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An Analytic Approach to Assess Galaxy Projection Along A Line of Sight

An Analytic Approach to Assess Galaxy Projection Along A Line of Sight. Anbo Chen University of Michigan. In Collaboration. University of Michigan Gus Evrard, Jiangang Hao, Tim Mckay University of Chicago Matt Becker. Outline. Building a halo model to assess the projection effect

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An Analytic Approach to Assess Galaxy Projection Along A Line of Sight

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  1. An Analytic Approachto Assess Galaxy ProjectionAlong A Line of Sight Anbo Chen University of Michigan

  2. In Collaboration • University of Michigan • Gus Evrard, Jiangang Hao, Tim Mckay • University of Chicago • Matt Becker

  3. Outline • Building a halo model to assess the projection effect • Tuning model parameters to SDSS • Making predictions on expected projection effect • Monte Carlo realizations and applications • Future directions

  4. Building the Analytic Model • Initial power spectrum (Eisenstein & Hu) • Halo-halo correlation (Seljak & Warren) • HOD (Brown et al.) • N(M,z,MB)~(M-Mmin)/Mscale • Color Model (Hao et al.) • G-R mean and sigma for Red and Blue galaxies • Blue fraction in central and satellite galaxies

  5. The Current Color Model

  6. The Color Model (Ctd.) • z~0.6 turn around is not currently well characterized • Crucial on background projections from Red population

  7. Mean Projection Effect Targeting on a dark matter halo (cluster) and calculate the expected projection of galaxies

  8. Projection from Different Epoch

  9. Sensitivity to Magnitude Limit

  10. Comparison to SDSS M-N200 Relationship • Johnston et al. (right panel) has slope = 1.28 +/- 0.04 • Consistent only considering projection effect

  11. Monte Carlo Simulation • Method • Calculate the probability of finding a halo within each volume in space and mass • Calculate the probability of having a galaxy in each volume in N-dim space • Application • Distribution of contamination • Velocity dispersion

  12. Realization in Color Diagram

  13. Application to Velocity Dispersion • The analytic model can help interpret the non-Gaussianity in velocity dispersion and henceforth put corrections on the velocity dispersion

  14. Conclusion • An analytic model built to address the projection effect along line of sight • Parameters tuned to the result from SDSS • Expected projection predicted with cluster size and magnitude limit • Application via Monte Carlo method • Future directions • high redshift • M-N relation • velocity dispersion

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