Research

Some current research and recent publications

  • Formation of Galaxies at Epoch of Reionization
  • Galaxy formation at the epoch of reionization (EoR) at redshift z>6 is one of the most exciting frontiers in astrophysics. A number of premier observational facilities in the coming decade is in a large part driven to study this epoch. In this epoch a large number of ``firsts" occurred, including the first stars, black holes, supernovae, which shape the subsequent evolution of the universe. The universe also experienced a phase transition from a cold, neutral and opaque to an ionized, hot and transparent one, which also shapes its later evolution. While the Hubble Space Telescope has started to probe into this epoch, upcoming observations by the James Webb Space Telescope (JWST), the thirty-meter class ground-based telescopes, the Square Kilometer Array (SKA) radio telescope and others will provide data so rich that theorists are very worried about lagging behind. My group's work on this front is intended to provide observers insight and guidance to their observational campaign and to provide a theoretical framework to understand and interpret upcoming observations.

    Delayed Photons from Binary Evolution Help Reionize the Universe Amy Secunda, Renyue Cen, Taysun Kimm, Ylva Gotberg, Selma E. de Mink 2020 ApJ 901 72

    Physics of Prodigious Lyman Continuum Leakers Cen, R. (2020), ApJ Letters, 889, L22

    Formation of globular clusters in atomic-cooling halos via rapid gas condensation and fragmentation during the epoch of reionization, Kimm, Taysun, Cen, Renyue, Rosdahl, Joakim, Yi, Sukyoung (2016) ApJ, 823, 52

    Quantifying Distributions of the Lyman Continuum Escape Fraction Cen, Renyue; Kimm, Taysun (2015) ApJ, 801, L25

    Escape fraction of ionizing photons during reionization: effects due to supernova feedback and runaway OB stars Taysum Kimm, Renyue Cen (2014) ApJ, 788, 121


  • Physics of Cosmological Reionization
  • The phase transition of the gas in the universe - reionization of the universe - thought to have taken place in the redshift range of 6-20 is a fundamental landmark cosmological event. The cosmic microwave background experiments (e.g, Planck) have provided some information on the overall integrated electron optical depth of the universe. Upcoming 21cm observations (e.g., by SKA) will provide a wealth of information to allow us to study the sources of the cosmological reionization in unprecedented detail. My group's work is a collaboration with Dr. Hy Trac at CMU and lead the world on this front, developing and using the most advanced radiation hydrodynamic simulations of cosmological reionization, along with analytic methods calibrated by the simulations, to provide a theoretical framework to understand and interpret upcoming cosmic microwave background and 21cm observations.

    SCORCH. III. Analytical Models of Reionization with Varying Clumping Factors Chen, Nianyi; Doussot, Aristide; Trac, Hy; Cen, Renyue 2021 ApJ 905 132

    Helium Reionization Simulations. III. The Helium Lyman-$\alpha$ Forest La Plante, Paul; Trac, Hy; Croft, Rupert; Cen, Renyue (2018) ApJ, 868, 10

    Helium Reionization Simulations. II. Signatures of Quasar Activity on the IGM, La Plante, Paul; Trac, Hy; Croft, Rupert; Cen, Renyue (2018) ApJ, 841, 87

    SCORCH I: The Galaxy-Halo Connection in the First Billion Years Hy Trac, Renyue Cen, Philip Mansfield (2015) ApJ, 813, 54


  • Physics of the Missing Baryons
  • I have led the proponents to suggest that about 50% of the cosmic baryons that were missing reside in the cosmic web, a filament network with moderate electron density of about one electron per cubic meter. This prediction has been widely confirmed by ultra-violet absorption observations by high ionized ions (e.g., O VI) from the Hubble Space Telescope. My group is currently developing the next-generation, large-scale cosmological hydrodynamic simulations of 70-500 billion cells using both CPUs and GPUs on supercomputers to make detailed predictions on the emission of the filaments that may be probed by the next-generation UV and X-ray observations.

    The Physical Origins of the Identified and Still Missing Components of the Warm-Hot Intergalactic Medium: Insights from Deep Surveys in the Field of Blazar 1ES1553+113, Sean D. Johnson, John S. Mulchaey, Hsiao-Wen Chen, Nastasha A. Wijers, Thomas Connor, Sowgat Muzahid, Joop Schaye, Renyue Cen, Scott G. Carlsten, Jane Charlton, Maria R. Drout, Andy D. Goulding, Terese T. Hansen, Gregory L. Walth (2019), ApJL 884, L31

    Chandra View of the Warm-Hot IGM toward 1ES 1553+113: Absorption Line Detections and Identifications (Paper I) Nicastro, F.; Elvis, M.; Krongold, Y.; Mathur, S.; Gupta, A.; Danforth, C.; Barcons, X.; Borgani, S.; Branchini, E.; Cen, R.; Davé, R.; Kaastra, J.; Paerels, F.; Piro, L.; Shull, J. M.; Takei, Y.; Zappacosta, L. (2013) ApJ, 769 13

    Where Are the Baryons? III: Non-Equilibrium Effects and Observables, Renyue Cen and Taotao Fang (2006), ApJ, 650, 573


  • Galaxy Formation and Evolution
  • I have pioneered in galaxy formation more than three decades ago and continue to lead effort to understand galaxy formation in physical details. My group's current focus is to understand feedback processes, from stellar evolution (supernovae) and supermassive black hole growth, in a physical manner while having a strong desire to minimize subgrid parameters so as to enable more falsifiable calculations and predictions. Our recent simulations have resolutions ranging from 0.1pc to 400pc, depending on the problem at hand, ranging from formation of globular clustera, Lyman alpha emitters, Lyman alpha blobs, global galaxy color migration to environmental effects.

    Assembly Conformity of Structure Growth: Fossil versus Normal Groups of Galaxies Zack Li & Renyue Cen (2020), ApJ 898 39L

    Infalling gas in a Lyman alpha blob Ao, Yiping; Zheng, Zheng; Henkel, Christian; Nie, Shiyu; Beelen, Alexandre; Cen, Renyue; Dijkstra, Mark; Francis, Paul J.; Geach, James E.; Kohno, Kotaro; Lehnert, Matthew D.; Menten, Karl M.; Wang, Junzhi; Weiss, Axel (2020), Nature Astronomy tmp 44A

    Where do quasar hosts lie with respect to the size-mass relation of galaxies? John D. Silverman, Tommaso Treu, Xuheng Ding, Knud Jahnke, Vardha N. Bennert, Simon Birrer, Malte Schramm, Andreas Schulze, Jeyhan S. Kartaltepe, David B. Sanders, Renyue Cen (2019), ApJ Letters, 887, L5

    Lyman alpha view around a z=2.84 hyperluminous QSO at a node of the cosmic web Satoshi Kikuta, Yuichi Matsuda, Renyue Cen, Charles C. Steidel, Masafumi Yagi, Tomoki Hayashino, Masatoshi Imanishi, Yutaka Komiyama, Rieko Momose, Tomoki Saito (2019), PASJ 71 L2

    Large-scale clustering of Lyman α emission intensity from SDSS/BOSS Croft, Rupert A. C.; Miralda-Escudé, Jordi; Zheng, Zheng; Bolton, Adam; Dawson, Kyle S.; Peterson, Jeffrey B.; York, Donald G.; Eisenstein, Daniel; Brinkmann, Jon; Brownstein, Joel; Cen, Renyue; Delubac, Timothée; Font-Ribera, Andreu; Hamilton, Jean-Christophe; Lee, Khee-Gan; Myers, Adam; Palanque-Delabrouille, Nathalie; Pâris, Isabelle; Petitjean, Patrick; Pieri, Matthew M.; Ross, Nicholas P.; Rossi, Graziano; Schlegel, David J.; Schneider, Donald P.; Slosar, Anže; Vazquez, José; Viel, Matteo; Weinberg, David H.; Yèche, Christophe (2016) MNRAS, 457, 3541


  • Lyman Alpha Forest and Damped Lyman Alpha Systems
  • I was the chief architect of the theory of the Lyman alpha forest, laying the foundation for its cosmological applications. I was also one of the main theorists of the damped Lyman alpha systems. My group has continued these line of investigations.

    The Physical Nature of the Most Metal-Poor Damped Lyman Alpha Systems Sihan Yuan & Renyue Cen (2016) MNRAS, 457 487

    The Non-Linear Power Spectrum of the Lyman Alpha Forest, Andreu Arinyo-i-Prats, Jordi Miralda-Escudé, Matteo Viel, Renyue Cen (2015) JCAP, 12, 17

    The Nature of Damped Lyman Alpha Systems and Their Hosts in the Standard Cold Dark Matter Universe Renyue Cen (2012) ApJ, 748, 121