Do Filaments Influence Galaxies Beyond Local Environment? A Roman Census of Galaxy-Filament Connectivity
| Program ID | 19054 |
|---|---|
| Science Category | Galaxies |
| Program Type | Analysis |
| Category | Medium |
| Principal Investigator | Jiani Ding |
| PI Institution | University of Arizona |
| Co-Investigators |
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| Abstract | Large-scale structure (LSS) in the Universe forms a cosmic web of clusters, filaments, sheets, and voids that connect the dark matter halos where galaxies form and evolve. In the standard paradigm, galaxy evolution is primarily regulated by local environments such as halo mass and galaxy density. However, recent observations suggest that the LSS may also play a direct role, with galaxies near filaments showing systematically different properties at fixed halo mass. Current spectroscopic surveys lack the depth and uniform coverage required to reconstruct filaments beyond the local Universe, leaving the role of LSS at z > 0.5 largely unconstrained. We propose a large statistical test of galaxy–filament connectivity at z~0.5-1 using emission-line galaxies (ELGs) from the Roman HLWAS deep-tier G150 grism. Roman’s wide-area slitless grism will enable the construction of multiple redshift snapshots across this key epoch following the peak of cosmic star formation. In each snapshot, we will reconstruct the filaments and measure each galaxy’s distance to the nearest filament skeleton. By comparing the cumulative distance distributions of extreme emission-line galaxies (EELGs) and normal ELGs while controlling for stellar mass and local density, we will perform a decisive yes–or–no test for whether cosmic filaments directly regulate galaxy evolution. We will further quantify correlations between filaments and galaxy stellar mass, star-formation rate, and morphology. With ~10^6 spectroscopically confirmed line emitters, this program represents the most statistically powerful experiment at z~0.5-1 for testing whether cosmic filaments directly regulate galaxy evolution beyond the influence of halo mass and local environment. The main deliverables are: (1) A high purity emission line galaxy atlas and the automatic ELG survey pipeline. (2) A catalog of filaments, overdensities, and protoclusters. (3) Galaxy property statistics as a function of their large-scale environments. |