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URL: http://talks.cam.ac.uk/show/index/54089
Updated: 46 min 21 sec ago

Mon 13 Oct 13:00: Title to be confirmed

Sun, 07/09/2025 - 11:56
Title to be confirmed

Abstract not available

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Fri 26 Sep 11:30: The curious case of metal-poor DLAs at cosmic noon

Mon, 01/09/2025 - 21:26
The curious case of metal-poor DLAs at cosmic noon

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Fri 24 Oct 11:30: Learning galaxy properties with machine learning and simulation based inference

Fri, 29/08/2025 - 12:02
Learning galaxy properties with machine learning and simulation based inference

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Fri 14 Nov 11:30: Physics of Ultra-Faint Dwarfs

Thu, 28/08/2025 - 09:05
Physics of Ultra-Faint Dwarfs

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Fri 28 Nov 11:30: Dwarf Galaxies in the Local Universe

Thu, 28/08/2025 - 09:03
Dwarf Galaxies in the Local Universe

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Fri 07 Nov 11:30: JWST Spectroscopic Insights Into the Evolution and Diversity of Galaxies within the First Billion Years

Wed, 27/08/2025 - 12:39
JWST Spectroscopic Insights Into the Evolution and Diversity of Galaxies within the First Billion Years

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Fri 28 Nov 11:30: Local satellite galaxies

Wed, 27/08/2025 - 12:38
Local satellite galaxies

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Fri 07 Nov 10:00: JWST Spectroscopic Insights Into the Evolution and Diversity of Galaxies within the First Billion Years

Mon, 25/08/2025 - 14:50
JWST Spectroscopic Insights Into the Evolution and Diversity of Galaxies within the First Billion Years

Abstract not available

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Tue 23 Sep 13:00: Planetary Evolution Across Stellar Lifetimes

Mon, 25/08/2025 - 10:48
Planetary Evolution Across Stellar Lifetimes

Over the past thirty years, nearly 6,000 planets have been confirmed. These systems provide key insights into how planet populations evolve over time, sculpted by planetary dynamics and stellar processes. Such mechanisms can drive dramatic changes on the planet and, in extreme cases, lead to its destruction. However, there are many gaps in our understanding of the evolution of planetary systems. In particular, the ultimate fate of these systems as their host stars evolve off the main sequence remains largely unknown. In this talk, I will present my work probing the mechanisms that shape planets over their lifetime. First, I will examine the impact of migration and photoevaporation on main-sequence systems. The recently confirmed planet, TOI -5800 b, provides a unique case study of an eccentric sub-Neptune on a close-in orbit, and may provide insight into how evolutionary processes contribute to population-level features such as the Neptunian desert. Second, I will describe how stellar evolution transforms planetary systems. In addition to destroying inner planets and dramatically altering the dynamics of outer planets, this process may also fundamentally alter the atmospheric composition of giant planets through a phase called common envelope evolution. Finally, I will discuss the ultimate fate of planet populations as their host stars evolve to their final state as white dwarfs. Even in these mature systems, planets can be destroyed through scattering into their host’s Roche radius, leaving an observational signature called “pollution.” I will also highlight ongoing efforts to probe the surviving planet population around white dwarf stars with JWST .

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Tue 19 Aug 10:00: Mid-Infrared diversity in nearby AGN: New insights from JWST/MIRI

Thu, 07/08/2025 - 13:24
Mid-Infrared diversity in nearby AGN: New insights from JWST/MIRI

Type-2 quasars (QSO2s) are luminous active galactic nuclei characterized by narrow optical emission lines. They are the torus-obscured counterparts of type-1 quasars, although in some cases, part of the obscuration arises from galactic scales. Thanks to JWST , it is now possible to study the properties of nuclear gas and dust in local AGN with unprecedented spatial and spectral resolution and sensitivity. In this talk, I will present recent results from Cycle 2 JWST /MIRI observations of nearby QSO2s from the QSOFEED sample, which revealed a striking diversity of mid-infrared spectral shapes and features, and compare them with JWST /MIRI data of Seyfert galaxies from the Galactic Activity, Torus, and Outflow Survey (GATOS). Our findings highlight the complexity of these nuclear environments and underscore the need for larger JWST samples to disentangle the roles of obscuration, ionizing continuum, gas density, and other factors in shaping their mid-infrared spectra.

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Tue 19 Aug 10:00: Title to be confirmed

Wed, 06/08/2025 - 15:14
Title to be confirmed

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Fri 21 Nov 11:30: Title to be confirmed

Wed, 06/08/2025 - 15:09
Title to be confirmed

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Fri 08 Aug 11:30: The Reionization of our Local Universe

Tue, 05/08/2025 - 11:46
The Reionization of our Local Universe

The neighborhood in the immediate cosmological vicinity of our Milky Way is known as the Near-Field. Due to its proximity to us, it is the best-observed region of the Universe. As such it is the most interesting to study, to understand and to try and simulate, as there is a wealth of observational information available that could allow us to significantly advance our knowledge on e.g. large-scale structure and galaxy formation, feedback processes and the nature of dark matter in a range of different local environments. I will present the work we have been doing over the years to address this problem. This has been largely based on constrained simulations of the Near-Field from the CLUES project, which use our ever expanding knowledge of the local structures and their velocity fields to create numerical structure formation simulations that faithfully reproduce the local universe at present. The main focus of our work has been on understanding the potentially detectable local signatures of Cosmic Reionization, for example on the number and properties of satellites of the Local Group and locations where some of the First Stars may be located (cosmic archaeology), which I will both discuss.

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Fri 08 Aug 11:30: Title to be confirmed

Sat, 02/08/2025 - 22:05
Title to be confirmed

Abstract not available

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Wed 23 Jul 13:15: The primary role of jets in exploding all core-collapse supernovae

Mon, 21/07/2025 - 11:09
The primary role of jets in exploding all core-collapse supernovae

I will present evidence in core-collapse supernova remnants for the action of jets in the supernova explosion process. Two main types of observations appear in many, but not all, core-collapse supernova remnants: (i) the well-established presence of a pair of opposite `ears’ and (ii) the recently identified point-symmetrical structure in 15 remnants, including SN 1987A , Cassiopeia A, Vela, and the Crab Nebula. The pair of opposite ears suggests that two opposite jets inflate the ears. The point-symmetrical structure results from two or more pairs of jets along different axes, as the jittering jets explosion mechanism (JJEM) predicts. I will compare the JJEM with the neutrino-driven mechanism and conclude that the neutrino-driven mechanism comes short in explaining observations, leaving the JJEM as the primary explosion mechanism of CCS Ne. The JJEM has some unique signatures in addition to its point-symmetric morphology, such as gravitational waves and energetic explosions. I will comment on the overrated popularity of the neutrino-driven mechanism in scientific meetings and literature.

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Wed 16 Jul 13:45: Direct Images of the Cosmic Web of Intergalactic and Circumgalactic Gas

Mon, 14/07/2025 - 07:27
Direct Images of the Cosmic Web of Intergalactic and Circumgalactic Gas

The filamentary pattern in which the Universe’s matter concentrates, the cosmic web, is predicted by the ΛCDM cosmological model and contains the majority of the universe’s matter. Detailed mapping of this interconnected structure of gaseous filaments, galaxies, quasars, dark matter, and voids, is central to a comprehensive understanding of the origin and evolution of our Universe. I will describe very deep narrow band imaging observations obtained using the Condor Array Telescope in New Mexico, centered on the Cosmic Evolution Survey (COSMOS) field at a redshift of z=2.45. We use several hydrodynamical simulations to predict the cosmic web Lyman-alpha emission properties. The simulation results show good agreement with the Condor data, supporting the notion that Condor has detected wide-field cosmic web emission, potentially marking the beginning of a new field of cosmology – detailed baryonic and dark matter cartography of the diffuse Universe. I will describe the details of these data and simulations and then discuss the construction of a new Condor in the Atacama that will go even deeper and which we hope will see first light towards the end of 2025.

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Wed 16 Jul 13:15: Chasing the First Stars With Outliers

Mon, 14/07/2025 - 07:25
Chasing the First Stars With Outliers

he OUTLIERS project aims to find and study the most ancient stars in our Galaxy — stars that formed shortly after the Big Bang. These stars carry unique chemical fingerprints that tell us about the very first generations of stars, the first supernovae, and the early stages of galaxy formation. Although extremely rare and faint, they can still be found today thanks to the combined power of Gaia — which maps the positions and motions of over a billion stars — and new large spectroscopic surveys like DESI , WEAVE, and 4MOST. OUTLIERS uses this data to select and follow up the most promising candidates. By studying these stellar fossils in detail, we hope to answer long-standing questions about how the first stars formed, what elements they created, and how the Universe evolved in its earliest phases.

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Wed 16 Jul 13:15: Chasing the First Stars With Outliers

Mon, 14/07/2025 - 07:25
Chasing the First Stars With Outliers

he OUTLIERS project aims to find and study the most ancient stars in our Galaxy — stars that formed shortly after the Big Bang. These stars carry unique chemical fingerprints that tell us about the very first generations of stars, the first supernovae, and the early stages of galaxy formation. Although extremely rare and faint, they can still be found today thanks to the combined power of Gaia — which maps the positions and motions of over a billion stars — and new large spectroscopic surveys like DESI , WEAVE, and 4MOST. OUTLIERS uses this data to select and follow up the most promising candidates. By studying these stellar fossils in detail, we hope to answer long-standing questions about how the first stars formed, what elements they created, and how the Universe evolved in its earliest phases.

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Fri 18 Jul 11:30: Dust grains across the universe: JWST and ALMA insights from cosmic noon to the early universe

Thu, 10/07/2025 - 18:12
Dust grains across the universe: JWST and ALMA insights from cosmic noon to the early universe

Abstract not available

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Wed 09 Jul 13:15: Double black hole mergers in nuclear star clusters: eccentricities, spins, masses, and the growth of massive seeds

Tue, 08/07/2025 - 09:58
Double black hole mergers in nuclear star clusters: eccentricities, spins, masses, and the growth of massive seeds

We investigate the formation of intermediate-mass black holes (IMBHs) through hierarchical mergers of stellar-origin black holes (BHs), as well as BH mergers formed dynamically in nuclear star clusters. Using a semi-analytical approach that incorporates probabilistic, mass-function–dependent double-BH (DBH) pairing, binary–single encounters, and a mass-ratio–dependent prescription for energy dissipation in hardening binaries, we find that IMB Hs with masses of order 10²–10⁴ M⊙ can be formed solely through hierarchical mergers on timescales of a few hundred Myr to a few Gyr. Clusters with escape velocities ≳ 400 km s⁻¹ inevitably form high-mass IMB Hs. The spin distribution of IMB Hs with masses ≳ 10³ M⊙ is strongly clustered at χ ≈ 0.15, while for lower masses it peaks at χ ≈ 0.7. Eccentric mergers are more frequent for equal-mass binaries containing first- and second-generation BHs. Metal-rich, young, dense clusters can produce up to 20 of their DBH mergers with eccentricity ≥ 0.1 at 10 Hz, and ~ 2–9 of all in-cluster mergers form at > 10 Hz. Nuclear star clusters are therefore promising environments for the formation of highly eccentric DBH mergers, detectable with current gravitational-wave detectors. Clusters of extreme mass (∼ 10⁸ M⊙) and density (∼ 10⁸ M⊙ pc⁻³) can have about half of their DBH mergers with primary masses ≥ 100 M⊙. The fraction of in-cluster mergers increases rapidly with increasing escape velocity, approaching unity for Vesc ≳ 200 km s⁻¹. The cosmological DBH merger rate from nuclear clusters varies from ≲ 0.01 to 1 Gpc⁻³ yr⁻¹, where the large uncertainties stem from cluster initial conditions, number-density distributions, and the redshift evolution of nucleated galaxies.

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