Abstract
We study the spatially resolved outflow properties of CSWA13, an intermediate-mass (M* = 109 M⊙), gravitationally lensed star-forming galaxy at z = 1.87. We use Keck/KCWI to map outflows in multiple rest-frame UV interstellar medium (ISM) absorption lines, along with fluorescent Si ii* emission, and nebular emission from C iii] tracing the local systemic velocity. The spatial structure of the outflow velocity mirrors that of the nebular kinematics, which we interpret to be a signature of a young galactic wind that is pressurizing the ISM of the galaxy but is yet to burst out. From the radial extent of Si ii* emission, we estimate that the outflow is largely encapsulated within 3.5 kpc. We explore the geometry (e.g., patchiness) of the outflow by measuring the covering fraction at different velocities, finding that the maximum covering fraction is at velocities v ≃ −150 km s−1. Using the outflow velocity (vout), radius (R), column density (N), and solid angle (Ω) based on the covering fraction, we measure the mass-loss rate log m ̇ out / ( M ⊙ yr − 1 ) = 1.73 ± 0.23 and mass loading factor log η = 0.04 ± 0.34 for the low-ionization outflowing gas in this galaxy. These values are relatively large and the bulk of the outflowing gas is moving with speeds less than the escape velocity of the galaxy halo, suggesting that the majority of the outflowing mass will remain in the circumgalactic medium and/or recycle back into the galaxy. The results support a picture of high outflow rates transporting mass and metals into the inner circumgalactic medium, providing the gas reservoir for future star formation.
| Original language | English |
|---|---|
| Article number | 105 |
| Journal | Astrophysical Journal |
| Volume | 981 |
| Issue number | 2 |
| DOIs | |
| State | Published - Mar 10 2025 |
Bibliographical note
Publisher Copyright:© 2025. The Author(s). Published by the American Astronomical Society.
Funding
We would like to thank Simon Gazagnes for his help with the Voigt fitting code, and Danielle Berg, Bethan James, and John Chisholm for their insightful discussions. K.V.G.C., T.J., S.R., and K.M. gratefully acknowledge financial support from the National Science Foundation through grant AST-2108515, the Gordon and Betty Moore Foundation through Grant GBMF8549, NASA through grant HST-GO-16773, and from a Dean's Faculty Fellowship. A.J.S. was supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51492 from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. This research was supported by the Australian Research Council Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), through project number CE170100013. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
| Funders | Funder number |
|---|---|
| John Chisholm | |
| W. M. Keck Foundation | |
| University of California, Los Angeles | |
| National Aeronautics and Space Administration | HST-GO-16773, HST-HF2-51492 |
| National Aeronautics and Space Administration | |
| Gordon and Betty Moore Foundation | GBMF8549 |
| Gordon and Betty Moore Foundation | |
| Space Telescope Science Institute | NAS5-26555 |
| Space Telescope Science Institute | |
| U.S. Department of Energy Chinese Academy of Sciences Guangzhou Municipal Science and Technology Project Oak Ridge National Laboratory Extreme Science and Engineering Discovery Environment National Science Foundation National Energy Research Scientific Computing Center National Natural Science Foundation of China | AST-2108515 |
| U.S. Department of Energy Chinese Academy of Sciences Guangzhou Municipal Science and Technology Project Oak Ridge National Laboratory Extreme Science and Engineering Discovery Environment National Science Foundation National Energy Research Scientific Computing Center National Natural Science Foundation of China | |
| Centre of Excellence for Integrative Brain Function, Australian Research Council | CE170100013 |
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science