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Euclid Quick Data Release (Q1). The role of cosmic connectivity in shaping galaxy clusters
No full textInternational audienceThe matter distribution around galaxy clusters is distributed over several filaments, reflecting their positions as nodes in the large-scale cosmic web. The number of filaments connected to a cluster, namely its connectivity, is expected to affect the physical properties of clusters. Using the first Euclid galaxy catalogue from the Euclid Quick Release 1 (Q1), we investigate the connectivity of galaxy clusters and how it correlates with their physical and galaxy member properties. Around 220 clusters located within the three fields of Q1 (covering ), are analysed in the redshift range 0.2 < z < 0.7. Due to the photometric redshift uncertainty, we reconstruct the cosmic web skeleton, and measure cluster connectivity, in 2-D projected slices with a thickness of 170 comoving and centred on each cluster redshift, by using two different filament finder algorithms on the most massive galaxies (M_*\ > 10^{10.3} \ M_\odot). In agreement with previous measurements, we recover the mass-connectivity relation independently of the filament detection algorithm, showing that the most massive clusters are, on average, connected to a larger number of cosmic filaments, consistent with hierarchical structure formation models. Furthermore, we explore possible correlations between connectivities and two cluster properties: the fraction of early-type galaxies and the Sérsic index of galaxy members. Our result suggests that the clusters populated by early-type galaxies exhibit higher connectivity compared to clusters dominated by late-type galaxies. These preliminary investigations highlight our ability to quantify the impact of the cosmic web connectivity on cluster properties with Euclid
Flow and thermal modelling of the argon volume in the DarkSide-20k TPC
No full textInternational audienceThe DarkSide-20k dark matter experiment, currently under construction at LNGS, features a dual-phase time projection chamber (TPC) with a ~50 t argon target from an underground well. At this scale, it is crucial to optimise the argon flow pattern for efficient target purification and for fast distribution of internal gaseous calibration sources with lifetimes of the order of hours. To this end, we have performed computational fluid dynamics simulations and heat transfer calculations. The residence time distribution shows that the detector is well-mixed on time-scales of the turnover time (~40 d). Notably, simulations show that despite a two-order-of-magnitude difference between the turnover time and the half-life of Kr of 1.83 h, source atoms have the highest probability to reach the centre of the TPC 13 min after their injection, allowing for a homogeneous distribution before undergoing radioactive decay. We further analyse the thermal aspects of dual-phase operation and define the requirements for the formation of a stable gas pocket on top of the liquid. We find a best-estimate value for the heat transfer rate at the liquid-gas interface of 62 W with an upper limit of 144 W and a minimum gas pocket inlet temperature of 89 K to avoid condensation on the acrylic anode. This study also informs the placement of liquid inlets and outlets in the TPC. The presented techniques are widely applicable to other large-scale, noble-liquid detectors
Dark Energy Search by Atom Interferometry in the Einstein-Elevator
No full textInternational audienceThe DESIRE project aims to test chameleon field theories as potential candidates for dark energy. The chameleon field is a light scalar field that is subject to screening mechanisms in dense environments making them hardly detectable. The project is designed to overcome this challenge. To this end, a specially designed source mass generates periodic gravitational and chameleon potentials. The design of the source mass allows for adjustment of the amplitude and periodicity of the gravitational potential while keeping the chameleon potential unchanged. The periodicity of the potentials makes them distinguishable from the environment and allows for resonant detection using multiloop atom interferometry under microgravity conditions
Quantum circuit complexity for linearly polarized light
No full textInternational audienceIn this study, we explore a form of quantum circuit complexity that extends to open systems. To illustrate our methodology, we focus on a basic model where the projective Hilbert space of states is depicted by the set of orientations in the Euclidean plane. Specifically, we investigate the dynamics of mixed quantum states as they undergo interactions with a sequence of gates. The latter aim to accurately adjust the path from referent to target, aligning it as closely as possible with the path we have chosen. Our approach involves the analysis of sequences of real 2×2 density matrices. This mathematical model is physically exemplified by the Stokes density matrices, which delineate the linear polarization of a quasimonochromatic light beam, and the gates, which are viewed as quantum polarizers, whose states are also real 2×2 density matrices. The interaction between polarizer-linearly polarized light is construed within the context of this quantum formalism. Each density matrix for the light evolves in an approach analogous to a Gorini-Kossakowski-Lindblad-Sudarshan (GKLS) process during the time interval between consecutive gates. Notably, when considering an upper limit for the tolerance or accuracy, we unearth that the number of gates follows a power-law relationship which gives an upper bound of the complexity
Effects of secular growth and mergers on the evolution of metallicity gradients and azimuthal variations in a Milky Way-like galaxy
No full textInternational audienceWe analyzed the evolution of the radial profiles and the azimuthal variations of the stellar metallicities from the VINTERGATAN simulation of a Milky Way-like galaxy. We find that negative gradients exist as soon as the disk settles at high redshift, and are maintained throughout the long-term evolution of the galaxy, including during major merger events. The inside-out growth of the disk and an overall outward radial migration tend to flatten these gradients in time. Major merger events only have a moderate and shortlived imprint on the [Fe/H] distributions with almost no radial dependence. The reason lies in the timescale for enrichment in Fe being significantly longer than the duration of the starbursts episodes, themselves slower than dynamical mixing during typical interactions. It results in signatures of major mergers becoming undetectable in [Fe/H] only a few megayears after pericenter passages. We note that considering other tracers like the warm interstellar medium, or monitoring the evolution of the metallicity gradient as a single value instead of a radial full profile could lead to different interpretations; we warn against oversimplifying this complex problem
Abundance ties: Nephele and the globular cluster population accreted with ω Cen: Based on APOGEE DR17 and Gaia EDR3
No full textInternational audienceContext. The peculiar Galactic globular cluster ω Centauri (NGC 5139) has drawn attention for its unique features, such as an unusually high stellar mass compared to other Galactic globular clusters and a broad distribution of chemical elements. These features have led to the hypothesis that ω Centauri might be the nuclear remnant of an ancient dwarf galaxy accreted by the Milky Way, potentially bringing along its own globular cluster system.Aims. In this work, we adopt an innovative approach by examining the individual chemical abundances of Galactic globular clusters to identify shared patterns with ω Centauri.Methods. Applying Gaussian mixture models to globular cluster stars, whose membership is based on the analysis of the Gaia EDR3 release, and whose chemical abundances have been obtained from APOGEE DR17, we depart from traditional kinematic-based procedures and search for globular clusters that are chemically compatible with ω Centauri in an eight-dimensional space defined by [Fe/H], α-elements such as [Mg/Fe], [Si/Fe], and [Ca/Fe], light+odd-Z elements such as [C/Fe], [Al/Fe], and [K/Fe], and an iron-peak element as [Mn/Fe]. With this approach, clusters that are chemically compatible with ω Centauri are clusters whose chemical patterns are contained in the abundance domain defined by ω Centauri stars.Results. Our analysis leads to the identification of six globular clusters – NGC 6752, NGC 6656, NGC 6809, NGC 6273, NGC 6205, and NGC 6254 – that exhibit strong chemical similarities with ω Centauri, and that have metallicities that coincide with those of the two known peaks (primary and secondary) of ω Centauri’s metallicity distribution. They all exhibit non-null intrinsic [Fe/H] dispersions, ranging between 0.07 and 0.12 dex, unless the ASPCAP uncertainties had been severely underestimated, and three of them have statistically significant skewed [Fe/H] distributions. Furthermore, the chemical patterns of these clusters lead to the exclusion that they were formed in progenitor galaxies with chemical enrichment histories similar to those of the Large and Small Magellanic Clouds, Sagittarius, and Fornax. Once placed in kinematic spaces such as the energy – angular momentum plane, these clusters result scatter across an extended region, which is predicted by N-body simulations if their common progenitor was sufficiently massive compared to the Milky Way.Conclusions. Our novel approach suggests a common origin for NGC 6752, NGC 6656, NGC 6809, NGC 6273, NGC 6205, NGC 6254, and ω Centauri, indicating that Nephele, as we propose to call the progenitor in which all these clusters formed, played a substantial role in the Galaxy’s history. The finding that a set of globular clusters can be associated with ω Centauri reinforces the hypothesis that this system is the remnant of a galaxy, and not simply an unusual globular cluster. This study also shows that the spectroscopic data at our disposal have reached the quality needed to compare chemical patterns of stellar systems, to reveal their common origins or exclude their association with specific progenitor galaxies
The e-TidalGCs project: Modeling the extra-tidal features generated by Galactic globular clusters (Corrigendum)
No full textInternational audienceNo abstract availabl
EQUIPEMENT SPECTRO-POLARIMETRIQUE DES GRANDS INSTRUMENTS SOLAIRES DE MEUDON ET DU PIC DU MIDI
No full textNous présentons dans ce document les grands spectrographes professionnels de la Tour Solaire de Meudon (TSM) et de la Lunette « Jean Rösch » du Pic du Midi (LJR) ainsi que leurs équipements en analyse de la polarisation de la lumière et acquisition numérique. La spectroscopie des raies photosphériques et chromosphériques combinée à la polarimétrie (ou spectro-polarimétrie) est une technique fondamentale en physique solaire à la base de la détermination à distance des mouvements de matière (par effet Doppler) et des champs magnétiques (par effet Zeeman)
Interpreting the multi-TeV emission from GRB 221009A with a second electron component accelerated by turbulence in the Jet
No full textInternational audienceThe detection of very high-energy afterglow emission of the gamma-ray burst (GRB) 221009A by the Large High Altitude Air Shower Observatory (LHAASO) provides a unique opportunity to probe particle acceleration in relativistic outflows. The hard spectrum at the multi-TeV band cannot be fully explained by synchrotron-self-Compton radiation of the conventional one-zone afterglow model. In this work, we introduce a second component of relativistic electrons from stochastic acceleration via downstream turbulence of the external shock. Using a Fokker–Planck approach to model the evolution of protons and electrons, and the nonlinear feedback of turbulence damping, we show that the inverse Compton radiation of the second electron component may harden the observed spectrum above multi-TeV energy, and significantly ameliorate the fitting to the spectral evolution measured by LHAASO without violating lower-energy observations. We also discuss the potential presence of the second electron component in other GRB afterglows, which may provide a possible observational signature for future studies
JWST reveals a supernova following a gamma-ray burst at z 7.3
No full textInternational audienceThe majority of energetic long-duration gamma-ray bursts (GRBs) are thought to arise from the collapse of massive stars, making them powerful tracers of star formation across cosmic time. Evidence for this origin comes from the presence of supernovae in the aftermath of the GRB event, whose properties in turn link back to those of the collapsing star. In principle, with GRBs we can study the properties of individual stars in the distant universe. Here, we present JWST/NIRCAM observations that detect both the host galaxy and likely supernova in the SVOM GRB 250314A with a spectroscopically measured redshift of z 7.3, deep in the era of reionisation. The data are well described by a combination of faint blue host, similar to many z 7 galaxies, with a supernova of similar luminosity to the proto-type GRB supernova, SN 1998bw. Although larger galaxy contributions cannot be robustly excluded, given the evidence from the blue afterglow colours of low dust extinction, supernovae much brighter than SN 1998bw can be. These observations suggest that, despite disparate physical conditions, the star that created GRB 250314A was similar to GRB progenitors in the local universe