Yue Hu (胡越), Astrophysicist
NASA Hubble Fellow, Institute for Advanced Study
Burke Fellow, Caltech
My research delves into turbulence and magnetic fields in astrophysics. Though invisible to the naked eye, turbulence and magnetism are pivotal forces interwoven through vast galaxy clusters down to the microphysics of cosmic rays.
I seek to answer key questions: Where do these forces originate? How do they shape the Universe? My work aims to understand their roles in different physical processes, including (1) turbulent dynamo, (2) cosmic ray transport, (3) star formation, (4) Seyfert activity within galactic nuclei, (5) the evolution of galaxy clusters, (6) and the properties of axion-like particles.
To tackle these challenges, I employ a multidisciplinary approach that combines (1) MHD turbulence theories, (2) MHD + PIC simulations, (3) machine learning tools, (4) and observational data.
Email: yuehu@ias.edu
Research
Magnetic field in the El Gordo cluster (Hu et al. 2024)
Mega-parsec magnetic fields in galaxy clusters
Magnetic fields interwoven within the Intracluster Medium (ICM) exert a substantial influence on the evolution of galaxy clusters. Despite their fundamental role, the properties of these magnetic fields remain largely enigmatic, with their measurement presenting a significant challenge. This project aims to probe the magnetic fields in the ICM by examining their association with both thermal X-ray emission, and non-thermal radio emission. By applying advanced methodologies to these observations, we have achieved the first-ever measurement of magnetic field topology within radio halos.
Magnetic fields in the galaxy clusters:
Probing the magnetic field in galaxy clusters with the gradient technique. arXiv:2007.06219.
Synchrotron intensity gradient revealing magnetic fields in galaxy clusters, Nature Communications.
Tracing magnetic fields with the GT: spatial filtering and use of interferometers. arXiv:2208.06074.
Artificial intelligence (AI) in astrophysics
We are using artificial intelligence (AI) tools to trace 3D interstellar magnetic fields and study turbulence in the ISM and ICM. Crucially, our approach transcends mere algorithmic application: we aim to understand the fundamental physical principles. Compared to traditional methods, AI offers significant advantages: it processes vast datasets efficiently, identifies complex patterns with higher accuracy, and provides a more comprehensive view of magnetic field structures. This innovative approach unlocks deeper insights into cosmic magnetism and turbulence.
Tracing 3D magnetic fields with AI:
Probing three-dimensional magnetic fields: II -- interpretable convolutional neural network. arXiv:2310.12555.
Probing three-dimensional magnetic fields: III -- synchrotron emission and machine learning. arXiv:2404.07806.
Probing three-dimensional magnetic fields: IV -- synchrotron polarization and vision transformer. arXiv:2410.09294.
Machine learning approach for estimating magnetic field strength in galaxy clusters from synchrotron emission. arXiv:2411.07080.
Estimate sonic Mach number in the interstellar medium with the convolutional neural network. arXiv:2411.11157.
3D Galactic magnetic field distribution (Hu & Lazarian 2023)
3D magnetic field traced by young stellar objects (Hu et al. 2021)
Probing 3D magnetic fields in ISM
The intricate web of magnetic fields threading the Galaxy plays a fundamental role in a plethora of astrophysical phenomena, from the enigmatic origins of ultra-high-energy cosmic rays to the process of star formation. Despite their significance, directly measuring the three-dimensional (3D) magnetic fields within the interstellar medium (ISM) remains a formidable challenge. Driven by an enriched comprehension of magnetohydrodynamic (MHD) turbulence, this research proposes innovative methodologies to trace and characterize the orientation and strength of 3D magnetic fields:
3D Galactic magnetic field:
Mapping the Galactic magnetic field orientation and strength in three dimensions. arXiv:2302.05047.
Anisotropic turbulence in PPV space: probing three-dimensional magnetic fields. arXiv:2104.02842.
Anisotropies in compressible MHD turbulence: probing magnetic fields. arXiv:2012.06039.
3D magnetic fields in star-forming regions:
Probing three-dimensional magnetic fields: I -- polarized dust emission. arXiv:2203.09745.
Characterizing three-dimensional magnetic field, turbulence, and self-gravity in the star-forming region L1688. arXiv:2210.11023.
Velocity gradients: magnetic field tomography towards the supernova remnant W44. arXiv: 2109.13670.
Magnetic field around the Sgr A* (Hu et al. 2022)
Image credit: SOFIA
Magnetic fields in the Galactic center and extragalaxy
The magnetic field is a pivotal yet enigmatic force within the Central Molecular Zone (CMZ) and galaxies at large. To elucidate the complexities of magnetic fields in the CMZ and neighboring galaxies, this research uses a multi-wavelength observational strategy. We combine neutral and ionized gas spectroscopic observations, radio polarization data, and far-infrared polarization measurements. Through this rich dataset, we generate detailed magnetic field maps, facilitating an in-depth analysis of how magnetic fields contribute to the dynamics of galactic nuclei and the orchestration of interstellar processes.
Multi-scale and 3D magnetic fields in the Central Molecular Zone:
Multi-scale magnetic fields in the central molecular zone. arXiv:2105.03605.
Decomposing magnetic fields in three dimensions over the central molecular zone. arXiv:2201.07970.
Magnetic fields in nearby galaxies:
Role of magnetic fields in fueling Seyfert nuclei. arXiv:2206.05423.
Multiphase magnetic fields in the galaxy NGC 3627. arXiv:2208.06090.
Anisotropic velocity fluctuations in galaxy mergers: a probe of the magnetic field. arXiv:2410.08157.
Two-fluid Athena++ simulations of turbulence (Hu et al. 2023)
MHD turbulence in astrophysics
Magnetohydrodynamic (MHD) turbulence represents a cornerstone component within the Interstellar Medium (ISM) and Intracluster Medium (ICM), with its influence extending across a vast spectrum of scales—from hundreds of parsecs down to sub-astronomical units. This project is dedicated to an in-depth examination of MHD turbulence and its related astrophysical manifestations through the lens of cutting-edge simulations.
Cosmic ray transport:
Superdiffusion of CRs in compressible magnetized turbulence. arxiv:2111.15066.
Turbulent dynamo:
Turbulent magnetic field amplification by the interaction of shock wave and inhomogeneous medium. arXiv:2207.06941.
Turbulence damping due to neutral-ion decoupling:
Damping of turbulence in a partially ionized medium. arXiv:2306.10005.
Simulation of star formation with stellar feedback (Hu et al. 2022)
Turbulence and magnetic fields in star formation
Deciphering the regulatory mechanisms of star formation necessitates a comprehensive analysis of the interplay among turbulence, magnetic fields, stellar feedback, and gravitational forces within molecular clouds. This research endeavors to dissect the characteristics of turbulence and magnetic field structures within star-forming regions. By integrating state-of-the-art numerical simulations with high-resolution spectroscopic observations, we aim to illuminate the intricate dynamics at play in these stellar nurseries.
Turbulence in star formation:
The velocity statistics of turbulent clouds in the presence of outflow feedback. arXiv:2203.01508.
Velocity gradient in the presence of self-gravity: identifying inflows. arXiv:2002.06754.
Magnetic fields in star formation:
Magnetic field morphology with velocity gradient technique in Interstellar Clouds. Nature Astronomy
Revealing gravitational collapse in the Serpens G3-G6 molecular cloud. arXiv:2102.06225.
Tracing multi-scale magnetic field structure in GMC. arXiv:1904.04391.
Magnetic field in the Smith HI cloud (Hu et al. 2019)
The CMB foreground polarization
Observations of the Cosmic Microwave Background (CMB) polarization yield invaluable insights into the primordial inhomogeneities of the universe. However, these signals are contaminated by the polarization of the Galactic foreground. This research aims to model the Galactic foreground with the aid of atomic neutral hydrogen data. Our goal is to model the Galactic foreground polarization, thereby facilitating the detection of the B-mode signal in the CMB polarization.
Modeling of the Galactic foreground polarization:
Predictions of CMB foregrounds dust polarization using velocity gradient. arXiv:1910.05637.
Modeling of galactic foreground polarization with velocity gradients. arXiv:2007.02184.
Improving the accuracy of magnetic field tracing by velocity gradients: PCA. arXiv:1802.08772.
Intensity gradients technique: synergy with velocity gradients and polarization. arXiv:1908.09488.
Nature of striation in 21 cm channel Maps: Velocity caustics. arXiv:2306.10005.