Collaborative Research: Tracing Galaxy Quenching in the Cosmic Web With Spatially-Resolved Star-Formation Maps

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That galaxies in dense clusters appear markedly different from galaxies outside these regions (i.e., in the "field") was recognized even before the true nature of galaxies was recognized. Underlying this observation is the fact that a galaxy’s gas supply and star formation activity also show a marked dependence on environment. The objective of this project is to better understand how both are altered as a galaxy moves through the cosmic web to the cluster centers. The team will quantify environmental "quenching" of star formation by measuring the relative extent of the star-forming and stellar disks for 14,000 nearby galaxies - a factor of 20 increase over previous studies - to disentangle the correlated effects of environment, galaxy mass, and morphology. This award will also involve undergraduate students at both institutions in research, and support outreach efforts to area K-12 students as well as a summer teacher training program. This work will (1) constrain the quenching timescale for the densest environments where gas stripping is known to occur, (2) determine how the network of cosmic filaments around clusters alters the spatial distribution of star formation within galaxies, (3) shed light on how these processes act in different environments to produce the observed changes, and (4) produce a data set with lasting legacy value for studies of galaxy evolution in the nearby universe. The team will fit Sersic models to the sample galaxies and determine the effective radii of the stars (optical grz from the DESI Legacy Surveys and infrared 3.4um from WISE) and star formation (WISE 12um). Non-parametric profiles and total fluxes will also be derived for these galaxies through elliptical aperture photometry using ultraviolet (GALEX), optical grz, and infrared (WISE) images. These complementary techniques will yield robust structural parameters for to galaxy sample. Custom software designed by the team to overcome the challenges associated with measuring photometry of large galaxies will be used, and self-consistent stellar mass and star-formation rates (SFR) will be estimated for the entire sample through the analysis of their ultraviolet through infrared spectral energy distributions. The team will adopt a more sophisticated characterization of galaxy environment by considering filaments as well as cluster and field membership. This is an important addition as recent hydrodynamic simulations suggest that filaments may be important sites of galaxy transformation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.