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Institute of Astronomy

 

Nearby stellar substructures in the Galactic halo from DESI Milky Way Survey Year 1 Data Release

Near-field cosmology - Tue, 20/05/2025 - 10:36
arXiv:2504.20327v2 Announce Type: replace Abstract: We report five nearby ($d_{\mathrm{helio}} < 5$ kpc) stellar substructures in the Galactic halo from a subset of 138,661 stars in the Dark Energy Spectroscopic Instrument (DESI) Milky Way Survey Year 1 Data Release. With an unsupervised clustering algorithm, HDBSCAN*, these substructures are independently identified in Integrals of Motion ($E_{\mathrm{tot}}$, $L_{\mathrm z}$, $\log{J_r}$, $\log{J_z}$) space and Galactocentric cylindrical velocity space ($V_{R}$, $V_{\phi}$, $V_{z}$). We associate all identified clusters with known nearby substructures (Helmi streams, M18-Cand10/MMH-1, Sequoia, Antaeus, and ED-2) previously reported in various studies. With metallicities precisely measured by DESI, we confirm that the Helmi streams, M18-Cand10, and ED-2 are chemically distinct from local halo stars. We have characterised the chemodynamic properties of each dynamic group, including their metallicity dispersions, to associate them with their progenitor types (globular cluster or dwarf galaxy). Our approach for searching substructures with HDBSCAN* reliably detects real substructures in the Galactic halo, suggesting that applying the same method can lead to the discovery of new substructures in future DESI data. With more stars from future DESI data releases and improved astrometry from the upcoming Gaia Data Release 4, we will have a more detailed blueprint of the Galactic halo, offering a significant improvement in our understanding of the formation and evolutionary history of the Milky Way Galaxy.

Nearby stellar substructures in the Galactic halo from DESI Milky Way Survey Year 1 Data Release

Stars and stellar evolution - Tue, 20/05/2025 - 10:36
arXiv:2504.20327v2 Announce Type: replace Abstract: We report five nearby ($d_{\mathrm{helio}} < 5$ kpc) stellar substructures in the Galactic halo from a subset of 138,661 stars in the Dark Energy Spectroscopic Instrument (DESI) Milky Way Survey Year 1 Data Release. With an unsupervised clustering algorithm, HDBSCAN*, these substructures are independently identified in Integrals of Motion ($E_{\mathrm{tot}}$, $L_{\mathrm z}$, $\log{J_r}$, $\log{J_z}$) space and Galactocentric cylindrical velocity space ($V_{R}$, $V_{\phi}$, $V_{z}$). We associate all identified clusters with known nearby substructures (Helmi streams, M18-Cand10/MMH-1, Sequoia, Antaeus, and ED-2) previously reported in various studies. With metallicities precisely measured by DESI, we confirm that the Helmi streams, M18-Cand10, and ED-2 are chemically distinct from local halo stars. We have characterised the chemodynamic properties of each dynamic group, including their metallicity dispersions, to associate them with their progenitor types (globular cluster or dwarf galaxy). Our approach for searching substructures with HDBSCAN* reliably detects real substructures in the Galactic halo, suggesting that applying the same method can lead to the discovery of new substructures in future DESI data. With more stars from future DESI data releases and improved astrometry from the upcoming Gaia Data Release 4, we will have a more detailed blueprint of the Galactic halo, offering a significant improvement in our understanding of the formation and evolutionary history of the Milky Way Galaxy.

Nancy Grace Roman’s 100th Birthday

Astronomy News - Tue, 20/05/2025 - 10:28
NASA

Dr. Nancy Grace Roman, NASA’s first Chief of Astronomy and namesake of the Nancy Grace Roman Telescope, briefs astronaut Edwin “Buzz” Aldrin on celestial objects in 1965 in Washington, D.C. Nancy Grace Roman passed away on December 25, 2018, in Germantown, Maryland at the age of 93. May 16, 2025, would have been her 100th birthday.

Prior to joining NASA in 1959, Dr. Roman was a well-respected and influential astronomer, publishing some of the most cited papers in the mid-20th century, one included in a list of 100 most influential papers in 100 years. At the agency, Roman worked to gain science support for space-based observatories. She established NASA’s scientific ballooning and airborne science, oversaw the start of the Great Observatory program with the first decade of Hubble Space Telescope development, and invested early in charge-coupled devices technology development used on Hubble – and now in digital cameras everywhere.  

She was also key to the decision to link the development of the Large Space Telescope (that became Hubble) and the Space Transportation System – more commonly known as the Space Shuttle. Finally, after retiring from NASA, Dr. Roman often worked with young students in underserved communities, hoping her story and mentoring could inspire them to join humanity’s quest for knowledge in a STEM field.

Learn more about Dr. Roman.

Text credit: NASA/Jackie Townsend

Image credit: NASA

Webb Finds Icy Disk

Astronomy News - Tue, 20/05/2025 - 10:28
NASA, ESA, CSA, Ralf Crawford (STScI)

This artist’s concept illustration, released on May 14, 2025, shows a Sun-like star encircled by a disk of dusty debris containing crystalline water ice. Astronomers long expected that frozen water was scattered in systems around stars. By using detailed data known as spectra from NASA’s James Webb Space Telescope, researchers confirmed the presence of crystalline water ice — definitive evidence of what astronomers expected. Water ice is a vital ingredient in disks around young stars — it heavily influences the formation of giant planets and may also be delivered by small bodies like comets and asteroids to fully formed rocky planets.

Read more about what this discovery means.

Image credit: NASA, ESA, CSA, Ralf Crawford (STScI)

Moon dust 'rarer than gold' arrives in UK from China

Astronomy News - Tue, 20/05/2025 - 10:26

First Moon samples collected in nearly 50 years and loaned by China for the first time are now in the UK.

Tue 27 May 13:00: Understanding the initial stages of planet-driven gap formation 

IoA Institute of Astronomy Talk Lists - Tue, 20/05/2025 - 10:24
Understanding the initial stages of planet-driven gap formation 

Gaps and rings are ubiquitous in observations of protoplanetary discs, and their existence may be attributed to (proto-)planets interacting with their natal environments. However, constraining protoplanet masses or ages – or even just confirming that protoplanets are the cause of these substructures – in any given observation requires a clear theoretical understanding of large numbers of different gap processes.

While theoretical and semi-analytical works exist for the viscously dominated end stages of gap evolution, due to the near inviscid nature of protoplanetary discs, time-dependent theories that can account for the nature of the mutual evolution between planet and disc are required to correctly interpret observations. I will first present on how planets form gaps in the simplest possible case: that of a low mass planet in an two-dimensional inviscid isothermal disc and show new analytical theory that is able to predict the initial stages of gap evolution in this case. Using both Athena++ numerical simulations and analytical arguments, I will then discuss how this picture is modified in the cases of viscous, thermodynamically active, or three-dimensional discs. I will show that the treatment of disc thermodynamics has significant effects on the planet disc interaction whereas viscosity – at the levels expected in protoplanetary discs – does not have a significant impact at the early stages of gap formation.

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Tue 27 May 14:00: Exploring the Vertical Shear Instability in starlight-heated protoplanetary disks

Next External Talks - Mon, 19/05/2025 - 16:32
Exploring the Vertical Shear Instability in starlight-heated protoplanetary disks

In weakly ionized regions of protoplanetary disks, hydrodynamic instabilities likely play a key role in the development of turbulence, the formation of structures, and the transport of angular momentum. Among these, the vertical shear instability (VSI) stands out as a robust mechanism, requiring only baroclinic stratification and short thermal relaxation timescales to operate. In this talk, I will present results from axisymmetric radiation-hydrodynamical simulations of the VSI in passive, irradiated T Tauri disks, focusing on angular momentum redistribution, the emergence of secondary instabilities, and their role in VSI saturation. I will also discuss how dust and molecular cooling shape the regions where the VSI can operate, and compare these results with current observations of protoplanetary disks.

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Categories: Talks

Mon 19 May 13:15: Impact of XRB Stochasticity on 21-cm Observables from CD-EoR

IoA Institute of Astronomy Talk Lists - Mon, 19/05/2025 - 12:46
Impact of XRB Stochasticity on 21-cm Observables from CD-EoR

Abstract: High Mass X-ray Binaries (HMXBs) are thought to be one of the key contributors to the X-ray background during the Cosmic Dawn (CD) and Epoch of Reionization (EoR). However, in traditional semi-numerical simulations of the CD-EoR, the LX-SFR relation is assumed to be fixed across cosmic time, which may not be accurate, especially for low star-forming regions. To mitigate this problem, we model the total luminosity in a stochastic manner and implement it in our 21-cm simulation from the CD-EoR to see its imprints on the 21-cm signal statistics like the Power Spectrum and 21-cm brightness temperature maps. We find the effects of XRB stochasticity in the small-scale PS (k > 0.9) and in the 21-cm maps that may have the potential for detection via the lunar based observations.

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Mon 19 May 13:15: Impact of XRB Stochasticity on 21-cm Observables from CD-EoR

Next Wednesday Seminars - Mon, 19/05/2025 - 12:46
Impact of XRB Stochasticity on 21-cm Observables from CD-EoR

Abstract: High Mass X-ray Binaries (HMXBs) are thought to be one of the key contributors to the X-ray background during the Cosmic Dawn (CD) and Epoch of Reionization (EoR). However, in traditional semi-numerical simulations of the CD-EoR, the LX-SFR relation is assumed to be fixed across cosmic time, which may not be accurate, especially for low star-forming regions. To mitigate this problem, we model the total luminosity in a stochastic manner and implement it in our 21-cm simulation from the CD-EoR to see its imprints on the 21-cm signal statistics like the Power Spectrum and 21-cm brightness temperature maps. We find the effects of XRB stochasticity in the small-scale PS (k > 0.9) and in the 21-cm maps that may have the potential for detection via the lunar based observations.

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Categories: Talks

A Cosmic Miracle: A Remarkably Luminous Galaxy at $z_{\rm{spec}}=14.44$ Confirmed with JWST

Recent IoA Publications - Mon, 19/05/2025 - 10:41
arXiv:2505.11263v1 Announce Type: new Abstract: JWST has revealed a stunning population of bright galaxies at surprisingly early epochs, $z>10$, where few such sources were expected. Here we present the most distant example of this class yet -- MoM-z14, a luminous ($M_{\rm{UV}}=-20.2$) source in the COSMOS legacy field at $z_{\rm{spec}}=14.44^{+0.02}_{-0.02}$ that expands the observational frontier to a mere 280 million years after the Big Bang. The redshift is confirmed with NIRSpec/prism spectroscopy through a sharp Lyman-$\alpha$ break and $\approx3\sigma$ detections of five rest-UV emission lines. The number density of bright $z_{\rm{spec}}\approx14-15$ sources implied by our "Mirage or Miracle" survey spanning $\approx350$ arcmin$^{2}$ is $>100\times$ larger ($182^{+329}_{-105}\times$) than pre-JWST consensus models. The high EWs of UV lines (${\approx}15{-}35$ \AA) signal a rising star-formation history, with a ${\approx}10\times$ increase in the last 5 Myr ($\rm{SFR_{\rm{5Myr}}}/\rm{SFR_{\rm{50Myr}}}=9.9^{+3.0}_{-5.8}$). The source is extremely compact (circularized $r_{\rm{e}} = 74^{+15}_{-12}$ pc), and yet resolved, suggesting an AGN is not the dominant source of light. The steep UV slope ($\beta=-2.5^{+0.2}_{-0.2}$) implies negligible dust attenuation and a young stellar population. The absence of a strong damping wing may indicate that the immediate surroundings of MoM-z14 are partially ionized at a redshift where virtually every reionization model predicts a $\approx100\%$ neutral fraction. The nitrogen emission and highly super-solar [N/C]$>1$ hint at an abundance pattern similar to local globular clusters that may have once hosted luminous supermassive stars. Since this abundance pattern is also common among the most ancient stars born in the Milky Way, we may be directly witnessing the formation of such stars in dense clusters, connecting galaxy evolution across the entire sweep of cosmic time.

A Cosmic Miracle: A Remarkably Luminous Galaxy at $z_{\rm{spec}}=14.44$ Confirmed with JWST

Galaxy Evolution and AGN - Mon, 19/05/2025 - 10:41
arXiv:2505.11263v1 Announce Type: new Abstract: JWST has revealed a stunning population of bright galaxies at surprisingly early epochs, $z>10$, where few such sources were expected. Here we present the most distant example of this class yet -- MoM-z14, a luminous ($M_{\rm{UV}}=-20.2$) source in the COSMOS legacy field at $z_{\rm{spec}}=14.44^{+0.02}_{-0.02}$ that expands the observational frontier to a mere 280 million years after the Big Bang. The redshift is confirmed with NIRSpec/prism spectroscopy through a sharp Lyman-$\alpha$ break and $\approx3\sigma$ detections of five rest-UV emission lines. The number density of bright $z_{\rm{spec}}\approx14-15$ sources implied by our "Mirage or Miracle" survey spanning $\approx350$ arcmin$^{2}$ is $>100\times$ larger ($182^{+329}_{-105}\times$) than pre-JWST consensus models. The high EWs of UV lines (${\approx}15{-}35$ \AA) signal a rising star-formation history, with a ${\approx}10\times$ increase in the last 5 Myr ($\rm{SFR_{\rm{5Myr}}}/\rm{SFR_{\rm{50Myr}}}=9.9^{+3.0}_{-5.8}$). The source is extremely compact (circularized $r_{\rm{e}} = 74^{+15}_{-12}$ pc), and yet resolved, suggesting an AGN is not the dominant source of light. The steep UV slope ($\beta=-2.5^{+0.2}_{-0.2}$) implies negligible dust attenuation and a young stellar population. The absence of a strong damping wing may indicate that the immediate surroundings of MoM-z14 are partially ionized at a redshift where virtually every reionization model predicts a $\approx100\%$ neutral fraction. The nitrogen emission and highly super-solar [N/C]$>1$ hint at an abundance pattern similar to local globular clusters that may have once hosted luminous supermassive stars. Since this abundance pattern is also common among the most ancient stars born in the Milky Way, we may be directly witnessing the formation of such stars in dense clusters, connecting galaxy evolution across the entire sweep of cosmic time.

Tracing the formation and migration history: molecular signatures in the atmosphere of misaligned hot Jupiter WASP-94Ab using JWST NIRSpec/G395H

Planetary systems - Mon, 19/05/2025 - 10:40
arXiv:2505.11224v1 Announce Type: new Abstract: The discovery of hot Jupiters that orbit very close to their host stars has long challenged traditional models of planetary formation and migration. Characterising their atmospheric composition - mainly in the form of the carbon-to-oxygen (C/O) ratio and metallicity - can provide insights into their formation locations and evolution pathways. With JWST we can characterise the atmospheres of these types of planets more precisely than previously possible, primarily because it allows us to determine both their atmospheric oxygen and carbon composition. Here, we present a JWST NIRSpec/G395H transmission spectrum from 2.8-5.1$\mu m$ of WASP-94Ab, an inflated hot Jupiter with a retrograde misaligned orbit around its F-type host star. We find a relatively cloud-free atmosphere, with absorption features of H$_2$O and CO$_2$ at detection significances of $\sim 4\sigma$ and $\sim 11\sigma$, respectively. In addition, we detect tentative evidence of CO absorption at $\sim3\sigma$, as well as hints of sulphur with the detection of H$_2$S at a $\sim 2.5\sigma$ confidence level. Our favoured equilibrium chemistry model determines a C/O ratio of $0.49^{+0.08}_{-0.13}$ for WASP-94Ab's atmosphere, which is substellar compared to the star's C/O ratio of $0.68 \pm 0.10$. The retrieved atmospheric metallicity is similar to the star's metallicity as both are $\sim 2\times$ solar. We find that this sub-stellar C/O ratio and stellar metallicity can be best explained by pebble accretion or planetesimal accretion in combination with large-distance migration of the planet.

Tracing the formation and migration history: molecular signatures in the atmosphere of misaligned hot Jupiter WASP-94Ab using JWST NIRSpec/G395H

Recent IoA Publications - Mon, 19/05/2025 - 10:40
arXiv:2505.11224v1 Announce Type: new Abstract: The discovery of hot Jupiters that orbit very close to their host stars has long challenged traditional models of planetary formation and migration. Characterising their atmospheric composition - mainly in the form of the carbon-to-oxygen (C/O) ratio and metallicity - can provide insights into their formation locations and evolution pathways. With JWST we can characterise the atmospheres of these types of planets more precisely than previously possible, primarily because it allows us to determine both their atmospheric oxygen and carbon composition. Here, we present a JWST NIRSpec/G395H transmission spectrum from 2.8-5.1$\mu m$ of WASP-94Ab, an inflated hot Jupiter with a retrograde misaligned orbit around its F-type host star. We find a relatively cloud-free atmosphere, with absorption features of H$_2$O and CO$_2$ at detection significances of $\sim 4\sigma$ and $\sim 11\sigma$, respectively. In addition, we detect tentative evidence of CO absorption at $\sim3\sigma$, as well as hints of sulphur with the detection of H$_2$S at a $\sim 2.5\sigma$ confidence level. Our favoured equilibrium chemistry model determines a C/O ratio of $0.49^{+0.08}_{-0.13}$ for WASP-94Ab's atmosphere, which is substellar compared to the star's C/O ratio of $0.68 \pm 0.10$. The retrieved atmospheric metallicity is similar to the star's metallicity as both are $\sim 2\times$ solar. We find that this sub-stellar C/O ratio and stellar metallicity can be best explained by pebble accretion or planetesimal accretion in combination with large-distance migration of the planet.

Thu 22 May 14:00: Classical and Quantum Density Functional Theory for Materials Science

IoA Institute of Astronomy Talk Lists - Mon, 19/05/2025 - 10:39
Classical and Quantum Density Functional Theory for Materials Science

This presentation reports on the work carried out during a six-month PhD placement at SECQAI , which focused on the application of both classical and quantum density functional theory (DFT) methods to problems in materials science. Two main research directions were pursued.

The first project aimed to identify desirable material properties for single-photon avalanche diodes (SPADs), devices that are widely used in quantum optics and quantum communication. The approach was to relate key performance metrics such as photon detection efficiency, timing jitter, and dark count rate to underlying material parameters. These dependencies were derived using analytical models and linked to quantities accessible via first-principles calculations. This work forms the basis for the development of high-throughput computational workflows for automated materials screening in SPAD applications.

The second project explored the implementation of plane-wave DFT calculations on quantum hardware using the variational quantum eigensolver (VQE) algorithm. An analysis of the numerical complexity of classical DFT was carried out, and a prototype VQE implementation was developed within the ABINIT simulation package. The project identified the main computational challenges involved and outlined the necessary steps for realizing a quantum advantage in this context.

The presentation will provide an overview of both projects, including theoretical background, methods, and results

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Automated quasar continuum estimation using neural networks: a comparative study of deep-learning architectures

Recent IoA Publications - Mon, 19/05/2025 - 10:31
arXiv:2505.10976v1 Announce Type: new Abstract: Context. Ongoing and upcoming large spectroscopic surveys are drastically increasing the number of observed quasar spectra, requiring the development of fast and accurate automated methods to estimate spectral continua. Aims. This study evaluates the performance of three neural networks (NN) - an autoencoder, a convolutional NN (CNN), and a U-Net - in predicting quasar continua within the rest-frame wavelength range of $1020~\text{\AA}$ to $2000~\text{\AA}$. The ability to generalize and predict galaxy continua within the range of $3500~\text{\AA}$ to $5500~\text{\AA}$ is also tested. Methods. The performance of these architectures is evaluated using the absolute fractional flux error (AFFE) on a library of mock quasar spectra for the WEAVE survey, and on real data from the Early Data Release observations of the Dark Energy Spectroscopic Instrument (DESI) and the VIMOS Public Extragalactic Redshift Survey (VIPERS). Results. The autoencoder outperforms the U-Net, achieving a median AFFE of 0.009 for quasars. The best model also effectively recovers the Ly$\alpha$ optical depth evolution in DESI quasar spectra. With minimal optimization, the same architectures can be generalized to the galaxy case, with the autoencoder reaching a median AFFE of 0.014 and reproducing the D4000n break in DESI and VIPERS galaxies.

Automated quasar continuum estimation using neural networks: a comparative study of deep-learning architectures

Cosmology and Fundamental physics - Mon, 19/05/2025 - 10:31
arXiv:2505.10976v1 Announce Type: new Abstract: Context. Ongoing and upcoming large spectroscopic surveys are drastically increasing the number of observed quasar spectra, requiring the development of fast and accurate automated methods to estimate spectral continua. Aims. This study evaluates the performance of three neural networks (NN) - an autoencoder, a convolutional NN (CNN), and a U-Net - in predicting quasar continua within the rest-frame wavelength range of $1020~\text{\AA}$ to $2000~\text{\AA}$. The ability to generalize and predict galaxy continua within the range of $3500~\text{\AA}$ to $5500~\text{\AA}$ is also tested. Methods. The performance of these architectures is evaluated using the absolute fractional flux error (AFFE) on a library of mock quasar spectra for the WEAVE survey, and on real data from the Early Data Release observations of the Dark Energy Spectroscopic Instrument (DESI) and the VIMOS Public Extragalactic Redshift Survey (VIPERS). Results. The autoencoder outperforms the U-Net, achieving a median AFFE of 0.009 for quasars. The best model also effectively recovers the Ly$\alpha$ optical depth evolution in DESI quasar spectra. With minimal optimization, the same architectures can be generalized to the galaxy case, with the autoencoder reaching a median AFFE of 0.014 and reproducing the D4000n break in DESI and VIPERS galaxies.

Automated quasar continuum estimation using neural networks: a comparative study of deep-learning architectures

Instrumentation and Surveys - Mon, 19/05/2025 - 10:31
arXiv:2505.10976v1 Announce Type: new Abstract: Context. Ongoing and upcoming large spectroscopic surveys are drastically increasing the number of observed quasar spectra, requiring the development of fast and accurate automated methods to estimate spectral continua. Aims. This study evaluates the performance of three neural networks (NN) - an autoencoder, a convolutional NN (CNN), and a U-Net - in predicting quasar continua within the rest-frame wavelength range of $1020~\text{\AA}$ to $2000~\text{\AA}$. The ability to generalize and predict galaxy continua within the range of $3500~\text{\AA}$ to $5500~\text{\AA}$ is also tested. Methods. The performance of these architectures is evaluated using the absolute fractional flux error (AFFE) on a library of mock quasar spectra for the WEAVE survey, and on real data from the Early Data Release observations of the Dark Energy Spectroscopic Instrument (DESI) and the VIMOS Public Extragalactic Redshift Survey (VIPERS). Results. The autoencoder outperforms the U-Net, achieving a median AFFE of 0.009 for quasars. The best model also effectively recovers the Ly$\alpha$ optical depth evolution in DESI quasar spectra. With minimal optimization, the same architectures can be generalized to the galaxy case, with the autoencoder reaching a median AFFE of 0.014 and reproducing the D4000n break in DESI and VIPERS galaxies.

Euclid Quick Data Release (Q1): From images to multiwavelength catalogues: the Euclid MERge Processing Function

Recent IoA Publications - Mon, 19/05/2025 - 10:07
arXiv:2503.15305v4 Announce Type: replace Abstract: The Euclid satellite is an ESA mission that was launched in July 2023. \Euclid is working in its regular observing mode with the target of observing an area of $14\,000~\text{deg}^2$ with two instruments, the Visible Camera (VIS) and the Near IR Spectrometer and Photometer (NISP) down to $I_{\rm E} = 24.5~\text{mag}$ ($10\, \sigma$) in the Euclid Wide Survey. Ground-based imaging data in the \textit{ugriz} bands complement the \Euclid data to enable photo-$z$ determination and VIS PSF modeling for week lensing analysis. Euclid investigates the distance-redshift relation and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies out to $z\sim 2$. Generating the multi-wavelength catalogues from \Euclid and ground-based data is an essential part of the \Euclid data processing system. In the framework of the \Euclid Science Ground Segment (SGS), the aim of the MER Processing Function (PF) pipeline is to detect objects in the \Euclid imaging data, measure their properties, and MERge them into a single multi-wavelength catalogue. The MER PF pipeline performs source detection on both visible (VIS) and near-infrared (NIR) images and offers four different photometric measurements: Kron total flux, aperture photometry on PSF-matched images, template fitting photometry, and S\'ersic fitting photometry. Furthermore, the MER PF pipeline measures a set of ancillary quantities, spanning from morphology to quality flags, to better characterise all detected sources. In this paper, we show how the MER PF pipeline is designed, detailing its main steps, and we show that the pipeline products meet the tight requirements that Euclid aims to achieve on photometric accuracy. We also present the other measurements (e.g. morphology) that are included in the OU-MER output catalogues and we list all output products coming out of the MER PF pipeline.

Euclid Quick Data Release (Q1): From images to multiwavelength catalogues: the Euclid MERge Processing Function

Instrumentation and Surveys - Mon, 19/05/2025 - 10:07
arXiv:2503.15305v4 Announce Type: replace Abstract: The Euclid satellite is an ESA mission that was launched in July 2023. \Euclid is working in its regular observing mode with the target of observing an area of $14\,000~\text{deg}^2$ with two instruments, the Visible Camera (VIS) and the Near IR Spectrometer and Photometer (NISP) down to $I_{\rm E} = 24.5~\text{mag}$ ($10\, \sigma$) in the Euclid Wide Survey. Ground-based imaging data in the \textit{ugriz} bands complement the \Euclid data to enable photo-$z$ determination and VIS PSF modeling for week lensing analysis. Euclid investigates the distance-redshift relation and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies out to $z\sim 2$. Generating the multi-wavelength catalogues from \Euclid and ground-based data is an essential part of the \Euclid data processing system. In the framework of the \Euclid Science Ground Segment (SGS), the aim of the MER Processing Function (PF) pipeline is to detect objects in the \Euclid imaging data, measure their properties, and MERge them into a single multi-wavelength catalogue. The MER PF pipeline performs source detection on both visible (VIS) and near-infrared (NIR) images and offers four different photometric measurements: Kron total flux, aperture photometry on PSF-matched images, template fitting photometry, and S\'ersic fitting photometry. Furthermore, the MER PF pipeline measures a set of ancillary quantities, spanning from morphology to quality flags, to better characterise all detected sources. In this paper, we show how the MER PF pipeline is designed, detailing its main steps, and we show that the pipeline products meet the tight requirements that Euclid aims to achieve on photometric accuracy. We also present the other measurements (e.g. morphology) that are included in the OU-MER output catalogues and we list all output products coming out of the MER PF pipeline.

Euclid Quick Data Release (Q1): From images to multiwavelength catalogues: the Euclid MERge Processing Function

Galaxy Evolution and AGN - Mon, 19/05/2025 - 10:07
arXiv:2503.15305v4 Announce Type: replace Abstract: The Euclid satellite is an ESA mission that was launched in July 2023. \Euclid is working in its regular observing mode with the target of observing an area of $14\,000~\text{deg}^2$ with two instruments, the Visible Camera (VIS) and the Near IR Spectrometer and Photometer (NISP) down to $I_{\rm E} = 24.5~\text{mag}$ ($10\, \sigma$) in the Euclid Wide Survey. Ground-based imaging data in the \textit{ugriz} bands complement the \Euclid data to enable photo-$z$ determination and VIS PSF modeling for week lensing analysis. Euclid investigates the distance-redshift relation and the evolution of cosmic structures by measuring shapes and redshifts of galaxies and clusters of galaxies out to $z\sim 2$. Generating the multi-wavelength catalogues from \Euclid and ground-based data is an essential part of the \Euclid data processing system. In the framework of the \Euclid Science Ground Segment (SGS), the aim of the MER Processing Function (PF) pipeline is to detect objects in the \Euclid imaging data, measure their properties, and MERge them into a single multi-wavelength catalogue. The MER PF pipeline performs source detection on both visible (VIS) and near-infrared (NIR) images and offers four different photometric measurements: Kron total flux, aperture photometry on PSF-matched images, template fitting photometry, and S\'ersic fitting photometry. Furthermore, the MER PF pipeline measures a set of ancillary quantities, spanning from morphology to quality flags, to better characterise all detected sources. In this paper, we show how the MER PF pipeline is designed, detailing its main steps, and we show that the pipeline products meet the tight requirements that Euclid aims to achieve on photometric accuracy. We also present the other measurements (e.g. morphology) that are included in the OU-MER output catalogues and we list all output products coming out of the MER PF pipeline.