CLEAR: Paschen-β Star Formation Rates and Dust Attenuation of Low-redshift Galaxies

We use Paschen-beta (Pa beta; 1282 nm) observations from the Hubble Space Telescope G141 grism to study the star formation and dust-attenuation properties of a sample of 29 low-redshift (z < 0.287) galaxies in the CANDELS Ly alpha Emission at Reionization survey. We first compare the nebular attenuation from Pa beta/H alpha with the stellar attenuation inferred from the spectral energy distribution, finding that the galaxies in our sample are consistent with an average ratio of the continuum attenuation to the nebular gas of 0.44, but with a large amount of excess scatter beyond the observational uncertainties. Much of this scatter is linked to a large variation between the nebular dust attenuation as measured by (space-based) Pa beta to (ground-based) H alpha to that from (ground-based) H alpha/H beta. This implies there are important differences between attenuation measured from grism-based/wide-aperture Pa beta fluxes and the ground-based/slit-measured Balmer decrement. We next compare star formation rates (SFRs) from Pa beta to those from dust-corrected UV. We perform a survival analysis to infer a census of Pa beta emission implied by both detections and nondetections. We find evidence that galaxies with lower stellar mass have more scatter in their ratio of Pa beta to attenuation-corrected UV SFRs. When considering our Pa beta detection limits, this observation supports the idea that lower-mass galaxies experience burstier star formation histories. Together, these results show that Pa beta is a valuable tracer of a galaxy's SFR, probing different timescales of star formation and potentially revealing star formation that is otherwise missed by UV and optical tracers.

Automated summary

By using observations from the Hubble Space Telescope, we studied the properties of star formation and dust attenuation in a sample of low-redshift galaxies. We found that there is a correlation between the stellar and nebular attenuation, and that Paschen-beta can be a valuable tracer of a galaxy's star formation rate.