Fiber Collision Correction Method for SDSS DR12 BOSS Power Spectrum

BOSS/eBOSS Collaboration Meeting

Transcript

1. Fiber collisions on the Powerspectrum and Bispectrum ChangHoon Hahn, Mike Blanton, and Roman Scoccmarro 
 NYU CCPP
2. Fiber Collisions Fiber fed spectrographs ~ 7% of galaxies do not have spectroscopic redshift 62’’ angular fiber collision scale BOSS Galaxy weight:
 Nearest neighbor up-weighting Simulations: Las Damas PTHalo Tiling Mock ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM w = wstarwseeing(wrf + wfc 1)
3. Impact on the Powerspectrum ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM Las Damas Simulation Tiling Mock Simulation P(k) nearest neighbor /P(k) true > 10% at k > 0.2 > 20% at k > 0.2
4. Impact on the Powerspectrum ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM Las Damas Simulation Tiling Mock Simulation P(k) nearest neighbor /P(k) true > 10% at k > 0.2 > 20% at k > 0.2 P P using PATCHY (DR12)
5. Impact on the Bispectrum ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM Tiling Mock Simulation B(k) Nearest Neighbor /B(k) True Q(k) Nearest Neighbor /Q(k) True
6. Impact on the Bispectrum ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM Effect of fiber collisions different for bispectrum triangle shape Acute Triangles Obtuse Triangles Extended Triangles PTHalo Simulation
7. Impact on the Bispectrum ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM Effect of fiber collisions different for bispectrum triangle shape Acute Triangles Obtuse Triangles Extended Triangles PTHalo Simulation PATCHY (DR12)
8. Fiber Collision Correction Guo et al. 2012 Fiber collision correction for two-point correlation function using overlapping regions Overlapping region window function is too complex for P(k) and B(k) ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM Guo et al. 2012 Las Damas Simulation
9. Line-of-Sight displacement Distribution ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM ⇠ e | x | ~50-60% fiber collided are correlated (fpeak) Fitting an exponential gives us sigma ~ 5-6 Mpc
10. Fibercollided Pairs dLOS Correction ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM Determine fibercollided galaxies based on 62’’ angular separation Displace galaxies based on the dLOS distribution Recompute nbar(z) and reconstruct random catalogs Reduce systematic effects in P(k) and B(k)! Obtain dLOS distribution from fiber collided galaxies with z (get sigma and fpeak)
11. Results: Powerspectrum ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM fpeak = 100% Las Damas Simulation ⇠ 5% at k > 0.2
12. Results: Bispectrum ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM Acute Triangles Obtuse Triangles Extended Triangles PTHalo Simulation
13. Summary P(k) residuals at k ~ 0.2 reduced by ~5% and B(k)/Q(k) residuals by ~10% using the dLOS distribution of fiber collided galaxies
 Incorporate shot-noise correction that accounts for fiber collisions Compare FKP 1994, Cole et al. 2005, Beutler et al. 2013, etc shot noise calculation methods Further constrain triangle shape dependence in bispectrum
 Ultimately, apply fiber collision correction to CMASS data for P(k) and B(k) measurements ChangHoon Hahn NYU CCPP Dec 5, 2014 Cloudcroft, NM