About

Simon Huang is an Assistant Professor of Finance at the University of Massachusetts Amherst's Isenberg School of Management, where he has been serving since 2018. He holds a PhD in Finance from Yale University, earned in 2015, along with a Master’s degree in Statistics from the University of California at Berkeley and a Bachelor’s degree in Applied Mathematics, Computer Science, Economics, and Statistics from the same university. His research interests include asset pricing, behavioral finance, investment management, financial history, and general data science for finance. Huang has contributed to the field through publications such as 'The Momentum Gap and Return Predictability' in the Review of Financial Studies and 'Momentum in Imperial Russia' in the Journal of Financial Economics. Prior to his current role, he was a visiting faculty member at the University of Connecticut and held assistant professorships at Southern Methodist University. His academic achievements include fellowships from Yale University and Whitebox Advisors, reflecting his recognition in the field of finance.

Research topics

• Physics
• Computer Science
• Astrophysics
• Astronomy
• Meteorology
• Thermodynamics

Selected publications

• ELUCID. VIII. Simulating the Coma Galaxy Cluster to Calibrate Model and Understand Feedback

  The Astrophysical Journal · 2024-05-01 · 9 citations

  articleOpen accessSenior author

  Abstract We conducted an investigation of the Coma cluster of galaxies by running a series of constrained hydrodynamic simulations with GIZMO-SIMBA and GADGET-3 based on initial conditions reconstructed from the SDSS survey volume in the ELUCID project. We compared simulation predictions and observations for galaxies, intracluster medium (ICM) and intergalactic medium (IGM) in and around the Coma cluster to constrain galaxy formation physics. Our results demonstrate that this type of constrained investigation allows us to probe in more detail the implemented physical processes, because the comparison between simulations and observations is free of cosmic variance and hence can be conducted in a “one-to-one” manner. We found that an increase in the earlier star formation rate and the supernova feedback of the original GIZMO-SIMBA model is needed to match observational data on stellar, interstellar medium, and ICM metallicity. The simulations without active galactic nucleus (AGN) feedback can well reproduce the observational ICM electron density, temperature, and entropy profiles, ICM substructures, and the IGM temperature–density relation, while the ones with AGN feedback usually fail. However, one requires something like AGN feedback to reproduce a sufficiently large population of quiescent galaxies, particularly in low-density regions. The constrained simulations of the Coma cluster thus provide a test bed to understand processes that drive galaxy formation and evolution.

  PublisherOA PDFDOI

• ELUCID. VII. Using Constrained Hydro Simulations to Explore the Gas Component of the Cosmic Web

  The Astrophysical Journal · 2022 · 13 citations

  • Computer Science
  • Physics
  • Computer Science

  Abstract Using reconstructed initial conditions in the Sloan Digital Sky Survey (SDSS) survey volume, we carry out constrained hydrodynamic simulations in three regions representing different types of the cosmic web: the Coma cluster of galaxies; the SDSS Great Wall; and a large low-density region at z ∼ 0.05. These simulations, which include star formation and stellar feedback but no active galactic nucleus formation and feedback, are used to investigate the properties and evolution of intergalactic and intracluster media. About half of the warm-hot intergalactic gas is associated with filaments in the local cosmic web. Gas in the outskirts of massive filaments and halos can be heated significantly by accretion shocks generated by mergers of filaments and halos, respectively, and there is a tight correlation between the gas temperature and the strength of the local tidal field. The simulations also predict some discontinuities associated with shock fronts and contact edges, which can be tested using observations of the thermal Sunyaev–Zel’dovich effect and X-rays. A large fraction of the sky is covered by Ly α and O vi absorption systems, and most of the O vi systems and low-column-density H i systems are associated with filaments in the cosmic web. The constrained simulations, which follow the formation and heating history of the observed cosmic web, provide an important avenue to interpret observational data. With full information about the origin and location of the cosmic gas to be observed, such simulations can also be used to develop observational strategies.

  PublisherOA PDFDOI

• A new model for including galactic winds in simulations of galaxy formation II: Implementation of PhEW in cosmological simulations

  Monthly Notices of the Royal Astronomical Society · 2021-11-23 · 1 citations

  preprintOpen access1st authorCorresponding

  ABSTRACT Although galactic winds play a critical role in regulating galaxy formation, hydrodynamic cosmological simulations do not resolve the scales that govern the interaction between winds and the ambient circumgalactic medium (CGM). We implement the Physically Evolved Wind (PhEW) model of Huang et al. in the gizmo hydrodynamics code and perform test cosmological simulations with different choices of model parameters and numerical resolution. PhEW adopts an explicit subgrid model that treats each wind particle as a collection of clouds that exchange mass and metals with their surroundings and evaporate by conduction and hydrodynamic instabilities as calibrated on much higher resolution cloud scale simulations. In contrast to a conventional wind algorithm, we find that PhEW results are robust to numerical resolution and implementation details because the small scale interactions are defined by the model itself. Compared to our previous wind simulations with the same resolution, our PhEW simulations are in better agreement with low-redshift galactic stellar mass functions at M* < 1011M⊙ because PhEW particles shed mass to the CGM before escaping low mass haloes. PhEW radically alters the CGM metal distribution because PhEW particles disperse metals to the ambient medium as their clouds dissipate, producing a CGM metallicity distribution that is skewed but unimodal and is similar between cold and hot gas. While the temperature distributions and radial profiles of gaseous haloes are similar in simulations with PhEW and conventional winds, these changes in metal distribution will affect their predicted UV/X-ray properties in absorption and emission.

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• A new model for including galactic winds in simulations of galaxy formation – I. Introducing the Physically Evolved Winds (PhEW) model

  Monthly Notices of the Royal Astronomical Society · 2020 · 28 citations

  1st authorCorresponding
  • Physics
  • Astrophysics
  • Astronomy

  ABSTRACT The propagation and evolution of cold galactic winds in galactic haloes is crucial to galaxy formation models. However, modelling of this process in hydrodynamic simulations of galaxy formation is oversimplified owing to a lack of numerical resolution and often neglects critical physical processes such as hydrodynamic instabilities and thermal conduction. We propose an analytic model, Physically Evolved Winds, that calculates the evolution of individual clouds moving supersonically through a uniform ambient medium. Our model reproduces predictions from very high resolution cloud-crushing simulations that include isotropic thermal conduction over a wide range of physical conditions. We discuss the implementation of this model into cosmological hydrodynamic simulations of galaxy formation as a subgrid prescription to model galactic winds more robustly both physically and numerically.

  PublisherOA PDFDOI

• The impact of wind scalings on stellar growth and the baryon cycle in cosmological simulations

  Monthly Notices of the Royal Astronomical Society · 2020-01-16 · 10 citations

  articleOpen access1st authorCorresponding

  ABSTRACT Many phenomenologically successful cosmological simulations employ kinetic winds to model galactic outflows. Yet systematic studies of how variations in kinetic wind scalings might alter observable galaxy properties are rare. Here we employ gadget-3 simulations to study how the baryon cycle, stellar mass function, and other galaxy and CGM predictions vary as a function of the assumed outflow speed and the scaling of the mass-loading factor with velocity dispersion. We design our fiducial model to reproduce the measured wind properties at 25 per cent of the virial radius from the Feedback In Realistic Environments simulations. We find that a strong dependence of η ∼ σ5 in low-mass haloes with $\sigma \lt 106\mathrm{\, km\, s^{-1}}$ is required to match the faint end of the stellar mass functions at $z$ > 1. In addition, faster winds significantly reduce wind recycling and heat more halo gas. Both effects result in less stellar mass growth in massive haloes and impact high ionization absorption in halo gas. We cannot simultaneously match the stellar content at $z$ = 2 and 0 within a single model, suggesting that an additional feedback source such as active galactic nucleus might be required in massive galaxies at lower redshifts, but the amount needed depends strongly on assumptions regarding the outflow properties. We run a 50 $\mathrm{Mpc}\, h^{-1}$, 2 × 5763 simulation with our fiducial parameters and show that it matches a range of star-forming galaxy properties at $z$ ∼ 0–2.

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• The robustness of cosmological hydrodynamic simulation predictions to changes in numerics and cooling physics

  Monthly Notices of the Royal Astronomical Society · 2019-01-06 · 17 citations

  articleOpen access1st authorCorresponding

  We test and improve the numerical schemes in our smoothed particle hydrodynamics (SPH) code for cosmological simulations, including the pressure–entropy formulation (PESPH), a time-dependent artificial viscosity, a refined time-step criterion, and metal-line cooling that accounts for photoionization in the presence of a recently refined Haardt & Madau model of the ionizing background. The PESPH algorithm effectively removes the artificial surface tension present in the traditional SPH formulation, and in our test simulations, it produces better qualitative agreement with mesh-code results for Kelvin–Helmholtz instability and cold cloud disruption. Using a set of cosmological simulations, we examine many of the quantities we have studied in previous work. Results for galaxy stellar and H I mass functions, star formation histories, galaxy scaling relations, and statistics of the Lyα forest are robust to the changes in numerics and microphysics. As in our previous simulations, cold gas accretion dominates the growth of high-redshift galaxies and of low-mass galaxies at low redshift, and recycling of winds dominates the growth of massive galaxies at low redshift. However, the PESPH simulation removes spurious cold clumps seen in our earlier simulations, and the accretion rate of hot gas increases by up to an order of magnitude at some redshifts. The new numerical model also influences the distribution of metals among gas phases, leading to considerable differences in the statistics of some metal absorption lines, most notably Ne VIII.

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• ELUCID. IV. Galaxy Quenching and its Relation to Halo Mass, Environment, and Assembly Bias

  The Astrophysical Journal · 2018-01-01 · 73 citations

  articleOpen access

  Abstract We examine the quenched fraction of central and satellite galaxies as a function of galaxy stellar mass, halo mass, and the matter density of their large-scale environment. Matter densities are inferred from our ELUCID simulation, a constrained simulation of the local universe sampled by SDSS, while halo masses and central/satellite classification are taken from the galaxy group catalog of Yang et al. The quenched fraction for the total population increases systematically with the three quantities. We find that the “environmental quenching efficiency,” which quantifies the quenched fraction as a function of halo mass, is independent of stellar mass. And this independence is the origin of the stellar mass independence of density-based quenching efficiency found in previous studies. Considering centrals and satellites separately, we find that the two populations follow similar correlations of quenching efficiency with halo mass and stellar mass, suggesting that they have experienced similar quenching processes in their host halo. We demonstrate that satellite quenching alone cannot account for the environmental quenching efficiency of the total galaxy population, and that the difference between the two populations found previously arises mainly from the fact that centrals and satellites of the same stellar mass reside, on average, in halos of different mass. After removing these effects of halo mass and stellar mass, there remains a weak, but significant, residual dependence on environmental density, which is eliminated when halo assembly bias is taken into account. Our results therefore indicate that halo mass is the prime environmental parameter that regulates the quenching of both centrals and satellites.

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• X-ray Spectroscopy of the Andromeda Galaxy's Nuclear Feedback

  HEAD · 2017-08-01

  articleSenior author
  Publisher

• The minimum halo mass for star formation at<i>z</i> = 6–8

  Monthly Notices of the Royal Astronomical Society · 2016-09-23 · 28 citations

  articleOpen accessSenior author

  Recent analysis of strongly-lensed sources in the Hubble Frontier Fields indicates that the rest-frame UV luminosity function of galaxies at $z=$6--8 rises as a power law down to $M_\mathrm{UV}=-15$, and possibly as faint as -12.5. We use predictions from a cosmological radiation hydrodynamic simulation to map these luminosities onto physical space, constraining the minimum dark matter halo mass and stellar mass that the Frontier Fields probe. While previously-published theoretical studies have suggested or assumed that early star formation was suppressed in halos less massive than $10^9$--$10^{11} M_\odot$, we find that recent observations demand vigorous star formation in halos at least as massive as (3.1, 5.6, 10.5)$\times10^9 M_\odot$ at $z=(6,7,8)$. Likewise, we find that Frontier Fields observations probe down to stellar masses of (8.1, 18, 32)$\times10^6 M_\odot$; that is, they are observing the likely progenitors of analogues to Local Group dwarfs such as Pegasus and M32. Our simulations yield somewhat different constraints than two complementary models that have been invoked in similar analyses, emphasizing the need for further observational constraints on the galaxy-halo connection.

  PublisherOA PDFDOI

• nIFTY galaxy cluster simulations – III. The similarity and diversity of galaxies and subhaloes

  Monthly Notices of the Royal Astronomical Society · 2016-02-15 · 36 citations

  articleOpen access

  We examine subhaloes and galaxies residing in a simulated cold dark matter galaxy cluster (M crit 200 = 1.1 10 15 h -1 M ) produced by hydrodynamical codes ranging from classic smooth particle hydrodynamics (SPH), newer SPH codes, adaptive and moving mesh codes. These codes use subgrid models to capture galaxy formation physics. We compare how well these codes reproduce the same subhaloes/galaxies in gravity-only, non-radiative hydrodynamics and full feedback physics runs by looking at the overall subhalo/galaxy distribution and on an individual object basis. We find that the subhalo population is reproduced to within 10 per cent for both dark matter only and non-radiative runs, with individual objects showing code-to-code scatter of 0.1 dex, although the gas in non-radiative simulations shows significant scatter. Including feedback physics significantly increases the diversity. Subhalo mass and V max distributions vary by 20 per cent. The galaxy populations also show striking code-to-code variations. Although the Tully-Fisher relation is similar in almost all codes, the number of galaxies with 10 9 h -1 M M * 10 12 h -1 M can differ by a factor of 4. Individual galaxies show code-to-code scatter of 0.5 dex in stellar mass. Moreover, systematic differences exist, with some codes producing galaxies 70 per cent smaller than others. The diversity partially arises from the inclusion/absence of active galactic nucleus feedback. Our results combined with our companion papers demonstrate that subgrid physics is not just subject to fine-tuning, but the complexity of building galaxies in all environments remains a challenge. We argue that even basic galaxy properties, such as stellar mass to halo mass, should be treated with errors bars of 0.2-0.4 dex.

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Frequent coauthors

• Romeel Davé

  University of Edinburgh

  48 shared

• Weiguang Cui

  Royal Observatory

  21 shared

• Chris Power

  14 shared

• Neal Katz

  University of Massachusetts Amherst

  12 shared

• Alexander M. Beck

  Ludwig-Maximilians-Universität München

  12 shared

• A. Saro

  Institute for Fundamental Physics of the Universe

  10 shared

• Federico Sembolini

  9 shared

• Gustavo Yepes

  7 shared

Awards & honors

• Yale University Graduate Fellowship (2009-2014)
• Whitebox Advisors Doctoral Fellowship (2013)