Spatially Resolved Galactic Winds at Cosmic Noon: Outflow Kinematics and Mass Loading in a Lensed Star-Forming Galaxy at z=1.87
arxiv(2024)
摘要
We study the spatially resolved outflow properties of CSWA13, an intermediate
mass (M_*=10^9 M_⊙), gravitationally lensed star-forming
galaxy at z=1.87. We use Keck/KCWI to map outflows in multiple rest-frame
ultraviolet ISM absorption lines, along with fluorescent Si II^* emission,
and nebular emission from C III] tracing the local systemic velocity. The
spatial structure of 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
kms^-1. Using the outflow velocity (v_out), radius (R), column
density (N), and solid angle (Ω) based on the covering fraction, we
measure the mass loss rate
logṁ_out/(M_⊙yr^-1) = 1.73±0.23 and mass
loading factor logη = 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 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.
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