An optical observational cluster mass function at z ∼ 1 with the ORELSE survey
Abstract
We present a new mass function of galaxy clusters and groups using optical/nearinfrared (NIR) wavelength spectroscopic and photometric data from the Observations of Redshift Evolution in LargeScale Environments (ORELSE) survey. At z ~ 1, cluster mass function studies are rare regardless of wavelength and have never been attempted from an optical/NIR perspective. This work serves as a proof of concept that z ~ 1 cluster mass functions are achievable without supplemental Xray or SunyaevZel'dovich data. Measurements of the cluster mass function provide important contraints on cosmological parameters and are complementary to other probes. With ORELSE, a new cluster finding technique based on Voronoi tessellation Monte Carlo (VMC) mapping, and rigorous purity and completeness testing, we have obtained ~240 galaxy overdensity candidates in the redshift range 0.55 < z < 1.37 at a mass range of 13.6 < log (M/M_{⊙}) < 14.8. This mass range is comparable to existing optical cluster mass function studies for the local universe. Our candidate numbers vary based on the choice of multiple input parameters related to detection and characterization in our cluster finding algorithm, which we incorporated into the mass function analysis through a Monte Carlo scheme. We find cosmological constraints on the matter density, Ω_{m}, and the amplitude of fluctuations, σ_{8}, of $\Omega _{m} = 0.250^{+0.104}_{0.099}$ and $\sigma _{8} = 1.150^{+0.260}_{0.163}$. While our Ω_{m} value is close to concordance, our σ_{8} value is ~2σ higher because of the inflated observed number densities compared to theoretical mass function models owing to how our survey targeted overdense regions. With Euclid and several other large, unbiased optical surveys on the horizon, VMC mapping will enable optical/NIR cluster cosmology at redshifts much higher than what has been possible before.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 April 2021
 DOI:
 10.1093/mnras/stab300
 arXiv:
 arXiv:2101.02215
 Bibcode:
 2021MNRAS.502.3942H
 Keywords:

 techniques: photometric;
 techniques: spectroscopic;
 galaxies: clusters: general;
 galaxies: groups: general;
 cosmological parameters;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 13 pages, 8 figures, submitted to MNRAS