We use Paschen-β (Paβ; 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 Lyα Emission at Reionization survey. We first compare the nebular attenuation from Paβ/Hα 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) Paβ to (ground-based) Hα to that from (ground-based) Hα/Hβ. This implies there are important differences between attenuation measured from grism-based/wide-aperture Paβ fluxes and the ground-based/slit-measured Balmer decrement. We next compare star formation rates (SFRs) from Paβ to those from dust-corrected UV. We perform a survival analysis to infer a census of Paβ emission implied by both detections and nondetections. We find evidence that galaxies with lower stellar mass have more scatter in their ratio of Paβ to attenuation-corrected UV SFRs. When considering our Paβ detection limits, this observation supports the idea that lower-mass galaxies experience “burstier” star formation histories. Together, these results show that Paβ 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.

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We present accretion-disk structure measurements from UV–optical reverberation mapping (RM) observations of a sample of eight quasars at 0.24 < z < 0.85. Ultraviolet photometry comes from two cycles of Hubble Space Telescope monitoring, accompanied by multiband optical monitoring by the Las Cumbres Observatory network and Liverpool Telescopes. The targets were selected from the Sloan Digital Sky Survey Reverberation Mapping project sample with reliable black hole mass measurements from Hβ RM results. We measure significant lags between the UV and various optical griz bands using JAVELIN and CREAM methods. We use the significant lag results from both methods to fit the accretion-disk structure using a Markov Chain Monte Carlo approach. We study the accretion disk as a function of disk normalization, temperature scaling, and efficiency. We find direct evidence for diffuse nebular emission from Balmer and Fe ii lines over discrete wavelength ranges. We also find that our best-fit disk color profile is broadly consistent with the Shakura & Sunyaev disk model. We compare our UV–optical lags to the disk sizes inferred from optical–optical lags of the same quasars and find that our results are consistent with these quasars being drawn from a limited high-lag subset of the broader population. Our results are therefore broadly consistent with models that suggest longer disk lags in a subset of quasars, for example, due to a nonzero size of the ionizing corona and/or magnetic heating contributing to the disk response.