James Webb Space Telescope Feed Post

FRESCO: The Paschen-a Star Forming Sequence at Cosmic Noon

SFR, derived from Paa emission line measurements, plotted against stellar mass, derived from EAzY SED fitting. Galaxies in our sample are shown as either star forming (blue points) or quenched (red points), defined using the UVJ diagram in Figure 2. The SFS scatter is similar to that found in the empirical relation between L(PaA) and rest-frame NIR magnitude. The dashed grey horizontal line indicates our completeness limit for compact sources, below which we cannot make any definitive statements on the SFR distributions. Spatially resolved Paschen-a emission line maps are shown for a selection of galaxies in our sample, with their locations relative to the distribution of data. For each galaxy, the left panel shows the RGB image, constructed by combining the F182M, F210M, and F444W bands, and the right panel shows the Paschen-a emission line map with 1” scaling shown. The size of the 0.7” circular aperture used for the photometric measurements are shown in both panels as well. Abstract: We present results from the JWST First Reionization Epoch Spectroscopically Complete Observations survey (FRESCO) on the star forming sequence of galaxies at 1.09.5M? that are lower than found in many earlier studies by up to 0.6 dex, but in good agreement with recent results obtained with the Prospector fitting framework. The difference log(SFR(Paa)-SFR(Prospector)) is -0.09 ± 0.04 dex at 1010-11M?. We also measure the empirical relation between Paschen-a luminosity and rest-frame H band magnitude and find that the scatter is only 0.04 dex lower than that of the SFR-M* relation and is much lower than the systematic differences among relations in the literature due to various methods of converting observed measurements to physical properties. We additionally identify examples of sources -- that, with standard cutoffs via the UVJ diagram, would be deemed quiescent -- with significant, typically extended, Paschen-a emission. Our results may be indicative of the potential unification of methods used to derive the star forming sequence with careful selection of star forming galaxies and independent star formation rate and stellar mass indicators.