The Astrophysical Journal最新文献_第5页

Stream Members Only: Data-driven Characterization of Stellar Streams with Mixture Density Networks

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/ad94f2

Nathaniel Starkman, Jacob Nibauer, Jo Bovy, Jeremy J. Webb, Kiyan Tavangar, Adrian Price-Whelan and Ana Bonaca

{"title":"Stream Members Only: Data-driven Characterization of Stellar Streams with Mixture Density Networks","authors":"Nathaniel Starkman, Jacob Nibauer, Jo Bovy, Jeremy J. Webb, Kiyan Tavangar, Adrian Price-Whelan and Ana Bonaca","doi":"10.3847/1538-4357/ad94f2","DOIUrl":"https://doi.org/10.3847/1538-4357/ad94f2","url":null,"abstract":"Stellar streams are sensitive probes of the Milky Way’s gravitational potential. The mean track of a stream constrains global properties of the potential, while its fine-grained surface density constrains galactic substructure. A precise characterization of streams from potentially noisy data marks a crucial step in inferring galactic structure, including the dark matter, across orders of magnitude in mass scales. Here we present a new method for constructing a smooth probability density model of stellar streams using all of the available astrometric and photometric data. To characterize a stream’s morphology and kinematics, we utilize mixture density networks to represent its on-sky track, width, stellar number density, and kinematic distribution. We model the photometry for each stream as a single-stellar population, with a distance track that is simultaneously estimated from the stream’s inferred distance modulus (using photometry) and parallax distribution (using astrometry). We use normalizing flows to characterize the distribution of background stars. We apply the method to the stream GD-1, and the tidal tails of Palomar 5. For both streams we obtain a catalog of stellar membership probabilities that are made publicly available. Importantly, our model is capable of handling data with incomplete phase-space observations, making our method applicable to the growing census of Milky Way stellar streams.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Influence of Modeling Assumptions on the Inferred Dynamical State of Resonant Systems: A Case Study of the HD 45364 System

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/adae8d

Ian Chow and Sam Hadden

{"title":"Influence of Modeling Assumptions on the Inferred Dynamical State of Resonant Systems: A Case Study of the HD 45364 System","authors":"Ian Chow and Sam Hadden","doi":"10.3847/1538-4357/adae8d","DOIUrl":"https://doi.org/10.3847/1538-4357/adae8d","url":null,"abstract":"Planetary systems exhibiting mean motion resonances (MMRs) offer unique opportunities to study the imprint of disk-induced migration on the orbital architectures of planetary systems. The HD 45364 system, discovered via the radial velocity (RV) method to host two giant planets in a 3:2 MMR, has been the subject of several studies attempting to reconstruct the system’s orbital migration history based on its present-day resonant configuration. Recently, Z. Li et al. called into question the system’s residence in the 3:2 MMR based on a revised orbital solution derived from an expanded set of RV observations that extend the time baseline of the original discovery data by over a decade. However, we show that inferences about the planets’ dynamical state with respect to the 3:2 MMR are sensitive to the particular prior assumptions adopted in the orbital modeling. Using N-body dynamical models, we show that orbital solutions constrained to reside deep in the 3:2 MMR fit the RV data with a similar quality to unconstrained orbital solutions. We conclude that the RV observations of HD 45364 are consistent with orbital configurations produced by smooth migration and resonance capture. We further show that past convergent orbital migration can reproduce the system’s present-day orbital configuration provided that the ratio of migration to eccentricity damping timescales, K, was in the range 11 ≲ K ≲ 144. We also find that dynamical interactions in the system can break the usual mass–inclination degeneracy inherent to Keplerian models of RV observations and constrain the planets’ absolute masses to within a factor of ∼1.5.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Radio Polarization from Runaway Star Bowshocks. I. The General Case

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/adae0a

M. V. del Valle, R. Santos-Lima and M. Pohl

{"title":"Radio Polarization from Runaway Star Bowshocks. I. The General Case","authors":"M. V. del Valle, R. Santos-Lima and M. Pohl","doi":"10.3847/1538-4357/adae0a","DOIUrl":"https://doi.org/10.3847/1538-4357/adae0a","url":null,"abstract":"High velocity stars move through the interstellar medium with V > 30 km s−1. When the star has powerful winds, under the appropriate conditions, the interaction of the wind with the interstellar material produces a system of shocks. The outer shock, called the bowshock, perturbs the ambient medium, heating and compressing the gas. The dust in the compressed bowshock cools, producing infrared radiation. This emission appears as extended coma-shape structures. The discovery of radio nonthermal emission from two stellar bowshock nebulae indicates that these sources might be accelerating electrons up to relativistic energies. The produced nonthermal radio emission is most probably synchrotron, which has a high degree of polarization. In this work we model the synchrotron emission of runaway massive star bowshocks aiming to produce synthetic radio emission and polarization maps for two frequencies: 1.40 and 4.86 GHz. We model the interacting plasmas in a steady-state regime by means of magnetohydrodynamics simulations and we compute the injection and transport of the relativistic electrons in the diffusion approximation. We include in the model the most important depolarization effects. Our main conclusions are (i) the effects of Faraday rotation within the source are important at the lowest frequency considered, (ii) inferring the local magnetic field direction from polarization measurements only can be misleading, (iii) thermal radio emission produced by ionized plasma within the bowshock structure and surroundings can surpass the polarized one for the considered frequencies, and (iv) the contribution from the background electrons is minor.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"133 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Simultaneous NICER and NuSTAR Observations of the Neutron Star Low-mass X-Ray Binary Serpens X-1

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/adaeaa

H. Hall, R. M. Ludlam, J. M. Miller, A. C. Fabian, J. A. Tomsick, J. Coley, J. A. García and B. M. Coughenour

{"title":"Simultaneous NICER and NuSTAR Observations of the Neutron Star Low-mass X-Ray Binary Serpens X-1","authors":"H. Hall, R. M. Ludlam, J. M. Miller, A. C. Fabian, J. A. Tomsick, J. Coley, J. A. García and B. M. Coughenour","doi":"10.3847/1538-4357/adaeaa","DOIUrl":"https://doi.org/10.3847/1538-4357/adaeaa","url":null,"abstract":"We present the first contemporaneous NICER and NuSTAR analysis of the low-mass X-ray binary Serpens X-1 obtained in 2023 June, performing broadband X-ray spectral analysis modeling of the reprocessed emission with relxillNS from 0.4 to 30 keV. We test various continuum and background estimation models to ensure that our results do not hinge on the choice of model used, and found that the detection of reflection features is independent of the choice of both continuum and background model. The position of the inner accretion disk is consistent with the last stable circular orbit (Rin ≤ 1.2 RISCO) and a low inclination of i ≤ 8.3°. Additionally, we investigate the presence of the low-energy (∼1 keV) Fe L complex in the data from NICER and the Reflection Grating Spectrometer on XMM-Newton that was previously reported in the literature. We find that the line is at most a 2% feature relative to the reprocessed continuum, and are unable to claim a definitive detection for the current data set. However, we discuss plausible conditions and systems that would increase the likelihood of detecting this feature in the future.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of Lyα Radiative Transfer on Intensity Mapping Power Spectra

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/ada8a3

Maja Lujan Niemeyer

{"title":"Effect of Lyα Radiative Transfer on Intensity Mapping Power Spectra","authors":"Maja Lujan Niemeyer","doi":"10.3847/1538-4357/ada8a3","DOIUrl":"https://doi.org/10.3847/1538-4357/ada8a3","url":null,"abstract":"Clustering of Lyα-emitting galaxies (LAEs) and Lyα line intensity mapping (LIM) are useful probes of cosmology. However, Lyα radiative transfer (RT) effects, such as absorption, line shift, and line broadening, and their dependence on the large-scale density and velocity fields can modify the measured LAE clustering and LIM statistics. We explore the effects of RT on the Lyα LIM power spectrum in two ways: using an analytic description based on linear approximations, and using lognormal mocks. The qualitative effects of intergalactic Lyα absorption on the LIM auto- and cross-power spectrum include a scale-dependent, reduced effective bias, reduced mean intensity, and modified redshift-space distortions. The linear absorption model does not describe the results of the lognormal simulations well. The random line shift suppresses the redshift-space power spectrum similar to the Fingers-of-God effect. In cross-correlation of LAEs or Lyα intensity with a non-Lyα tracer, the Lyα line shift leads to a phase shift of the complex power spectrum, i.e., a cosine damping of the real part. We study the impact of Lyα RT effects on the Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) LAE and LIM power spectra using lognormal mocks. We find that even small amounts of IGM absorption will significantly change the measured LAE auto-power spectrum. The LAE-intensity cross-power spectrum stays within the measurement uncertainty. Therefore, HETDEX will be able to constrain Lyα RT effects.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443238","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

A Method for Estimating X-Ray Pulsar Period and Pulse Time Delay: Applying the Improved Z n ...

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/adad5f

T. H. Xie, 天昊解, W. J. Zhang, 文佳张, J. R. Li, 君儒李, Y. Hao, 元郝, P. L. Cui, 培玲崔, X. L. Ning, 晓琳宁, X. Ma and 辛马

{"title":"A Method for Estimating X-Ray Pulsar Period and Pulse Time Delay: Applying the Improved Z n ...","authors":"T. H. Xie, 天昊解, W. J. Zhang, 文佳张, J. R. Li, 君儒李, Y. Hao, 元郝, P. L. Cui, 培玲崔, X. L. Ning, 晓琳宁, X. Ma and 辛马","doi":"10.3847/1538-4357/adad5f","DOIUrl":"https://doi.org/10.3847/1538-4357/adad5f","url":null,"abstract":"In order to apply the Z2 statistic to the estimation of the navigation pulsar period and time delay, and thus further improve the accuracy of X-ray pulsar navigation, this paper proposes a method for estimating the pulsar period and time delay with complex profiles based on the improved -test. Based on the prior information of the amount of photon data in the observation task, this method adaptively determines the optimal harmonic truncation order under different data qualities. In order to solve the problem of the change rate of complex profile signals being too fast, the binned data is rephased according to the principle of equal photon intensity segmentation within the bin, and the optimal number of bins suitable for the PSR B0531+21 pulsar is selected. Through simulation, a quantitative analysis was conducted on factors that affect the performance of the estimation algorithm, such as observation time, detector area, noise interference, etc. Simulation results show that the proposed estimation method has greater advantages when the observation time is short, the detector area is small, and the interference noise is large. In addition, the observation data of the PSR B0531+21 pulsar is processed and analyzed. The period estimation accuracy of the method proposed is 3.6532 ns, which is 39.57% higher than that of the χ2-test method. The method we proposed has the advantages of being suitable for navigation pulsars, strong environmental adaptability, high estimation accuracy, and strong estimation stability, which can further improve the performance of X-ray pulsar navigation.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"80 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Testing Galaxy Formation Models with the Stellar Mass–Halo Mass Relations for Star-forming and Quiescent Galaxies

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/adaf1a

Kai Wang and Yingjie Peng

{"title":"Testing Galaxy Formation Models with the Stellar Mass–Halo Mass Relations for Star-forming and Quiescent Galaxies","authors":"Kai Wang and Yingjie Peng","doi":"10.3847/1538-4357/adaf1a","DOIUrl":"https://doi.org/10.3847/1538-4357/adaf1a","url":null,"abstract":"The tight relationship between the stellar mass and halo mass of galaxies is one of the most fundamental scaling relations in galaxy formation and evolution. It has become a critical constraint for galaxy formation models. Over the past decade, growing evidence has convincingly shown that the stellar mass–halo mass relations (SHMRs) for star-forming and quiescent central galaxies differ significantly: at a given stellar mass, the average host halo mass of quiescent centrals is more massive than that of star-forming centrals. Despite the importance of this feature, its scientific implications have not yet been fully recognized or thoroughly explored in the field. In this work, we demonstrate that the semi-analytical model L-GALAXIES successfully reproduces these observational results, whereas three state-of-the-art hydrodynamic galaxy formation simulations (TNG, Illustris, and EAGLE) do not. Consequently, in L-GALAXIES, star-forming central galaxies are more efficient at converting baryons into stars than quiescent central galaxies at a given halo mass, while the other models predict similar efficiencies for both populations. Further analysis reveals that these fundamental discrepancies stem from distinct evolutionary paths on the stellar mass–halo mass plane. We show that the observed SHMRs for star-forming and quiescent galaxies support galaxy formation models in which quenching only weakly correlates with halo assembly histories and the stellar mass of star-forming galaxies can increase significantly after cosmic noon. In contrast, models in which quenching strongly preferentially happens in early-formed halos are not very favored. Additionally, we find that galaxy downsizing is present in L-GALAXIES and TNG but absent in Illustris and EAGLE.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Measuring the Intracluster Light Fraction with Machine Learning

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/adabc7

Louisa Canepa, Sarah Brough, Francois Lanusse, Mireia Montes and Nina Hatch

{"title":"Measuring the Intracluster Light Fraction with Machine Learning","authors":"Louisa Canepa, Sarah Brough, Francois Lanusse, Mireia Montes and Nina Hatch","doi":"10.3847/1538-4357/adabc7","DOIUrl":"https://doi.org/10.3847/1538-4357/adabc7","url":null,"abstract":"The intracluster light (ICL) is an important tracer of a galaxy cluster’s history and past interactions. However, only small samples have been studied to date due to its very low surface brightness and the heavy manual involvement required for the majority of measurement algorithms. Upcoming large imaging surveys such as the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) are expected to vastly expand available samples of deep cluster images. However, to process this increased amount of data, we need faster, fully automated methods to streamline the measurement process. This paper presents a machine learning model designed to automatically measure the ICL fraction in large samples of images, with no manual preprocessing required. We train the fully supervised model on a training data set of 50,000 images with injected artificial ICL profiles. We then transfer its learning onto real data by fine-tuning with a sample of 101 real clusters with their ICL fraction measured manually using the surface brightness threshold method. With this process, the model is able to effectively learn the task and then adapt its learning to real cluster images. Our model can be directly applied to Hyper Suprime-Cam images, processing up to 500 images in a matter of seconds on a single GPU, or fine-tuned for other imaging surveys such as LSST, with the fine-tuning process taking just 3 minutes. The model could also be retrained to match other ICL measurement methods. Our model and the code for training it are made available on GitHub.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443233","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Comparing Methods for Calculating Solar Energetic Particle Intensities: Rebinning versus Spectral Binning

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/adaea9

M. E. Cuesta, L. Y. Khoo, G. Livadiotis, M. M. Shen, J. R. Szalay, D. J. McComas, J. S. Rankin, R. Bandyopadhyay, H. A. Farooki, J. T. Niehof, C. M. S. Cohen, R. A. Leske, Z. Xu, E. R. Christian, M. I. Desai and M. A. Dayeh

{"title":"Comparing Methods for Calculating Solar Energetic Particle Intensities: Rebinning versus Spectral Binning","authors":"M. E. Cuesta, L. Y. Khoo, G. Livadiotis, M. M. Shen, J. R. Szalay, D. J. McComas, J. S. Rankin, R. Bandyopadhyay, H. A. Farooki, J. T. Niehof, C. M. S. Cohen, R. A. Leske, Z. Xu, E. R. Christian, M. I. Desai and M. A. Dayeh","doi":"10.3847/1538-4357/adaea9","DOIUrl":"https://doi.org/10.3847/1538-4357/adaea9","url":null,"abstract":"Solar energetic particle (SEP) events have been observed for decades in the interplanetary medium by spacecraft measuring the intensity of energetic ions and electrons. These intensities provide valuable information about particle acceleration, the effects of bulk plasma dynamics on particle transport, and the anisotropy of particle distributions. Since measured intensities are typically reported in narrow energy bins, it is common to rebin intensities over a wider energy range to improve counting statistics. We investigate two methods for calculating intensities across multiple energy bins: (a) rebinned intensity ( ), which is calculated by integrating the intensity over energy space and corresponds to the intensity at an effective energy that depends on the time-varying spectral index, and (b) spectral binned intensity ( ), calculated by integrating the log intensity in log–energy space, yielding the intensity at the log-centered energy that is independent of the spectral index and remains constant over time. We compare these methods using Parker Solar Probe (PSP) IS⊙IS measurements of energetic protons, and we prescribe criteria for selecting the appropriate method for different scenarios. Our results show that the rebinned intensity is consistently larger (up to a factor of 5) than the spectral binned intensity for two SEP events observed by PSP, although the time series of the two methods are strongly correlated. Overall, both measures are important for SEP spectral analysis, and the selection of the appropriate measure depends on whether a physical (spectral binned intensity) or a statistical (rebinned intensity) representation is needed for a given analysis.","PeriodicalId":501813,"journal":{"name":"The Astrophysical Journal","volume":"129 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143443260","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Study of Hybrid Stars with Nonstrange Quark Matter Cores

The Astrophysical Journal Pub Date : 2025-02-19 DOI: 10.3847/1538-4357/adaf9a

Cheng-Ming Li, He-Rui Zheng, Shu-Yu Zuo, Ya-Peng Zhao, Fei Wang and Yong-Feng Huang

引用次数: 0