Research

Large spectroscopic surveys have transformed the study of quasars and active galactic nuclei by providing uniform, multi-wavelength observations across cosmic time. My work develops and applies spectral-fitting methods to measure the physical properties of large quasar samples and produce value-added catalogs for the broader community.

Sloan Digital Sky Survey (SDSS) quasars

SDSS-IV DR16Q

In Wu & Shen (2022), we measured spectral properties for the 750,414 quasars in the SDSS Data Release 16 Quasar (DR16Q) catalog (Lyke et al. 2020). This sample spans broad ranges in redshift ($0.1\lesssim z\lesssim 6$) and luminosity ($44\lesssim \log{L_{\rm bol}/{\rm erg\, s^{-1}} \lesssim 48}$). Following established approaches (e.g., Shen et al. 2011, 2019), we fit each spectrum with a global continuum and emission-line model using the public PyQSOFIT package (Guo et al. 2018), with minor, well-documented adjustments to the fitting constraints. The input parameter file and reproducible workflow are available in our GitHub repository.

SDSS-V DR19Q

We also performed visual inspection and measured spectral properties for 82,363 quasars observed in SDSS DR19. The value-added catalog is publicly available through SDSS.

Dark Energy Spectroscopic Instrument (DESI) quasars

DESI EDR

Wu & Shen (2023) provides improved systemic redshift estimates for approximately 95,000 quasars in the DESI Early Data Release (EDR) using refined emission-line fitting techniques. We are applying related methods to later DESI quasar samples.

Wu et al. (2025) compares observed UV emission-line properties and broad-line region (BLR) distances with photoionization models for a sample of reverberation-mapped quasars. These models reproduce key trends in UV and optical line strengths and their dependence on accretion properties, offering a way to infer the otherwise unobservable ionizing continuum from optical/UV line flux ratios. The same framework qualitatively recovers the radius-luminosity relation for the reverberation-mapped AGN sample, suggesting that BLR gas density and structure may evolve systematically with accretion rate.

Stellar-mass black holes in X-ray binaries provide important constraints on binary evolution, accretion physics, and jet launching. 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 (Zheng et al. 2022). Our work used dynamical measurements of the secondary star to refine black hole mass estimates and characterize the physical state of the accreting system.

The large-scale structure (LSS) of the Universe encodes information about cosmology and the growth of structure. A central goal 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 late-time 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 its connection to initial conditions. In Wu et al. (2021), we introduced a Lagrangian spin parameter and tidal-twist parameters to quantify spin conservation and predictability in N-body simulations.