Zixuan Peng (UCSB)

Galactic outflows drive the baryon cycle between galaxies and their circumgalactic media, regulating star formation and chemical enrichment across cosmic time. However, accurately measuring how much mass, momentum, and energy these outflows transport remains challenging. Most observational studies rely on integrated spectra, which blend distinct outflow structures and obscure outflow geometry. In this talk, I will present a spatially resolved outflow study of 37 local star-forming dwarf galaxies observed with Keck/ESI and Keck/KCWI+KCRM, comprising 16 high-mass and 21 low-mass systems divided at M* ~ 5 × 108 M. We constrain the outflow kinematics through multi-component analysis of the strongest emission lines ([O III] 5007 or H), disentangling slower expanding superbubbles from very-broad (VB) emission wings (≳ 1000 km/s) that trace fast-outflowing cold clouds (~ 104 K) entrained in hot winds (~ 106–107 K). In low-mass galaxies, these fast-outflowing cold clouds escape through highly anisotropic blowout channels rather than simple spherical or biconical geometries, with more spatially extended VB emission associated with rising star formation histories and higher star formation rate surface densities over the past 10 Myr. In contrast, high-mass galaxies exhibit more ordered velocity fields and relatively steady radial outflow properties shaped by disk rotation and large-scale biconical winds. We also find that low-mass galaxies show shallower emission-line broad wings (i.e., a more gradual decline in emission strength toward higher velocities) compared to high-mass galaxies. Our analysis suggests that reproducing the shallow wings in low-mass galaxies requires more rapid radial acceleration and a more slowly declining density profile than in high-mass systems. Finally, I will outline ongoing work toward constructing a self-consistent multiphase galactic wind model that jointly predicts emission-line surface brightnesses, absorption-line column densities, and their corresponding line profiles and kinematics.