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

Creators: Prusinski, Nikolaus Z.; Erb, Dawn K.; Martin, Crystal L.

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 (Σ_(SFR)), as well as the stellar mass and specific SFR (sSFR). The Fe ii and Mg ii equivalent widths (EWs) increase with both SFR and Σ_(SFR) at ≳3σ significance, while the composite spectra show larger Fe ii EWs and outflow velocities in galaxies with higher SFR, Σ_(SFR), 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.

Additional Information

© 2021. The American Astronomical Society. Received 2020 September 28; revised 2021 January 8; accepted 2021 February 18; published 2021 April 8. This work is based in part on observations taken by the 3D-HST Treasury Program (GO 12177 and 12328) with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors thank the referee for a thorough and constructive report, as well as Gabriel Brammer for useful discussions and support with Grizli. N.Z.P. was supported by the University of Wisconsin-Milwaukee's Office of Undergraduate Research through the Support for Undergraduate Research Fellows (SURF) Award and Senior Excellence in Research Award (SERA). D.K.E. and N.Z.P. are supported by the US National Science Foundation (NSF) through the Faculty Early Career Development (CAREER) Program grant AST-1255591 and the Astronomy & Astrophysics grant AST-1909198. C.L.M. is supported by NSF grant AST-1817125. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: HST (WFC3/G141), Keck:II (DEIMOS). Software: Grizli (Brammer 2019), astropy (The Astropy Collaboration et al. 2013, 2018), AstroDrizzle (Gonzaga 2012), DEEP2 Reduction Pipeline (Cooper et al. 2012; Newman et al. 2013).

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Accepted Version - 2102.10187.pdf

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