Research
Quasar Spectral Survey Analysis
Over the past decades, large-scale wide and deep field surveys such as the Sloan Digital Sky Survey (SDSS) with multi-wavelength coverage have facilitated the studies of quasars and AGNs. In Wu & Shen (2022), we measured spectral properties for the 750,414 quasars included in the latest SDSS Data Release 16 Quasar (DR16Q) catalog (Lyke et al. 2020). These quasars cover broad ranges in redshift (0.1≲z≲6) and luminosity (44≲logLbol/ergs−1≲48). Starting from this quasar catalog, we follow the practice in earlier work (e.g., Shen et al. 2011, 2019) to fit the SDSS spectra with a global continuum+emission lines model, using the public code PyQSOFIT (Guo et al. 2018) implemented minor custom adjustments to the fitting constraints. The input fitting parameter file is conveniently accessible online through our GitHub repository.
With the upcoming Dark Energy Spectroscopic Instrument (DESI) survey expected to provide optical spectra for ∼3 million quasars, precise redshift measurements are essential for maximizing scientific returns. In Wu & Shen (2023), we provided improved systemic redshift estimates for ∼95k quasars in the DESI Early Data Release (EDR) using refined emission-line fitting techniques. Similar methods will be applied to the DESI Data Release 1 upon its publication.
AGN Line-Emitting Region Photoionization
My recent publication (Wu et al. 2025) statistically compares observed UV emission-line properties and BLR cloud distances with photoionization modeling for a subsample of quasars with reverberation mapping (RM) observations. These models successfully reproduce key trends in UV/optical line strengths and their dependence on accretion parameters, offering a new method to infer the unobservable ionizing continuum using optical/UV line flux ratios. Furthermore, my work qualitatively recovers the size-luminosity relation for the RM AGN sample, suggesting that BLR gas density and structure may evolve systematically with accretion rate.
Black Hole Binary Dynamics
Stellar-mass black holes identified in X-ray binaries provide crucial insights into binary evolution and jet launching mechanisms. During my undergraduate studies, I collaborated with Prof. Jianfeng Wu on spectroscopic and photometric observations of black hole binary systems, including MAXI J1820+070 and A0620-00. Our work focused on the dynamical analysis of the secondary star in these systems to refine mass estimates and investigate accretion properties.
Cosmological N-body Simulation
The large-scale structure (LSS) of the universe encodes key information about cosmology. One of the major goals of LSS studies is to reconstruct the initial conditions of the Universe from the present-day galaxy distribution. To explore the connection between cosmic initial conditions and present-day structure, I collaborated with Prof. Haoran Yu on cosmological N-body simulations using the CUBE code. Our work examined the angular momentum evolution of dark matter halos and their connection to initial conditions. In Wu et al. 2021, we introduced a Lagrangian spin parameter and tidal twist parameters, quantifying their impact on spin conservation and predictability in N-body simulations (Poster).