Lile Wang @ Princeton

Graduate Student in Astrophysics

Department of Astrophysical Sciences

Princeton University

Astrophysics

About: Lile Wang

WANG, Lile (Chinese: ηŽ‹ εŠ›δΉ) is a 5th year graduate student in the Department of Astrophysical Sciences in Princeton University.

I am now interested in theoretical/computational astrophysics.

I work on combining dynamics (hydro/MHD) with consistent thermochemistry, applied to, e.g.:

  • Protoplanetary disk wind
  • Photoevaporation of low-mass exoplanet atmosphere
  • AGN disk corona and outflow

I also directly work on GPU programming to accelerate computations, especially on thermochemical networks and Monte Carlo radiative transfer. Currently my desktop computer (AMD Ryzen 1800X + NVIDIA GTX 1080 TI) beats 128 cores on latest InfiniBand clusters by more than 1.5 times in speed for (radiation + thermochemistry + dynamics) simulations.

Before coming to Princeton in 2013, I received my B.S. degree in physics from Tsinghua University (Beijing, China) in July, 2012. Then I visited Lawrence Berkeley National Laboratory (LBNL) as an affiliate, working mainly on cosmological perturbation theory of large scale structures.

Research

Photoevaporation of protoplanetary disks
( 2015 -- present; PhD thesis project )

Photoevaporation is an important dispersal mechanism for protoplanetary disks and planet atmosphere. We conduct hydrodynamic simulations coupled with radiative transfer and consistent thermochemistry to study photoevaporative winds. Observable molecules including CO, OH and H2O survive at relatively high wind temperatures due to reactions being out of equilibrium. We prove that mass-loss rates are sensitive to the intensity of radiation in energy bands that interact directly with hydrogen. Comparison with previous works shows that mass loss rates are also sensitive to the treatment of both the hydrodynamics and the thermochemistry.

Dispersal of exoplanet atmosphere
( 2017 -- present )

We construct numerical simulations, coupled with consistent thermochemistry and ray-tracing radiative transfer, to understand the physics of planet atmosphere photoevaporation by high energy photons radiated by central stars. Results emphasize the importance of consistent microphysics, including non-equilibrium processes, being coupled with hydrodynamics. We believe that the conventional "recombination-limited" mechanisms do not work; the key limit is rather atomic/molecular cooling processes. The results may also explain the observed decrease in the number of planets with rich atmosphere at low masses (< 6 earth mass).
Click Here for a gif animation showing how a very strong stellar wind does not quench planetary photoevaporation.

AGN corona and radiation
( 2013 -- present )

Using 3-D simulations, it is shown that the composite bremsstrahlung emission spectrum due to coronal gas of various temperatures are in reasonable agreement with the overall ensemble spectrum of AGNs and hard X-ray background. Taking into account inverse Compton processes, in the context of the simulation-produced coronal gas, our model can readily account for the wide variety of AGN spectral shape, which can now be understood physically. The distinguishing feature of our model is that X-ray coronal gas is, for the first time, an integral part of the inflow gas and its observable characteristics are physically coupled to the concomitant inflow gas. One natural prediction of our model is the anti-correlation between accretion disk luminosity and spectral hardness: as the luminosity of SMBH accretion disk decreases, the hard X-ray luminosity increases relative to the UV/optical luminosity.

Perturbation theory for structure formation
( 2012 -- 2013 )

Perturbation theory provide us a useful tool to understand the large scale structures of the universe. Working with Prof. Martin White (UC Berkeley) and Dr. Beth Raid (LBNL), we extended the application of the Convolution Lagrangian Perturbation Theory (CLPT) so that we can obtain pairwise velocity statistics with it. Those statistics enable us to calculate the correlation function in redshift-space, with pretty good precision and accuracy. Cross-correlations between halos in differnt mass bins are also possible to be calculated.
The code is available at: CLPT_GSRSD ; Paper: arXiv: 1306.1804

Publications

In preparation

  • Evaporation of Low-Mass Planet Atmospheres: Multidimensional Hydrodynamics with Consistent Thermochemistry
    Lile Wang, Fei Dai, 2017, Submitted to ApJ
    ADS / arXiv: 1710.03826

Refereed

  • Hydrodynamic Photoevaporation of Protoplanetary Disks with Consistent Thermochemistry,
    Lile Wang, Jeremy Goodman, 2017, ApJ, 847, 11
    ADS / arXiv: 1706.03155
  • Wind-driven Accretion in Transitional Protostellar Disks,
    Lile Wang, Jeremy Goodman, 2017, ApJ, 835, 59
    ADS / arXiv: 1609.07510
  • Searching for Binary Supermassive Black Holes via Variable Broad Emission Line Shifts: Low Binary Fraction,
    Lile Wang et al., 2017, ApJ, 834, 129
    ADS / arXiv: 1611.00039
  • Inflow Generated X-ray Corona Around Supermassive Black Holes and Unified Model for X-ray Emission,
    Lile Wang, Renyue Cen, 2016, ApJ, 817, 99
    ADS / arXiv: 1511.02890
  • Steady-state Axisymmetric Nonlinear Magnetohydrodynamic Solutions with Various Boundary Conditions,
    Lile Wang, Yu-Qing Lou, 2014, MNRAS, 439, 2323
    ADS / arXiv: 1401.2150
  • An analytic model for redshift-space distortions,
    Lile Wang, Beth Reid, Martin White, 2014, MNRAS, 437, 588
    ADS / arXiv: 1306.1804
  • Dynamic voids surrounded by shocked conventional polytropic gas envelopes,
    Yu-Qing Lou, Lile Wang, 2012, MNRAS, 420, 1897
    ADS / arXiv: 1109.2682


Code

My Github Repo

https://github.com/wll745881210

Projects

  • Microthena (interal tests on-going, will be released in the future...) :
    Extension to Athena++ , Microthena evolves thermochemical network and solves radiative transfer problems constistently on-the-fly. It is well-organized and highly extendable (e.g. I have an extension specifically for protoplanetary disks), using either CPU or (preferably) GPU as the backend.

Smaller projects

  • KDTPCF :
    A two-point correlation function calculator using k-d tree [time complexity: O(N3/2)] algorithm.
  • ICIC :
    Count-in-cell angular statistics calculator using integration method.
  • CLPT_GSRSD :
    Convolution-Lagrangian Perturbation Theory code with Gaussian Streaming for Redshift-Space Distortions.
  • Stock_Crawler :
    A GUI crawler fetching balance sheets (and other statistics) for securities in Chinese stock market.


Scientific talks

30 Mar 2013
Pairwise velocity statistics in convolution Lagrangian perturbation theory
BigBOSS (MS-DESI) Collaboration Meeting, SHAO, Shanghai.
Click here for slides

12 Oct 2011
Self-similar gas dynamics of voids and supernova ejecta
The 3rd Galileo-Xu Guangqi Meeting, NAOC, Beijing
Click here for slides

Contact: Lile Wang


  • E-mail:
    lilew (-at-) astro.princeton.edu
    wll9004 (-at-) gmail.com
  • Address:
    032 Peyton Hall,
    Department of Astrophysical Sciences,
    Princeton University,
    4 Ivy Ln, Princeton NJ 08540
  • Tel:
    +1-(510)-926-6831
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