Galaxy Cluster Mass Estimation from Stacked Spectroscopic Analysis

Arya Farahi; August E. Evrard; Eduardo Rozo; Eli S. Rykoff; Risa H. Wechsler

doi:10.1093/mnras/stw1143

paper

Galaxy Cluster Mass Estimation from Stacked Spectroscopic Analysis

arXiv:1601.05773 · doi:10.1093/mnras/stw1143

Abstract

We use simulated galaxy surveys to study: i) how galaxy membership in redMaPPer clusters maps to the underlying halo population, and ii) the accuracy of a mean dynamical cluster mass, $M_{σ} (λ)$ , derived from stacked pairwise spectroscopy of clusters with richness $λ$ . Using $\sim 130, 000$ galaxy pairs patterned after the SDSS redMaPPer cluster sample study of Rozo et al. (2015 RMIV), we show that the pairwise velocity PDF of central--satellite pairs with $m_{i} < 19$ in the simulation matches the form seen in RMIV. Through joint membership matching, we deconstruct the main Gaussian velocity component into its halo contributions, finding that the top-ranked halo contributes $\sim 60%$ of the stacked signal. The halo mass scale inferred by applying the virial scaling of Evrard et al. (2008) to the velocity normalization matches, to within a few percent, the log-mean halo mass derived through galaxy membership matching. We apply this approach, along with mis-centering and galaxy velocity bias corrections, to estimate the log-mean matched halo mass at $z = 0.2$ of SDSS redMaPPer clusters. Employing the velocity bias constraints of Guo et al. (2015), we find $⟨ ln (M_{200 c}) ∣ λ ⟩ = ln (M_{30}) + α_{m} ln (λ /30)$ with $M_{30} = 1.56 \pm 0.35 \times 1 0^{14} M_{⊙}$ and $α_{m} = 1.31 \pm 0.0 6_{s t a t} \pm 0.1 3_{sy s}$ . Systematic uncertainty in the velocity bias of satellite galaxies overwhelmingly dominates the error budget.

14 pages, 7 figures

Galaxy Cluster Mass Estimation from Stacked Spectroscopic Analysis

Abstract

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