Revisiting the gas kinematics in SSA22 Lyman-α Blob 1 with radiative transfer modelling in a multiphase, clumpy medium
Abstract
We present new observations of Lyman-α (Lyα) Blob 1 (LAB1) in the SSA22 protocluster region (z = 3.09) using the Keck Cosmic Web Imager and Keck Multi-object Spectrometer for Infrared Exploration. We have created a narrow-band Lyα image and identified several prominent features. By comparing the spatial distributions and intensities of Lyα and Hβ, we find that recombination of photo-ionized H I gas followed by resonant scattering is sufficient to explain all the observed Lyα/Hβ ratios. We further decode the spatially resolved Lyα profiles using both moment maps and radiative transfer modelling. By fitting a set of multiphase, 'clumpy' models to the observed Lyα profiles, we manage to reasonably constrain many parameters, namely the H I number density in the interclump medium (ICM), the cloud volume filling factor, the random velocity and outflow velocity of the clumps, the H I outflow velocity of the ICM, and the local systemic redshift. Our model has successfully reproduced the diverse Lyα morphologies, and the main results are: (1) the observed Lyα spectra require relatively few clumps per line of sight as they have significant fluxes at the line centre; (2) the velocity dispersion of the clumps yields a significant broadening of the spectra as observed; (3) the clump bulk outflow can also cause additional broadening if the H I in the ICM is optically thick; (4) and the H I in the ICM is responsible for the absorption feature close to the Lyα line centre.
Additional Information
© 2020 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model) Accepted 2020 December 16. Received 2020 November 17; in original form 2020 August 24. We thank the referee for insightful comments that have significantly improved the paper. We also thank Phil Hopkins for providing us with adequate computational resources. ZL acknowledges Michael Zhang, for his professional guidance and kind company during the excruciating debugging process. 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. DATA AVAILABILITY. The data underlying this article will be shared on reasonable request to the corresponding author.Attached Files
Published - staa3951.pdf
Accepted Version - 2008.09130.pdf
Supplemental Material - staa3951_online_appendix.pdf
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Additional details
- Eprint ID
- 105263
- Resolver ID
- CaltechAUTHORS:20200908-075612693
- W. M. Keck Foundation
- HST-HF2-51409
- NASA Hubble Fellowship
- NAS5-26555
- NASA
- TG-AST130039
- NSF
- OAC-1713353
- NSF
- SMD-16-7592
- NASA
- ACI-1440620
- NSF
- NCC5-626
- NASA
- Created
-
2020-09-08Created from EPrint's datestamp field
- Updated
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2021-10-05Created from EPrint's last_modified field
- Caltech groups
- Astronomy Department