2020ApJ...904..164N -
Astrophys. J., 904, 164-164 (2020/December-1)
The CGM at Cosmic Noon with KCWI: outflows from a star-forming galaxy at z = 2.071.
NIELSEN N.M., KACPRZAK G.G., POINTON S.K., MURPHY M.T., CHURCHILL C.W. and DAVE R.
Abstract (from CDS):
We present the first results from our "CGM at Cosmic Noon with KCWI" program to study gas flows in the circumgalactic medium (CGM) at z = 2-3. Combining the power of a high-resolution VLT/UVES quasar spectrum, a Hubble Space Telescope/Advanced Camera for Surveys image, and integral field spectroscopy with Keck/KCWI (Keck Cosmic Web Imager), we detected Lyα emission from a 1.7L* galaxy at zgal = 2.0711 associated with a Lyman limit system with weak Mg II (Wr(2796) = 0.24 Å) in quasar field J143040+014939. The galaxy is star-forming (SFRFUV = 37.8 M☉ yr–1) and clumpy: either an edge-on disk (i = 85°) or, less likely, a major merger. The background quasar probes the galaxy at an impact parameter of D = 66 kpc along the projected galaxy minor axis (Φ = 89°). From photoionization modeling of the absorption system, we infer a total line-of-sight CGM metallicity of [Si/H]=-1.5–0.3+0.4. The absorption system is roughly kinematically symmetric about zgal, with a full Mg II velocity spread of ∼210 km s–1. Given the galaxy-quasar orientation, CGM metallicity, and gas kinematics, we interpret this gas as an outflow that has likely swept up additional material. By modeling the absorption as a polar outflow cone, we find the gas is decelerating with average radial velocity Vout = 109-588 km s–1 for half-opening angles of θ0 = 14°-75°. Assuming a constant Vout, it would take on average tout ∼ 111-597 Myr for the gas to reach 66 kpc. The outflow is energetic, with a mass outflow rate of {dot}Mout< 52±37M☉ yr–1 and mass loading factor of η < 1.4 ± 1.0. We aim to build a sample of ∼50 Mg II absorber-galaxy pairs at this epoch to better understand gas flows when they are most actively building galaxies.
Abstract Copyright:
© 2020. The American Astronomical Society. All rights reserved.
Journal keyword(s):
Lyman-alpha galaxies - High-redshift galaxies - Quasar absorption line spectroscopy - Galaxy evolution - Circumgalactic medium
Nomenclature:
Fig. 1, Table 1: [NKP2020] G N=1.
Simbad objects:
8
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