Ming-Feng Ho
Ming-Feng Ho

Ming-Feng Ho 何銘峰

Postdoctoral Fellow · University of Michigan

Originally from Taiwan, I am a computational astrophysicist, with a particular interest in how we can learn about cosmology while accounting for the astrophysics that complicates the inference. Much of my work involves Bayesian inference across different topics, ranging from quasar spectra and gravitational waves to numerical simulations.

CVPapers
01 · RESEARCH

From quasar light to small-scale structure

Light from a distant quasar crosses the cosmic web before it reaches us. Diffuse hydrogen follows its filaments and sheets, absorbing the light at different wavelengths. Together, these absorption features form what we call the Lyman-alpha (Lyα) forest. The field above is one simulated slice of this web, with each row a sightline through it.

The forest lets us probe very small scales. A running primordial spectrum changes how much structure is seeded on different scales, while warm dark matter can suppress the smallest structures.

One sightline

Follow one row across the field and it becomes a spectrum. Most of the absorption comes from the diffuse hydrogen that makes up the forest. Sometimes the sightline crosses much denser neutral hydrogen in and around galaxies, producing broad damping wings that can cover a large part of the spectrum.

These dense absorbers are often difficult to see directly in emission. Against a bright quasar, however, their absorption lets us probe this neutral gas in and around galaxies. Measuring them means inferring the quasar light hidden beneath the damping wings, together with the absorber's redshift and column density. Across many quasars, those inferences constrain the absorber population.

Many sightlines

Keep enough sightlines and the correlation function ξ above begins to develop structure. The individual absorption lines fade from view, but their correlations remain. Those correlations contain information about the small-scale clustering of matter, as well as the thermal state of the gas.

Simulations connect forest statistics to small-scale matter power.

Dense absorbers in the forest statistics

Dense absorbers such as damped Lyman-alpha absorbers (DLAs) are rare, but their broad damping wings still affect forest statistics after many sightlines are combined. Changes in the absorber population can shift the same statistics used for cosmology, sometimes in ways that resemble changes in small-scale matter power.

Their population therefore enters the cosmological likelihood.

light → forest → sightlines → statistics → matter power

02 · PLAY

Play

Ink Forest

You have ten sightlines into a simulated universe that you cannot see directly. Follow each Lyα forest spectrum, reconstruct the structure between the sightlines, and decide where to look next.

Some sightlines help reveal the structure; others can distort the inferred map.

status · v1.1, simulated spectra (PRIYA, z = 3)
stack · web, WebGL 2, no backend
Play ↗

Also playable: the PRIYA parameter sweep ↗, a small live widget: move a cosmological or astrophysical parameter and watch the forest power spectrum respond.

toy model · not a hydro simulation Explore · fourteen scenes

Lyα: from gas to forest

How the hydrogen between a distant quasar and us becomes a forest of absorption lines. Hold the gas, drag the light, and read a spectrum backwards.

 simulated · PRIYA Watch · animation, 56 s

The Lyman-alpha forest and its DLA

One sightline through the PRIYA simulation. Each hydrogen cloud the quasar's light crosses leaves a line in its spectrum. Where the light passes a galaxy and its gas, it meets a damped Lyman-alpha absorber.

Design after Andrew Pontzen's DLA animation; gas view after an idea by Yueying Ni.

 simulated · PRIYA Talk · 20 min · MIT LITP gathering

The Lyman-alpha Forest

A public talk built as a live web page: the light of distant quasars, read through one simulated universe.

 data · DESI DR1 Talk · 10 min · Leinweber Foundation site visit, 2026

The Lyman-alpha Forest, in ten minutes

From the Dark Energy Spectroscopic Instrument (DESI) 3D map of galaxies and quasars into the PRIYA simulation: the forest of lines, and a galaxy in its shadow.
03 · PROJECTS

Selected work

a sightline read from the field · simulated · PRIYA
Small-scale cosmologyJCAP 2026

Small-scale Lyα cosmology with high-resolution spectra

High-resolution quasar spectra resolve the Lyα forest out to wavenumbers of order k ~ 10 h Mpc−1, smaller scales than those usually used in cosmological analyses. Using KODIAQ-SQUAD (the Keck Observatory Database of Ionized Absorption toward Quasars, combined with the Spectral Quasar Absorption Database) and XQ-100 (a survey of 100 quasars observed with X-shooter on the Very Large Telescope), we constrain the amplitude and slope of the small-scale matter power spectrum.

For KODIAQ-SQUAD, the amplitude is consistent with DESI DR1 and Planck, but the inferred slope is somewhat higher; XQ-100 agrees with the extended Baryon Oscillation Spectroscopic Survey (eBOSS) and Planck.

arXiv ↗JCAP 07 (2026) 094 ↗
How it works
Spectra
KODIAQ-SQUAD and XQ-100
Model
PRIYA multi-fidelity emulators, with dense absorbers included in the likelihood
Inference
Small-scale matter-power amplitude and slope
synthetic · illustrative
Absorbers · inference2020 → DESI

Finding damped absorbers automatically

Some sightlines contain more than the diffuse forest. A dense, self-shielded neutral-hydrogen system can remove enough quasar light to strongly affect downstream analyses. That is why we need a DLA finder.

Rather than making only a yes-or-no detection, it keeps a posterior over the absorber's redshift and column density. It is now one of the complementary finders used for the DESI DR2 DLA catalogue.

DR12 ↗DR16Q ↗DESI DR2 ↗code ↗
How it works
Missing light
Infer the unabsorbed quasar continuum with a Gaussian process
Absorbers
Compare models with zero, one, or more systems
Output
Posterior over redshift and column density

From the Sloan Digital Sky Survey (SDSS) DR12 to DR16Q and now DESI DR2.

one sightline, resolution rising · simulated · PRIYA
Emulation · uncertainty2022 – 2023

Multi-fidelity emulation

High-resolution cosmological simulations are expensive, making it difficult to densely cover the parameter space needed for inference. Multi-fidelity (MF) emulation combines many lower-resolution simulations with a smaller number of high-resolution runs and learns the correction between them.

This lets the emulator use information from both resolutions without treating the lower-resolution simulations as exact.

MF emulator ↗MF-Box ↗forest ↗code ↗watch the method ↗
How it works

Learn the low-to-high-fidelity correction as part of the Gaussian-process model.

First used for matter power, then extended to the Lyα forest.

simulated · PRIYA
Dense absorbers · emulationin preparation

What dense absorbers do to the Lyα forest

Even a small number of dense absorbers can change forest statistics through their broad damping wings. Changing the absorber population changes those statistics as well, sometimes in ways that resemble changes in small-scale matter power.

HCDEmu models this dependence by emulating how the forest responds to different populations of high-column-density (HCD) absorbers. That response then enters the likelihood.

hcd_priya ↗
How it works

Split PRIYA synthetic spectra by absorber class and emulate each class's response.

The change in ξ when you kept a dense sightline above is the same effect in a simpler setting.

Population inferencePRD 2024

One population of black holes, or two?

Gravitational-wave events in the third Gravitational-Wave Transient Catalog (GWTC-3) present a different population-inference problem. The objects are merging black holes rather than absorbers, but the inference is again about a population rather than a single object.

Using hierarchical population inference, we constrained how much two proposed black-hole populations could mix.

arXiv ↗PRD 110, 063031 ↗
How it works

Hierarchical population inference on GWTC-3.

Related work includes microlensing searches for primordial black holes.

More work
04 · PAPERS

Papers

First-author work first. Full list below.

  1. 2026
    JCAP 07 (2026) 094 · arXiv:2509.18271
  2. 2024
    Investigating the mixing between two black hole populations in LIGO-Virgo-KAGRA GWTC-3
    M.-F. Ho, S. E. Perkins, S. Bird, W. Dawson, N. Golovich, J. R. Lu, P. McGill
    Phys. Rev. D 110, 063031 · arXiv:2408.09024
  3. 2023
    MNRAS 526, 2903 · arXiv:2306.03144
  4. 2022
    MNRAS 509, 2551 · arXiv:2105.01081
  5. 2021
    MNRAS 507, 704 · arXiv:2103.10964
  6. 2020
    MNRAS 496, 5436 · arXiv:2003.11036
Google Scholar ↗ ORCID ↗
05 · ABOUT

Ming-Feng Ho 何銘峰

NOW

I am currently a postdoctoral fellow at the University of Michigan. Most of my work is on the Lyα forest, dense absorbers, and the inference problems that come with them. I have also worked on emulation and black-hole population inference.

I did my PhD at UC Riverside with Simeon Bird, after studying physics and astrophysics at National Taiwan University. As an undergraduate, I also spent quite a bit of time in the philosophy department. I pursued a philosophy minor for several years, although I never formally completed it. At times, I probably took philosophy more seriously than physics.

Outside physics, I play cello, brew coffee, cook, and make wagashi and Suzhou-style mooncakes. I also enjoy hiking, road trips, and exploring natural landscapes across the US.

Before graduate school, I worked on text mining and digital editions of classical Chinese texts. I no longer work in philosophy, but I think that background still influences how I approach physics. I tend to spend a lot of time thinking about the assumptions behind a problem, whether the question is framed correctly, and things that are easy to leave unexamined.

emailmfho@umich.edu
cvCurriculum vitae
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