Adam Lidz

Adam Lidz
Standing Faculty

Associate Professor

Research Areas: Theoretical Astrophysics, Cosmology

(215) 898-9597

DRL 4N2a

  • Assistant Professor, University of Pennsylvania (2009-)
  • Postdoctoral Research Associate, Harvard-Smithsonian Center for Astrophysics (2007-2009)
  • ITC Postdoctoral Fellow, Harvard-Smithsonian Center for Astrophysics (2004-2007) 



Ph.D., Physics, Columbia University (2004)
B.A., Physics, The University of Chicago (1996)

Research Interests

I work in theoretical astrophysics and cosmology. I am interested in the formation and evolution of large scale structure, i.e., in understanding how the Universe evolves from a smooth, simple initial state to its present day complexity with galaxies, galaxy clusters, and other structures. A key period in our story of cosmological structure formation is the Epoch of Reionization (EoR), when the first generations of galaxies and/or quasars formed, emitted ultraviolet light, and ionized "bubbles" of hydrogen gas around them. The ionized bubbles grew, merged, and eventually filled essentially the entire volume of the Universe. The EoR and the preceding "dark ages" -- the period after cosmological recombination but before the birth of the first luminous sources -- are the only remaining phases of structure formation as yet to be directly observed. While we know relatively little about this important epoch thus far, we anticipate a confluence of data sets from a variety of wavebands, promising significant advances over the next few years. In particular we expect a wealth of observational data from high redshift quasar absorption spectra, increasingly deep narrow band surveys for Lyman-alpha emitting galaxies, optical afterglow spectra of gamma ray bursts, improved measurements of the cosmic microwave background (CMB) polarization, small-scale CMB fluctuations, and 21 cm observations, among other probes. Much of my recent work involves constructing theoretical models of the EoR to make predictions for these upcoming observations, and to interpret existing observations. I attack these problems using a combination of cosmological simulations, analytic methods, and analysis of observational data. While helium very likely becomes singly ionized along with hydrogen, the first luminous sources may not emit energetic enough photons to also doubly ionize helium. Helium may be doubly ionized only later on, perhaps around z~3 when the Universe is roughly 2 billion years old. I am actively trying to understand the impact of this event on the hydrogen Lyman-alpha forest, and to search for its signatures in observational Lyman-alpha forest data. Other research interests include modeling quasar clustering -- examining how clustering observations inform models for quasar fueling and lifecyles; and extracting constraints on cosmological parameters from Lyman-alpha forest observations.

Courses Taught

Phys 533 - Topics in Cosmology

Phys 433 - Order of Magnitude Physics

Selected Publications


  • "HeII Reionization and its Effect on the IGM", McQuinn, M., Lidz, A., Zaldarriaga, M., Hernquist, L., Hopkins, P.F., Dutta, S., & Faucher-Giguere, C.A. 2009, ApJ, 694, 842
  • "A Flat Photoionization Rate at 2 < z < 4.2: Evidence for a Stellar-Dominated UV Background and against a Decline of Cosmic Star Formation beyond z ~3", Faucher-Giguere, C.A, Lidz, A., Hernquist, L., Zaldarriaga, M. 2008, ApJL, 682, 9
  • "Detecting the Rise and Fall of 21 cm Fluctuations with the Murchison Widefield Array", Lidz, A., Zahn, O., McQuinn, M., Zaldarriaga, M., Hernquist, L. 2008, ApJ, 680, 962
  • "Quasar Proximity Zones and Patchy Reionization", Lidz, A., McQuinn, M., Zaldarriaga, M., Hernquist, L., Dutta, S. 2007, ApJ, 670, 39
  • "Higher Order Contributions to the 21 cm Power Spectrum", Lidz, A., Zahn, O., McQuinn, M., Zaldarriaga, M., Dutta, S., Hernquist, L. 2007, ApJ, 659, 865
  • "Simulations and Analytic Calculations of Bubble Growth During Hydrogen Reionization", Zahn, O., Lidz, A., McQuinn, M., Dutta, S., Hernquist, L., Zaldarriaga, M., Furlanetto, S.R. 2006, ApJ, 654, 12
  • "Have we Detected Patchy Reionization in Quasar Spectra?", Lidz, A., Oh, S.P., Furlanetto, S.R. 2006, ApJL, 639, 47
  • "The Luminosity Dependence of Quasar Clustering", Lidz, A., Hopkins, P.F., Cox, T.J., Hernquist, L., Robertson, B. 2006, ApJ, 641, 41 


CV (file)