TY - JOUR
T1 - The Keck Baryonic Structure Survey
T2 - Using foreground/background galaxy pairs to trace the structure and kinematics of circumgalactic neutral hydrogen at z ∼ 2
AU - Chen, Yuguang
AU - Steidel, Charles C.
AU - Hummels, Cameron B.
AU - Rudie, Gwen C.
AU - Dong, Bili
AU - Trainor, Ryan F.
AU - Bogosavljević, Milan
AU - Erb, Dawn K.
AU - Pettini, Max
AU - Reddy, Naveen A.
AU - Shapley, Alice E.
AU - Strom, Allison L.
AU - Theios, Rachel L.
AU - Faucher-Giguère, Claude André
AU - Hopkins, Philip F.
AU - Kereš, Dušan
N1 - Funding Information:
This work was supported in part by grant AST-1313472 from the US NSF, and by a grant from the Caltech/JPL President's and Director's Program. CAFG was supported by NSF through grants AST-1517491, AST-1715216, and CAREER award AST- 1652522, byNASAthrough grant 17-ATP17-0067, by STScI through grants HST-GO-14681.011, HST-GO-14268.022-A, and HST-AR- 14293.001-A, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement
Publisher Copyright:
© 2020 The Author(s).
PY - 2020/12/1
Y1 - 2020/12/1
N2 - We present newmeasurements of the spatial distribution and kinematics of neutral hydrogen in the circumgalactic and intergalactic medium surrounding star-forming galaxies at z ∼ 2. Using the spectra of ≃3000 galaxies with redshifts 〈z〉 = 2.3 ± 0.4 from the Keck Baryonic Structure Survey,we assemble a sample ofmore than 200 000 distinct foreground-background pairs with projected angular separations of 3-500 arcsec and spectroscopic redshifts, with 〈zfg〉 = 2.23 and 〈zbg〉 = 2.57 (foreground, background redshifts, respectively.) The ensemble of sightlines and foreground galaxies is used to construct a 2D map of the mean excess HI Ly α optical depth relative to the intergalactic mean as a function of projected galactocentric distance (20 ≲ Dtran/pkpc ≲ 4000) and line-of-sight velocity. We obtain accurate galaxy systemic redshifts, providing significant information on the line-of-sight kinematics of HI gas as a function of projected distance Dtran. We compare the map with cosmological zoom-in simulation, finding qualitative agreement between them. A simple two-component (accretion, outflow) analytical model generally reproduces the observed line-of-sight kinematics and projected spatial distribution of HI. The best-fitting model suggests that galaxy-scale outflows with initial velocity vout ≃ 600 km s-1 dominate the kinematics of circumgalactic HI out to Dtran ≃ 50 kpc, while HI at Dtran ≳100 kpc is dominated by infall with characteristic vin ≲circular velocity. Over the impact parameter range 80≲Dtran/pkpc ≲ 200, the HI line-of-sight velocity range reaches a minimum, with a corresponding flattening in the rest-frame Ly α equivalent width. These observations can be naturally explained as the transition between outflow-dominated and accretion-dominated flows. Beyond Dtran ≃ 300 pkpc (∼1 cMpc), the line-of-sight kinematics are dominated by Hubble expansion.
AB - We present newmeasurements of the spatial distribution and kinematics of neutral hydrogen in the circumgalactic and intergalactic medium surrounding star-forming galaxies at z ∼ 2. Using the spectra of ≃3000 galaxies with redshifts 〈z〉 = 2.3 ± 0.4 from the Keck Baryonic Structure Survey,we assemble a sample ofmore than 200 000 distinct foreground-background pairs with projected angular separations of 3-500 arcsec and spectroscopic redshifts, with 〈zfg〉 = 2.23 and 〈zbg〉 = 2.57 (foreground, background redshifts, respectively.) The ensemble of sightlines and foreground galaxies is used to construct a 2D map of the mean excess HI Ly α optical depth relative to the intergalactic mean as a function of projected galactocentric distance (20 ≲ Dtran/pkpc ≲ 4000) and line-of-sight velocity. We obtain accurate galaxy systemic redshifts, providing significant information on the line-of-sight kinematics of HI gas as a function of projected distance Dtran. We compare the map with cosmological zoom-in simulation, finding qualitative agreement between them. A simple two-component (accretion, outflow) analytical model generally reproduces the observed line-of-sight kinematics and projected spatial distribution of HI. The best-fitting model suggests that galaxy-scale outflows with initial velocity vout ≃ 600 km s-1 dominate the kinematics of circumgalactic HI out to Dtran ≃ 50 kpc, while HI at Dtran ≳100 kpc is dominated by infall with characteristic vin ≲circular velocity. Over the impact parameter range 80≲Dtran/pkpc ≲ 200, the HI line-of-sight velocity range reaches a minimum, with a corresponding flattening in the rest-frame Ly α equivalent width. These observations can be naturally explained as the transition between outflow-dominated and accretion-dominated flows. Beyond Dtran ≃ 300 pkpc (∼1 cMpc), the line-of-sight kinematics are dominated by Hubble expansion.
KW - galaxies: ISM
KW - galaxies: evolution
KW - galaxies: high-redshift
KW - galaxies: intergalatic medium
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U2 - 10.1093/mnras/staa2808
DO - 10.1093/mnras/staa2808
M3 - Article
AN - SCOPUS:85096896469
VL - 499
SP - 1721
EP - 1746
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
SN - 0035-8711
IS - 2
ER -