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arXiv:2403.03974v1 Announce Type: new Abstract: We present new ALMA observations of CO, CN, CS, HCN and HCO$^{+}$ absorption seen against the bright and compact radio continuum sources of eight massive galaxies. Combined with archival observations, they reveal two distinct populations of molecular clouds, which we identify by combining CO emission and absorption profiles to unambiguously reveal each cloud's direction of motion and likely location. In galaxy disks, we see clouds with low velocity dispersions, low line of sight velocities and a lack of any systemic inflow or outflow. In galactic cores, we find high velocity dispersion clouds inflowing at up to 550 km/s. This provides observational evidence in favour of cold accretion onto galactic centres, which likely contributes to the fuelling of active galactic nuclei. We also see a wide range in the CO(2-1)/CO(1-0) ratios of the absorption lines. This is likely the combined effect of hierarchical substructure within the molecular clouds and continuum sources which vary in size with frequency.

By rotating a tank of water at 75 revolutions per minute, it’s possible to replicate some of the stunning, swirling patterns on Jupiter’s surface

All known natural phenomena fit into just a few categories and unifying them all is quantum field theory, says physicist Matt Strassler

Science, Volume 383, Issue 6687, Page 1038-1039, March 2024.

Exclusive: Significant discovery, made by James Webb telescope, provokes disagreement over conditions on planet’s surface

Astronomers have observed a distant planet that could be entirely covered in a deep water ocean, in findings that advance the search for habitable conditions beyond Earth.

The observations, by Nasa’s James Webb space telescope (JWST), revealed water vapour and chemical signatures of methane and carbon dioxide in the atmosphere of the exoplanet, which is twice Earth’s radius and about 70 light years away. This chemical mix is consistent with a water world where the ocean would span the entire surface, and a hydrogen-rich atmosphere, according to researchers from the University of Cambridge, although they do not envisage a balmy, inviting seascape.

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International Women's Day at the IoA

• 13.00 pm-14.00:Keynote Speaker: Ghina Halabi

• 14.00 pm-14.45:Flash Talks: Sandro Tacchella & Alejandra Castro

• 14.45 pm-15.15:Tea, Coffee and Cake

• 15.15 pm-16.30:An Interactive Session on Recognising Accomplishments

• 16.30 pm-16.50: Flash Talk: Greg Cooke

• 16.50 pm-17.00: Closing Remarks

• Speaker:
• Friday 08 March 2024, 13:00-17:00
• Venue: Hoyle Lecture Theatre, IoA .
• Series: Institute of Astronomy Extra Talks; organiser: iwd.

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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.

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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.

Add to your calendar or Include in your list

International Women's Day at the IoA

• 13.00 pm-14.00:Keynote Speaker: Ghina Halabi

• 14.00 pm-14.45:Flash Talks: Sandro Tacchella & Alejandra Castro

• 14.45 pm-15.15:Tea, Coffee and Cake

• 15.15 pm-16.30:An Interactive Session on Recognising Accomplishments

• 16.30 pm-16.50: Flash Talk: Greg Cooke

• 16.50 pm-17.00: Closing Remarks

• Speaker:
• Friday 08 March 2024, 13:00-17:00
• Venue: Hoyle Lecture Theatre, IoA .
• Series: Institute of Astronomy Extra Talks; organiser: .

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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.

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Parity Violation in Cosmology

Parity symmetry is known to be violated in the weak interaction. Do the physical laws behind the unsolved problems of modern cosmology – cosmic inflation, dark matter, and dark energy – also violate parity symmetry? In this talk, we will discuss theoretical and observational possibilities of parity violation in cosmology, a topic that has received much attention in recent years.

• Speaker: Eiichiro Komatsu (MPA Garching)
• Monday 11 March 2024, 13:00-14:00
• Venue: CMS, Pav. B, CTC Common Room (B1.19) [Potter Room].
• Series: Cosmology Lunch; organiser: Inigo Zubeldia.

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arXiv:2403.03872v1 Announce Type: new Abstract: Recent observations have found a large number of supermassive black holes already in place in the first few hundred million years after Big Bang. The channels of formation and growth of these early, massive black holes are not clear, with scenarios ranging from heavy seeds to light seeds experiencing bursts of high accretion rate. Here we present the detection, from the JADES survey, of broad Halpha emission in a galaxy at z=6.68, which traces a black hole with mass of ~ 4 * 10^8 Msun and accreting at a rate of only 0.02 times the Eddington limit. The host galaxy has low star formation rate (~ 1 Msun/yr, a factor of 3 below the star forming main sequence). The black hole to stellar mass ratio is ~ 0.4, i.e. about 1,000 times above the local relation, while the system is closer to the local relations in terms of dynamical mass and velocity dispersion of the host galaxy. This object is most likely the tip of the iceberg of a much larger population of dormant black holes around the epoch of reionisation. Its properties are consistent with scenarios in which short bursts of super-Eddington accretion have resulted in black hole overgrowth and massive gas expulsion from the accretion disk; in between bursts, black holes spend most of their life in a dormant state.

arXiv:2403.03244v1 Announce Type: new Abstract: The JWST has ushered in a new era in atmospheric characterisations of temperate low-mass exoplanets with recent detections of carbon-bearing molecules in the candidate Hycean world K2-18 b. We investigated JWST observations of the TOI-270 system, with two sub-Neptunes simultaneously transiting the nearby M dwarf during the visit. We report our atmospheric characterisation of the outer planet TOI-270 d, a candidate Hycean world, with JWST transmission spectroscopy using the NIRSpec G395H instrument in the 2.7-5.2 $\mu$m range, combined with previous observations obtained with the HST WFC3 spectrograph (1.1-1.6 $\mu$m). The spectrum reveals strong signatures of CH4 and CO2 at 3.8-4.9$\sigma$ and 2.9-3.9$\sigma$ confidence, respectively, and no evidence of NH3. The abundant CH4 and CO2, at ~0.1-1% mixing ratios, and the non-detection of NH3 are similar to the findings reported for K2-18 b and consistent with predictions for a Hycean world with a planet-wide ocean under a H2-rich atmosphere. We also report evidence of CS2 at a 2.3-3.0$\sigma$ confidence and a potential inference of H2O at 1.6-4.4$\sigma$, depending on the data analysis approach, and discuss possible interpretations of these results. The spectrum does not provide strong constraints on the presence of clouds or hazes in the observable atmosphere, nor any evidence for the effects of stellar heterogeneities, which is consistent with previous studies. For the smaller inner planet TOI-270 b, we find that the spectrum is inconsistent with a featureless spectrum at ~3$\sigma$, showing some preference for an H2-rich atmosphere in a super-Earth. We discuss the implications of our findings and future prospects.

Nature, Published online: 06 March 2024; doi:10.1038/s41586-024-07102-y

A population of freezing white dwarf stars maintaining a constant luminosity for a duration comparable with the age of the universe can be explained by a solid–liquid distillation mechanism interrupting cooling for billions of years.

Nature, Published online: 06 March 2024; doi:10.1038/s41586-024-07046-3

An axisymmetric, equatorial jet in Jupiter’s interior has a wavelike fluctuation with a 4-year period, revealing hidden aspects of the magnetic field within the metallic hydrogen region and constraining the dynamo that generates the magnetic field.

Nature, Published online: 06 March 2024; doi:10.1038/s41586-024-07227-0

A recently quenched galaxy 700 million years after the Big Bang

The James Webb Space Telescope has revealed that a distant galaxy stopped forming stars extraordinarily fast, making it the furthest dead galaxy ever spotted

Some white dwarfs seem to stop ageing for billions of years, and this may be due to the behaviour of unusual ice crystals that heat up the stars

Using the James Webb Space Telescope, an international team of astronomers led by the University of Cambridge have spotted a ‘dead’ galaxy when the universe was just 700 million years old, the oldest such galaxy ever observed.

This galaxy appears to have lived fast and died young: star formation happened quickly and stopped almost as quickly, which is unexpected for so early in the universe’s evolution. However, it is unclear whether this galaxy’s ‘quenched’ state is temporary or permanent, and what caused it to stop forming new stars.

The results, reported in the journal Nature, could be important to help astronomers understand how and why galaxies stop forming new stars, and whether the factors affecting star formation have changed over billions of years.

“The first few hundred million years of the universe was a very active phase, with lots of gas clouds collapsing to form new stars,” said Tobias Looser from the Kavli Institute for Cosmology, the paper’s first author. “Galaxies need a rich supply of gas to form new stars, and the early universe was like an all-you-can-eat buffet.”

“It’s only later in the universe that we start to see galaxies stop forming stars, whether that’s due to a black hole or something else,” said co-author Dr Francesco D’Eugenio, also from the Kavli Institute for Cosmology.

Astronomers believe that star formation can be slowed or stopped by different factors, all of which will starve a galaxy of the gas it needs to form new stars. Internal factors, such as a supermassive black hole or feedback from star formation, can push gas out of the galaxy, causing star formation to stop rapidly. Alternatively, gas can be consumed very quickly by star formation, without being promptly replenished by fresh gas from the surroundings of the galaxy, resulting in galaxy starvation.

“We’re not sure if any of those scenarios can explain what we’ve now seen with Webb,” said co-author Professor Roberto Maiolino. “Until now, to understand the early universe, we’ve used models based on the modern universe. But now that we can see so much further back in time, and observe that the star formation was quenched so rapidly in this galaxy, models based on the modern universe may need to be revisited.”

Using data from JADES (JWST Advanced Deep Extragalactic Survey), the astronomers determined that this galaxy experienced a short and intense period of star formation over a period between 30 and 90 million years. But between 10 and 20 million years before the point in time where it was observed with Webb, star formation suddenly stopped.

“Everything seems to happen faster and more dramatically in the early universe, and that might include galaxies moving from a star-forming phase to dormant or quenched,” said Looser.

Astronomers have previously observed dead galaxies in the early universe, but this galaxy is the oldest yet – just 700 million years after the big bang, more than 13 billion years ago. This observation is one of the deepest yet made with Webb.

In addition to the oldest, this galaxy is also relatively low mass – about the same as the Small Magellanic Cloud (SMC), a dwarf galaxy near the Milky Way, although the SMC is still forming new stars. Other quenched galaxies in the early universe have been far more massive, but Webb’s improved sensitivity allows smaller and fainter galaxies to be observed and analysed.

The astronomers say that although it appears dead at the time of observation, it’s possible that in the roughly 13 billion years since, this galaxy may have come back to life and started forming new stars again.

“We’re looking for other galaxies like this one in the early universe, which will help us place some constraints on how and why galaxies stop forming new stars,” said D’Eugenio. “It could be the case that galaxies in the early universe ‘die’ and then burst back to life – we’ll need more observations to help us figure that out.”

The research was supported in part by the European Research Council, the Royal Society, and the Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

 

Reference:
Tobias J. Looser et al. ‘A recently quenched galaxy 700 million years after the Big Bang.’ Nature (2024). DOI: 10.1038/s41586-024-07227-0

A galaxy that suddenly stopped forming new stars more than 13 billion years ago has been observed by astronomers.

JADES CollaborationFalse-colour JWST image of a small fraction of the GOODS South field, with JADES-GS-z7-01-QU highlighted

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Which universes does the no-boundary wave function favour?

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.

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