NOAO >   Observing Info >   Approved Programs >   2016B-0200

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Program Information for 2016B-0200


PI: Anja von der Linden, SUNY, anja.vonderlinden@stonybrook.edu
Address: Department of Physics and Astronomy, Stony Brook, NY, 11794-2100 USA

CoI: Steven Allen, Stanford U.
CoI: Adam Mantz, Stanford U.
CoI: Adam Wright, Stanford U.
CoI: Douglas Applegate, Universitat Bonn
CoI: Patrick Kelly, UC Berkeley
CoI: Glenn Morris, Stanford U.
CoI: David Rapetti, Dark Cosmology Centre, Copenhagen

Title: Weighing the f_gas Giants

Abstract: The most massive clusters of galaxies are expected to provide nearly fair samples of the matter content of the Universe. Since the X-ray-emitting cluster gas is by far the dominant baryonic mass component in clusters, measurements of the gas-to-total mass ratio in dynamically relaxed clusters (f_gas) provide an excellent estimate of Omega_b/Omega_m. Employing standard priors on Omega_b and H_0, these data yield some of the most robust constraints on Omega_m, largely independent of the assumed cosmological model. The currently dominant systematic uncertainty on Omega_m stems from uncertainties in total cluster mass estimates, jointly due to temperature calibration uncertainties of X-ray telescopes and the unknown level of non-thermal pressure support in clusters. By comparing X-ray-derived mass estimates with high-quality weak-lensing mass estimates for a subset of f_gas clusters, we can address this uncertainty directly. Currently, the precision on the weak-lensing mass normalization of relaxed clusters is at the 10% level. We here request a modest amount of time to take additional weak lensing observations for a complete subsample of relaxed clusters, which will allow us to cut this uncertainty in half. These observations will enable a 5% precision measurement of Omega_m - a remarkable prospect for the determination of one of the key cosmological parameters from a single experiment.

Program Type: Standard/Extragalactic

Scheduled Nights:
Run 1 (2016B):  GEM-N/HSC -- 1n on Dec 28 2016


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NOAO >   Observing Info >   Approved Programs >   2016B-0200

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