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Institute of Astronomy

 

The HOSTS Survey: Suspected variable dust emission and constraints on companions around {\theta} Boo

Recent IoA Publications - Tue, 15/07/2025 - 11:17
arXiv:2505.07585v2 Announce Type: replace Abstract: During the HOSTS survey by the LBTI, an excess emission from the main sequence star {\theta} Boo (F7V spectral type, 14.5pc distance) was observed. This excess indicates the presence of exozodiacal dust near the habitable zone (HZ) of the star. Previous observations from Spitzer and Herschel showed no sign of outer cold dust within their respective detection limits. Additional nulling and high-contrast AO observations were taken to spatially constrain the dust distribution, search for variability, and directly image potential companions in the system. This study presents the results of these observations and provides an interpretation of the inner system's architecture. The star was observed using the LBTI's N'-band nulling mode during three epochs in 2017, 2018, and 2023. The dust distribution is modeled and constrained for each epoch using the standard LBTI nulling pipeline, assuming a vertically thin disk with a face-on inclination. In addition, high-contrast AO observations are performed in the L'-band and H-band to constrain the presence of substellar companions around the star. Several solutions are found for the dust distribution, and for each epoch. However, the LBTI nulling observations are not able to discriminate between them. Using the upper limits from previous observations, we constrain the representative size of the dust grains around 3-5$\mu$m. A tentative increase in dust brightness is also measured at the Earth-equivalent insolation distance between 2017 and 2023. Several options are considered to explain the origin of the observed dust and its variability, but no clear sources could be identified from the current observations. Partly because our high-contrast AO observations could only constrain the presence of companions down to $11M_\text{Jup}$ at 1.3" separation.

Alleviating the Hubble tension with Torsion Condensation (TorC)

Cosmology and Fundamental physics - Tue, 15/07/2025 - 10:51
arXiv:2507.09228v1 Announce Type: new Abstract: Constraints on the cosmological parameters of Torsion Condensation (TorC) are investigated using Planck 2018 Cosmic Microwave Background data. TorC is a case of Poincar\'e gauge theory -- a formulation of gravity motivated by the gauge field theories underlying fundamental forces in the standard model of particle physics. Unlike general relativity, TorC incorporates intrinsic torsion degrees of freedom while maintaining second-order field equations. At specific parameter values, it reduces to the $\Lambda$CDM model, providing a natural extension to standard cosmology. The base model of TorC introduces two parameters beyond those in $\Lambda$CDM: the initial value of the torsion scalar field and its time derivative -- one can absorb the latter by allowing the dark energy density to float. To constrain these parameters, `PolyChord` nested sampling algorithm is employed, interfaced via `Cobaya` with a modified version of `CAMB`. Our results indicate that TorC allows for a larger inferred Hubble constant, offering a potential resolution to the Hubble tension. Tension analysis using the $R$-statistic shows that TorC alleviates the statistical tension between the Planck 2018 and SH0Es 2020 datasets, though this improvement is not sufficient to decisively favour TorC over $\Lambda$CDM in a Bayesian model comparison. This study highlights TorC as a compelling theory of gravity, demonstrating its potential to address cosmological tensions and motivating further investigations of extended theories of gravity within a cosmological context. As current and upcoming surveys -- including Euclid, Roman Space Telescope, Vera C. Rubin Observatory, LISA, and Simons Observatory -- deliver data on gravity across all scales, they will offer critical tests of gravity models like TorC, making the present a pivotal moment for exploring extended theories of gravity.

Alleviating the Hubble tension with Torsion Condensation (TorC)

Recent IoA Publications - Tue, 15/07/2025 - 10:51
arXiv:2507.09228v1 Announce Type: new Abstract: Constraints on the cosmological parameters of Torsion Condensation (TorC) are investigated using Planck 2018 Cosmic Microwave Background data. TorC is a case of Poincar\'e gauge theory -- a formulation of gravity motivated by the gauge field theories underlying fundamental forces in the standard model of particle physics. Unlike general relativity, TorC incorporates intrinsic torsion degrees of freedom while maintaining second-order field equations. At specific parameter values, it reduces to the $\Lambda$CDM model, providing a natural extension to standard cosmology. The base model of TorC introduces two parameters beyond those in $\Lambda$CDM: the initial value of the torsion scalar field and its time derivative -- one can absorb the latter by allowing the dark energy density to float. To constrain these parameters, `PolyChord` nested sampling algorithm is employed, interfaced via `Cobaya` with a modified version of `CAMB`. Our results indicate that TorC allows for a larger inferred Hubble constant, offering a potential resolution to the Hubble tension. Tension analysis using the $R$-statistic shows that TorC alleviates the statistical tension between the Planck 2018 and SH0Es 2020 datasets, though this improvement is not sufficient to decisively favour TorC over $\Lambda$CDM in a Bayesian model comparison. This study highlights TorC as a compelling theory of gravity, demonstrating its potential to address cosmological tensions and motivating further investigations of extended theories of gravity within a cosmological context. As current and upcoming surveys -- including Euclid, Roman Space Telescope, Vera C. Rubin Observatory, LISA, and Simons Observatory -- deliver data on gravity across all scales, they will offer critical tests of gravity models like TorC, making the present a pivotal moment for exploring extended theories of gravity.

NASA Research Shows Path Toward Protocells on Titan

Astronomy News - Tue, 15/07/2025 - 10:07
Hydrocarbon lake and methane rain clouds on Titan Jenny McElligott/eMITS

NASA research has shown that cell-like compartments called vesicles could form naturally in the lakes of Saturn’s moon Titan.

Titan is the only world apart from Earth that is known to have liquid on its surface. However, Titan’s lakes and seas are not filled with water. Instead, they contain liquid hydrocarbons like ethane and methane. 

On Earth, liquid water is thought to have been essential for the origin of life as we know it. Many astrobiologists have wondered whether Titan’s liquids could also provide an environment for the formation of the molecules required for life – either as we know it or perhaps as we don’t know it – to take hold there.

New NASA research, published in the International Journal of Astrobiology, outlines a process by which stable vesicles might form on Titan, based on our current knowledge of the moon’s atmosphere and chemistry. The formation of such compartments is an important step in making the precursors of living cells (or protocells).

The process involves molecules called amphiphiles, which can self-organize into vesicles under the right conditions. On Earth, these polar molecules have two parts, a hydrophobic (water-fearing) end and a hydrophilic (water-loving) end. When they are in water, groups of these molecules can bunch together and form ball-like spheres, like soap bubbles, where the hydrophilic part of the molecule faces outward to interact with the water, thereby ‘protecting’ the hydrophobic part on the inside of the sphere. Under the right conditions, two layers can form creating a cell-like ball with a bilayer membrane that encapsulates a pocket of water on the inside.

When considering vesicle formation on Titan, however, the researchers had to take into account an environment vastly different from the early Earth.

Uncovering Conditions on Titan Huygens captured this aerial view of Titan from an altitude of 33,000 feet. ESA/NASA/JPL/University of Arizona

Titan is Saturn’s largest moon and the second largest in our solar system. Titan is also the only moon in our solar system with a substantial atmosphere.

The hazy, golden atmosphere of Titan kept the moon shrouded in mystery for much of human history. However, when NASA’s Cassini spacecraft arrived at Saturn in 2004, our views of Titan changed forever.

Thanks to Cassini, we now know Titan has a complex meteorological cycle that actively influences the surface today. Most of Titan’s atmosphere is nitrogen, but there is also a significant amount of methane (CH4). This methane forms clouds and rain, which falls to the surface to cause erosion and river channels, filling up the lakes and seas. This liquid then evaporates in sunlight to form clouds once again.

This atmospheric activity also allows for complex chemistry to happen. Energy from the Sun breaks apart molecules like methane, and the pieces then reform into complex organic molecules. Many astrobiologists believe that this chemistry could teach us how the molecules necessary for the origin of life formed and evolved on the early Earth.

Building Vesicles on Titan An artist’s concept of the proposed mechanism for vesicle formation on Titan. (1) Methane lakes and seas on Titan’s surface become coated with a film of amphiphiles. (2) Methane raindrops splash the lake surface. (3) Splashes create a mist of droplets coated in the same film. (4) Droplets settle back onto the lake and sink, becoming coated in a bilayer which becomes a vesicle. Christian Mayer (Universität Duisburg-Essen) and Conor Nixon (NASA Goddard)

The new study considered how vesicles might form in the freezing conditions of Titan’s hydrocarbon lakes and seas by focusing on sea-spray droplets, thrown upwards by splashing raindrops. On Titan, both spray droplets and the sea surface could be coated in layers of amphiphiles. If a droplet then lands on the surface of a pond, the two layers of amphiphiles meet to form a double-layered (or bilayer) vesicle, enclosing the original droplet. Over time, many of these vesicles would be dispersed throughout the pond and would interact and compete in an evolutionary process that could lead to primitive protocells.

If the proposed pathway is happening, it would increase our understanding of the conditions in which life might be able to form. 

“The existence of any vesicles on Titan would demonstrate an increase in order and complexity, which are conditions necessary for the origin of life,” explains Conor Nixon of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “We’re excited about these new ideas because they can open up new directions in Titan research and may change how we search for life on Titan in the future.”

NASA’s first mission to Titan is the upcoming Dragonfly rotorcraft, which will explore the surface of the Saturnian moon. While Titan’s lakes and seas are not a destination for Dragonfly (and the mission won’t carry the light-scattering instrument required to detect such vesicles), the mission will fly from location to location to study the moon’s surface composition, make atmospheric and geophysical measurements, and characterize the habitability of Titan’s environment.

News Media Contacts

Karen Fox / Molly Wasser
Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov

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Giant radio telescope was ‘a natural magnet’ for African talent

Astronomy News - Tue, 15/07/2025 - 10:06

Nature, Published online: 14 July 2025; doi:10.1038/d41586-025-01984-2

Roger Deane has seen the investment in astronomy on the continent pay off both in his own career and with more young scientists joining the field.

Astronomers find a giant hiding in the ‘fog’ around a young star

Astronomy News - Tue, 15/07/2025 - 10:04

Earlier observations of this star, called MP Mus, suggested that it was all alone without any planets in orbit around it, surrounded by a featureless cloud of gas and dust.

However, a second look at MP Mus, using a combination of results from the Atacama Large Millimeter/submillimeter Array (ALMA) and the European Space Agency’s Gaia mission, suggests that the star is not alone after all.

The international team of astronomers, led by the University of Cambridge, detected a large gas giant in the star’s protoplanetary disc: the pancake-like cloud of gases, dust and ice where the process of planet formation begins. This is the first time that Gaia has detected an exoplanet within a protoplanetary disc. The results, reported in the journal Nature Astronomy, suggest that similar methods could be useful in the hunt for young planets around other stars.

By studying how planets form in the protoplanetary discs around young stars, researchers can learn more about how our own Solar System evolved. Through a process known as core accretion, gravity causes particles in the disc to stick to each other, eventually forming larger solid bodies like asteroids or planets. As young planets form, they start to carve gaps in the disc, like grooves on a vinyl record.

However, observing these young planets is extremely challenging, due to the interference from the gas and dust in the disc. To date, only three robust detections of young planets in a protoplanetary disc have been made.

Dr Álvaro Ribas from Cambridge’s Institute of Astronomy, who led the research, specialises in studying protoplanetary discs. “We first observed this star at the time when we learned that most discs have rings and gaps, and I was hoping to find features around MP Mus that could hint at the presence of a planet or planets,” he said.

Using ALMA, Ribas observed the protoplanetary disc around MP Mus (PDS 66) in 2023. The results showed a young star seemingly all alone in the universe. Its surrounding disc showed none of the gaps where planets might be forming, and was completely flat and featureless.

“Our earlier observations showed a boring, flat disc,” said Ribas. “But this seemed odd to us, since the disc is between seven and ten million years old. In a disc of that age, we would expect to see some evidence of planet formation.”

Now, Ribas and his colleagues from Germany, Chile, and France have given MP Mus another chance. Once again using ALMA, they observed the star at the 3mm range, a longer wavelength than the earlier observations, allowing them to probe deeper into the disc.

The new observations turned up a cavity close to the star and two gaps further out, which were obscured in the earlier observations, suggesting that MP Mus may not be alone after all.

At the same time, Miguel Vioque, a researcher at the European Southern Observatory, was uncovering another piece of the puzzle. Using data from Gaia, he found MP Mus was ‘wobbling’.

“My first reaction was that I must have made a mistake in my calculations, because MP Mus was known to have a featureless disc,” said Vioque. “I was revising my calculations when I saw Álvaro give a talk presenting preliminary results of a newly-discovered inner cavity in the disc, which meant the wobbling I was detecting was real and had a good chance of being caused by a forming planet.”

Using a combination of the Gaia and ALMA observations, along with some computer modelling, the researchers say the wobbling is likely caused by a gas giant – less than ten times the mass of Jupiter – orbiting the star at a distance between one and three times the distance of the Earth to the Sun.

“Our modelling work showed that if you put a giant planet inside the new-found cavity, you can also explain the Gaia signal,” said Ribas. “And using the longer ALMA wavelengths allowed us to see structures we couldn’t see before.”

This is the first time an exoplanet embedded in a protoplanetary disc has been indirectly discovered in this way – by combining precise star movement data from the Gaia with deep observations of the disc. It also means that many more hidden planets might exist in other discs, just waiting to be found.

“We think this might be one of the reasons why it’s hard to detect young planets in protoplanetary discs, because in this case, we needed the ALMA and Gaia data together,” said Ribas. “The longer ALMA wavelength is incredibly useful, but to observe at this wavelength requires more time on the telescope.”

Ribas says that upcoming upgrades to ALMA, as well as future telescopes such as the next generation Very Large Array (ngVLA), may be used to look deeper into more discs and better understand the hidden population of young planets, which could in turn help us learn how our own planet may have formed.

The research was supported in part by the European Union’s Horizon Programme, the European Research Council, and the UK Science and Technology Facilities Council (STFC), part of UK Research and Innovation (UKRI).

Reference:
Álvaro Ribas et al. ‘A young gas giant and hidden substructures in a protoplanetary disc.’ Nature Astronomy (2025). DOI: 10.1038/s41550-025-02576-w 

Astronomers have detected a giant exoplanet – between three and ten times the size of Jupiter – hiding in the swirling disc of gas and dust surrounding a young star.

ALMA(ESO/NAOJ/NRAO)/A. Ribas et al.Protoplanetary disc around MP Mus


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The THESAN-ZOOM project: Mystery N/O more -- uncovering the origin of peculiar chemical abundances and a not-so-fundamental metallicity relation at $3<z<12$

Galaxy Evolution and AGN - Mon, 14/07/2025 - 10:34
arXiv:2507.08787v1 Announce Type: new Abstract: We present an analysis of metallicities and chemical abundances at $3-0.6$) without the need for exotic yields in our chemical network. Instead, bursty star formation naturally generates order-of-magnitude excursions in N/O on $\lesssim$100 Myr timescales due to temporally differential galactic winds; after a starburst, stellar feedback expels gas, leaving a large population of asymptotic-giant-branch stars to dominate the enrichment of the relatively low-mass interstellar medium. NRGs lie below the main sequence and typically exhibit $\mathrm{EW}[H$\beta$]\lesssim40$ \r{A}, in apparent tension with observed high-EW NRGs. This tension is reconciled if observed NRGs are in the initial stages of a subsequent starburst, illuminating previously enriched gas, which is supported by the finding of high SFR surface density nitrogen-rich giant molecular clouds.

The THESAN-ZOOM project: Mystery N/O more -- uncovering the origin of peculiar chemical abundances and a not-so-fundamental metallicity relation at $3<z<12$

Recent IoA Publications - Mon, 14/07/2025 - 10:34
arXiv:2507.08787v1 Announce Type: new Abstract: We present an analysis of metallicities and chemical abundances at $3-0.6$) without the need for exotic yields in our chemical network. Instead, bursty star formation naturally generates order-of-magnitude excursions in N/O on $\lesssim$100 Myr timescales due to temporally differential galactic winds; after a starburst, stellar feedback expels gas, leaving a large population of asymptotic-giant-branch stars to dominate the enrichment of the relatively low-mass interstellar medium. NRGs lie below the main sequence and typically exhibit $\mathrm{EW}[H$\beta$]\lesssim40$ \r{A}, in apparent tension with observed high-EW NRGs. This tension is reconciled if observed NRGs are in the initial stages of a subsequent starburst, illuminating previously enriched gas, which is supported by the finding of high SFR surface density nitrogen-rich giant molecular clouds.

Constraining the survival of HCN during cometary impacts

Planetary systems - Mon, 14/07/2025 - 10:32
arXiv:2507.08727v1 Announce Type: new Abstract: Cometary impacts have been invoked as an atmosphere-independent method of stockpiling hydrogen cyanide (HCN), a key prebiotic feedstock molecule, into environments favourable for the onset of prebiotic chemistry on the early Earth. This work revisits the prospects for cometary delivery of HCN through new impacts simulations of idealised cometary bodies using the shock physics code iSALE combined with simple chemical modelling. Using temperature and pressure profiles for material within spherical, non-porous comets with a high resolution of Lagrangian tracer particles, we assess the survival rate of HCN across a range of impact velocities, sizes and angles, assuming both steady state and equilibrium chemistry. We find that HCN survival is extremely limited at impact velocities above the escape velocity of the Earth, unless the impact occurs at extreme obliquity ($\theta \sim 15^\circ$). We present a parametrisation of the survival of HCN as a function of impact velocity, angle, and cometary diameter, which provides an upper limit to survival in more realistic scenarios to aid with future studies investigating the role of comets in the origins of life. Although successful HCN delivery may be possible in our idealised model, we neglect to consider the effect of atmospheric passage and our results suggest that delivery alone is not likely to be sufficient for the onset of prebiotic chemistry.

Constraining the survival of HCN during cometary impacts

Recent IoA Publications - Mon, 14/07/2025 - 10:32
arXiv:2507.08727v1 Announce Type: new Abstract: Cometary impacts have been invoked as an atmosphere-independent method of stockpiling hydrogen cyanide (HCN), a key prebiotic feedstock molecule, into environments favourable for the onset of prebiotic chemistry on the early Earth. This work revisits the prospects for cometary delivery of HCN through new impacts simulations of idealised cometary bodies using the shock physics code iSALE combined with simple chemical modelling. Using temperature and pressure profiles for material within spherical, non-porous comets with a high resolution of Lagrangian tracer particles, we assess the survival rate of HCN across a range of impact velocities, sizes and angles, assuming both steady state and equilibrium chemistry. We find that HCN survival is extremely limited at impact velocities above the escape velocity of the Earth, unless the impact occurs at extreme obliquity ($\theta \sim 15^\circ$). We present a parametrisation of the survival of HCN as a function of impact velocity, angle, and cometary diameter, which provides an upper limit to survival in more realistic scenarios to aid with future studies investigating the role of comets in the origins of life. Although successful HCN delivery may be possible in our idealised model, we neglect to consider the effect of atmospheric passage and our results suggest that delivery alone is not likely to be sufficient for the onset of prebiotic chemistry.

Multi-frequency analysis of the ALMA and VLA high resolution continuum observations of the substructured disc around CI Tau. Preference for sub-mm-sized low-porosity amorphous carbonaceous grains

Planetary systems - Mon, 14/07/2025 - 10:20
arXiv:2507.08797v1 Announce Type: new Abstract: (Abridged) We present high angular resolution and sensitivity ALMA 3.1 mm and VLA 9.1 mm observations of the disc around CI Tau. These new data were combined with similar-resolution archival ALMA 0.9 and 1.3 mm observations and new and archival VLA 7.1 mm, 2.0, 3.0, and 6.0 cm photometry to study the properties of dust in this system. At wavelengths <3.1 mm, CI Tau's continuum emission is very extended and highly substructured (with three gaps, four rings, and two additional gap-ring pairs identified by non-parametric visibility modelling). Instead, the VLA 9.1 mm data are dominated by a bright central component, only partially (< 50%) due to dust emission, surrounded by a marginally detected, faint, and smooth halo. We fitted the ALMA and VLA 9.1 mm data together, adopting a physical model that accounts for the effects of dust absorption and scattering. For our fiducial dust composition ("Ricci" opacities), we retrieved a flat maximum grain size distribution across the disc radius of $(7.1\pm0.8)\times10^{-2}$ cm, that we tentatively attributed to fragmentation of fragile dust or bouncing. We tested, for the first time, the dependence of our results on the adopted dust composition model to assess which mixture can best reproduce the observations. We found that the "Ricci" opacities work better than the traditionally adopted "DSHARP" ones, while graphite-rich mixtures perform significantly worse. We also show that, for our fiducial composition, the data prefer low-porosity (< 70%) grains, in contrast with claims of highly porous aggregates in younger sources, which we tentatively justified by time-dependent compaction. Our results are in line with constraints from disc population synthesis models and naturally arise from CI Tau's peculiar spectral behaviour, making this disc an ideal target for deeper cm-wavelength and dust polarisation follow-ups.

Multi-frequency analysis of the ALMA and VLA high resolution continuum observations of the substructured disc around CI Tau. Preference for sub-mm-sized low-porosity amorphous carbonaceous grains

Recent IoA Publications - Mon, 14/07/2025 - 10:20
arXiv:2507.08797v1 Announce Type: new Abstract: (Abridged) We present high angular resolution and sensitivity ALMA 3.1 mm and VLA 9.1 mm observations of the disc around CI Tau. These new data were combined with similar-resolution archival ALMA 0.9 and 1.3 mm observations and new and archival VLA 7.1 mm, 2.0, 3.0, and 6.0 cm photometry to study the properties of dust in this system. At wavelengths <3.1 mm, CI Tau's continuum emission is very extended and highly substructured (with three gaps, four rings, and two additional gap-ring pairs identified by non-parametric visibility modelling). Instead, the VLA 9.1 mm data are dominated by a bright central component, only partially (< 50%) due to dust emission, surrounded by a marginally detected, faint, and smooth halo. We fitted the ALMA and VLA 9.1 mm data together, adopting a physical model that accounts for the effects of dust absorption and scattering. For our fiducial dust composition ("Ricci" opacities), we retrieved a flat maximum grain size distribution across the disc radius of $(7.1\pm0.8)\times10^{-2}$ cm, that we tentatively attributed to fragmentation of fragile dust or bouncing. We tested, for the first time, the dependence of our results on the adopted dust composition model to assess which mixture can best reproduce the observations. We found that the "Ricci" opacities work better than the traditionally adopted "DSHARP" ones, while graphite-rich mixtures perform significantly worse. We also show that, for our fiducial composition, the data prefer low-porosity (< 70%) grains, in contrast with claims of highly porous aggregates in younger sources, which we tentatively justified by time-dependent compaction. Our results are in line with constraints from disc population synthesis models and naturally arise from CI Tau's peculiar spectral behaviour, making this disc an ideal target for deeper cm-wavelength and dust polarisation follow-ups.

CLASS_SZ II: Notes and Examples of Fast and Accurate Calculations of Halo Model, Large Scale Structure and Cosmic Microwave Background Observables

Cosmology and Fundamental physics - Mon, 14/07/2025 - 10:12
arXiv:2507.07346v2 Announce Type: replace Abstract: These notes are very much work-in-progress and simply intended to showcase, in various degrees of details (and rigour), some of the cosmology calculations that class_sz can do. We describe the class_sz code in C, Python and Jax. Based on the Boltzmann code class, it can compute a wide range of observables relevant to current and forthcoming CMB and Large Scale Structure surveys. This includes galaxy shear and clustering, CMB lensing, thermal and kinetic Sunyaev and Zeldovich observables, Cosmic Infrared Background, cross-correlations and three-point statistics. Calculations can be done either within the halo model or the linear bias model. For standard $\Lambda$CDM cosmology and extensions, class_sz uses high-accuracy cosmopower emulators of the CMB and matter power spectrum to accelerate calculations. With this, along with efficient numerical integration routines, most class_sz output can be obtained in less than 500 ms (CMB $C_\ell$'s or matter $P(k)$ take $\mathcal{O}(1\mathrm{ms})$), allowing for fast or ultra-fast parameter inference analyses. Parts of the calculations are "jaxified", so the software can be integrated into differentiable pipelines.

CLASS_SZ II: Notes and Examples of Fast and Accurate Calculations of Halo Model, Large Scale Structure and Cosmic Microwave Background Observables

Recent IoA Publications - Mon, 14/07/2025 - 10:12
arXiv:2507.07346v2 Announce Type: replace Abstract: These notes are very much work-in-progress and simply intended to showcase, in various degrees of details (and rigour), some of the cosmology calculations that class_sz can do. We describe the class_sz code in C, Python and Jax. Based on the Boltzmann code class, it can compute a wide range of observables relevant to current and forthcoming CMB and Large Scale Structure surveys. This includes galaxy shear and clustering, CMB lensing, thermal and kinetic Sunyaev and Zeldovich observables, Cosmic Infrared Background, cross-correlations and three-point statistics. Calculations can be done either within the halo model or the linear bias model. For standard $\Lambda$CDM cosmology and extensions, class_sz uses high-accuracy cosmopower emulators of the CMB and matter power spectrum to accelerate calculations. With this, along with efficient numerical integration routines, most class_sz output can be obtained in less than 500 ms (CMB $C_\ell$'s or matter $P(k)$ take $\mathcal{O}(1\mathrm{ms})$), allowing for fast or ultra-fast parameter inference analyses. Parts of the calculations are "jaxified", so the software can be integrated into differentiable pipelines.

Observatory marks 230 years of recording weather

Astronomy News - Mon, 14/07/2025 - 10:03

The building holds the longest sequence of continuous weather data anywhere in the UK and Ireland.

LIGO has spotted the most massive black hole collision ever detected

Astronomy News - Mon, 14/07/2025 - 10:03

A puzzling gravitational wave was detected, and astronomers have determined that it comes from a record-breaking black hole merger

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

IoA Institute of Astronomy Talk Lists - 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.

Add to your calendar or Include in your list

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

Next Wednesday Seminars - 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.

Add to your calendar or Include in your list

Categories: Talks

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

IoA Institute of Astronomy Talk Lists - 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.

Add to your calendar or Include in your list

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

Next Wednesday Seminars - 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.

Add to your calendar or Include in your list

Categories: Talks