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The physics of Lyman α escape from high-redshift galaxies

Smith, Aaron and Ma, Xiangcheng and Bromm, Volker and Finkelstein, Steven L. and Hopkins, Philip F. and Faucher-Giguère, Claude-André and Kereš, Dušan (2019) The physics of Lyman α escape from high-redshift galaxies. Monthly Notices of the Royal Astronomical Society, 484 (1). pp. 39-59. ISSN 0035-8711. doi:10.1093/mnras/sty3483.

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Lyman α (Lyα) photons from ionizing sources and cooling radiation undergo a complex resonant scattering process that generates unique spectral signatures in high-redshift galaxies. We present a detailed Lyα radiative transfer study of a cosmological zoom-in simulation from the Feedback In Realistic Environments (FIRE) project. We focus on the time, spatial, and angular properties of the Lyα emission over a redshift range of z = 5–7, after escaping the galaxy and being transmitted through the intergalactic medium (IGM). Over this epoch, our target galaxy has an average stellar mass of M⋆ ≈ 5×10^8M⊙ .We find that many of the interesting features of the Lyα line can be understood in terms of the galaxy’s star formation history. The time variability, spatial morphology, and anisotropy of Lyα properties are consistent with current observations. For example, the rest-frame equivalent width has an EW_(Lyα,0) > 20˚A duty cycle of 62 per cent with a non-negligible number of sightlines with >100˚A⁠, associated with outflowing regions of a starburst with greater coincident UV continuum absorption, as these conditions generate redder, narrower (or single-peaked) line profiles. The lowest equivalent widths correspond to cosmological filaments, which have little impact on UV continuum photons but efficiently trap Lyα and produce bluer, broader lines with less transmission through the IGM. We also show that in dense self-shielding, low-metallicity filaments and satellites, Lyα radiation pressure can be dynamically important. Finally, despite a significant reduction in surface brightness with increasing redshift, Lyα detections and spectroscopy of high-z galaxies with the upcoming James Webb Space Telescope is feasible.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Smith, Aaron0000-0002-2838-9033
Ma, Xiangcheng0000-0001-8091-2349
Finkelstein, Steven L.0000-0001-8519-1130
Hopkins, Philip F.0000-0003-3729-1684
Faucher-Giguère, Claude-André0000-0002-4900-6628
Kereš, Dušan0000-0002-1666-7067
Alternate Title:The physics of Lyman-alpha escape from high-redshift galaxies
Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 December 19. Received 2018 December 11; in original form 2018 October 18. Published: 22 December 2018. We thank the referee Luke Barnes for constructive comments that improved the content of this paper. The authors thank Peter Laursen who kindly provided IGM transmission data and helpful correspondence. AS benefited from numerous discussions with Benny Tsang, Intae Jung, Miloš Milosavljević, and Yao-Lun Yang. AS also thanks Jérémy Blaizot, Max Gronke, Dawn Erb, Anne Verhamme, Andrea Ferrara, Edward Robinson, Paul Shapiro, Alaina Henry, and Jorryt Matthee for insightful conversations. Support for Program number HST-HF2-51421.001-A was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. VB acknowledges support from NSF grant AST-1413501. CAFG was supported by NSF through grants AST-1412836, AST-1517491, AST-1715216, and CAREER award AST-1652522, by NASA through grant NNX15AB22G, by STScI through grant HST-AR-14562.001, and by a Cottrell Scholar Award from the Research Corporation for Science Advancement. DK was supported by NSF grant AST-1715101 and the Cottrell Scholar Award from the Research Corporation for Science Advancement. Support for PFH was provided by an Alfred P. Sloan Research Fellowship, NSF Collaborative Research Grant #1715847 and CAREER grant #1455342, and NASA grants NNX15AT06G, JPL 1589742, 17-ATP17-0214. 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. The authors acknowledge the Texas Advanced Computing Center (TACC) at the University of Texas at Austin for providing HPC resources.
Group:TAPIR, Astronomy Department
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF2-51421.001-A
NASA Hubble FellowshipHST-AR-14562.001
Research CorporationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:radiative transfer, galaxies: formation, galaxies: high-redshift
Issue or Number:1
Record Number:CaltechAUTHORS:20190206-112124271
Persistent URL:
Official Citation:Aaron Smith, Xiangcheng Ma, Volker Bromm, Steven L Finkelstein, Philip F Hopkins, Claude-André Faucher-Giguère, Dušan Kereš; The physics of Lyman α escape from high-redshift galaxies, Monthly Notices of the Royal Astronomical Society, Volume 484, Issue 1, 21 March 2019, Pages 39–59,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92738
Deposited By: Tony Diaz
Deposited On:06 Feb 2019 19:39
Last Modified:16 Nov 2021 03:53

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