Connecting Galactic Outflows and Star Formation: Inferences from Hα Maps and Absorption-line Spectroscopy at 1 ≲ z ≲ 1.5* †

Abstract

Abstract We investigate the connection between galactic outflows and star formation using two independent data sets covering a sample of 22 galaxies between 1 ≲ z ≲ 1.5. The Hubble Space Telescope WFC3/G141 grism provides low spectral resolution, high spatial resolution spectroscopy yielding Hα emission-line maps from which we measure the spatial extent and strength of star formation. In the rest-frame near-UV, Keck/DEIMOS observes Fe ii and Mg ii interstellar absorption lines, which provide constraints on the intensity and velocity of the outflows. We compare outflow properties from individual and composite spectra with the star formation rate (SFR) and SFR surface density (ΣSFR), as well as the stellar mass and specific SFR (sSFR). The Fe ii and Mg ii equivalent widths (EWs) increase with both SFR and ΣSFR at ≳3σ significance, while the composite spectra show larger Fe ii EWs and outflow velocities in galaxies with higher SFR, ΣSFR, and sSFR. Absorption-line profiles of the composite spectra further indicate that the differences between subsamples are driven by outflows rather than the interstellar medium. While these results are consistent with those of previous studies, the use of Hα images makes them the most direct test of the relationship between star formation and outflows at z > 1 to date. Future facilities such as the James Webb Space Telescope and the upcoming Extremely Large Telescopes will extend these direct, Hα-based studies to lower masses and SFRs, probing galactic feedback across orders of magnitude in galaxy properties and augmenting the correlations we find here.