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

Abstract

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$1~kpc per pixel) Balmer decrement ($H\hat{I}\pm /H{\hat{I}}^2$) 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 ${\mathrm{A}}_{10\%}^{\mathrm{SFR}}$, ${\mathrm{A}}_{50\%}^{\mathrm{SFR}}$, and ${\mathrm{A}}_{90\%}^{\mathrm{SFR}}$ 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 (${\mathrm{A}}_{50\%}^{\mathrm{SFR}}$). This indicates that the bulk of star formation in these galaxies is significantly attenuated by dust. The value of ${\mathrm{A}}_{10\%}^{\mathrm{SFR}}$ 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 ${\mathrm{A}}_{10\%}^{\mathrm{SFR}}$ than ${\mathrm{A}}_{50\%}^{\mathrm{SFR}}$. 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.

12 pages, 5 figures, 2 tables