Yue Hu (胡越), Astrophysicist

NASA Hubble Fellow, Institute for Advanced Study

Burke Fellow, Caltech


I am a NASA Hubble Fellow in the Institute for Advanced Study (IAS), jointly serving as a Burke Fellow at Caltech. I earned my Ph.D. in astrophysics from UW-Madison under the supervision of Prof. Alex Lazarian.
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:

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:

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:

3D magnetic fields in star-forming regions:

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:

Magnetic fields in nearby galaxies:

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:

Turbulent dynamo:

Turbulence damping due to neutral-ion decoupling:

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:

Magnetic fields in star formation:

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: