skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Robust Optical Richness Estimation with Reduced Scatter

Abstract

Reducing the scatter between cluster mass and optical richness is a key goal for cluster cosmology from photometric catalogs. We consider various modifications to the red-sequence matched filter richness estimator of Rozo et al. (2009b), and evaluate their impact on the scatter in X-ray luminosity at fixed richness. Most significantly, we find that deeper luminosity cuts can reduce the recovered scatter, finding that {sigma}{sub ln L{sub X}|{lambda}} = 0.63 {+-} 0.02 for clusters with M{sub 500c} {approx}> 1.6 x 10{sup 14} h{sub 70}{sup -1} M{sub {circle_dot}}. The corresponding scatter in mass at fixed richness is {sigma}{sub ln M|{lambda}} {approx} 0.2-0.3 depending on the richness, comparable to that for total X-ray luminosity. We find that including blue galaxies in the richness estimate increases the scatter, as does weighting galaxies by their optical luminosity. We further demonstrate that our richness estimator is very robust. Specifically, the filter employed when estimating richness can be calibrated directly from the data, without requiring a-priori calibrations of the red-sequence. We also demonstrate that the recovered richness is robust to up to 50% uncertainties in the galaxy background, as well as to the choice of photometric filter employed, so long as the filters span the 4000 {angstrom}more » break of red-sequence galaxies. Consequently, our richness estimator can be used to compare richness estimates of different clusters, even if they do not share the same photometric data. Appendix A includes 'easy-bake' instructions for implementing our optimal richness estimator, and we are releasing an implementation of the code that works with SDSS data, as well as an augmented maxBCG catalog with the {lambda} richness measured for each cluster.« less

Authors:
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1042662
Report Number(s):
SLAC-PUB-15068
Journal ID: ISSN 0004-637X; ASJOAB; arXiv:1104.2089; TRN: US201212%%866
DOE Contract Number:  
AC02-76SF00515
Resource Type:
Journal Article
Journal Name:
Astrophys.J.746:178,2012
Additional Journal Information:
Journal Volume: 746; Journal Issue: 2; Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGY; GALAXIES; IMPLEMENTATION; LUMINOSITY; MODIFICATIONS; Astrophysics,ASTRO

Citation Formats

Rykoff, E.S., /LBL, Berkeley, Koester, B.P., /Chicago U. /Chicago U., KICP, Rozo, E., /Chicago U. /Chicago U., KICP, Annis, J., /Fermilab, Evrard, A.E., /Michigan U. /Michigan U., MCTP, Hansen, S.M., /Lick Observ., Hao, J., /Fermilab, Johnston, D.E., /Fermilab, McKay, T.A., /Michigan U. /Michigan U., MCTP, Wechsler, R.H., and /KIPAC, Menlo Park /SLAC. Robust Optical Richness Estimation with Reduced Scatter. United States: N. p., 2012. Web. doi:10.1088/0004-637X/746/2/178.
Rykoff, E.S., /LBL, Berkeley, Koester, B.P., /Chicago U. /Chicago U., KICP, Rozo, E., /Chicago U. /Chicago U., KICP, Annis, J., /Fermilab, Evrard, A.E., /Michigan U. /Michigan U., MCTP, Hansen, S.M., /Lick Observ., Hao, J., /Fermilab, Johnston, D.E., /Fermilab, McKay, T.A., /Michigan U. /Michigan U., MCTP, Wechsler, R.H., & /KIPAC, Menlo Park /SLAC. Robust Optical Richness Estimation with Reduced Scatter. United States. doi:10.1088/0004-637X/746/2/178.
Rykoff, E.S., /LBL, Berkeley, Koester, B.P., /Chicago U. /Chicago U., KICP, Rozo, E., /Chicago U. /Chicago U., KICP, Annis, J., /Fermilab, Evrard, A.E., /Michigan U. /Michigan U., MCTP, Hansen, S.M., /Lick Observ., Hao, J., /Fermilab, Johnston, D.E., /Fermilab, McKay, T.A., /Michigan U. /Michigan U., MCTP, Wechsler, R.H., and /KIPAC, Menlo Park /SLAC. Thu . "Robust Optical Richness Estimation with Reduced Scatter". United States. doi:10.1088/0004-637X/746/2/178. https://www.osti.gov/servlets/purl/1042662.
@article{osti_1042662,
title = {Robust Optical Richness Estimation with Reduced Scatter},
author = {Rykoff, E.S. and /LBL, Berkeley and Koester, B.P. and /Chicago U. /Chicago U., KICP and Rozo, E. and /Chicago U. /Chicago U., KICP and Annis, J. and /Fermilab and Evrard, A.E. and /Michigan U. /Michigan U., MCTP and Hansen, S.M. and /Lick Observ. and Hao, J. and /Fermilab and Johnston, D.E. and /Fermilab and McKay, T.A. and /Michigan U. /Michigan U., MCTP and Wechsler, R.H. and /KIPAC, Menlo Park /SLAC},
abstractNote = {Reducing the scatter between cluster mass and optical richness is a key goal for cluster cosmology from photometric catalogs. We consider various modifications to the red-sequence matched filter richness estimator of Rozo et al. (2009b), and evaluate their impact on the scatter in X-ray luminosity at fixed richness. Most significantly, we find that deeper luminosity cuts can reduce the recovered scatter, finding that {sigma}{sub ln L{sub X}|{lambda}} = 0.63 {+-} 0.02 for clusters with M{sub 500c} {approx}> 1.6 x 10{sup 14} h{sub 70}{sup -1} M{sub {circle_dot}}. The corresponding scatter in mass at fixed richness is {sigma}{sub ln M|{lambda}} {approx} 0.2-0.3 depending on the richness, comparable to that for total X-ray luminosity. We find that including blue galaxies in the richness estimate increases the scatter, as does weighting galaxies by their optical luminosity. We further demonstrate that our richness estimator is very robust. Specifically, the filter employed when estimating richness can be calibrated directly from the data, without requiring a-priori calibrations of the red-sequence. We also demonstrate that the recovered richness is robust to up to 50% uncertainties in the galaxy background, as well as to the choice of photometric filter employed, so long as the filters span the 4000 {angstrom} break of red-sequence galaxies. Consequently, our richness estimator can be used to compare richness estimates of different clusters, even if they do not share the same photometric data. Appendix A includes 'easy-bake' instructions for implementing our optimal richness estimator, and we are releasing an implementation of the code that works with SDSS data, as well as an augmented maxBCG catalog with the {lambda} richness measured for each cluster.},
doi = {10.1088/0004-637X/746/2/178},
journal = {Astrophys.J.746:178,2012},
issn = {0004-637X},
number = 2,
volume = 746,
place = {United States},
year = {2012},
month = {6}
}