The Outflowing [OII] Nebulae of Compact Starburst Galaxies at z $\sim$ 0.5

• Main Authors: Perrotta, Serena, Coil, Alison L, Rupke, David S. N, Ning, Wenmeng, Duong, Brendan, Diamond-Stanic, Aleksandar M, Fielding, Drummond B, Geach, James E, Hickox, Ryan C, Moustakas, John, Rudnick, Gregory H, Sell, Paul H, Swiggum, Cameren N, Tremonti, Christy A
• Format: Journal Article
• Language: English
• Published: 16.09.2024
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.2409.10013

High-velocity outflows are ubiquitous in compact, massive (M$_* \sim$ 10$^{11}$ M$_{\odot}$), z $\sim$ 0.5 galaxies with extreme star formation surface densities ($\Sigma_{SFR} \sim$ 2000 M$_{\odot}$ yr$^{-1}$ kpc$^{-2}$). We have previously detected and characterized these outflows using MgII absorption lines. To probe their full extent, we present Keck/KCWI integral field spectroscopy of the [OII] and MgII emission nebulae surrounding all of the 12 galaxies in this study. We find that [OII] is more effective than MgII in tracing low surface brightness, extended emission in these galaxies. The [OII] nebulae are spatially extended beyond the stars, with radial extent R$_{90}$ between 10 and 40 kpc. The nebulae exhibit non-gravitational motions, indicating galactic outflows with maximum blueshifted velocities ranging from -335 to -1920 km s$^{-1}$. The outflow kinematics correlate with the bursty star formation histories of these galaxies. Galaxies with the most recent bursts of star formation (within the last $<$ 3 Myr) exhibit the highest central velocity dispersions ($\sigma >$ 400 km s$^{-1}$), while the oldest bursts have the lowest-velocity outflows. Many galaxies exhibit both high-velocity cores and more extended, slower-moving gas indicative of multiple outflow episodes. The slower, larger outflows occurred earlier and have decelerated as they propagate into the CGM and mix on timescales $>$ 50 Myr.