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The Atacama Cosmology Telescope: DR6 Power Spectra, Likelihoods and CDM Parameters
No full textInternational audienceWe present power spectra of the cosmic microwave background (CMB) anisotropy in temperature and polarization, measured from the Data Release 6 maps made from Atacama Cosmology Telescope (ACT) data. These cover 19,000 deg of sky in bands centered at 98, 150 and 220 GHz, with white noise levels three times lower than Planck in polarization. We find that the ACT angular power spectra estimated over 10,000 deg, and measured to arcminute scales in TT, TE and EE, are well fit by the sum of CMB and foregrounds, where the CMB spectra are described by the CDM model. Combining ACT with larger-scale Planck data, the joint P-ACT dataset provides tight limits on the ingredients, expansion rate, and initial conditions of the universe. We find similar constraining power, and consistent results, from either the Planck power spectra or from ACT combined with WMAP data, as well as from either temperature or polarization in the joint P-ACT dataset. When combined with CMB lensing from ACT and Planck, and baryon acoustic oscillation data from the Dark Energy Spectroscopic Instrument (DESI Y1), we measure a baryon density of , a cold dark matter density of , a Hubble constant of km/s/Mpc, a spectral index of , and an amplitude of density fluctuations of . We find no evidence for excess lensing in the power spectrum, and no departure from spatial flatness. The contribution from Sunyaev-Zel'dovich (SZ) anisotropy is detected at high significance; we find evidence for a tilt with suppressed small-scale power compared to our baseline SZ template spectrum, consistent with hydrodynamical simulations with feedback
Euclid: Detecting Solar System objects in Euclid images and classifying them using Kohonen self-organising maps
No full textInternational audienceThe ESA Euclid mission will survey more than 14 000 deg2 of the sky in visible and near-infrared wavelengths, mapping the extragalactic sky to constrain our cosmological model of the Universe. Although the survey focusses on regions further than 15° from the ecliptic, it should allow for the detection of more than about 105 Solar System objects (SSOs). After simulating the expected signal from SSOs in Euclid images acquired with the visible camera (VIS), we describe an automated pipeline developed to detect moving objects with an apparent velocity in the range of 0.1–10″ h−1, typically corresponding to sources in the outer Solar System (from Centaurs to Kuiper-belt objects). In particular, the proposed detection scheme is based on SExtractor software and on applying a new algorithm capable of associating moving objects amongst different catalogues. After applying a suite of filters to improve the detection quality, we study the expected purity and completeness of the SSO detections. We also show how a Kohonen self-organising neural network can be successfully trained (in an unsupervised fashion) to classify stars, galaxies, and SSOs. By implementing an early-stopping method in the training scheme, we show that the network can be used in a predictive way, allowing one to assign the probability of each detected object being a member of each considered class.Key words: methods: data analysis / methods: numerical / comets: general / Kuiper belt: general / minor planets, asteroids: general / Oort Cloud★ This paper is published on behalf of the Euclid Consortium
The Stochastic Light Confinement of LiquidO
No full textInternational audienceLight-based detectors have been widely used in fundamental research and industry since their inception in the 1930s. The energy particles deposit in these detectors is converted to optical signals via the Cherenkov and scintillation mechanisms that are then propagated through transparent media to photosensors placed typically on the detector's periphery, sometimes up to tens of metres away. LiquidO is a new technique pioneering the use of opaque media to stochastically confine light around each energy deposition while collecting it with an array of fibres that thread the medium. This approach preserves topological event information otherwise lost in the conventional approach, enabling real-time imaging down to the MeV scale. Our article demonstrates LiquidO's imaging principle with a ten-litre prototype, revealing successful light confinement of 90% of the detected light within a 5 cm radius sphere, using a custom opaque scintillator with a scattering length on the order of a few millimetres. These high-resolution imaging capabilities unlock opportunities in fundamental physics research and applications beyond. The absolute amount of light detected is also studied, including possible data-driven extrapolations to LiquidO-based detectors beyond prototyping limitations. Additionally, LiquidO's timing capabilities are explored through its ability to distinguish Cherenkov light from a slow scintillator
The role of Trees of Fragmenting Granules (TFG) in the formation of the solar supergranular pattern from Hinode observations
No full textWe present in this paper an exceptional scientific dataset allowing to investigate the structure and evolution of the interior of solar supergranulation cells. Trees of Fragmenting Granules (TFG) and associated flows were evidenced using Local Correlation Tracking techniques (LCT) from a 24 H duration sequence of Hinode (JAXA/NASA) observations. The treatment of the dataset exhibits the evolution of the TFG and shows that their mutual interactions are able to build horizontal flows with longer lifetime than granules (1 to 2 hours) over a scale of 10 arcsec (the mesogranulation). These flows act on the diffusion of the intranetwork magnetic elements and also on the location and shape of the network. Hence, the TFG appear as one of the major elements involved in supergranular formation and evolution
Keplerian molecular gas disk and black hole mass of NGC 4751
No full textInternational audienceAims. We aim to measure the mass of the supermassive black hole (SMBH) in the S0 galaxy NGC 4751 using CO J:3−2 emission from the 5″-scale nuclear rotating molecular disk.Methods. We imaged the kpc-scale molecular gas disk in NGC 4751 at 0.″22 (∼28 pc) spatial and 28 km s−1 spectral resolution in the CO J:3−2 emission line and neighboring continuum, with the Atacama Large Millimeter Array (ALMA). We used Hubble Space Telescope (HST) imaging and stellar and ionized gas kinematics at 100 pc to kpc-scales, derived from integral field spectroscopy, to determine the galaxy morphology and the circular velocity attributed to the stellar potential. We used the Markov chain Monte Carlo (MCMC) algorithm in the KINematic Molecular Simulation (KinMS) package to obtain the model parameters that best fit the observed molecular gas kinematics in the ALMA datacube.Results. Strong CO emission was detected over radii of ∼0.″2 to 5″, with isolated CO clumps detected out to 7″. The molecular disk kinematics is axisymmetric and rotation-dominated, with radial velocities between 400 km s−1 and 660 km s−1, a kinematic major axis position angle (PA) of 355°, and an inclination close to 78°. The intrinsic velocity dispersion is ∼16 km s−1, and there is no evidence for significant non-rotational kinematics. The kinematic center of the disk coincides with the compact nuclear 345 GHz source. The SMBH sphere of influence (SOI) is well resolved along all position angles. The (rotation) velocity curve due to the stellar potential (Vradialmax ∼ 430 km s−1) is determined by fitting the luminosity profile of NGC 4751 in an (H-band) image from the Wide Field Camera 3 (WFC3) aboard HST, and constraining the mass-to-light ratio (M/L) at this waveband using the molecular- and ionized-gas kinematics at radii ≳4″, outside the SMBH SOI. Several KinMS fits, all using a distance (D) of 26.3 Mpc, but with variations in other input quantities, resulted in SMBH masses of 3.22 − 4.33 × 109 M⊙ and M/L values of 1.1−2.3 in the F160W band. In each fit, the statistical errors of these values are on the level of a few percent.Conclusions. Based on the results of the multiple KinMS fits, we argued for and adopted a value of 3.3 × 109 (D/26.3) M⊙ for the black hole mass, along with a (constant with radius) M/L of 2.28/(26.3/D)2 in the F160W band. We estimated the (one sigma) errors to be 20% in each of these. We find that the primary driver of the uncertainty (apart from distance) is the stellar potential in this dusty S0 galaxy. This CO-based mass is ∼2.4 times higher than a previous stellar-dynamics based SMBH mass measurement using the same distance. We argue that this new value is more robust given the clear and well resolved Keplerian-rotation dominated signature in the molecular disk, as well as its robust values of inclination (78°) and PA (355°), further supported by the consistency among derived values across different datasets and methods
Spectroscopic confirmation of the galaxy clusters CARLA J0950+2743 at z = 2.363 and CARLA-Ser J0950+2743 at z = 2.243
No full textInternational audienceGalaxy clusters are the largest gravitationally bound structures in the Universe and therefore are a powerful tool for studying mass assembly at different epochs. At z > 2, they provide the unique opportunity to place solid constraints not only on the growth of the dark matter halo, but also on the mechanisms of galaxy quenching and morphological transformation when the Universe was younger than 3.3 Gyr. However, the currently available sample of confirmed z > 2 clusters remains very limited. We present the spectroscopic confirmation of the galaxy cluster CARLA J0950+2743 at z = 2.363 ± 0.005 and a new serendipitously discovered cluster, CARLA-Ser J0950+2743 at z = 2.243 ± 0.008, in the same region. We confirm eight star-forming galaxies in the first and five in the second cluster by detecting [OII], [OIII], and Hα emission lines. The analysis of an archival X-ray Chandra dataset that covers the cluster position revealed a counterpart with a total luminosity of L0.5−5keV = 2.9 ± 0.6 × 1045 erg s−1. Because the depth of the X-ray observations is limited, we cannot distinguish the 1D profile of the source from a point spread function model, but our statistical analysis of the 2D profile favors an extended component that might be associated with a thermal contribution from the intracluster medium. If the extended X-ray emission is due to the hot intracluster medium, the total combined dark matter mass for the two clusters would be M200 ≈ 3.0−0.23(stat)+0.20−0.85(sys)+1.13 × 1014 M⊙, assuming a ∼30% contribution from the active galactic nucleus. Our two clusters are therefore interesting targets for studies of the structure growth in the cosmological context. However, future investigation will require deeper high-resolution X-ray and spectroscopic observations to rule out the hypotheses that the emission is entirely due to the active galactic nucleus or that it originates from other contaminating radio galaxies and structures
Massive black hole binaries in LISA: constraining cosmological parameters at high redshifts
No full textInternational audienceOne of the primary scientific objectives of the Laser Interferometer Space Antenna (LISA) is to probe the expansion of the Universe using gravitational wave observations. Indeed, as gravitational waves from the coalescence of a massive black hole binary (MBHB) carry direct information of the luminosity distances, an accompanying electromagnetic (EM) counterpart can be used to determine the redshift. This method of enables one to build a gravitational Hubble diagram to high redshift when applied to LISA. In this work, we forecast the ability of LISA-detected MBHB bright sirens to constrain cosmological models. As the expected EM emission from MBHBs can be detected up to redshift with future astronomical facilities, we focus on the ability of LISA to constrain the expansion of the Universe at , a poorly charted epoch in cosmography. We find that a model-independent approach to cosmology based on a spline interpolation of the luminosity distance-redshift relation, can constrain the Hubble parameter at with a relative precision of at least
Euclid preparation. Angular power spectra from discrete observations
No full textInternational audienceWe present the framework for measuring angular power spectra in the Euclid mission. The observables in galaxy surveys, such as galaxy clustering and cosmic shear, are not continuous fields, but discrete sets of data, obtained only at the positions of galaxies. We show how to compute the angular power spectra of such discrete data sets, without treating observations as maps of an underlying continuous field that is overlaid with a noise component. This formalism allows us to compute exact theoretical expectations for our measured spectra, under a number of assumptions that we track explicitly. In particular, we obtain exact expressions for the additive biases ("shot noise") in angular galaxy clustering and cosmic shear. For efficient practical computations, we introduce a spin-weighted spherical convolution with a well-defined convolution theorem, which allows us to apply exact theoretical predictions to finite-resolution maps, including HEALPix. When validating our methodology, we find that our measurements are biased by less than 1% of their statistical uncertainty in simulations of Euclid's first data release
Detection of jovian kilometric and hectometric auroral radio harmonics with juno/waves in situ measurements.
No full textInternational audienceAuroral radio emissions from Earth, Saturn, and Jupiter are now known to all be generated by the cyclotron maser instability near the electron cyclotron fundamental frequency f_ce. This common generation mechanism results in similar wave properties in terms of beaming and polarization. However, while harmonics at 2 × f_ce and 3 × f_ce have been identified in the terrestrial and kronian cases, none of the components of Jupiter’s auroral radio spectrum had been associated with harmonics. In this study, we confirm the existence of first harmonic emissions for the Jovian broadband-kilometric (bKOM) and hectometric (HOM) components (200-700 kHz) in 6 cases using in situ data from Juno/Waves observations close to the source. Among these cases, 2 second harmonics were also identified. These harmonics are three orders of magnitude weaker than the associated fundamental and were identified in regions where the f_pe/f_ce(f_pe the electron plasma frequency) ratio is of the order of 10^-2. This discovery confirms the universality of the CMI and suggests that harmonics in the decametric range could exist
Rediscovering the Milky Way with an orbit superposition approach and APOGEE data
No full textInternational audienceWe introduce a novel orbit superposition method designed to reconstruct the stellar density structure, kinematics, and chemical abundance distribution of the entire Milky Way by leveraging 6D phase-space information from its resolved stellar populations, limited by the spatial coverage of APOGEE DR17