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# Cosmological Constraints on Ω m and σ 8 from Cluster Abundances Using the GalWCat19 Optical-spectroscopic SDSS Catalog

## Details

**Authors** Abdullah et al.

**Year** 2020

**Publisher** The Astrophysical Journal

**Discipline** Mathematics

[Read it at the publisher](https://doi.org/10.3847/1538-4357/aba619) 
10.3847/1538-4357/aba619

## In authors' words

### Abstract

We derive cosmological constraints on the matter density, , and the amplitude of fluctuations, , using , a catalog of 1800 galaxy clusters we identified in the Sloan Digital Sky Survey-DR13 spectroscopic data set using our GalWeight technique to determine cluster membership. By analyzing a subsample of 756 clusters in a redshift range of 0.045 ≤ z ≤ 0.125 and virial masses of M ≥ 0.8 × 10 14 with mean redshift of z = 0.085, we obtain (systematic) and (systematic), with a cluster normalization relation of . There are several unique aspects to our approach: we use the largest spectroscopic data set currently available, and we assign membership using the GalWeight technique, which we have shown to be very effective at simultaneously maximizing the number of bona fide cluster members while minimizing the number of contaminating interlopers. Moreover, rather than employing scaling relations, we calculate cluster masses individually using the virial mass estimator. Since is a low-redshift cluster catalog we do not need to make any assumptions about evolution either in cosmological parameters or in the properties of the clusters themselves. Our constraints on and are consistent and very competitive with those obtained from non-cluster abundance cosmological probes such as cosmic microwave background, baryonic acoustic oscillation (BAO), and supernovae. The joint analysis of our cluster data with Planck18+BAO+Pantheon gives and .

### What they set out to do (purpose)

To determine how much of the universe is made up of matter.

### What they found (results)

They determined that 31% of the universe is made up of matter, while the other 69% consists of dark energy.

## Commentary

### In short

Their Distinction-making between matter and dark energy lead to a greater understanding of our universe. In fact, using the identity-other rule, we can even say that most of our universe is not matter, or an “other” to matter.

### In more detail

Abdullah et al. set out to measure the total amount of matter in the universe. They determined that 31% of the universe is made up of matter, while the other 69% consists of dark energy. Their

Distinction-making between matter and dark energy lead to a greater understanding of our universe. In fact, using the identity-other rule, we can even say that most of our universe is not matter, or an “other” to matter. In order to measure this, they used a part-whole Systems mentality, where they measured the mass and number of known galaxy clusters, and used numerical predictions to extrapolate to the whole universe showing the utility of both the Distinction and Systems rule to answer complex questions that have huge implications.

**Patterns it shows** D

**How to cite this** Abdullah et al. (2020). Cosmological Constraints on Ω m and σ 8 from Cluster Abundances Using the GalWCat19 Optical-spectroscopic SDSS Catalog. The Astrophysical Journal.