What this research found
How does the cosmic web seen by the James Webb Space Telescope in the early universe compare with the web we see nearby and with the one cosmological simulations predict? Three galaxy distributions — the COSMOS-Web catalogue at redshift 5 to 7, a local Sloan Digital Sky Survey sample, and the IllustrisTNG300 simulation at redshift 6 — were sub-sampled to identical galaxy counts inside the same 100-megaparsec comoving cube so that density could not confound the comparison. Nearest-neighbour spacing then separates them, with the simulation landing close to the high-redshift observations and the local survey noticeably more compact.
- Density was matched by construction. All three catalogues were reduced to 3,179 galaxies inside a 100-by-100-by-100 megaparsec comoving cube, a mean number density of 3.179 thousandths per cubic megaparsec, so remaining structural differences cannot be an artefact of one dataset simply containing more objects.
- Median nearest-neighbour separation is 2.54 megaparsecs in the COSMOS-Web field at redshift 5 to 7 and 2.39 megaparsecs in the IllustrisTNG300 simulation at redshift 6, placing the simulation close to the observed high-redshift spacing.
- The local Sloan Digital Sky Survey sample is the most compact of the three at 1.65 megaparsecs, which is attributed to its radial coordinate being measured in redshift space rather than to a physical difference in how tightly its galaxies cluster.
How it was done
Three galaxy distributions were put on a common footing: the COSMOS-Web catalogue observed at redshift 5 to 7, a local sample from Sloan Digital Sky Survey Data Release 17, and the IllustrisTNG300 cosmological simulation at redshift 6. Each was sub-sampled to the same number of galaxies inside a 100-megaparsec comoving reference cube, equalising mean number density and removing the most obvious confounder in any clustering comparison. The standardised three-dimensional point clouds were then characterised by their nearest-neighbour distance distributions and projected for visual inspection, forming the input to a graph-topology comparison of the three.
Data sources
- COSMOS-Web catalogue from the James Webb Space Telescope — galaxies at redshift 5 to 7
- Sloan Digital Sky Survey Data Release 17 — local galaxy sample
- IllustrisTNG300 cosmological simulation at redshift 6
Limitations
The Sloan sample's radial coordinate is measured in redshift space rather than real space, which compresses its apparent galaxy spacing and limits how directly it can be compared with the other two distributions.
How this research was produced
K-Dense Web planned and ran this astrophysics investigation end to end — gathering the sources, carrying out the analysis, producing the figures, and drafting the report. The full session transcript, including every intermediate step, is available to view.
