The formation of galaxies is a complicated process involving baryonic physics on a range of spatial and temporal scales. The distribution of galaxies, therefore, does not necessarily follow that of the underlying dark matter. This difference, called galaxy bias, cannot be accurately predicted because we lack a perfect theory of galaxy formation. An empirical determination of galaxy bias, however, can provide important information about galaxy formation, and it also constitutes a crucial step towards constraining cosmology with galaxy clustering data. A large part of my research is devoted to interpreting galaxy clustering in a meaningful way, so as to extract the relation between distributions of galaxies and dark matter and to learn about galaxy formation and cosmology.

The basis of my work is the framework of the Halo Occupation Distribution (HOD). The HOD describes the relation between galaxies and dark matter at the level of individual dark matter halos whose properties can be readily predicted for a given cosmological model. The HOD framework provides a powerful tool to model galaxy clustering and to connect galaxy clustering to cosmology through linking galaxies to dark matter halos.

I performed theoretical studies of the HOD and developed accurate analytic methods to model galaxy clustering within the HOD framework. I have applied HOD modeling to galaxy clustering data in the Sloan Digital Sky Survey (SDSS) and other datasets to learn about galaxy formation and evolution and cosmology.

• demonstrated the existence of a break in the galaxy two-point correlation functions with SDSS data and interpreted it as the transition between contributions by intra-halo and inter-halo galaxy pairs (Zehavi, Weinberg, Zheng, et al. 2004)
• predicted strong departures of high-z galaxy two-point correlation functions from power law, which has since been confirmed by observation (Zheng 2004)
• with a comprehensive theoretical analysis, showed the ability of modeling of multiple clustering statistics to separately constrain HOD and cosmology and thus the ability of HOD modeling to greatly improve our understanding of galaxy formation and our constraints on cosmological parameters (Zheng & Weinberg 2007)
• inferred the luminosity and color dependence of the HOD with SDSS data (Zehavi, Zheng, et al. 2005, 2010)
• obtained cosmological constraints, in particular on Omega_m and sigma_8 from HOD modeling of galaxy two-point correlation functions and the mass-to-light ratio of large scale structures (Abazajian, Zheng, et al. 2005, Tinker, Weinberg, Zheng, & Zehavi, 2005)
• inferred interesting trends in galaxy evolution from HOD modeling of galaxy clustering at multiple redshifts (Zheng, Coil, & Zehavi 2007, White, Zheng, et al. 2007, Brown, Zheng, et al. 2008)

• Extending Recovery of the Primordial Matter Power Spectrum
  Jaiyul Yoo, David H. Weinberg, Jeremy L. Tinker, Zheng Zheng, & Michael S. Warren, ApJ, 698, 967 (2009)
• Environmental Effects on Real-Space and Redshift-Space Galaxy Clustering
  Ying Zu, Zheng Zheng, Guangtun Zhu, & Y.P. Jing, ApJ, 686, 41 (2008)
• The Dependence of Occupation of Galaxies on Halo Formation Time
  Guangtun Zhu, Zheng Zheng, W.P. Lin, Y.P. Jing, Xi Kang, & Liang Gao, ApJ, 639, L5 (2006)
• Breaking the Degeneracies Between Cosmology and Galaxy Bias
  Zheng Zheng & David H. Weinberg, ApJ, 659, 1 (2007)
• From Galaxy-Galaxy Lensing to Cosmological Parameters
  Jaiyul Yoo, Jeremy L. Tinker, David H. Weinberg, Zheng Zheng, Neal Katz, & Romeel Davé , ApJ, 652, 26 (2006)
• Redshift-Space Distortions with the Halo Occupation Distribution I: Numerical Simulations
  J.L. Tinker, D.H. Weinberg, & Z. Zheng, MNRAS, 368, 85 (2006)
• Theoretical Models of the Halo Occupation Distribution: Separating Central and Satellite Galaxies
  Zheng Zheng, et al. ApJ, 633, 791 (2005)
• Projected Three-Point Correlation Functions and Galaxy Bias
  Zheng Zheng, ApJ, 614, 527 (2004)
• Do Distinct Cosmological Models Predict Degenerate Halo Populations?
  Zheng Zheng, Jeremy L. Tinker, David H. Weinberg, & Andreas A. Berlind, ApJ, 575, 617 (2002)

• Galaxy Clustering in the Completed SDSS Redshift Survey: The Dependence on Color and Luminosity
  Idit Zehavi, Zheng Zheng, David H. Weinberg, Michael R.R Blanton, et al. ApJ, submitted
• Interpreting the Clustering of Distant Red Galaxies
  Jeremy L. Tinker, Risa H. Wechsler, & Zheng Zheng, ApJ, 709, 67 (2010)
• Halo Occupation Distribution Modeling of Clustering of Luminous Red Galaxies
  Zheng Zheng, et al., ApJ, 707, 554
• Red Galaxy Growth and the Halo Occupation Distribution
  Michael J.I. Brown, Zheng Zheng, et al., ApJ, 682, 937 (2008)
• Galaxy Evolution from Halo Occupation Distribution Modeling of DEEP2 and SDSS Galaxy Clustering
  Zheng Zheng, Alison L. Coil, & Idit Zehavi, ApJ, 667, 760 (2007)
• Evidence for Merging or Disruption of Red Galaxies from the Evolution of Their Clustering
  Martin White, Zheng Zheng, et al., ApJ, 655, L69 (2007)
• On the Mass-to-Light Ratio of Large Scale Structure
  J.L. Tinker, D.H. Weinberg, Z. Zheng, & I. Zehavi, ApJ, 631, 41 (2005)
• The Luminosity and Color Dependence of the Galaxy Correlation Function
  I. Zehavi, Z. Zheng, et al., ApJ, 630, 1 (2005)
• Cosmology and the Halo Occupation Distribution from Small-Scale Galaxy Clustering in the Sloan Digital Sky Survey
  Kevork Abazajian, Zheng Zheng, et al., ApJ, 625, 613 (2005)
• Interpreting the Observed Clustering of Red Galaxies at z~3
  Zheng Zheng, ApJ, 610, 61 (2004)
• On Departures from a Power Law in the Galaxy Correlation Function
  Zehavi, I., Weinberg, D., Zheng, Z., Berlind, A., Frieman, J., et al., ApJ, 608, 16 (2004)

• The Clustering of Massive Galaxies at z~0.5 from the First Semester of BOSS Data
  Martin White, et al. ApJ, submitted
• Primordial Non-Gaussianity from LAMOST Surveys
  Yan Gong, Xin Wang, Zheng Zheng, & Xuelei Chen, RAA, 10, 107 (2010)
• Forecasting the Dark Energy Measurement with Baryon Acoustic Oscillations: Prospects for the LAMOST surveys
  Xin Wang, Xuelei Chen, Zheng Zheng, Fengquan Wu, Pengjie Zhang, & Yongheng Zhao, MNRAS, 394, 1775 (2009)
• Detection of the Baryon Acoustic Peak in the Large-Scale Correlation Function of SDSS Luminous Red Galaxies
  D.J. Eisenstein, I. Zehavi, D.W. Hogg, R. Scoccimarro, M.R. Blanton, R.C. Nichol, R. Scranton, H. Seo, M. Tegmark, Z. Zheng, et al., ApJ, 633, 560 (2005)