NGDEEP: A New Non-Parametric Measure of Local Star-Formation and Attenuation at Cosmic Noon

We introduce a new non-parametric technique to quantify the spatially-resolved relationship between the local star-formation rate (SFR) and dust attenuation. We then apply it to 14 star-forming galaxies at $1.0<z<2.5$ using JWST/NIRISS slitless spectroscopy from the NGDEEP survey. First, we construct spatially resolved ($\sim$1~kpc per pixel) Balmer decrement ($Hα/Hβ$) maps of these galaxies and derive their corresponding dust attenuation and intrinsic SFR maps. We then rank-order the map pixels by attenuation and construct a cumulative distribution curve of the total SFR as a function of increasing attenuation. We define $\mathrm{A}^{\mathrm{SFR}}{10%}$, $\mathrm{A}^{\mathrm{SFR}}{50%}$, and $\mathrm{A}^{\mathrm{SFR}}{90%}$ as the dust attenuation levels behind which 10%, 50%, and 90% of the total integrated SFR is screened, respectively. These metrics quantify the probability that a given star-forming region lies behind a given level of attenuation. Across the full sample, 50% of the local star formation occurs behind an attenuation of 3.41 mag or higher ($\mathrm{A}^{\mathrm{SFR}}{50%}$). This indicates that the bulk of star formation in these galaxies is significantly attenuated by dust. The value of $\mathrm{A}^{\mathrm{SFR}}{10%}$ equals 1.45 for the average profile, indicating that even the least attenuated star-forming regions are still highly attenuated. The globally measured attenuation more closely matches $\mathrm{A}^{\mathrm{SFR}}{10%}$ than $\mathrm{A}^{\mathrm{SFR}}_{50%}$. This suggests that the global value is weighted toward the least dust-obscured star-forming regions and significantly underestimates the typical attenuation a star-forming region encounters. Our results demonstrate a new approach for understanding the extremely dusty local conditions of the star-forming interstellar medium in SF galaxies at cosmic noon.

💡 Research Summary

This paper presents a novel non-parametric technique to quantify the spatially resolved relationship between local dust attenuation and star formation in galaxies at cosmic noon (redshift 1.0 < z < 2.5), utilizing data from the JWST NGDEEP survey.

The study analyzes 14 star-forming galaxies observed with the JWST/NIRISS slitless spectrograph. The core methodology involves creating spatially resolved maps (with ~1 kpc per pixel resolution) of the Balmer decrement (Hα/Hβ ratio), a direct tracer of dust attenuation. Assuming an intrinsic ratio of 2.86 for Case-B recombination and applying the Calzetti dust attenuation law, the authors convert these maps into pixel-level measurements of dust attenuation at Hα