmology and Fundamental physics - Fri, 30/05/2025 - 10:53
arXiv:2505.22567v2 Announce Type: replace Abstract: The recent discovery of a large number of massive black holes within the first two billion years after the Big Bang, as well as their peculiar properties, have been largely unexpected based on the extrapolation of the properties of luminous quasars. These findings have prompted the development of several theoretical models for the early formation and growth of black holes, which are, however, difficult to differentiate. We report the metallicity measurement around a gravitationally lensed massive black hole at redshift 7.04, hosted in a galaxy with very low dynamical mass. The weakness of the [OIII]5007 emission line relative to the narrow Hbeta emission indicates an extremely low chemical enrichment, less than 0.01 solar. We argue that such properties cannot be uncommon among accreting black holes around this early cosmic epoch. Explaining such a low chemical enrichment in a system that has developed a massive black hole is challenging for most theories. Models assuming heavy black hole seeds (such as Direct Collapse Black Holes) or super-Eddington accretion scenarios struggle to explain the observations, although they can potentially reproduce the observed properties in rare cases. Models invoking "primordial black holes" (i.e. putative black holes formed shortly after the Big Bang) may potentially explain the low chemical enrichment associated with this black hole.

A black hole in a near-pristine galaxy 700 million years after the Big Bang

Galaxy Evolution and AGN - Fri, 30/05/2025 - 10:53
arXiv:2505.22567v2 Announce Type: replace Abstract: The recent discovery of a large number of massive black holes within the first two billion years after the Big Bang, as well as their peculiar properties, have been largely unexpected based on the extrapolation of the properties of luminous quasars. These findings have prompted the development of several theoretical models for the early formation and growth of black holes, which are, however, difficult to differentiate. We report the metallicity measurement around a gravitationally lensed massive black hole at redshift 7.04, hosted in a galaxy with very low dynamical mass. The weakness of the [OIII]5007 emission line relative to the narrow Hbeta emission indicates an extremely low chemical enrichment, less than 0.01 solar. We argue that such properties cannot be uncommon among accreting black holes around this early cosmic epoch. Explaining such a low chemical enrichment in a system that has developed a massive black hole is challenging for most theories. Models assuming heavy black hole seeds (such as Direct Collapse Black Holes) or super-Eddington accretion scenarios struggle to explain the observations, although they can potentially reproduce the observed properties in rare cases. Models invoking "primordial black holes" (i.e. putative black holes formed shortly after the Big Bang) may potentially explain the low chemical enrichment associated with this black hole.

A black hole in a near-pristine galaxy 700 million years after the Big Bang

Recent IoA Publications - Fri, 30/05/2025 - 10:53
arXiv:2505.22567v2 Announce Type: replace Abstract: The recent discovery of a large number of massive black holes within the first two billion years after the Big Bang, as well as their peculiar properties, have been largely unexpected based on the extrapolation of the properties of luminous quasars. These findings have prompted the development of several theoretical models for the early formation and growth of black holes, which are, however, difficult to differentiate. We report the metallicity measurement around a gravitationally lensed massive black hole at redshift 7.04, hosted in a galaxy with very low dynamical mass. The weakness of the [OIII]5007 emission line relative to the narrow Hbeta emission indicates an extremely low chemical enrichment, less than 0.01 solar. We argue that such properties cannot be uncommon among accreting black holes around this early cosmic epoch. Explaining such a low chemical enrichment in a system that has developed a massive black hole is challenging for most theories. Models assuming heavy black hole seeds (such as Direct Collapse Black Holes) or super-Eddington accretion scenarios struggle to explain the observations, although they can potentially reproduce the observed properties in rare cases. Models invoking "primordial black holes" (i.e. putative black holes formed shortly after the Big Bang) may potentially explain the low chemical enrichment associated with this black hole.