Connecting Galactic Outflows and Star Formation: Inferences from H-alpha Maps and Absorption Line Spectroscopy at 1 < z < 1.5

TL;DR

This study uses H-alpha maps and absorption spectroscopy to directly link star formation activity with galactic outflows in galaxies at redshifts 1 to 1.5, providing new insights into feedback processes in early universe galaxies.

Contribution

It presents the first direct test of the star formation-outflow relationship at z>1 using H-alpha imaging, combining spectroscopic and imaging data for a comprehensive analysis.

Findings

Fe II and Mg II EWs increase with SFR and SigmaSFR

Outflow velocities are higher in galaxies with elevated SFR, SigmaSFR, and sSFR

Outflows are the primary driver of absorption line profile differences

Abstract

We investigate the connection between galactic outflows and star formation using two independent data sets covering a sample of 22 galaxies between $1 \lesssim z \lesssim 1.5$. The HST WFC3/G141 grism provides low spectral resolution, high spatial resolution spectroscopy yielding H$\alpha$ 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 (SigmaSFR), as well as the stellar mass and specific star formation rate (sSFR). The Fe II and Mg II equivalent widths (EWs) increase with both SFR and SigmaSFR at $\gtrsim 3\sigma$ significance, while the composite spectra show larger Fe II EWs and outflow velocities in galaxies with higher SFR, SigmaSFR, and sSFR. Absorption line profiles of the composite spectra further indicate that the differences between subsamples are driven by outflows rather than the ISM. While these results are consistent with those of previous studies, the use of H$\alpha$ 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, H$\alpha$-based studies to lower masses and star formation rates, probing galactic feedback across orders of magnitude in galaxy properties and augmenting the correlations we find here.