Pengfei Li

Researcher Associate
Department of Astronomy, Case Western Reserve University

PhD: August 2020, Astronomy, Case Western Reserve University (OH, USA);
Master: July 2015, Theoretical Physics, Peking University (Beijing, China);
Bachelor: July 2012, Engineering, Huazhong University of Science and Technology (Wuhan, China).

Research interests: dynamics of disk galaxies, clusters of galaxies, dark matter.

Curriculum Vitae

Download my Curriculum Vitae

Title: The Dark Matter Problem in Rotationally Supported Galaxies

Advisors: Stacy McGaugh & Federico Lelli

Defense: June 19, 2020

Download my PhD thesis

Research & Publications

Research interests

Pengfei is interested in testing the cosmological model using galaxies, galaxy clusters. He has broadly applied Bayesian technique to 175 late-type galaxies in the SPARC database, and investigated seven dark matter halo models (NFW, pISO, Burkert, Einasto, coreNFW, DC14, Lucky13). He obtained 2100 rotation curve fits and determined the properties of these dark matter halos. These halos can be used to constrain the nature of dark matter, test cosmological models.

He is currently looking at the baryonic effects on dark matter halos. When baryons settle into, dark matter halos are supposed to experience a period of adiabatic contraction. By simulating the process, he studies how the baryonic effect could affect the nature of dark matter halos.

His recent interests is to extend the study to include galaxy clusters, the largest gravitationally bound systems. His goal is to explore a unified picture of dark matter model for galaxies and galaxy clusters. This will deepen our understanding of the nature of dark matter that contributes more than 80% of the mass in the Universe.

Introduction to my halo sample of 175 late-type galaxies

By fitting rotation curves, I have derived the dark matter halos for the 175 disk galaxies in the SPARC database. See 25 example rotation curve fits below.

Figure: 25 rotation curve fits using the Einasto model with LCDM priors imposed. All 2100 fits and associated data are available upon requested.

This sample can be used to test the dark matter model. For example, I established the tight correlation between H I line widths and dark matter halo masses using my halo sample. This relation enables the determation of the halo mass for a large unresolved galaxies, (1388 galaxies from the HIPASS survey in this case). I then measured the halo mass functions as shown below.

Figure: The halo mass function measured using the HIPASS galaxies compared with the dark matter-only simulation. The halo masses of the HIPASS galaxies are derived based on the relation established using my halo sample assuming the NFW, Einasto and DC14 profiles.

Publications

See my complete publication list at ADS.

First-author publications in Astronomy

(5) Li P., Lelli F., McGaugh S.S., Schombert J.M., Chae K., 2020, "A cautionary tale in the application of Bayesian techniques in Astronomy: does Newton's constant vary from galaxy to galaxy?", submitted to A&A Letters.

(4) Li P., Lelli F., McGaugh S.S., Schombert J.M. 2019, “A comprehensive catalog of dark matter halo models for SPARC galaxies”, ApJS, 247, 31L. See it on ADS

(3) Li P., Lelli F., McGaugh S.S., Pawlowski M.S., Zwaan M.A., Schombert J.M. 2019, “The halo mass function of late-type galaxies from the observed H I kinematics”, ApJ Letters, 866:L11. See it on ADS

(2) Li P., Lelli F., McGaugh S.S., Starkman N., Schombert J.M. 2019, “A constant characteristic volume density of dark matter haloes from SPARC rotation curve fits”, MNRAS, 482, 5106L. See it on ADS

(1) Li P., Lelli F., McGaugh S.S., Schombert J.M. 2018, “Fitting the radial acceleration relation to individual SPARC galaxies”, A&A, 615, A3. See it on ADS

Contributions to international conferences

(5) Talk, Galaxies & Cosmology & Stars & Planets Seminar, at CfA, 08 Septermber, 2020
Watch my talk on YouTube (starting at 23 minutes)

(4) Thesis talk, “235th Meeting of the American Astronomical Society”. Session: Spiral Galaxies. Honolulu, 4-8 January 2020

(3) Session Chair, “235th Meeting of the American Astronomical Society”. Four Sessions: Galaxy Clusters II & III, Dwarf & Irregular Galaxies II, Galaxy Evolution and Cosmology. Honolulu, 4-8 January 2020

(2) Talk, “The functioning of galaxies: challenges for Newtonian and Milgromian dynamics”. Bonn, 23-27 September 2019

(1) Poster, “Galactic Dynamics in the Era of Large Surveys”. Shanghai, 30 June-5 July, 2019

Co-author papers in Astronomy

(2) Tian Y., Yu P.C., Li P., McGaugh S.S., Ko C.M., 2020, "Mass velocity dispersion relation in HIFLUGCS galaxy clusters", submitted to ApJ. See it on ADS

(1) Chae K., Lelli F., Desmond H., McGaugh S.S., Li P., Schombert J., 2020, "Testing the Strong Equivalence Principle by the External Field Effect in Galaxy Rotation Curves", ApJ accepted. See it on ADS

Co-author papers in Physics

(3) Jiang L., Li P., Song H. 2016, “Multiplicity fluctuations of net protons on the hydrodynamic freeze-out surface”, Nuclear Physics A, 956, 360. See it on ADS

(2) Jiang L., Li P., Song H. 2016, “Correlated fluctuations near the QCD critical point”, Physics Review C, 94, 024918. See it on ADS

(1) Zhou Y., Zhu X., Li P., Song H. 2015, “Investigation of possible hadronic flow in √s = 5.02 TeV p-Pb collisions”, Physics Review C, 91, 064908. See it on ADS

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