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The MOSDEF-LRIS Survey: Driving Mechanisms of Galactic-scale Outflows in z~2 Star-forming Galaxies

Presentation #224.08 in the session Evolution of Galaxies IV.

Published onJun 29, 2022
The MOSDEF-LRIS Survey: Driving Mechanisms of Galactic-scale Outflows in z~2 Star-forming Galaxies

Galactic-scale outflows of gas from star-forming galaxies are a crucial component of galaxy evolution, regulating star formation, modulating the metallicity within galaxies, and enriching the intergalactic medium with metals. However, the physical mechanisms that generate and sustain outflows remain an open question. We use a sample of galaxies with moderate-resolution rest-optical spectra from the MOSFIRE Deep Evolution Field (MOSDEF) Survey with additional deep rest-UV spectra from the Keck Low Resolution Imaging Spectrometer (LRIS) to study outflows and physical properties of z~2 galaxies. Using systemic redshifts from strong rest-optical lines, low-ionization interstellar (LIS) metal absorption lines, and Lyα emission, we measure centroid outflow velocities and the highest-velocity component of the outflow from the blue wings of the LIS absorption lines. Outflow velocities are found to be marginally correlated with the global star-formation-rate (SFR). The scaling between outflow velocity and SFR agrees with predictions of outflows driven by mechanical energy from supernovae explosions, as opposed to radiation pressure acting on dusty material. On the other hand, we find no significant correlation between outflow velocity and star-formation rate surface density (ΣSFR), which may be due to the limited dynamic range of ΣSFR probed by our sample. The relationship between outflow velocity and ΣSFR normalized by stellar mass (ΣsSFR) suggests that strong outflows (e.g., >200 km s-1) appear ubiquitous above a threshold ΣsSFR and outflow velocity uncouples from ΣsSFR above the threshold. These results suggest the importance of gravitational potential in the launching of outflows in high-redshift galaxies.

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