Accelerating galaxy winds during the big bang of starbursts

Abstract

We develop a new method to infer the temporal, geometric, and energetic properties of galaxy outflows, by combining stellar spectral modeling to infer starburst ages, and absorption lines to measure velocities. If winds are accelerated with time during a starburst event, then these two measurements enable us to solve for the wind radius, similarly to length scales and the Hubble parameter in Big Bang cosmology. This wind radius is the vital, but hard-to-constrain parameter in wind physics. We demonstrate the method using spectra of 87 starburst galaxies at z = 0.05 − 0.44, finding that winds accelerate throughout the starburst phase and grow to typical radii of ≈1 kpc in ≈10 Myr. Mass flow rates increase rapidly with time, and the mass-loading factor exceeds unity at about 10 Myr – while still being accelerated, the gas will likely unbind from the local potential and enrich the circumgalactic medium. We model the mechanical energy available from stellar winds and supernovae, and estimate that a negligible amount is accounted for in the cool outflow at early times. However, the energy deposition increases rapidly and ∼10% of the budget is accounted for in the cool flow at 10 Myr, similar to some recent hydrodynamical simulations. We discuss how this model can be developed, especially for high-redshift galaxies.

Spectral Shapes of the Lya Emission from Galaxies. II. the influence of stellar properties and nebular conditions on the emergent Lya profiles

“…Our interpretation is that the larger amounts of absorbing gas are actually due to a more extended halo -in this scenario the line-of-sight distance grows to provide a greater column density and deeper absorption. Since the galaxies with strongest absorption are also found to be more evolved, this would also support the scenario in which wind envelopes are built up successively with time (Hayes 2023). At larger foreground distances, both scattering into the line of sight ('resonant infilling') and fluorescent emission towards the observer become successively less likely for geometric reasons.…”

“…𝑄 0 for H ) and the mechanical energy returned to the interstellar medium by both winds from massive stars and supernova explosions. Inferences from these quantities were the subject of Hayes (2023) and the software formed the basis for calculations in Sirressi et al (2022). Finally we also obtain a measurement of the internal dust reddening experienced by the stellar continuum, in addition to the nebular reddening from H Balmer emission.…”

“…Indeed, it is for this reason that we resort to stacking analyses for UV absorption line measurements. However, we studied these quantities in detail in Hayes (2023) in exactly the same dataset, using the same sub-bins for stacking. In that paper we showed that the covering of cool gas, and consequently the outflow rate and mass loading factors increase over the duration of the starburst episode.…”

On the Sizes of Ionized Bubbles Around Galaxies During the Reionization Epoch. The Spectral Shapes of the Lyα Emission from Galaxies

“…All spectra are first continuum-subtracted using the modeled continuum spectra described in Hayes et al (2023) and Hayes (2023). We then shift all spectra into the rest frame, using the systemic redshifts measured from optical emission linesaverage stacks of these spectra are shown in the left panel of Figure 2, where each has been normalized by the luminosity in the red Lyα peak before combination.…”

CLusters in the Uv as EngineS (CLUES). II. Subkiloparsec-scale Outflows Driven by Stellar Feedback

“…In this study, we primarily make use of far-ultraviolet (FUV) observations provided by the Hubble Space Telescope (HST) to trace the neutral and ionized phases of the atomic gas. FUV spectroscopy contains a wealth of information, not only about the stellar population (Wofford et al 2013;Chisholm et al 2019;Hernandez et al 2019;Leitherer 2020;Sirressi et al 2022;Hayes 2023) but also about the ISM that lies along the line of sight to the starburst. The gas absorbs the FUV light produced by the FUV continuum source, allowing the observer to infer the kinematics, the column density, and the size of the gas clouds in the surrounding ISM, and tracing for example outflowing gas.…”