Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202452770
Michel-Andrès Breton
We present PySCo, a fast and user-friendly Python library designed to run cosmological N-body simulations across various cosmological models, such as ΛCDM (Λ with cold dark matter) and w0waCDM, and alternative theories of gravity, including f (R), MOND (modified newtonian dynamics) and time-dependent gravitational constant parameterisations. PySCo employs particle-mesh solvers, using multigrid or fast Fourier transform (FFT) methods in their different variations. Additionally, PySCo can be easily integrated as an external library, providing utilities for particle and mesh computations. The library offers key features, including an initial condition generator based on up to third-order Lagrangian perturbation theory (LPT), power spectrum estimation, and computes the background and growth of density perturbations. In this paper, we detail PySCo’s architecture and algorithms and conduct extensive comparisons with other codes and numerical methods. Our analysis shows that, with sufficient small-scale resolution, the power spectrum at redshift z = 0 remains independent of the initial redshift at the 0.1% level for zini ≥ 125, 30, and 10 when using first, second, and third-order LPT, respectively. Moreover, we demonstrate that acceleration (or force) calculations should employ a configuration-space finite-difference stencil for central derivatives with at least five points, as three-point derivatives result in significant power suppression at small scales. Although the seven-point Laplacian method used in multigrid also leads to power suppression on small scales, this effect can largely be mitigated when computing ratios. In terms of performance, PySCo only requires approximately one CPU hour to complete a Newtonian simulation with 5123 particles (and an equal number of cells) on a laptop. Due to its speed and ease of use, PySCo is ideal for rapidly generating vast ensemble of simulations and exploring parameter spaces, allowing variations in gravity theories, dark energy models, and numerical approaches. This versatility makes PySCo a valuable tool for producing emulators, covariance matrices, or training datasets for machine learning.
{"title":"PySCo: A fast particle-mesh N-body code for modified gravity simulations in Python","authors":"Michel-Andrès Breton","doi":"10.1051/0004-6361/202452770","DOIUrl":"https://doi.org/10.1051/0004-6361/202452770","url":null,"abstract":"We present PySCo, a fast and user-friendly Python library designed to run cosmological <i>N<i/>-body simulations across various cosmological models, such as ΛCDM (Λ with cold dark matter) and <i>w<i/><sub>0<sub/><i>w<i/><sub><i>a<i/><sub/>CDM, and alternative theories of gravity, including <i>f<i/> (<i>R<i/>), MOND (modified newtonian dynamics) and time-dependent gravitational constant parameterisations. PySCo employs particle-mesh solvers, using multigrid or fast Fourier transform (FFT) methods in their different variations. Additionally, PySCo can be easily integrated as an external library, providing utilities for particle and mesh computations. The library offers key features, including an initial condition generator based on up to third-order Lagrangian perturbation theory (LPT), power spectrum estimation, and computes the background and growth of density perturbations. In this paper, we detail PySCo’s architecture and algorithms and conduct extensive comparisons with other codes and numerical methods. Our analysis shows that, with sufficient small-scale resolution, the power spectrum at redshift <i>z<i/> = 0 remains independent of the initial redshift at the 0.1% level for <i>z<i/><sub>ini<sub/> ≥ 125, 30, and 10 when using first, second, and third-order LPT, respectively. Moreover, we demonstrate that acceleration (or force) calculations should employ a configuration-space finite-difference stencil for central derivatives with at least five points, as three-point derivatives result in significant power suppression at small scales. Although the seven-point Laplacian method used in multigrid also leads to power suppression on small scales, this effect can largely be mitigated when computing ratios. In terms of performance, PySCo only requires approximately one CPU hour to complete a Newtonian simulation with 512<sup>3<sup/> particles (and an equal number of cells) on a laptop. Due to its speed and ease of use, PySCo is ideal for rapidly generating vast ensemble of simulations and exploring parameter spaces, allowing variations in gravity theories, dark energy models, and numerical approaches. This versatility makes PySCo a valuable tool for producing emulators, covariance matrices, or training datasets for machine learning.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"70 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202449189
Shota Chiba, Munehito Shoda, Takeshi Imamura
Context. Recent in situ observations and numerical models indicate that various types of magnetohydrodynamic (MHD) waves contribute to the solar wind acceleration. Among them is an MHD wave decomposition at distances closer than 50 R⊙ using data taken by the first perihelion pass of Parker Solar Probe (PSP). However, the underlying physical processes responsible for the formation of the solar wind have not yet been observationally confirmed at distances closer than 10 R⊙.Aims. We aim to infer the mode population of density fluctuations observed by radio occultation, which has all been attributed to slow magnetoacoustic waves.Methods. We compare the radio occultation observations conducted in 2016 using the JAXA’s Venus orbiter Akatsuki with the MHD simulation. The time-frequency analysis was applied to the density fluctuations observed by the radio occultation and those reproduced in the MHD model.Results. The time-spatial spectrum of the density fluctuation in the model exhibits two components that are considered to be fast and slow magnetoacoustic waves. The fast magnetoacoustic waves in the model tend to have periods shorter than the slow magnetoacoustic waves, and the superposition of these modes has a broadened spectrum extending in the range of approximately 20−1000 s, which resembles that of the observed waves.Conclusions. Based on this comparison, it is probable that the density oscillations observed by radio occultation include fast and slow magnetoacoustic waves, and that fast magnetoacoustic waves are predominant at short periods and slow magnetoacoustic waves are prevalent at long periods. This is qualitatively similar to the results of the mode decomposition obtained from the PSP’s first perihelion at more distance regions.
{"title":"Density fluctuation in the solar corona and solar wind: A comparative analysis of radio-occultation observations and magnetohydrodynamic simulation","authors":"Shota Chiba, Munehito Shoda, Takeshi Imamura","doi":"10.1051/0004-6361/202449189","DOIUrl":"https://doi.org/10.1051/0004-6361/202449189","url":null,"abstract":"<i>Context.<i/> Recent in situ observations and numerical models indicate that various types of magnetohydrodynamic (MHD) waves contribute to the solar wind acceleration. Among them is an MHD wave decomposition at distances closer than 50 <i>R<i/><sub>⊙<sub/> using data taken by the first perihelion pass of Parker Solar Probe (PSP). However, the underlying physical processes responsible for the formation of the solar wind have not yet been observationally confirmed at distances closer than 10 <i>R<i/><sub>⊙<sub/>.<i>Aims.<i/> We aim to infer the mode population of density fluctuations observed by radio occultation, which has all been attributed to slow magnetoacoustic waves.<i>Methods.<i/> We compare the radio occultation observations conducted in 2016 using the JAXA’s Venus orbiter <i>Akatsuki<i/> with the MHD simulation. The time-frequency analysis was applied to the density fluctuations observed by the radio occultation and those reproduced in the MHD model.<i>Results.<i/> The time-spatial spectrum of the density fluctuation in the model exhibits two components that are considered to be fast and slow magnetoacoustic waves. The fast magnetoacoustic waves in the model tend to have periods shorter than the slow magnetoacoustic waves, and the superposition of these modes has a broadened spectrum extending in the range of approximately 20−1000 s, which resembles that of the observed waves.<i>Conclusions.<i/> Based on this comparison, it is probable that the density oscillations observed by radio occultation include fast and slow magnetoacoustic waves, and that fast magnetoacoustic waves are predominant at short periods and slow magnetoacoustic waves are prevalent at long periods. This is qualitatively similar to the results of the mode decomposition obtained from the PSP’s first perihelion at more distance regions.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"51 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202451524
I. Márquez, C. Boisson, M. Joly, D. Pelat, F. Durret
Context. The relationship between an active galactic nucleus (AGN) and its host galaxy is still far from being understood. Properties of the host galaxies of Seyfert nuclei, such as luminosity concentration, morphological type, metallicity, and age of the stellar population, are expected to be related with nuclear activity – either at the epoch of galaxy formation or at the present day via feeding of the central black hole.Aims. In this paper, we investigate whether stellar ages and metallicities are linked to the activity within the nucleus in a sample of AGNs of various types.Methods. Our sample includes seven AGNs, from Seyfert 1 to LINERs, observed with VLT/ISAAC and VLT/SINFONI. Based on an inverse method using a stellar library, we analysed H band infrared spectra, in a wavelength region devoid of emission lines, at a spectral resolution of ≈3000, in the few central 100 pc. Hubble Space Telescope images were used to visualise the regions defined in each galaxy.Results. For each galaxy, we give the results of the spectral synthesis, in particular the percentages of the stellar, power law, and black-body continua, and the percentages of various stellar types that account for the stellar lines.Conclusions. Out of the seven galaxies, three show strong and recent star formation in the inner 100 pc, while no star formation is detected in the three genuine Seyfert 2 galaxies. Beyond a radius of 100 pc, all show more or less recent star formation. Moreover, we can conclude that the star formation history of the inner nucleus is highly heterogeneous.
{"title":"Stellar populations from H-band VLT spectroscopy in a sample of seven active galaxies⋆","authors":"I. Márquez, C. Boisson, M. Joly, D. Pelat, F. Durret","doi":"10.1051/0004-6361/202451524","DOIUrl":"https://doi.org/10.1051/0004-6361/202451524","url":null,"abstract":"<i>Context.<i/> The relationship between an active galactic nucleus (AGN) and its host galaxy is still far from being understood. Properties of the host galaxies of Seyfert nuclei, such as luminosity concentration, morphological type, metallicity, and age of the stellar population, are expected to be related with nuclear activity – either at the epoch of galaxy formation or at the present day via feeding of the central black hole.<i>Aims.<i/> In this paper, we investigate whether stellar ages and metallicities are linked to the activity within the nucleus in a sample of AGNs of various types.<i>Methods.<i/> Our sample includes seven AGNs, from Seyfert 1 to LINERs, observed with VLT/ISAAC and VLT/SINFONI. Based on an inverse method using a stellar library, we analysed <i>H<i/> band infrared spectra, in a wavelength region devoid of emission lines, at a spectral resolution of ≈3000, in the few central 100 pc. Hubble Space Telescope images were used to visualise the regions defined in each galaxy.<i>Results.<i/> For each galaxy, we give the results of the spectral synthesis, in particular the percentages of the stellar, power law, and black-body continua, and the percentages of various stellar types that account for the stellar lines.<i>Conclusions.<i/> Out of the seven galaxies, three show strong and recent star formation in the inner 100 pc, while no star formation is detected in the three genuine Seyfert 2 galaxies. Beyond a radius of 100 pc, all show more or less recent star formation. Moreover, we can conclude that the star formation history of the inner nucleus is highly heterogeneous.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"183 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661342","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202451570
G. Perrin
Context. The coherence of long-baseline interferometers is affected by the polarization properties of the instrument. This is a possible source of biases, which would need to be calibrated.Aims. The goal of this paper is to study the biases due to retardance and diattenuation in long-baseline interferometers. In principle, the results can be applied to both optical and radio interferometers.Methods. We derived theoretical expressions for biases on fringe contrast and fringe visibility phase for interferometers whose polarizing properties can be described by beam rotation, retardance, and diattenuation. The nature of these biases are discussed for natural light, circular and linear polarization, and partially polarized light. Expansions were obtained for small degrees of polarization, small differential retardance, and small diattenuation.Results. The biases on fringe contrasts were already known. It is shown in this paper that retardance and diattenuation are also sources of bias on the visibility phases and derived quantities. In some cases, the bias is zero (for non-polarizing interferometers with natural or partially circulary polarized light.) If the retardance is achromatic, differential phases are not affected. Closure phases are not affected to the second order for an interferometer with weak diattenuation and weak differential retardance and for moderately polarized sources whatever the type of light. Otherwise, a calibration procedure is required. It has been shown that astrometric measurements are biased in the general case. The bias depends on both the polarization properties of the interferometer and on the (u, v) sampling. In the extreme case where the samples are aligned on a line crossing the origin of the spatial frequency plane, the bias is undetermined and can be arbitrarily large. In all other cases, it can be calibrated if the polarizing characteristics of the interferometer are known. In the case of a low differential retardance and low degree of polarization, the bias lies on a straight line, crossing the astrometric reference point. If the degree of linear polarization varies during the observations, then the astrometric bias has a remarkable signature, which describes a section of the line. For slightly polarizing interferometers, a fixed offset is added without changing the shape of the bias.Conclusions. A polarizing interferometer does generate bias on visibility contrast and visibility phase. The bias depends on the polarization characteristics of the source. In any case, the bias can be computed if the polarization characteristics of the interferometer are known. Astrometric biases can also be corrected and depend on the (u, v) sampling achieved for the measurements.
{"title":"Biases induced by retardance and diattenuation in the measurements of long-baseline interferometers","authors":"G. Perrin","doi":"10.1051/0004-6361/202451570","DOIUrl":"https://doi.org/10.1051/0004-6361/202451570","url":null,"abstract":"<i>Context.<i/> The coherence of long-baseline interferometers is affected by the polarization properties of the instrument. This is a possible source of biases, which would need to be calibrated.<i>Aims.<i/> The goal of this paper is to study the biases due to retardance and diattenuation in long-baseline interferometers. In principle, the results can be applied to both optical and radio interferometers.<i>Methods.<i/> We derived theoretical expressions for biases on fringe contrast and fringe visibility phase for interferometers whose polarizing properties can be described by beam rotation, retardance, and diattenuation. The nature of these biases are discussed for natural light, circular and linear polarization, and partially polarized light. Expansions were obtained for small degrees of polarization, small differential retardance, and small diattenuation.<i>Results.<i/> The biases on fringe contrasts were already known. It is shown in this paper that retardance and diattenuation are also sources of bias on the visibility phases and derived quantities. In some cases, the bias is zero (for non-polarizing interferometers with natural or partially circulary polarized light.) If the retardance is achromatic, differential phases are not affected. Closure phases are not affected to the second order for an interferometer with weak diattenuation and weak differential retardance and for moderately polarized sources whatever the type of light. Otherwise, a calibration procedure is required. It has been shown that astrometric measurements are biased in the general case. The bias depends on both the polarization properties of the interferometer and on the (<i>u<i/>, <i>v<i/>) sampling. In the extreme case where the samples are aligned on a line crossing the origin of the spatial frequency plane, the bias is undetermined and can be arbitrarily large. In all other cases, it can be calibrated if the polarizing characteristics of the interferometer are known. In the case of a low differential retardance and low degree of polarization, the bias lies on a straight line, crossing the astrometric reference point. If the degree of linear polarization varies during the observations, then the astrometric bias has a remarkable signature, which describes a section of the line. For slightly polarizing interferometers, a fixed offset is added without changing the shape of the bias.<i>Conclusions.<i/> A polarizing interferometer does generate bias on visibility contrast and visibility phase. The bias depends on the polarization characteristics of the source. In any case, the bias can be computed if the polarization characteristics of the interferometer are known. Astrometric biases can also be corrected and depend on the (<i>u<i/>, <i>v<i/>) sampling achieved for the measurements.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"56 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661343","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202452011
S. Karpov, O. Malkov, A. Avdeeva
Context. Thirty years after the discovery of brown dwarfs, the search for these objects continues, particularly in the vicinity of the Sun. Objects near the Sun are characterized by large proper motions, making them be seen as fast-moving objects. While the Gaia DR3 catalog is a comprehensive source of proper motions, it lacks the depth needed for discovering fainter objects. Modern multi-epoch surveys, with their greater depth, offer a new opportunity to systematically search for ultracool dwarfs.Aims. The study aims to systematically search for high-proper-motion objects using the newly released catalog of epochal Wide-field Infrared Survey Explorer (WISE) data in order to identify new brown dwarf candidates in the solar neighborhood, estimate their spectral types, distances, and spatial velocities.Methods. We used recently released unTimely catalog of epochal detections in unWISE coadds to search for objects with high proper motions using a simple motion detection algorithm, combined with machine-learning-based artifact rejection routine. This method was used to identify objects with proper motions exceeding approximately 0.3 arcseconds per year. The identified objects were then cross-referenced with data from other large-scale sky surveys to further analyze their characteristics.Results. The search yielded 21 885 moving objects with significant proper motions, 258 of which had not been previously published. All except 6 of them are compatible with being ultracool dwarfs. Among these, at least 33 were identified as most promising new T dwarf candidates, with estimated distances of closer than about 40 parsecs, and effective temperatures of less than 1300 K.
{"title":"New ultracool dwarf candidates from multi-epoch WISE data","authors":"S. Karpov, O. Malkov, A. Avdeeva","doi":"10.1051/0004-6361/202452011","DOIUrl":"https://doi.org/10.1051/0004-6361/202452011","url":null,"abstract":"<i>Context.<i/> Thirty years after the discovery of brown dwarfs, the search for these objects continues, particularly in the vicinity of the Sun. Objects near the Sun are characterized by large proper motions, making them be seen as fast-moving objects. While the <i>Gaia<i/> DR3 catalog is a comprehensive source of proper motions, it lacks the depth needed for discovering fainter objects. Modern multi-epoch surveys, with their greater depth, offer a new opportunity to systematically search for ultracool dwarfs.<i>Aims.<i/> The study aims to systematically search for high-proper-motion objects using the newly released catalog of epochal Wide-field Infrared Survey Explorer (WISE) data in order to identify new brown dwarf candidates in the solar neighborhood, estimate their spectral types, distances, and spatial velocities.<i>Methods.<i/> We used recently released unTimely catalog of epochal detections in unWISE coadds to search for objects with high proper motions using a simple motion detection algorithm, combined with machine-learning-based artifact rejection routine. This method was used to identify objects with proper motions exceeding approximately 0.3 arcseconds per year. The identified objects were then cross-referenced with data from other large-scale sky surveys to further analyze their characteristics.<i>Results.<i/> The search yielded 21 885 moving objects with significant proper motions, 258 of which had not been previously published. All except 6 of them are compatible with being ultracool dwarfs. Among these, at least 33 were identified as most promising new T dwarf candidates, with estimated distances of closer than about 40 parsecs, and effective temperatures of less than 1300 K.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"2 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661496","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202451384
F. Jankowski, J.-M. Grießmeier, M. Surnis, G. Theureau, J. Pétri
Context. Radio pulsars exhibit a plethora of complex phenomena at the single-pulse level. However, the intricacies of their radio emission remain poorly understood.Aims. We aim to elucidate the pulsar radio emission by studying several single-pulse phenomena, how they relate, and how they evolve with observing frequency. We intend to inspire models for the pulsar radio emission and fast radio bursts.Methods. We set up an observing programme called the SUSPECT project running at the Nançay Radio Observatory telescopes in France (10–85 MHz, 110–240 MHz, and 1.1–3.5 GHz) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in India. This first paper focuses on high sensitivity data of PSR B1822−09 obtained with the uGMRT between 550 and 750 MHz. The pulsar has precursor (PC), main pulse (MP), and interpulse (IP) emission and exhibits mode switching. We present its single-pulse stacks, investigate its mode switching using a hidden Markov switching model, and analyse its single-pulse morphology.Results. PSR B1822−09’s pulse profile decomposes into seven components. We show that its mode switching is well described using a hidden Markov switching model operating on single-pulse profile features. The pulsar exhibits at least three stable emission modes, one of which is a newly discovered bright flaring Bf-mode. We confirm that the PC and MP switch synchronously to each other and both asynchronously to the IP, indicating information transfer between the polar caps. Additionally, we performed a fluctuation spectral analysis and discovered three fluctuation features in its quiescent Q-mode emission, one of which is well known. We conclude that the latter feature is due to longitude-stationary amplitude modulation. Finally, we visually classified the single pulses into four categories. We found extensive microstructure in the PC with a typical duration of 0.2–0.4 ms and a quasi-periodicity of 0.8 ms. There is clear evidence of mode mixing. We discovered low-intensity square-like pulses and extremely bright pulses in the MP, which suggest bursting.Conclusions. PSR B1822−09’s PC resembles magnetar radio emission, while its MP and IP are canonical radio pulsar-like. Hence, the pulsar combines both attributes, which is rare. This work introduces several new data analysis techniques to pulsar astrophysics.
{"title":"Science Using Single-Pulse Exploration with Combined Telescopes","authors":"F. Jankowski, J.-M. Grießmeier, M. Surnis, G. Theureau, J. Pétri","doi":"10.1051/0004-6361/202451384","DOIUrl":"https://doi.org/10.1051/0004-6361/202451384","url":null,"abstract":"<i>Context.<i/> Radio pulsars exhibit a plethora of complex phenomena at the single-pulse level. However, the intricacies of their radio emission remain poorly understood.<i>Aims.<i/> We aim to elucidate the pulsar radio emission by studying several single-pulse phenomena, how they relate, and how they evolve with observing frequency. We intend to inspire models for the pulsar radio emission and fast radio bursts.<i>Methods.<i/> We set up an observing programme called the SUSPECT project running at the Nançay Radio Observatory telescopes in France (10–85 MHz, 110–240 MHz, and 1.1–3.5 GHz) and the upgraded Giant Metrewave Radio Telescope (uGMRT) in India. This first paper focuses on high sensitivity data of PSR B1822−09 obtained with the uGMRT between 550 and 750 MHz. The pulsar has precursor (PC), main pulse (MP), and interpulse (IP) emission and exhibits mode switching. We present its single-pulse stacks, investigate its mode switching using a hidden Markov switching model, and analyse its single-pulse morphology.<i>Results.<i/> PSR B1822−09’s pulse profile decomposes into seven components. We show that its mode switching is well described using a hidden Markov switching model operating on single-pulse profile features. The pulsar exhibits at least three stable emission modes, one of which is a newly discovered bright flaring Bf-mode. We confirm that the PC and MP switch synchronously to each other and both asynchronously to the IP, indicating information transfer between the polar caps. Additionally, we performed a fluctuation spectral analysis and discovered three fluctuation features in its quiescent Q-mode emission, one of which is well known. We conclude that the latter feature is due to longitude-stationary amplitude modulation. Finally, we visually classified the single pulses into four categories. We found extensive microstructure in the PC with a typical duration of 0.2–0.4 ms and a quasi-periodicity of 0.8 ms. There is clear evidence of mode mixing. We discovered low-intensity square-like pulses and extremely bright pulses in the MP, which suggest bursting.<i>Conclusions.<i/> PSR B1822−09’s PC resembles magnetar radio emission, while its MP and IP are canonical radio pulsar-like. Hence, the pulsar combines both attributes, which is rare. This work introduces several new data analysis techniques to pulsar astrophysics.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"21 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202450621
S. Menchiari, G. Morlino, E. Amato, N. Bucciantini, G. Peron, G. Sacco
Context. Young massive stellar clusters (YMSCs) have emerged as potential γ-ray sources after the recent association of a dozen YMSCs with extended γ-ray emission. The large size of the detected halos, comparable to that of the wind-blown bubble expected around YMSCs, makes the γ-ray detection of individual YMSCs rather challenging. As a result, the emission from most of the Galactic YMSCs could be unresolved, thus contributing to the diffuse γ-ray radiation observed along the Galactic Plane.Aims. In this study, we estimate the possible contribution to the Galactic diffuse γ-ray emission from a synthetic population of YMSCs, and we compare it with observations obtained with different experiments, from 1 GeV to hundreds of teraelectronvolt, in three regions of the Galactic Plane.Methods. As the population of galactic YMSCs is only known locally, we evaluated the contribution of γ-ray emission relying on the simulation of synthetic populations of YMSCs based on the observed properties of local clusters. We computed the γ-ray emission from each cluster assuming that the radiation is purely hadronic in nature and produced by cosmic rays that are accelerated at the cluster’s collective wind termination shock.Results. We find that the γ-ray emission from unresolved YMSCs can significantly contribute to the observed Galactic diffuse flux, especially in the inner part of the Galaxy, and that an important role is played by kinetic power injected by the Wolf-Rayet stellar winds. The predicted γ-ray flux should be considered as a lower limit, given that our calculation does not include the contribution of supernovae exploding in YMSCs.
{"title":"Contribution of young massive stellar clusters to the Galactic diffuse γ-ray emission","authors":"S. Menchiari, G. Morlino, E. Amato, N. Bucciantini, G. Peron, G. Sacco","doi":"10.1051/0004-6361/202450621","DOIUrl":"https://doi.org/10.1051/0004-6361/202450621","url":null,"abstract":"<i>Context.<i/> Young massive stellar clusters (YMSCs) have emerged as potential γ-ray sources after the recent association of a dozen YMSCs with extended γ-ray emission. The large size of the detected halos, comparable to that of the wind-blown bubble expected around YMSCs, makes the γ-ray detection of individual YMSCs rather challenging. As a result, the emission from most of the Galactic YMSCs could be unresolved, thus contributing to the diffuse γ-ray radiation observed along the Galactic Plane.<i>Aims.<i/> In this study, we estimate the possible contribution to the Galactic diffuse γ-ray emission from a synthetic population of YMSCs, and we compare it with observations obtained with different experiments, from 1 GeV to hundreds of teraelectronvolt, in three regions of the Galactic Plane.<i>Methods.<i/> As the population of galactic YMSCs is only known locally, we evaluated the contribution of γ-ray emission relying on the simulation of synthetic populations of YMSCs based on the observed properties of local clusters. We computed the γ-ray emission from each cluster assuming that the radiation is purely hadronic in nature and produced by cosmic rays that are accelerated at the cluster’s collective wind termination shock.<i>Results.<i/> We find that the γ-ray emission from unresolved YMSCs can significantly contribute to the observed Galactic diffuse flux, especially in the inner part of the Galaxy, and that an important role is played by kinetic power injected by the Wolf-Rayet stellar winds. The predicted γ-ray flux should be considered as a lower limit, given that our calculation does not include the contribution of supernovae exploding in YMSCs.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"22 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661340","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202452005
Tian Yi, Chris W. Ormel, Shuo Huang, Antoine C. Petit
Kepler-221 is a G-type star hosting four planets. In this system, planets b, c, and e are in (or near) a 6:3:1 three-body resonance even though the planets’ period ratios show significant departures from exact two-body commensurability. Importantly, the intermediate planet d is not part of the resonance chain. To reach this resonance configuration, we propose a scenario in which there were originally five planets in the system in a chain of first-order resonances. After disk dispersal, the resonance chain became unstable, and two planets quickly merged to become the current planet d. In addition, the (b, c, e) three-body resonance was re-established. We ran N body simulations using REBOUND to investigate the parameter space under which this scenario can operate. We find that our envisioned scenario is possible when certain conditions are met. First, the reformation of the three-body resonance after planet merging requires convergent migration between planets b and c. Second, as has been previously pointed out, an efficient damping mechanism must operate to power the expansion of the (b, c, e) system. We find that planet d plays a crucial role during the orbital expansion phase due to destabilizing encounters of a three-body resonance between c, d, and e. A successful orbital expansion phase puts constraints on the planet properties in the Kepler-221 system including the planet mass ratios and the tidal quality factors for the planets. Our model can also be applied to other planet systems in resonance, such as Kepler-402 and K2-138.
{"title":"The dynamical history of the Kepler-221 planet system","authors":"Tian Yi, Chris W. Ormel, Shuo Huang, Antoine C. Petit","doi":"10.1051/0004-6361/202452005","DOIUrl":"https://doi.org/10.1051/0004-6361/202452005","url":null,"abstract":"Kepler-221 is a G-type star hosting four planets. In this system, planets b, c, and e are in (or near) a 6:3:1 three-body resonance even though the planets’ period ratios show significant departures from exact two-body commensurability. Importantly, the intermediate planet d is not part of the resonance chain. To reach this resonance configuration, we propose a scenario in which there were originally five planets in the system in a chain of first-order resonances. After disk dispersal, the resonance chain became unstable, and two planets quickly merged to become the current planet d. In addition, the (b, c, e) three-body resonance was re-established. We ran <i>N<i/> body simulations using REBOUND to investigate the parameter space under which this scenario can operate. We find that our envisioned scenario is possible when certain conditions are met. First, the reformation of the three-body resonance after planet merging requires convergent migration between planets b and c. Second, as has been previously pointed out, an efficient damping mechanism must operate to power the expansion of the (b, c, e) system. We find that planet d plays a crucial role during the orbital expansion phase due to destabilizing encounters of a three-body resonance between c, d, and e. A successful orbital expansion phase puts constraints on the planet properties in the Kepler-221 system including the planet mass ratios and the tidal quality factors for the planets. Our model can also be applied to other planet systems in resonance, such as Kepler-402 and K2-138.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"67 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202453067
Lucie Cros, Françoise Combes, Anne-Laure Melchior, Thomas Martin
The 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.
{"title":"Central kiloparsec region of Andromeda","authors":"Lucie Cros, Françoise Combes, Anne-Laure Melchior, Thomas Martin","doi":"10.1051/0004-6361/202453067","DOIUrl":"https://doi.org/10.1051/0004-6361/202453067","url":null,"abstract":"The 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 H<i>α<i/> 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.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"5 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661504","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-03-19DOI: 10.1051/0004-6361/202451915
B. Wehmeyer, C. Kobayashi, A. Yagüe López, M. Lugaro
Context. The 1.8 MeV γ-rays corresponding to the decay of the radioactive isotope 26Al (with a half-life of 0.72 Myr ) have been observed by the SPI detector on the INTEGRAL spacecraft and extensively used as a tracer of star formation and current nucleosynthetic activity in the Milky Way Galaxy. Further information is encoded in the observation related to the higher 26Al content found in regions of the Galaxy with the highest line-of-sight (LoS) velocity relative to an observer located in the Solar System. However, this feature remains unexplained. Aims. We ran a cosmological “zoom-in” chemodynamical simulation of a Milky Way-type galaxy, including the production and decays of radioactive nuclei in a fully self-consistent way. We then analyzed the results to follow the evolution of 26Al throughout the lifetime of the simulated galaxy to provide a new method for interpreting the 26Al observations. Methods. We included the massive star sources of 26Al in the Galaxy and its radioactive decay into a state-of-the-art galactic chemical evolution model, coupled with cosmological growth and hydrodynamics. This approach allowed us to follow the spatial and temporal evolution of the 26Al content in the simulated galaxy. Results. Our results are in agreement with the observations with respect to the fact that gas particles in the simulation with relatively higher 26Al content also have the highest LoS velocities. On the other hand, gas particles with relatively lower 26Al content (i.e., not bright enough to be observed) generally display the lowest LoS velocities. However, this result is not conclusive because the overall rotational velocity of our simulated galaxy is higher than that observed for cold CO gas in the Milky Way Galaxy. Furthermore, we found no significant correlation between gas temperature, rotational velocity, and 26Al content at any given radius. We also found the presence of transient 26Al-rich spots at low LoS velocities and we show that one such spot had been captured by the INTEGRAL/SPI data. Based on our model, we present a prediction for the detection of 1.8 MeV γ-rays by the future COSI mission. We find that according to our model, the new instrument will be able to observe similar 26Al-emission patterns to those seen by INTEGRAL/SPI.
{"title":"The aluminium-26 distribution in a cosmological simulation of a Milky Way-type Galaxy","authors":"B. Wehmeyer, C. Kobayashi, A. Yagüe López, M. Lugaro","doi":"10.1051/0004-6361/202451915","DOIUrl":"https://doi.org/10.1051/0004-6361/202451915","url":null,"abstract":"<i>Context<i/>. The 1.8 MeV <i>γ<i/>-rays corresponding to the decay of the radioactive isotope <sup>26<sup/>Al (with a half-life of 0.72 Myr ) have been observed by the SPI detector on the INTEGRAL spacecraft and extensively used as a tracer of star formation and current nucleosynthetic activity in the Milky Way Galaxy. Further information is encoded in the observation related to the higher <sup>26<sup/>Al content found in regions of the Galaxy with the highest line-of-sight (LoS) velocity relative to an observer located in the Solar System. However, this feature remains unexplained. <i>Aims<i/>. We ran a cosmological “zoom-in” chemodynamical simulation of a Milky Way-type galaxy, including the production and decays of radioactive nuclei in a fully self-consistent way. We then analyzed the results to follow the evolution of <sup>26<sup/>Al throughout the lifetime of the simulated galaxy to provide a new method for interpreting the <sup>26<sup/>Al observations. <i>Methods<i/>. We included the massive star sources of <sup>26<sup/>Al in the Galaxy and its radioactive decay into a state-of-the-art galactic chemical evolution model, coupled with cosmological growth and hydrodynamics. This approach allowed us to follow the spatial and temporal evolution of the <sup>26<sup/>Al content in the simulated galaxy. <i>Results<i/>. Our results are in agreement with the observations with respect to the fact that gas particles in the simulation with relatively higher <sup>26<sup/>Al content also have the highest LoS velocities. On the other hand, gas particles with relatively lower <sup>26<sup/>Al content (i.e., not bright enough to be observed) generally display the lowest LoS velocities. However, this result is not conclusive because the overall rotational velocity of our simulated galaxy is higher than that observed for cold CO gas in the Milky Way Galaxy. Furthermore, we found no significant correlation between gas temperature, rotational velocity, and <sup>26<sup/>Al content at any given radius. We also found the presence of transient <sup>26<sup/>Al-rich spots at low LoS velocities and we show that one such spot had been captured by the INTEGRAL/SPI data. Based on our model, we present a prediction for the detection of 1.8 MeV <i>γ<i/>-rays by the future COSI mission. We find that according to our model, the new instrument will be able to observe similar <sup>26<sup/>Al-emission patterns to those seen by INTEGRAL/SPI.","PeriodicalId":8571,"journal":{"name":"Astronomy & Astrophysics","volume":"12 1","pages":""},"PeriodicalIF":6.5,"publicationDate":"2025-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143661491","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：