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تسجيل مستخدم جديدCLEAR: Paschen-$beta$ Star Formation Rates and Dust Attenuation of Low Redshift Galaxies
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We use Pa$beta$ (1282~nm) observations from the Hubble Space Telescope ($textit{HST}$) G141 grism to study the star formation and dust attenuation properties of a sample of 32 low redshift ($z < 0.287$) galaxies in the CLEAR survey. Many of the galaxies in the sample have significantly higher Pa$beta$ emission than expected from the star formation rates (SFRs) measured from their (attenuation-corrected) UV continuum or H$alpha$ emission, suggesting that Pa$beta$ is revealing star formation that is otherwise hidden within gas that is optically thick to UV-continuum and Balmer line emission. Galaxies with lower stellar mass tend to have more scatter in their ratio of Pa$beta$ to attenuation-corrected UV SFRs. When considering our Pa$beta$ detection limits, this observation is consistent with burstier star formation histories in lower mass galaxies. We also find a large amount of scatter between the nebular dust attenuation measured by Pa$beta$/H$alpha$ and H$alpha$/H$beta$, implying that the Balmer decrement underestimates the attenuation in galaxies across a broad range of stellar mass, morphology, and observed Balmer decrement. Comparing the nebular attenuation from Pa$beta$/H$alpha$ with the stellar attenuation inferred from the spectral energy distribution, our galaxies are consistent with an average stellar to nebular ratio of 0.44, but with a large amount of excess scatter beyond the observational uncertainties. Together, these results show that Pa$beta$ is a valuable tracer of a galaxys star formation rate, often revealing star formation that is otherwise missed by UV and optical tracers.
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