http://arxiv.org/abs/2002.08516
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, an HST/ACS image, and integral field spectroscopy with Keck/KCWI, we detected Lya emission from a $3.7L_{\ast}$ galaxy at $z_{\rm gal}=2.0711$ associated with a Lyman limit system with weak MgII ($W_r(2796)=0.24$ Ang) in quasar field J143040$+$014939. The galaxy is best modeled as a star-forming (SFR${\rm FUV}=37.8$ M${\odot}$ yr$^{-1}$) clumpy edge-on disk ($i=85^{\circ}$). The background quasar probes the galaxy at an impact parameter of $D=66$ kpc along the projected galaxy minor axis ($\Phi=89^{\circ}$). From photoionization modeling of the absorption system, which includes Lya, MgII, SiII, SiIII, SiIV, and CIV, we infer a total line-of-sight CGM metallicity of ${\rm [Si/H]}=-1.5^{+0.4}{-0.3}$. The absorption system is roughly kinematically symmetric about the galaxy redshift, with a full MgII velocity spread of $\sim210$ km s$^{-1}$. Given the galaxy–quasar orientation, CGM metallicity, and gas kinematics, we interpret this gas as outflowing from the host galaxy. By modeling the absorption as a polar outflow cone, we find the gas is decelerating with radial velocity $V{\rm out}=100-350$ km s$^{-1}$ for half opening angles of $\theta_0=20^{\circ}-80^{\circ}$. Assuming a constant $V_{\rm out}$, it would take $\sim190-650$ Myr for the gas to reach 66 kpc. The outflow is energetic, with a mass outflow rate of $\dot{M}{\rm out}=45-51$ M${\odot}$ yr$^{-1}$ and mass loading factor of $\eta\sim1.3$. We aim to build a sample of $\sim50$ MgII absorber–galaxy pairs at this epoch to better understand gas flows when they are most actively building galaxies.
N. Nielsen, G. Kacprzak, S. Pointon, et. al.
Fri, 21 Feb 20
33/67
Comments: 23 pages, 9 figures, 5 tables. Submitted to ApJ 5 Sep 2019, resubmitted to ApJ 19 Feb 2020
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