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A black hole 33 times the mass of the sun is the largest stellar black hole ever spotted, and its strange companion star could help explain how it got so huge

Wading through the wealth of data from ESA’s Gaia mission , scientists have uncovered a ‘sleeping giant’. A large black hole, with a mass of nearly 33 times the mass of the Sun, was hiding in the constellation Aquila, less than 2000 light-years from Earth. This is the first time a black hole of stellar origin this big has...

Studies of the reionization-era intergalactic and circumgalactic media using cosmological simulations

TBC

• Speaker: Dr. Caitlin Doughty (University of Leiden/MPA Garching)
• Tuesday 22 October 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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The ionising properties of galaxies at the Epoch of Reionisation with JWST

TBC

• Speaker: Dr. Charlotte Simmonds (Kavli Institute for Technology, University of Cambridge)
• Tuesday 11 June 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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The Black Hole Mass Metallicity Relation and Insights into Galaxy Quenching

TBC

• Speaker: William Baker (University of Cambridge)
• Tuesday 28 May 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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Liquid Crystal based adaptive optics

TBC

• Speaker: Oana Niculescu (University of Cambridge)
• Tuesday 14 May 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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Interferometric measurements of the 21-cm signal with SKA

The Cosmic Dawn marks the first star formations and preceded the Epoch-of-Reionization, when the Universe underwent a fundamental transformation propelled by the radiation from these first stars and galaxies. Interferometric 21-cm experiments aim to probe redshifted neutral hydrogen signals from these periods, constraining the conditions of the early Universe. The SKA -LOW instrument of the Square Kilometre Array telescope is envisaged to be the largest and most sensitive radio telescope at m and cm wavelengths. In this talk we present a data analysis pipeline that was used in the SKA Science Data Challenge 3a: Epoch of Reionisation (SKA SDC3a) to process the novel data products expected from the SKA . To determine whether a successful 21-cm detection is possible with the envisaged SKA , we implement predictive foreground and Bayesian Gaussian Process Regression models alongside a foreground avoidance strategy to isolate the 21-cm signal from that of the astrophysical radio frequency (RF) foregrounds.

• Speaker: Yuchen Liu and Oscar O'Hara (Cavendish Astrophysics)
• Tuesday 07 May 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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Radio observations of extra-galactic transients with the AMI-LA telescope

TBC

• Speaker: Dr. Lauren Rhodes (University of Oxford)
• Tuesday 30 April 2024, 11:15-12:00
• Venue: Coffee area, Battcock Centre.
• Series: Hills Coffee Talks; organiser: Charles Walker.

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arXiv:2310.01763v2 Announce Type: replace Abstract: We use semi-analytical models to study the effects of primordial black hole (PBH) accretion on the cosmic radiation background during the epoch of reionization ($z\gtrsim 6$). We consider PBHs floating in the intergalactic medium (IGM), and located inside haloes, where star formation can occur. For stars with a mass $\gtrsim 25 \rm\ M_{\odot}$, formed in suitable host haloes, we assume they quickly burn out and form stellar remnant black holes (SRBHs). Since SRBHs also accrete material from their surroundings, we consider them to have similar radiation feedback as PBHs in the halo environment. To estimate the background radiation level more accurately, we take into account the impact of PBHs on structure formation, allowing an improved modeling of the halo mass function. We consider the radiation feedback from a broad suite of black holes: PBHs, SRBHs, high-mass X-ray binaries (HMXBs), and supermassive black holes (SMBHs). We find that at $z\gtrsim 30$, the radiation background energy density is generated by PBHs accreting in the IGM, whereas at lower redshifts, the accretion feedback power from haloes dominates. We also analyze the total power density by modeling the accretion spectral energy distribution (SED), and break it down into select wavebands. In the UV band, we find that for $f_{\rm PBH} \lesssim 10^{-3}$, the H-ionizing and Lyman-$\alpha$ fluxes from PBH accretion feedback do not violate existing constraints on the timing of reionization, and on the effective Wouthuysen-Field coupling of the 21-cm spin temperature of neutral hydrogen to the kinetic temperature of the IGM. However, in the X-ray band, with the same abundance, PBHs contribute significantly and could account for the unresolved part of the cosmic X-ray background.

Title to be confirmed

Abstract not available

• Speaker: Florian Lienhard (Zurich)
• Tuesday 30 April 2024, 13:00-14:00
• Venue: Battcock coffee area + ONLINE - Details to be sent by email.
• Series: Exoplanet Seminars; organiser: Dr Dolev Bashi.

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Abstract not available

• Speaker: Nicolina Chrysaphi (Sorbonne)
• Tuesday 28 May 2024, 13:00-14:00
• Venue: Hoyle Committee Room + ONLINE - Details to be sent by email.
• Series: Exoplanet Seminars; organiser: Dr Dolev Bashi.

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Abstract not available

• Speaker: Hamish Innes (Freie Universität - Berlin)
• Tuesday 21 May 2024, 13:00-14:00
• Venue: Hoyle Committee Room + ONLINE - Details to be sent by email.
• Series: Exoplanet Seminars; organiser: Dr Dolev Bashi.

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The physical mechanism of the streaming instability, and whether it works in vortices

A major hurdle in planet formation theory is that we do not understand how small pebbles congregate into big planetesimals. A promising way to overcome this metre-scale barrier involves a fluid dynamics phenomenon called the streaming instability (SI). It concentrates the pebbles into clumps that are dense enough to collapse gravitationally, thereby forming planetesimals.

Unfortunately, the mechanism responsible for the onset of the instability remains mysterious. This makes it hard to evaluate the robustness of the instability, or to understand how it saturates. It has recently been shown that the SI is a Resonant Drag Instability (RDI) involving inertial waves. In the first part of this talk, I build on this insight to produce a clear physical picture of how the SI develops.

Another problem is that the SI can only devellop in regions containing a high density of similar-sized pebbles. Those conditions are met in large-scale vortices, but no one knows if the SI can feed on vorticial flows. Indeed, any instability can only devellop in specific flows, and a priori the SI is tailored to Keplerian disc flows, not vortex flows. I answer this question in the second part of the talk. To do so, I develop a simple pen-and-paper model of a dust-laden vortex in a protoplanetary disc. I find that if the vortex is weak and anticyclonic, dust drifts towards its centre. I then build a vortex analog of the shearing box to analyse the local linear stability of my dusty vortex. I find that the dust’s drift powers an instability which closely resembles the SI. This result strengthens the case for vortex-induced planetesimal formation.

• Speaker: Nathan Magnan (DAMTP)
• Tuesday 23 April 2024, 13:00-14:00
• Venue: Hoyle Committee Room + ONLINE - Details to be sent by email.
• Series: Exoplanet Seminars; organiser: Dr Dolev Bashi.

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The brightest burst of light ever recorded was caused by a supernova, but that prompts new questions.

2 min read

Hubble Spots a Galaxy Hidden in a Dark Cloud This Hubble image features the spiral galaxy IC 4633. ESA/Hubble & NASA, J. Dalcanton, Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA; Acknowledgement: L. Shatz

The subject of this image taken with the NASA/ESA Hubble Space Telescope is the spiral galaxy IC 4633, located 100 million light-years away from us in the constellation Apus. IC 4633 is a galaxy rich in star-forming activity and also hosts an active galactic nucleus at its core. From our point of view, the galaxy is tilted mostly towards us, giving astronomers a fairly good view of its billions of stars.

However, we can’t fully appreciate the features of this galaxy — at least in visible light — because it’s partially concealed by a stretch of dark dust (lower-right third of the image). This dark nebula is part of the Chamaeleon star-forming region, itself located only around 500 light-years from us, in a nearby part of our Milky Way galaxy. The dark clouds in the Chamaeleon region occupy a large area of the southern sky, covering their namesake constellation but also encroaching on nearby constellations, like Apus. The cloud is well-studied for its treasury of young stars, particularly the cloud Cha I, which both Hubble and the NASA/ESA/CSA James Webb Space Telescope have imaged.

The cloud overlapping IC 4633 lies east of the well-known Cha I, II, and III, and is also known as MW9 and the South Celestial Serpent. Classified as an integrated flux nebula (IFN) — a cloud of gas and dust in the Milky Way galaxy that’s not near to any single star and is only faintly lit by the total light of all the galaxy’s stars — this vast, narrow trail of faint gas that snakes over the southern celestial pole is much more subdued looking than its neighbors. Hubble has no problem making out the South Celestial Serpent, though this image captures only a tiny part of it.

Text credit: European Space Agency (ESA)

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Media Contact:

Claire Andreoli
NASA’s Goddard Space Flight Center, Greenbelt, MD
claire.andreoli@nasa.gov

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Details Last Updated Apr 12, 2024 Editor Andrea Gianopoulos Related Terms

• Astrophysics
• Astrophysics Division
• Galaxies
• Goddard Space Flight Center
• Hubble Space Telescope
• Missions
• Nebulae
• Spiral Galaxies
• The Universe

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