Sihao Cheng

Sihao Cheng
Johns Hopkins University | JHU · Department of Physics and Astronomy

Doctor of Philosophy

About

20
Publications
1,191
Reads
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221
Citations
Introduction
I am interested in combining physical insights and statistics to analyze astronomical survey data. I am working on applying a new statistical tool borrowing ideas from convolutional neural nets (CNNs) to astrophysics. I showed it is as powerful as CNN for weak lensing cosmology, without any training. I also work on Gaia data: I discovered a new population of white dwarfs with an extreme cooling anomaly, and I measured the rate of white dwarf mergers.
Additional affiliations
August 2017 - present
Johns Hopkins University
Position
  • PhD Student
Education
September 2017 - May 2019
Johns Hopkins University
Field of study
  • Physics and Astronomy
September 2012 - June 2016
Peking University
Field of study
  • Astronomy

Publications

Publications (20)
Preprint
Full-text available
Extracting information from stochastic fields or textures is a ubiquitous task in science, from exploratory data analysis to classification and parameter estimation. From physics to biology, it tends to be done either through a power spectrum analysis, which is often too limited, or the use of convolutional neural networks (CNNs), which require lar...
Article
White dwarf stars are the most common end point of stellar evolution. The ultramassive white dwarfs are of special interest as they are related to type Ia supernovae explosions, merger events, and fast radio bursts. Ultramassive white dwarfs are expected to harbour oxygen-neon (ONe) cores as a result of single standard stellar evolution. However, a...
Preprint
Full-text available
As weak lensing surveys become deeper, they reveal more non-Gaussian aspects of the convergence field which require statistics beyond the power spectrum to extract. In Cheng et al. (2020), we showed that the scattering transform, a novel statistic borrowing concepts from convolutional neural networks, is a powerful tool to perform cosmological para...
Article
Full-text available
While it is well-established that giant-planet occurrence rises rapidly with host star metallicity, it is not yet clear if small-planet occurrence around late-type dwarf stars depends on host star metallicity. Using the Kepler Data Release 25 planet candidate list and its completeness data products, we explore planet occurrence as a function of met...
Article
Full-text available
The initial–final mass relation (IFMR) links the birth mass of a star to the mass of the compact remnant left at its death. While the relevance of the IFMR across astrophysics is universally acknowledged, not all of its fine details have yet been resolved. A new analysis of a few carbon–oxygen white dwarfs in old open clusters of the Milky Way led...
Preprint
Full-text available
Parameter estimation with non-Gaussian stochastic fields is a common challenge in astrophysics and cosmology. In this paper, we advocate performing this task using the scattering transform, a statistical tool sharing ideas with convolutional neural networks (CNNs) but requiring no training nor tuning. It generates a compact set of coefficients, whi...
Preprint
While it is well established that giant-planet occurrence rises rapidly with host star metallicity, it is not yet clear if small-planet occurrence around late-type dwarf stars depends on host star metallicity. Using the Kepler Data Release 25 planet candidate list and its completeness data products, we explore planet occurrence as a function of met...
Preprint
Cooling white dwarfs (WDs) can yield accurate ages when theoretical cooling models fully account for the physics of the dense plasma of WD interiors. We use MESA to investigate cooling models for a set of massive and ultra-massive WDs (0.9-1.3 $M_\odot$) for which previous models fail to match kinematic age indicators based on Gaia DR2. We find tha...
Article
Full-text available
The mass–radius relation of white dwarfs is largely determined by the equation of state of degenerate electrons, which causes the stellar radius to decrease as mass increases. Here we observationally measure this relation using the gravitational redshift effect, a prediction of general relativity that depends on the ratio between stellar mass and r...
Preprint
Full-text available
White dwarf stars are the most common end point of stellar evolution. In particular, ultra-massive white dwarfs are expected to harbour oxygen-neon (ONe) cores as a result of single standard stellar evolution. However, a fraction of them could have carbon-oxygen (CO) cores and be born as a result of merger events. Recent observations provided by Ga...
Preprint
The mass-radius relation of white dwarfs is largely determined by the equation of state of degenerate electrons, which causes the stellar radius to decrease as mass increases. Here we observationally measure this relation using the gravitational redshift effect, a prediction of general relativity that depends on the ratio between stellar mass and r...
Preprint
Full-text available
The initial-final mass relation (IFMR) links the birth mass of a star to the mass of the compact remnant left at its death. While the relevance of the IFMR across astrophysics is universally acknowledged, not all of its fine details have yet been resolved. A new analysis of a few carbon-oxygen white dwarfs in old open clusters of the Milky Way led...
Article
Full-text available
Double white dwarf (double-WD) binaries may merge within a Hubble time and produce high-mass WDs. Compared to other high-mass WDs, the double-WD merger products have higher velocity dispersion because they are older. With the power of Gaia data, we show strong evidence for double-WD merger products among high-mass WDs by analyzing the transverse-ve...
Preprint
Full-text available
By comparing two age indicators of high-mass white dwarfs derived from Gaia data, two discoveries have been made recently: one is the existence of a cooling anomaly that produces the Q branch structure on the Hertzsprung--Russell diagram, the other is the existence of double-white-dwarf merger products. The former poses a challenge for white dwarf...
Article
Full-text available
Recently, the power of Gaia data has revealed an enhancement of high-mass white dwarfs (WDs) on the Hertzsprung─Russell diagram, called the Q branch. This branch is located at the high-mass end of the recently identified crystallization branch. Investigating its properties, we find that the number density and velocity distribution on the Q branch c...
Preprint
Full-text available
Double-white-dwarf (double-WD) binaries may merge within a Hubble time and produce high-mass WDs. Compared to other high-mass WDs, the double-WD merger products have higher velocity dispersion because they are older. With the power of Gaia data, we show strong evidence for double-WD merger products among high-mass WDs by analyzing the transverse-ve...
Article
Full-text available
By comparing two age indicators of high-mass white dwarfs (WDs) derived from Gaia data, two discoveries have been made recently: one is the existence of a cooling anomaly that produces the Q branch structure on the Hertzsprung–Russell diagram, and the other is the existence of high-mass WDs as double-WD merger products. The former poses a challenge...
Preprint
Full-text available
Recently, the power of Gaia data has revealed an enhancement of high-mass white dwarfs (WD) on the Hertzsprung--Russell diagram, called the Q branch. This branch is located at the high-mass end of the recently identified crystallization branch. Investigating its properties, we find that the number density and velocity distribution on the Q branch c...
Article
Full-text available
A method for recording meteor spectra using a digital single-lens reflex (DSLR) camera, a normal large aperture lens and custom designed prism is described. The complete setup is guided and directed to meteor shower's radiant. A detailed calculation of the performance of this setup and observations during Geminid's maximum in 2010 are presented: 13...

Projects

Projects (2)
Project
Textures and patterns are ubiquitous in physics data but challenging to quantify. Recently, a new statistic that shares ideas with convolutional neural networks has shown its great potential. We plan to explore its applications in physics research, including cosmology, astrophysics, oceanography, etc.
Project
Gaia has enormously expanded the field of white dwarf research. Particularly, it generated a precise white dwarf H--R diagram with rich kinematic information. We aim at using the comparison between kinematic information, which indicates the true stellar ages, and the white dwarf cooling ages derived from the H--R diagram to infer delays in the evolution of white dwarf, concerning white dwarf cooling physics and merger.