The Prevalence of Turbulence-Regulated Multiphase Galactic Winds in Star-Forming Galaxies

Abstract

We build upon our previously developed multi-ion radiative transfer (RT) framework, PEACOCK, to investigate the kinematic and energetic structure of cool-to-warm galactic winds in a sample of 50 nearby star-forming galaxies. Using self-consistent constraints derived from joint modeling of Ly-alpha and multiple ultraviolet metal lines, we analyze how bulk outflows and turbulent motions contribute to the dynamics and energy budget of galactic winds in the circumgalactic medium (CGM). We find that macroscopic turbulent velocities are often comparable to, and sometimes exceed, the coherent bulk outflow velocity. The associated turbulent pressure frequently dominates over both microscopic pressure and ram pressure, indicating that turbulence is a major contributor to the kinetic energy budget of the CGM wind. Wind kinematics, ionic column densities, and metal mass outflow rates all scale systematically with stellar mass and star formation rate, demonstrating a strong coupling between stellar feedback and CGM structure. Including turbulent motions strengthens these CGM-galaxy scaling relations and favors an energy-driven feedback regime. The total kinetic energy flux of the cool-to-warm CGM correlates tightly with the mechanical energy injection rate from star formation, implying that stellar feedback provides sufficient power to sustain both coherent outflows and turbulence. Comparisons with phenomenological line-profile fitting methods further show that simplified treatments can introduce systematic biases in inferred wind properties. Together these results support a turbulence-regulated picture of galactic winds in which a substantial fraction of feedback energy is stored in turbulent motions within a multiphase CGM.

Figures (18)

• Figure 1: Line-of-sight ionic column densities of clumps plotted as a function of global galaxy properties. The top panels show $\log N_{\rm ion,\,LOS}$ versus total SFR, and the bottom panels show $\log N_{\rm ion,\,LOS}$ versus total $M_\star$, for six ions: H i, C ii, Si ii, Si iii, C iv, and Si iv. Each panel lists the Spearman rank correlation coefficient $r$ and $p$-value. All ions exhibit positive correlations with both SFR and $M_\star$, with H i, C ii, and Si ii showing $>3\sigma$ significance, while Si iii, C iv and Si iv display weaker trends. These results suggest that the cool, metal-enriched wind component scales with global galaxy growth, consistent with a picture in which stellar feedback enriches and maintains the gas in the CGM.
• Figure 2: Total turbulent velocity of clumps plotted as a function of global galaxy properties. The panels show the correlation between the inferred total turbulent velocity of individual clumps, $v_{\rm turb} = \sqrt{b_{\rm D,\,cl}^2 + \sigma_{\rm cl}^2}$, and both the total SFR (top row) and stellar mass (bottom row) for six ions tracing the cool to warm phases of the CGM. For all metal ions, we find a clear and statistically significant increase of $v_{\rm turb}$ with both SFR and $M_\star$, whereas H i shows no significant correlation in either parameter space. The positive trends for the metal lines suggest that the dynamical state of the metal-enriched wind component scales with galaxy growth and star formation activity. In contrast, the absence of a similar trend in H i may indicate that a substantial fraction of the neutral gas traces a more extended or ambient halo component whose dynamical state is less directly coupled to global galaxy properties.
• Figure 3: Maximum outflow velocity of clumps as a function of global galaxy properties. The figure shows the maximum outflow velocity $v_{\mathrm{out,\,max}}$ inferred from the best-fit RT models. Left panels: maximum clump outflow velocities derived from Ly$\alpha$ alone. Right panels: maximum outflow velocities obtained from joint fitting of all available metal-line transitions. Pearson correlation coefficients $r$ and corresponding $p$-values are indicated in each panel. While $v_{\mathrm{out,\,max}}$ inferred from Ly$\alpha$ alone shows no statistically significant correlation with either SFR or $M_\star$, the joint velocity exhibits strong and highly significant positive correlations with both properties, indicating that the bulk outflow velocity traced by metal lines more closely scales with global star formation activity and stellar mass than measurements based solely on Ly$\alpha$.
• Figure 4: Ion mass outflow rates ($\dot{M}_{\rm ion}$) as a function of global galaxy properties. For H i, we adopt the Ly$\alpha$-derived outflow velocity (scaled by $10^{-2}$ for visual clarity), while metal ions use the joint best-fit outflow velocity obtained from simultaneous modeling of all available transitions. The metal species exhibit statistically significant positive correlations with both SFR and $M_\star$, whereas the H i trend is weaker and displays larger scatter, primarily due to the dispersion in $v_{\rm out,\,max}$. The relative ordering $\dot{M}_{\rm C\,II} \simeq \dot{M}_{\rm C\,IV}$ and $\dot{M}_{\rm Si\,III} > \dot{M}_{\rm Si\,IV} > \dot{M}_{\rm Si\,II}$ mirrors the hierarchy observed in the line-of-sight column densities and suggests that a substantial fraction of the silicon mass resides in intermediate ionization states. Spearman rank coefficients $r$ and corresponding $p$-values are indicated in each panel.
• Figure 5: Comparison between the total silicon mass outflow rate and the expected silicon production rate from star formation. Only galaxies in which all three Si ii/ Si iii/ Si iv profiles are reliably measured are included. The expected silicon production rate, $\dot{M}_{\mathrm{Si,\,prod}}=10^{-3}\,\mathrm{SFR}$, is inferred from Starburst99 models. A moderate positive correlation is observed, indicating that the cool-to-warm silicon mass flux broadly scales with the nucleosynthetic output from star formation. Most galaxies lie below the one-to-one relation (dashed line), suggesting that only a fraction of the freshly synthesized silicon is present in the cool-to-warm phase traced by these ions at a given time. This offset likely reflects incomplete entrainment of metals into the cool-to-warm component of the outflow, with the remaining silicon residing in other wind phases (e.g., highly ionized hot gas), being depleted due to dust extinction, or being recycled back into the ISM.