G. Riccio; Michele Cantiello; Rebecca Habas; Nandini Hazra; G. D’Ago; Gabriella Raimondo; John P. Blakeslee; Joseph B. Jensen; Marco Mirabile; E. Brocato; M. Brescia; C. M. Raiteri
Astronomy and Astrophysics · DOI ↗
Context. The surface brightness fluctuation (SBF) method is one of the most reliable and efficient ways of measuring distances to galaxies within 100 Mpc, a matter of crucial importance for all fields of astrophysics. While recent implementations have increasingly relied on space-based observations, SBF remains effective when applied to ground-based data. In particular, deep, wide-field imaging surveys with sub-arcsecond seeing conditions allows us to make accurate SBF measurements across large samples of galaxies. With the upcoming next generation of wide-area imaging surveys, the thousands of galaxies suitable for SBF measurements will give us the opportunity to constrain the 3D structure of the local Universe. Aims. We present FAST-SBF, a new Python-based pipeline for measuring SBF, developed to support the analysis of large datasets from upcoming wide-field imaging surveys such as LSST, Euclid , and Roman . The procedure, still in the testing and development stage, is designed for automation and minimal user intervention, offering a fast and flexible approach to SBF distance estimation. Methods. We validated the performance of the procedure on high-quality imaging data from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), a precursor to LSST, analyzing a sample of both luminous early-type galaxies and fainter dwarfs. Our measurements were also compared with recent results from the Next Generation Virgo Cluster Survey (NGVS) and with the SPoT stellar population synthesis models. Results. The results show excellent agreement with published distances, with the capability of measuring the SBF signal also for faint dwarf galaxies. The pipeline allows the user to completely analyze a galaxy in relatively short time (≈ minutes) and significantly reduces the need for user intervention. The FAST-SBF tool is planned for public release to support the community in using SBF as a distance indicator in next-generation surveys.
Isabella P. Carucci; José L Bernal; Steven Cunnington; Mário G. Santos; Jingying Wang; José Fonseca; Keith Grainge; Melis O Irfan; Yichao Li; Alkistis Pourtsidou; Marta Spinelli; Laura Wolz
Astronomy and Astrophysics · DOI ↗
Removing contaminants is a delicate, yet crucial step in neutral hydrogen (H I ) intensity mapping and often considered the technique’s greatest challenge. Here, we address this challenge by analysing H I intensity maps of about 100 deg 2 at redshift z ≈ 0.4 collected by the MeerKAT radio telescope, an SKA Observatory (SKAO) precursor, with a combined 10.5-hour observation. Using unsupervised statistical methods, we removed the contaminating foreground emission and systematically tested, step-by-step, some common pre-processing choices to facilitate the cleaning process. We also introduced and tested a novel multiscale approach: the data were redundantly decomposed into subsets referring to different spatial scales (large and small), where the cleaning procedure was performed independently. We confirm the detection of the H I cosmological signal in cross-correlation with an ancillary galactic data set, without the need to correct for signal loss. In the best set-up we achieved, we were able to constrain the H I distribution through the combination of its cosmic abundance (Ω H I ) and linear clustering bias ( b H I ) up to a cross-correlation coefficient ( r ). We measured Ω H I b H I r = [0.93 ± 0.17] × 10 −3 with a ≈6 σ confidence, which is independent of scale cuts at both edges of the probed scale range (0.04 ≲ k ≲ 0.3 h Mpc −1 ), corroborating its robustness. Our new pipeline has successfully found an optimal compromise in separating contaminants without incurring a catastrophic signal loss. This development instills an added degree of confidence in the outstanding science we can deliver with MeerKAT on the path towards H I intensity mapping surveys with the full SKAO.
Ian Selby; E. González-Solares; Anna Breger; Michael Roberts; Lorena Escudero Sánchez; James H.F. Rudd; Nicholas Walton; Judith Babar; Carola‐Bibiane Schönlieb; Evis Sala; Jonathan Weir‐McCall
The Royal College of Radiologists Open · DOI ↗
C. Tortora; G. Tozzi; Guido Agapito; F. La Barbera; Chiara Spiniello; Rui Li; Giulia Carlà; G. D’Ago; Essna Ghose; F. Mannucci; N. R. Napolitano; Enrico Pinna; M. Arnaboldi; Davide Bevacqua; Anna Ferré-Mateu; Anna Gallazzi; Johanna Hartke; L. K. Hunt; Michalina Maksymowicz-Maciata; C. Pulsoni; P. Saracco; Diana Scognamiglio; Marilena Spavone
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT Relics are massive, compact and quiescent galaxies that assembled the majority of their stars in the early Universe and lived untouched until today, completely missing any subsequent size growth caused by mergers and interactions. They provide the unique opportunity to put constraints on the first phase of mass assembly in the Universe with the ease of being nearby. While only a few relics have been found in the local Universe, the INSPIRE project has confirmed 38 relics at higher redshifts ($z \sim 0.2{\small --}0.4$), fully characterizing their integrated kinematics and stellar populations. However, given the very small sizes of these objects and the limitations imposed by the atmosphere, structural parameters inferred from ground-based optical imaging are possibly affected by systematic effects that are difficult to quantify. In this paper, we present the first high-resolution image obtained with Adaptive Optics Ks-band observations on SOUL-LUCI@LBT of one of the most extreme INSPIRE relics, KiDS J0842 + 0059 at $z \sim 0.3$. We confirm the discy morphology of this galaxy (axis ratio of 0.24) and its compact nature (circularized effective radius of $\sim 1$ kpc) by modelling its 2D surface brightness profile with a point-spread function-convolved Sérsic model. We demonstrate that the surface mass density profile of KiDS J0842 + 0059 closely resembles that of the most extreme local relic, NGC 1277, as well as of high-redshift red nuggets. We unambiguously conclude that this object is a remnant of a high-redshift compact and massive galaxy, which assembled all of its mass at $z>2$, and completely missed the merger phase of the galaxy evolution at high redshift.
Charles Yin; A. Lawrence; M. J. Ward; D. Homan; W. Kollatschny
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT We present flux measurements of the coronal lines [Fe vii] and [Fe x] spanning three decades, in the highly variable active galactic nucleus (AGN) MKN 110. These coronal lines are sensitive to the spectral energy distribution of AGNs in the extreme ultraviolet. Neither [Fe vii] nor [Fe x] demonstrates variability in the short term on a weekly or monthly time-scale. However, by taking advantage of a long-term decrease in the continuum flux of MKN 110 of the order of years, we were able to track the [Fe vii] and [Fe x] fluxes as they respond to the continuum. We were able to detect a lag for [Fe vii] relative to the continuum at 5100 Å, with a modal lag of 652 d, but were unable to detect a significant lag in the [Fe x] flux, though there exist significant uncertainties in the [Fe x] fit. These two lag results are not consistent and the line widths for the two line species also do not match. This provides strong evidence for stratification within the coronal line region (CLR). There is also evidence of a non-varying component within the coronal line flux, probably a result of a more extended region of origin. Taken together, these results suggest a CLR where the bulk of the [Fe vii] originates on parsec scales, but a portion of the [Fe vii] flux originates further out, at or beyond a 10 pc scale. These results also indicate the limitations of single-cloud models in describing the physical conditions of the CLR.
Johanna Hartke; E. Iodice; M. Gullieuszik; Marco Mirabile; Chiara Buttitta; Goran Doll; G. D’Ago; C.C. de la Casa; Kelley M. Hess; Ralf Kotulla; Bianca M. Poggianti; M. Arnaboldi; M. Cantiello; E. M. Corsini; J. Falcón-Barroso; Duncan A. Forbes; M. Hilker; S. Mieske; M. Rejkuba; M. Spavone; C. Spiniello
Astronomy and Astrophysics · DOI ↗
Context. UDG 32 is an ultra-diffuse galaxy (UDG) candidate in the Hydra I cluster that was discovered in the extended network of stellar filaments of the jellyfish galaxy NGC 3314A. This jellyfish galaxy is affected by ram pressure stripping and it is hypothesised that UDG 32 may have formed from this stripped material. Aims. The aim of this paper is to address whether UDG 32 can be associated with the stripped material of NGC 3314A and to constrain its formation scenario in relation to its environment. Methods. We use new integral-field spectroscopic data from the MUSE large programme ‘LEWIS’ in conjunction with deep multi-band photometry to constrain the kinematics of UDG 32 via spectral fitting and its stellar population properties with spectral energy distribution fitting. Results. The new MUSE data allow us to reveal that the stripped material from NGC 3314A, traced by emission lines such as H α , extends much further from its parent galaxy than previously known, completely overlapping with UDG 32 in projection, and with ram pressure induced star formation. We determine the line-of-sight velocity of UDG 32 to be v LOS = 3080 ± 120 km s −1 and confirm that UDG 32 is part of the same kinematic structure as NGC 3314A, the Hydra I cluster south-east subgroup. By fitting the UV and optical spectral energy distribution obtained from deep multi-band photometry, we constrain the stellar population properties of UDG 32. We determine its mass-weighted age to be 7.7 −2.8 +2.9 Gyr and its metallicity to be [M/H] = 0.07 −0.32 +0.19 dex. We confirm the presence of two globular clusters (GCs) in the MUSE field of view, bound to the Hydra I cluster rather than to UDG 32, making them part of the Hydra I intracluster GC population. Conclusions. The metal-rich and intermediate-age nature of UDG 32 points towards its formation from pre-enriched material in the south-east group of the Hydra I cluster that was liberated from a more massive galaxy via tidal or ram-pressure stripping, but we cannot establish a direct link to the ram-pressure stripped material from NGC 3314A.
Rui Li; N. R. Napolitano; G. D’Ago; V. N. Shalyapin; Kai Zhu; Xiaotong Guo; Ran Li; L. V. E. Koopmans; Chiara Spiniello; C. Tortora; Francesco La Barbera; Hai-Cheng Feng; Liang Gao; Zhiqi Huang; Konrad Kuijken; Hui Li; L. Xie; M. Radovich; A. V. Sergeyev
The Astrophysical Journal Letters · DOI ↗
Abstract We report the spectroscopic confirmation of a bright blue Einstein ring in the Kilo-Degree Survey (KiDS) footprint: the Einstein “blue eye.” Spectroscopic data from X-Shooter at the Very Large Telescope (VLT) show that the lens is a typical early-type galaxy (ETG) at z l = 0.9906, while the background source is a Ly α emitter at z s = 2.823. The reference lens modeling was performed on a high-resolution Y- band adaptive-optics image from HAWK-I at VLT. Assuming a singular isothermal ellipsoid total mass density profile, we inferred an Einstein radius R Ein = 10.47 ± 0.06 kpc. The average slope of the total mass density inside the Einstein radius, as determined by a joint analysis of lensing and isotropic Jeans equations, is <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML&quot; overflow="scroll"> <mml:msub> <mml:mi>γ</mml:mi> <mml:mi>tot</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>2.1</mml:mn> <mml:msubsup> <mml:mn>4</mml:mn> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.07</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.06</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , showing no systematic deviation from the slopes of lower-redshift galaxies. This can be the evidence of ETGs developing through dry mergers plus moderate dissipationless accretion. Stellar population analysis with eight-band ( gri ZYJHK s ) photometries from KiDS and VIKING shows that the total stellar mass of the lens is M * = (3.95 ± 0.35) × 10 11 M ⊙ (Salpeter initial mass function (IMF)), implying a dark matter fraction inside the effective radius of f DM = 0.307 ± 0.151. We finally explored the dark matter halo slope and found a strong degeneracy with the dynamic stellar mass. Dark matter adiabatic contraction is needed to explain the posterior distribution of the slope, unless an IMF heavier than Salpeter is assumed.
Anke Arentsen; Sarah G. Kane; Vasily Belokurov; Tadafumi Matsuno; Martin Montelius; Stephanie Monty; Jason L. Sanders
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT Carbon-rich (C-rich) stars can be found at all metallicities and evolutionary stages. They are often the result of mass transfer from a companion, but some of the most metal-poor C-rich objects are likely carrying the imprint of the metal-free First Stars from birth. In this work, we employ a neural network to predict metallicities and carbon abundances for over 10 million stars with Gaia low-resolution XP spectra, down to $\rm {[Fe/H]} = -3.0$ and up to $\rm {[C/Fe]} \approx +2$. We identify ${\sim} 2000$ high-confidence bright ($G\lt 16$) carbon-enhanced metal-poor stars with $\rm {[Fe/H]} \lt -2.0$ and $\rm {[C/Fe]} \gt +0.7$. The majority of our C-rich candidates have $\rm {[Fe/H]} \gt -2.0$ and are expected to be binary mass-transfer products, supported by high barium abundances in the GALAH (GALactic Archaeology with HERMES) survey and/or their Gaia Renormalised Unit Weight Error (RUWE) and radial velocity variations. We confirm previous findings of an increase in C-rich stars with decreasing metallicity, adopting a definition of $3\sigma$ outliers from the [C/Fe] distribution, although our frequency appears to flatten for $-3.0 \lt \rm {[Fe/H]} \lt -2.0$ at a level of $6\!\!-\!\!7{{\ \rm per\, cent}}$. We also find that the fraction of C-rich stars is low among globular cluster stars (connected to their lower binary fraction), and that it decreases for field stars more tightly bound to the Milky Way. We interpret these last results as evidence that disrupted globular clusters contribute more in the inner Galaxy, supporting previous work. Homogeneous samples such as these are key to understanding the full population properties of C-rich stars, and this is just the beginning.
Tristan Whitmarsh; Wei Cope; Julia Carmona-Bozo; Roido Manavaki; Stephen‐John Sammut; Ramona Woitek; Elena Provenzano; Emma Brown; Sarah E. Bohndiek; Ferdia A. Gallagher; Carlos Caldas; Fiona J. Gilbert; Florian Markowetz
Breast Cancer Research · DOI ↗
BACKGROUND: Tumour vascular density assessed from CD-31 immunohistochemistry (IHC) images has previously been shown to have prognostic value in breast cancer. Current methods to measure vascular density, however, are time-consuming, suffer from high inter-observer variability and are limited in describing the complex tumour vasculature morphometry. METHODS: We propose a method for automatically measuring a range of vascular parameters from CD-31 IHC images, which together provide a detailed description of the vasculature morphology. We first used a U-Net based convolutional neural network, trained and validated using 36 partially annotated whole slide images from 27 patients, to segment vessel structures and tumour regions from which the measurements are taken. The model also segments the vascular smooth muscle, benign epithelium, adipose tissue, stroma, lymphocyte clusters, nerves and CD-31 positive leukocytes, and we applied it to an additional 21 images from 15 patients. Using these segmentations, we investigated the relationship between the various tissue types and the vasculature and studied the relationship of various vascular parameters with clinical parameters. We also performed a 3D histology analysis on a separate tumour sample as a proof of principle, providing a more comprehensive visualization of vasculature morphology compared to the standard 2D cross-section of a tissue sample. RESULTS: ) and significant (p<0.001) correlations with measurements taken from the manual ground truth vessel segmentations. A significant relationship between the major/minor axis ratio, a measure of elongation, and the tumour grade was found. CONCLUSION: Our proposed method shows promise as a tool for studying the tumour vasculature and its relationship with surrounding cells and tissue types. Furthermore, the correlation with tumour grade highlights the clinical relevance of our approach. These findings suggest that our method could have substantial implications for improving prognostic assessments and personalizing therapeutic strategies in breast cancer treatment.
Melis O Irfan; E. A. González-Solares; Tristan Whitmarsh; Alireza Molaeinezhad; Mohammad Al Sa’d; Claire M. Mulvey; Marta Páez Ribes; Atefeh Fatemi; Dario Bressan; N. A. Walton
Frontiers in Genetics · DOI ↗
Cell segmentation is a crucial step in numerous biomedical imaging endeavors-so much so that the community is flooded with publicly available, state-of-the-art segmentation techniques ready for out-of-the-box use. Assessing the strengths and limitations of each method on a tissue sample set and then selecting the optimal method for each research objective and input image are time-consuming and exacting tasks that often monopolize the resources of biologists, biochemists, immunologists, and pathologists, despite not being the primary goal of their research projects. In this work, we present a segmentation software wrapper, coined CellSampler, which runs a selection of established segmentation methods and then combines their individual segmentation masks into a single optimized mask. This so-called "uber mask" selects the best of the established masks across local neighborhoods within the image, where both the neighborhood size and the statistical measure used to define what qualifies as "best" are user-defined.
Melis O Irfan; E. A. González-Solares; Tristan Whitmarsh; Alireza Molaeinezhad; Mohammad Al Sa’d; Claire M. Mulvey; Marta Ribes; Dario Bressan; N. A. Walton
bioRxiv (Cold Spring Harbor Laboratory) · DOI ↗
ABSTRACT Cell segmentation is a crucial step in numerous biomedical imaging endeavors; so much so that the community is flooded with publicly available, state-of-the-art segmentation techniques ready for out of the box use. Assessing the virtues and limitations of each method on a tissue sample set and then selecting the optimum method for each research objective and input image is a time consuming and exacting task that often monopolizes the resources of biologists, biochemists, immunologists and pathologists; despite not being their project primary research goal. In this work, we present a segmentation software wrapper, coined CellSampler , which runs a selection of established segmentation methods and then combines their individual segmentation masks into a single optimized mask. This, so called ‘uber mask’, selects the best of the established masks across local neighborhoods within the image, where the neighborhood size and the statistical measure which determines the qualitative term ‘best’ are both chosen by the user.
L. Delfini; Miguel Vioque; Álvaro Ribas; S. T. Hodgkin
Astronomy and Astrophysics · DOI ↗
Context. Accretion rates from protoplanetary discs onto forming stars are a key ingredient in star formation and protoplanetary disc evolution. Extensive efforts surveying different individual star-forming regions with spectroscopy and narrow-band photometry have been made to derive accretion rates on large populations of young stellar objects (YSOs). Aims. We use Gaia DR3 XP spectra to perform the first all-sky homogeneous analysis of YSO accretion properties within 500 pc. Methods. We characterise the H line emission of YSOs within 500 pc by using the H pseudo-equivalent widths and XP spectra provided by Gaia DR3. We derive accretion luminosities and mass accretion rates, together with stellar parameters, for 145 975 all-sky candidate YSO H emitters. We describe filtering strategies to select specific sub-samples of YSOs from this catalogue. Results. We identify a large population of low-accreting YSO candidates untraced by previous accretion rates surveys. We find previous surveys have mostly focused on YSO populations with significant infrared excess from disc emission. The population of low-accreting YSOs is mostly spatially dispersed, away from star-forming regions or the more clustered environments of star formation. Many YSOs appear entirely disconnected from young populations, and they are reminiscent of the long-lived ‘Peter Pan’ YSOs. We find L acc ∝ L ⋆ 1.41 ± 0.02 and Ṁ acc ∝ M ⋆ 2.4 ± 0.1 for the purest all-sky sample of YSO candidates. By fitting an exponential function to the fraction of accreting stars in clusters of different ages in the Sco-Cen complex, we obtain an accretion timescale of τ acc = 2.7 ± 0.4 Myr. The percentage of accretors found by fitting a power law function is 70% at 2 Myr and 2.8% at 10 Myr. Conclusions. With this new catalogue of H emitters, we significantly increase the number of YSO candidates with accretion rate estimations in the local neighbourhood. This allows us to study accretion timescales and the spatial and physical properties of YSO accretion from a large, all-sky, and homogeneous sample for the first time.
Elisabeth Sola; David Chemaly; Vasily Belokurov; Oliver Müller; Anke Arentsen; Elliot Y Davies; Júlia Laguna-Miralles; GyuChul Myeong; Konstantinos Panagiotakis; Hanyuan Zhang; Denis Erkal; S. E. Koposov; Dustin Lang; Jacob Nibauer
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT Tidal features from galaxy mergers, particularly stellar streams, offer valuable insights into galaxy assembly and dark matter halo properties. This paper aims to identify a large sample of nearby stellar streams suitable for detailed modelling and comparison with simulations to enable population-level constraints on halo properties. We visually inspect and compile a tidal feature catalogue for 19 387 galaxies with redshift $z \le 0.02$ from the Siena Galaxy Atlas 2020 using original, model, and residual images from the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys. Residual images, produced by subtracting models of all sources, enhance the detectability of faint asymmetries such as tidal features. We find that $11.9 \pm 0.2{{\ \rm per\ cent}}$ of galaxies host detectable tidal features, more frequently around early- than late-type galaxies. The tidal feature fraction increases with stellar mass, from $2.4 \pm 0.4{{\ \rm per\ cent}}$ at $\sim 10^8\, \mathrm{M}_\odot$ to $36.5 \pm 1.2{{\ \rm per\ cent}}$ at $\sim 5\times 10^{11}\, \mathrm{M}_\odot$. From this, we present the first release of STRRINGS: STReams in Residual Images of Nearby GalaxieS, a subsample of 35 galaxies with long, narrow streams suitable for modelling. We segment these streams and derive their geometry, surface brightness, colours, and stellar masses. The median g-band surface brightness is 26.8 mag arcsec$^{-2}$, reaching 27.5 mag arcsec$^{-2}$ for the faintest stream. Mass ratios are consistent with minor mergers, and we identify five potential dwarf galaxy progenitors. Our streams are typically longer (median 124 kpc) than the literature, with comparable widths. Stream mass correlates with length and colour, and wider streams lie at larger galactocentric radii. STRRINGS will be expanded and used to constrain halo properties in future work.
M. Montelius; Else Starkenburg; Hanneke C. Woudenberg; A. Angrilli Muglia; Anke Arentsen; Anand Viswanathan; Amanda Byström; A. Helmi; N. Martin; Tadafumi Matsuno; Camila Navarrete; Julio F. Navarro
Astronomy and Astrophysics · DOI ↗
Context. The most metal-poor stars in our Galaxy contain important clues of its earliest history, particularly those occupying the inner regions of the Galaxy. In the search for such metal-poor stars, large spectroscopic surveys are an invaluable tool. However, the spectra of metal-poor stars can be difficult to analyse because of the relative lack of available lines, which can also lead to misclassification. Aims. We aim to identify the stars observed by the APOGEE survey that are below the metallicity limit of APOGEE’s analysis. For the highest confidence candidates, we classify the orbital properties of the stars to investigate whether their orbital distribution matches what we would expect for stars that are this metal poor and to select especially interesting targets for spectroscopic follow-up purposes. Methods. We examined the properties derived by APOGEE for metal-poor stars from the literature to find signatures of stars with a metallicity below the range of the grid used for spectral analysis. Once identified within APOGEE, we computed the orbits of our metal-poor candidates using AGAMA. Results. The calibrated APOGEE stellar parameters provide a clear signature of the most metal-poor stars in the survey, indicated by null values for their metallicities while having effective temperatures and surface gravities determined by the pipeline. From comparison with the literature, we find that, within a temperature range of 3700–6700 K and above a threshold of S/N &gt; 30, the vast majority of APOGEE stars without calibrated metallicities are very metal poor. Additional cleaning by visual inspection of the spectra improved the purity of the sample further. The radial velocities provided by APOGEE, Gaia DR3 positions and astrometry along with spectrophotometric distances derived in this work allowed for the computation of their orbits. In this work, we carefully selected 289 very metal-poor red giant stars (likely below [Fe / H] = −2.5) from the APOGEE results. Our sample contains 16 very metal-poor member candidates of the Magellanic Clouds, 14 very metal-poor stars with orbits confined to the inner Galaxy, and 13 inner Galaxy halo interlopers. These samples significantly add to the very metal-poor stars known in these regions and allow for a more detailed picture of early chemical evolution across different environments.
Sara Vitali; Á. Rojas-Arriagada; P. Jofré; Federico Sestito; Joshua Povick; V. Hill; Emma Fernández-Alvar; Anke Arentsen; P. Jablonka; Nicolas F. Martin; Else Starkenburg; David S. Aguado
Astronomy and Astrophysics · DOI ↗
Context . The Sagittarius dwarf spheroidal galaxy (Sgr dSph) is a satellite orbiting the Milky Way that has experienced multiple stripping events due to tidal interactions with our Galaxy. Its accretion history has led to a distinct stellar overdensity, which is the remnant of the core of the progenitor. Aims . We present a complete chemical analysis of 111 giant stars in the core of Sgr dSph to investigate the chemical evolution and enrichment history of this satellite. Methods . Employing the metallicity-sensitive Ca H&amp;K photometry from the Pristine Inner Galaxy Survey, we selected stars that span a wide metallicity range and obtained high-resolution spectra with the ESO FLAMES/GIRAFFE multiobject spectrograph. For the stellar sample covering − 2.13 &lt; [Fe/H] &lt; − 0.35, we derived abundances for up to 14 chemical elements with average uncertainties of ∼ 0.09 dex and a set of stellar ages that allowed us to build an age-metallicity relation (AMR) for the entire sample. Results . With the most comprehensive set of chemical species measured for the core of Sgr (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Co, Ba, La, and Eu), we studied several [X/Fe] ratios. Most trends align closely with Galactic chemical trends, but notable differences emerge in the heavy n -capture elements, which offer independent insights into the star formation history of a stellar population. Conclusions . The deficiency in α elements with respect to the Milky Way suggests a slower, less efficient early star formation history, similar to other massive satellites. S -process element patterns indicate significant enrichment from Asymptotic giant branch stars over time. The AMR and chemical ratios point to an extended star formation history, with a rapid early phase in the first gigayears, followed by declining activity and later star-forming episodes. These findings are consistent with Sgr hosting multiple stellar populations, from young (∼4 Gyr) to old, metal-poor stars (∼10 Gyr).
Adam C. Schneider; F. J. Vrba; Justice Bruursema; Jeffrey A. Munn; M. J. Irwin; Mike Read; W. P. Varricatt; Tom Kerr; K. W. Hodapp; S. Dye; Stephen J. Williams; Andrew T. Cenko; T. Tilleman; Marc A. Murison; Barry Rothberg; S. E. Dahm; Bryan N. Dorland; A. Lawrence; K. C. Chambers
The Astronomical Journal · DOI ↗
Abstract This paper describes the second and third data releases (DR2 and DR3, respectively) from the ongoing United Kingdom Infrared Telescope Hemisphere Survey (UHS). DR2 is primarily comprised of the K -band portion of the UHS survey, and was released to the public on 2023 June 1. DR3 mainly includes the H -band portion of the survey, with a public release scheduled for September 2025. The H - and K -band data releases complement the previous J -band data release (DR1) from 2018. The survey covers approximately 12,700 square degrees between declinations of 0° and +60° and achieves median 5 σ point source sensitivities of 19.0 mag and 18.0 mag (Vega) for H and K , respectively. The data releases include images and source catalogs, which include ∼581 million H -band detections and ∼461 million K -band detections. DR2 and DR3 also include merged catalogs, created by combining J - and K -band detections (DR2) and J -, H -, and K -band detections (DR3). The DR2 merged catalog has a total of ∼513 million sources, while the DR3 merged catalog contains ∼560 million sources.
Thomas Hajnik; N. A. Walton; G. D’Ago; P. Bonifacio; Gavin Dalton; Lilian Domínguez-Palmero; E. Gafton; Irwin, Mike J.; Sergio Picó; David Terrett; Anke Arentsen; Rubén Sánchez-Janssen; David S. Aguado; J. A. L. Aguerri; Carlos Allende Prieto; M. Balcells; Chris Benn; A. Bragaglia; E. Caffau; Esperanza Carrasco; R. Carrera; S. Desidera; B. T. Gänsicke; Sarah Hughes; Shoko Jin; Ian Lewis; Alireza Molaeinezhad; D. N. A. Murphy; Ellen Schallig; S. C. Trager; A. Vallenari
arXiv (Cornell University) · DOI ↗
Current-day multi-object spectroscopic surveys are often limited in their ability to observe bright stars due to their low surface densities, resulting in increased observational overheads and reduced efficiency. Addressing this, we have developed a novel observing mode for WEAVE (William Herschel Telescope Enhanced Area Velocity Explorer) that enables efficient observations of low-surface-density target fields without incurring additional overheads from calibration exposures. As a pilot for the new mode, we introduce the WEAVE-TwiLight-Survey (WTLS), focusing on bright exoplanet-host stars and their immediate surroundings on the sky. High observational efficiency is achieved by superimposing multiple low-target-density fields and allocating the optical fibres in this configuration. We use a heuristic method to define fields relative to a central guide star, which serves as a reference for their superposition. Suitable guide fibres for each merged configuration are selected using a custom algorithm. Test observations have been carried out, demonstrating the feasibility of the new observing mode. We show that merged field configurations can be observed with WEAVE using the proposed method. The approach minimizes calibration times and opens twilight hours to WEAVE's operational schedule. WTLS is built upon the new observing mode and sourced from the ESA PLATO long-duration-phase fields. This survey will result in a homogeneous catalogue of approximately 6300 bright stars, including 62 known planet hosts, laying the groundwork for future elemental abundance studies tracing chemical patterns of planetary formation. This new observing mode (WEAVE-Tumble-Less) expands WEAVE's capabilities to rarely used on-sky time and low-density field configurations without sacrificing efficiency.
Thomas Hajnik; N. A. Walton; G. D’Ago; P. Bonifacio; Gavin Dalton; Lilian Domínguez-Palmero; E. Gafton; M. J. Irwin; Sergio Picó; David Terrett; Anke Arentsen; Rubén Sánchez-Janssen; David S. Aguado; J. A. L. Aguerri; Carlos Allende Prieto; Marc Balcells; Chris Benn; A. Bragaglia; E. Caffau; E. Carrasco; R. Carrera; S. Desidera; B. T. Gänsicke; Sarah Hughes; Shoko Jin; Ian Lewis; Alireza Molaeinezhad; D. N. A. Murphy; Ellen Schallig; S. C. Trager; A. Vallenari
RAS Techniques and Instruments · DOI ↗
ABSTRACT Current-day multi-object spectroscopic surveys are often limited in their ability to observe bright stars due to their low surface densities, resulting in increased observational overheads and reduced efficiency. Addressing this, we have developed a novel observing mode for WEAVE (William Herschel Telescope Enhanced Area Velocity Explorer) that enables efficient observations of low-surface-density target fields without incurring additional overheads from calibration exposures. As a pilot for the new mode, we introduce the WEAVE-TwiLight-Survey (WTLS), focusing on bright exoplanet-host stars and their immediate surroundings on the sky. High observational efficiency is achieved by superimposing multiple low-target-density fields and allocating the optical fibres in this configuration. We use a heuristic method to define fields relative to a central guide star, which serves as a reference for their superposition. Suitable guide fibres for each merged configuration are selected using a custom algorithm. Test observations have been carried out, demonstrating the feasibility of the new observing mode. We show that merged field configurations can be observed with WEAVE using the proposed method. The approach minimizes calibration times and opens twilight hours to WEAVE’s operational schedule. WTLS is built upon the new observing mode and sourced from the ESA PLATO long-duration-phase fields. This survey will result in a homogeneous catalogue of ∼6300 bright stars, including 62 known planet hosts, laying the groundwork for future elemental abundance studies tracing chemical patterns of planetary formation. This new observing mode (WEAVE-Tumble-Less) expands WEAVE’s capabilities to rarely used on-sky time and low-density field configurations without sacrificing efficiency.
Akshara Viswanathan; Else Starkenburg; Tadafumi Matsuno; Kim A. Venn; Nicolas F. Martin; Nicolas Longeard; Anke Arentsen; R. G. Carlberg; S. Fabbro; G. Kordopatis; Martin Montelius; Federico Sestito; Zhen Yuan
Astronomy and Astrophysics · DOI ↗
Context. Gaia DR3 has offered the scientific community a remarkable dataset of approximately one million spectra acquired with the radial velocity spectrometer (RVS) in the calcium II triplet region, which is well suited to identify very metal-poor (VMP) stars. However, over 40% of these spectra have no released parameters by Gaia ’s GSP-Spec pipeline in the domain of VMP stars, whereas VMP stars are key tracers of early Galactic evolution. Aims. We aim to provide spectroscopic metallicities for VMP stars using Gaia RVS spectra, thereby producing a catalogue of bright VMP stars distributed over the full sky that can serve as the basis for studies of early chemical evolution throughout the Galaxy. Methods. We selected VMP stars using photometric metallicities from the literature and analysed the Gaia RVS spectra to infer spectroscopic metallicities for these stars. Results. The inferred metallicities agree very well with literature high-resolution metallicities, with a median systematic offset of 0.1 dex and standard deviation of ∼0.15 dex. The purity of this sample in the VMP regime is ∼80%, with outliers representing a mere ∼3%. Conclusions. We have built an all-sky catalogue of ∼1500 stars available, featuring reliable spectroscopic metallicities down to [Fe/H] ∼ −4.0, of which ∼1000 are VMP stars. More than 75% of these stars have either no spectroscopic metallicity value in the literature to date or have been flagged as unreliable in their literature spectroscopic metallicity estimates. This catalogue of bright ( G &lt; 13) VMP stars is three times larger than the current sample of well-studied VMP stars in the literature in this magnitude range, making it ideal for high-resolution spectroscopic follow-ups and studies of the properties of VMP stars in different parts of our Galaxy.
S. Lalitha; Thomas A Baycroft; I. Boisse; N. Heidari; A. Santerne; A. H. M. J. Triaud; Gavin A. L. Coleman; Yasmin Davis; M. Deleuil; G. Hébrard; David V. Martin; P. F. L. Maxted; Richard P. Nelson; Daniel Sebastian; Owen J Scutt; Matthew R. Standing
Monthly Notices of the Royal Astronomical Society · DOI ↗
ABSTRACT Circumbinary planets, orbiting both stars in a binary system, offer the opportunity to study planet formation and orbital migration in an environment different from that around single stars. However, despite the fact that $\gt 90~\% $ of binary systems in the solar neighbourhood are spectrally resolved double-lined binaries, there has been only one detection of a circumbinary planet orbiting a double-lined binary using the radial velocity method so far. Spectrally disentangling binary components is challenging due to blending of spectral lines and inaccuracies in spectral modelling. These inaccuracies add scatter to the measurements, which can hide the weak radial velocity signature of circumbinary exoplanets. We have obtained new high signal-to-noise, high-resolution spectra with the SOPHIE spectrograph, mounted on the 193 cm telescope at Observatoire de Haute-Provence (OHP), for six bright, double-lined binaries for which circumbinary exoplanet detection has been attempted in the past. To extract radial velocities, we use the DOLBY code, a recent method of spectral disentangling using Gaussian processes to model the time-varying components. We analyse the resulting radial velocities with a diffusive nested sampler to seek planets, and compute sensitivity limits. We do not detect any new circumbinary planet. However, we show that the combination of new data, new radial velocity extraction methods, and improved statistical methods to determine a data set’s sensitivity to planets leads to an approximately one order of magnitude improvement compared to previous results. This improvement brings us into the range of known circumbinary exoplanets and paves the way for future observation campaigns targeting double-lined binaries.