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Sculpting the outer edge of accretion disks in pre-circumbinary binary black hole systems
No full textInternational audienceBinary black hole systems (BBHs) have become a vivid reality in astrophysics as stellar-mass black hole mergers are now detected through their related gravitational wave emission during the merger stage. If many studies were recently dedicated to the last stages of BBH where black holes are surrounded by a circumbinary disk (CBD), the structure of these systems prior to the formation of the CBD remains mostly unexplored. The aim of the present article is to investigate the potential modifications induced by the presence of a secondary black hole onto the structure of the accretion disk surrounding the primary black hole. We performed 2D classical hydrodynamical simulations of an accretion disk surrounding the primary black hole while taking into account all gravitational effects induced by both the primary black hole and the secondary black hole orbiting on circular orbits around the center of mass of the system.We report three main effects of the presence of a secondary black hole orbiting a circular orbit beyond the outer edge of the accretion disk: 1/ the outer radius of the accretion disk is significantly reduced and its ratio to the black hole separation is directly linked to only the mass ratio of the black holes; 2/ two spiral arms are visible in the gas density structure of the disk and 3/ the outer edge of the accretion disk exhibits an elliptical shape that mainly depends on the mass ratio of the black holes. Our results show that an accretion disk orbiting a primary black hole in a pre-CBD BBH exhibits specific features induced by the gravitational force generated by the presence of a secondary black hole beyond its outer edge. Such features, directly linked to the binary separation and mass ratio, has therefore the potential to help in the search and identification of BBH in the pre-CBD stage
Hunting Star-Forming Galaxies in the Gamma-Ray Domain
No full textInternational audienceContext. Star-forming galaxies emit γrays with relatively low luminosity, but the study of their emission is no less captivating. While it is known that their γ-ray luminosity in the GeV band is strongly linked to their star formation, the origin of their emission at higher energies remains uncertain due to limited observations. Aims. Our aim is to assemble the largest possible sample of star-forming galaxies with potential detectability by the new-generation of Cherenkov telescopes. Methods. To achieve this, we compile a comprehensive sample of galaxies, including those previously detected by Fermi-LAT in the GeV energy range as well as a larger sample of star-forming galaxies in the Local Volume that have been cataloged in the near-infrared band. We estimate their γ-ray flux assuming a proportional relationship with their star formation rate, and then select the brightest candidates. The predicted spectra in the TeV band are derived using a simple empirical model normalized to the star formation rate and a model based on extrapolating the latest Fermi-LAT data to higher energies. The ground-based detectability of γ-ray emission from these sources is assessed through a comparison to the most recent instrument response functions. Results. Our investigation reveals that almost a dozen star-forming galaxies may be detectable by upcoming γ-ray telescopes. Conclusions. The observation of numerous star-forming galaxies in the TeV band is a fundamental piece of the panchromatic puzzle for understanding the physics inside these galaxies. The significant increase in the number of galaxies that can be studied in detail in the near future, particularly with the Cherenkov Telescope Array Observatory, promises a major step forward in the study of the conditions of acceleration and transport of cosmic rays in nearby extragalactic environments
Spectral modelling of Cygnus A between 110 and 250 MHz. Impact on the LOFAR 21-cm signal power spectrum
No full textInternational audienceStudying the redshifted 21-cm signal from the the neutral hydrogen during the Epoch of Reionization and Cosmic Dawn is fundamental for understanding the physics of the early universe. One of the challenges that 21-cm experiments face is the contamination by bright foreground sources, such as Cygnus A, for which accurate spatial and spectral models are needed to minimise the residual contamination after their removal. In this work, we develop a new, high-resolution model of Cygnus A using Low Frequency Array (LOFAR) observations in the MHz range, improving upon previous models by incorporating physical spectral information through the forced-spectrum method during multi-frequency deconvolution. This approach addresses the limitations of earlier models by providing a more accurate representation of the complex structure and spectral behaviour of Cygnus A, including the spectral turnover in its brightest hotspots. The impact of this new model on the LOFAR 21-cm signal power spectrum is assessed by comparing it with both simulated and observed North Celestial Pole data sets. Significant improvements are observed in the cylindrical power spectrum along the Cygnus A direction, highlighting the importance of having spectrally accurate models of the brightest foreground sources. However, this improvement is washed out in the spherical power spectrum, where we measure differences of a few hundred mK at k<0.63\,h\,\text{cMpc}^{-1}, but not statistically significant. The results suggest that other systematic effects must be mitigated before a substantial impact on 21-cm power spectrum can be achieved
Understanding spatially unresolved measurements of molecular line emission
No full textInternational audienceContext. Observations of molecular emission lines are commonly used to derive the physical properties of cold molecular gas clouds. In external galaxies, these measurements suffer from limited spatial resolution, typically averaging a complex position–position– velocity distribution of emission over several tens of parsecs.Aims. We aim to quantify the variability in the basic parameters (peak brightness and line width) of spatially unresolved (>20 pc) line profiles that can be attributed to beam averaging. We focus on the commonly observed low-J transitions of CO isotopologues, HCN, HNC, HCO+, CS, SO and N2H+.Methods. We generated a sample of 1000 toy molecular cloud observations by resampling high-resolution (<0.05 pc) multiline Galactic observations of the Orion B molecular cloud. In the construction of our toy clouds, we imposed a range of density and velocity fields, characterised by their statistics and power spectra. These high-resolution molecular cloud observations were then averaged to single spatially unresolved spectra. We examined the resulting distribution of line profile parameters, and searched for potential correlations among line profile parameters and the underlying sub-beam density and velocity fields.Results. We find that unresolved line profiles’ parameters can vary significantly because of the sub-beam distribution of the emission. Emission lines that tend to be excited at higher densities show the most variability, up to a factor of two for N2H+ (J = 1 0). This variability in an emission line profile is related to the emission line’s covering fraction. As the spectral index of the velocity field increases, unresolved emission lines’ profiles increasingly diverge from a Gaussian shape.Conclusions. Line profile parameters exhibit non-negligible variability solely due to the sub-beam position-position-velocity distribution of the emission. This variability may exceed calibration and noise-related uncertainties
Euclid Quick Data Release (Q1): From images to multiwavelength catalogues: the Euclid MERge Processing Function
No full textInternational audienceThe 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 with two instruments, the Visible Camera (VIS) and the Near IR Spectrometer and Photometer (NISP) down to () in the Euclid Wide Survey. Ground-based imaging data in the \textit{ugriz} bands complement the \Euclid data to enable photo- 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 . 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 Sérsic 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
Cosmic topology. Part IIIb. Eigenmodes and correlation matrices of spin-2 perturbations in orientable Euclidean manifolds
No full textInternational audienceWe study the eigenmodes of the spin-2 Laplacian in orientable Euclidean manifolds and their implications for the tensor-induced part of the cosmic microwave background (CMB) temperature and polarization anisotropies. We provide analytic expressions for the correlation matrices of Fourier-mode amplitudes and of spherical harmonic coefficients. We demonstrate that non-trivial spatial topology alters the statistical properties of CMB tensor anisotropies, inducing correlations between harmonic coefficients of differing and and across every possible pair of temperature and - and -modes of polarization. This includes normally forbidden and correlations. We compute the Kullback-Leibler (KL) divergence between the pure tensor-induced CMB fluctuations in the usual infinite covering space and those in each of the non-trivial manifolds under consideration, varying both the size of the manifolds and the location of the observer. We find that the amount of information about the topology of the Universe contained in tensor-induced anisotropies does not saturate as fast as its scalar counterpart; indeed, the KL divergence continues to grow with the inclusion of higher multipoles up to the largest we have computed. Our results suggest that CMB polarization measurements from upcoming experiments can provide new avenues for detecting signatures of cosmic topology, motivating a full analysis where scalar and tensor perturbations are combined and noise is included
JENA Computing Initiative WP2 Report: Software and Heterogeneous Architectures
No full textInternational audienceThe scientific communities of nuclear, particle, and astroparticle physics are continuing to advance and are facing unprecedented software challenges due to growing data volumes, complex computing needs, and environmental considerations. As new experiments emerge, software and computing needs must be recognised and integrated early in design phases. This document synthesises insights from ECFA, NuPECC and APPEC, representing particle physics, nuclear physics, and astroparticle physics, and presents collaborative strategies for improving software, computing frameworks, infrastructure, and career development within these fields
Quantifying the Impact of LSST -band Survey Strategy on Photometric Redshift Estimation and the Detection of Lyman-break Galaxies
No full textInternational audienceThe Vera C. Rubin Observatory will conduct the Legacy Survey of Space and Time (LSST), promising to discover billions of galaxies out to redshift 7, using six photometric bands () spanning the near-ultraviolet to the near-infrared. The exact number of and quality of information about these galaxies will depend on survey depth in these six bands, which in turn depends on the LSST survey strategy: i.e., how often and how long to expose in each band. -band depth is especially important for photometric redshift (photo-z) estimation and for detection of high-redshift Lyman-break galaxies (LBGs). In this paper we use a simulated galaxy catalog and an analytic model for the LBG population to study how recent updates and proposed changes to Rubin's -band throughput and LSST survey strategy impact photo-z accuracy and LBG detection. We find that proposed variations in -band strategy have a small impact on photo-z accuracy for galaxies, but the outlier fraction, scatter, and bias for higher redshift galaxies varies by up to 50%, depending on the survey strategy considered. The number of -band dropout LBGs at is also highly sensitive to the -band depth, varying by up to 500%, while the number of -band dropouts is only modestly affected. Under the new -band strategy recommended by the Rubin Survey Cadence Optimization Committee, we predict -band dropout number densities of deg (3200 deg) in year 1 (10) of LSST. We discuss the implications of these results for LSST cosmology
Measurement of the inhomogeneity of the KATRIN tritium source electric potential by high-resolution spectroscopy of conversion electrons from Kr
No full textInternational audiencePrecision spectroscopy of the electron spectrum of the tritium -decay near the kinematic endpoint is a direct method to determine the effective electron antineutrino mass. The KArlsruhe TRItium Neutrino (KATRIN) experiment aims to determine this quantity with a sensitivity of better than 0.3eV (90% C.L.). An inhomogeneous electric potential in the tritium source of KATRIN can lead to distortions of the -spectrum, which directly impact the neutrino-mass observable. This effect can be quantified through precision spectroscopy of the conversion-electrons of co-circulated metastable Kr. Therefore, dedicated, several-weeks long measurement campaigns have been performed within the KATRIN data taking schedule. In this work, we infer the tritium source potential observables from these measurements, and present their implications for the neutrino-mass determination
Central kiloparsec region of Andromeda: I. Dynamical modeling
No full textInternational audienceThe Andromeda galaxy (M31) is the nearest giant spiral galaxy to our own, which offers an opportunity to study dynamical phenomena occurring in nuclear disks and bulges at high resolution to explain star formation quenching and galaxy evolution through collisions and tides. Multi-wavelength data have revealed strong dynamical perturbations in the central kiloparsec (kpc) region of M31, with an off-centered tilted disk and ring, coinciding with a dearth of atomic and molecular gas. Our goal is to understand the origin of these perturbations and, thus, we propose a dynamical model that reproduces the global features of the observations. We report on the integral field spectroscopy of the ionized gas with Hα and [N II] obtained with the Spectromètre Imageur à Transformée de Fourier pour l’Étude en Long et en Large de raies d’Émission (SITELLE), which is the optical imaging Fourier transform spectrometer (IFTS) at the Canada France Hawaii telescope (CFHT). Using the fully sampled velocity field of ionized gas, together with the more patchy molecular gas velocity field previously obtained with the CO lines at IRAM-30 m telescope and the dust photometry, we identified three dynamical components in the gas: the main disk, a tilted ring, and a nuclear warped disk. We computed a mass model for the central kpc, essentially from the stellar nuclear disk and bulge, with minimal contributions from the main stellar and gaseous disk, along with a dark matter halo. The kinematics of the ionized and molecular gas was then computed in this potential, and the velocity field confronted qualitatively to observations. The best fit helped us determine the physical parameters of the three identified gas components: size, morphology, and geometrical orientation. These results are qualitatively compatible with a recent head-on collision with a M-32 like galaxy, as previously proposed. The kinematical observations correspond to a dynamical re-orientation of the perturbed nuclear disk, through a series of warps and tearing of the disk into the ring, following the collision