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Where Outflows Meet Inflows: Gas Kinematics in SSA22 Lyman-α Blob 2 Decoded by Advanced Radiative Transfer Modelling

Li, Zhihui and Steidel, Charles C. and Gronke, Max and Chen, Yuguang and Matsuda, Yuichi (2021) Where Outflows Meet Inflows: Gas Kinematics in SSA22 Lyman-α Blob 2 Decoded by Advanced Radiative Transfer Modelling. . (Unpublished)

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We present new spectroscopic observations of Lyα Blob 2 (LAB2) in the SSA22 protocluster region (z∼ 3.1). By creating a narrow-band Lyα image, we observed extended Lyα emission in three distinct regions, in which the highest Lyα surface brightness (SB) center is far away from the known continuum sources. We have searched through the MOSFIRE slits that cover the high Lyα SB regions, but are unable to detect any significant nebular emission near the highest SB center. We further map the blue-to-red flux ratio and find that it is anti-correlated with Lyα SB with a power-law index of ∼ -0.4. To decode the spatially-resolved Lyα profiles using Monte-Carlo radiative transfer (MCRT) modelling, we use both multiphase, clumpy models and shell models and successfully reproduced the diverse Lyα morphologies with reasonable physical parameters. Significant correlations exist between parameters of two different models, and our multiphase, clumpy model parameters naturally alleviated the previously reported discrepancies between the shell model parameters and data. In addition, we have modeled Lyα spectra at different spatial positions simultaneously, and we find that the variation of the inferred clump outflow velocity can be approximately explained by line-of-sight projection effects. Our results support the 'central powering + scattering' scenario, i.e. the Lyα photons are generated by a central powering source and then scatter with outflowing, multiphase HI gas while propagating outwards. The infalling of cool gas near the blob outskirts shapes the observed blue-dominated Lyα profiles, but its energy contribution is likely to be minor compared to the photo-ionization by star-forming galaxies and/or AGNs.

Item Type:Report or Paper (Discussion Paper)
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URLURL TypeDescription Paper
Li, Zhihui0000-0001-5113-7558
Steidel, Charles C.0000-0002-4834-7260
Gronke, Max0000-0003-2491-060X
Chen, Yuguang0000-0003-4520-5395
Additional Information:Attribution 4.0 International (CC BY 4.0) We thank Phil Hopkins for providing computational resources. ZL, CCS and YC acknowledge financial support by NSF grant AST-2009278. YM acknowledges support from JSPS KAKENHI Grant (17H04831, 17KK0098, 19H00697 and 20H01953). 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. We are also grateful to the dedicated staff of the W.M. Keck Observatory who keep the instruments and telescopes running effectively. MG was supported by NASA through the NASA Hubble Fellowship grant HST-HF2-51409 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. Numerical calculations were run on the Caltech compute cluster “Wheeler,” allocations from XSEDE TG-AST130039 and PRAC NSF.1713353 supported by the NSF, and NASA HEC SMD-16-7592. This research made use of Montage. It is funded by the National Science Foundation under Grant Number ACI-1440620, and was previously funded by the National Aeronautics and Space Administration’s Earth Science Technology Office, Computation Technologies Project, under Cooperative Agreement Number NCC5-626 between NASA and the California Institute of Technology. We also acknowledge the use of the the following software packages: Astropy (Astropy Collaboration et al. 2018), the SciPy and NumPy system (Virtanen et al. 2020; Harris et al. 2020), seaborn (Waskom 2021) and QFitsView.
Group:Astronomy Department
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF2-51409
Japan Society for the Promotion of Science (JSPS)17H04831
Japan Society for the Promotion of Science (JSPS)17KK0098
Japan Society for the Promotion of Science (JSPS)19H00697
Japan Society for the Promotion of Science (JSPS)20H01953
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:galaxies: kinematics and dynamics—intergalactic medium—galaxies: high-redshift—galaxies: evolution
Record Number:CaltechAUTHORS:20210825-184654591
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110565
Deposited By: George Porter
Deposited On:26 Aug 2021 22:33
Last Modified:26 Aug 2021 22:33

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