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The Kinematics of Extended Lyα Emission in a Low-mass, Low-metallicity Galaxy at z = 2.3

Erb, Dawn K. and Steidel, Charles C. and Chen, Yuguang (2018) The Kinematics of Extended Lyα Emission in a Low-mass, Low-metallicity Galaxy at z = 2.3. Astrophysical Journal Letters, 862 (1). Art. No. L10. ISSN 2041-8213. doi:10.3847/2041-8213/aacff6.

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Lyα photons are resonantly scattered by neutral hydrogen, and may therefore trace both the spatial extent and the kinematics of the gas surrounding galaxies. We present new observations of the extended Lyα halo of Q2343-BX418, a low-mass (M⋆ = 5 x 10^8 M⊙), low-metallicity (Z ≈ 0.25 Z⊙) star-forming galaxy at z = 2.3. Using the Keck Cosmic Web Imager (KCWI), the blue-sensitive optical integral field spectrograph recently installed on the Keck II telescope, we detect Lyα in emission to a radius of 23 kpc, and measure an exponential scale length of 6 kpc in the outer region of the extended halo. We study the double-peaked spectroscopic Lyα profile in individual spectral pixels ("spaxels") over a ~25 × 30 kpc region, finding significant variations in the peak ratio and peak separation. The profile is dominated by the red peak in the central regions, while in the outskirts of the extended halo the red and blue peak strengths are roughly equal; these observations are consistent with a model in which the peak ratio is largely determined by the radial component of the outflow velocity. We find a gradient of 300 km s^(-1) in the Lyα peak separation across the extended halo, indicating variations in the column density, covering fraction, or velocity range of the gas. These new observations emphasize the need for realistic, spatially resolved models of Lyα radiative transfer in the halos of galaxies.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Erb, Dawn K.0000-0001-9714-2758
Steidel, Charles C.0000-0002-4834-7260
Chen, Yuguang0000-0003-4520-5395
Alternate Title:The Kinematics of Extended Lyman-alpha Emission in a Low Mass, Low Metallicity Galaxy at z = 2.3
Additional Information:© 2018 The American Astronomical Society. Received 2018 May 21; revised 2018 June 19; accepted 2018 June 28; published 2018 July 24. 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. The authors thank the referee for a thoughtful and constructive report, Max Gronke, David Kaplan, Aaron Smith, and Anne Verhamme for useful discussions and suggestions, KCWI team members Don Neill and Matt Matuszewski for their continued development of the KCWI DRP and for very useful conversations, and the organizers and participants of the "Sakura Cosmic Lyα Workshop" at the University of Tokyo in 2018 March. D.K.E. is supported by the US National Science Foundation through the Faculty Early Career Development (CAREER) Program, grant AST-1255591. C.C.S. and Y.C. acknowledge support from the Caltech/JPL President's and Director's Fund. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facility: Keck:II (KCWI). - Software: KCWI DRP,4 astropy (Astropy Collaboration et al. 2013), spectral_cube (Ginsburg et al. 2015), QFitsView,5 seaborn (Waskom et al. 2017).
Group:Astronomy Department
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Caltech/JPL President and Director FundUNSPECIFIED
Subject Keywords:cosmology: observations – galaxies: evolution – galaxies: high-redshift
Issue or Number:1
Record Number:CaltechAUTHORS:20180808-145514148
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Official Citation:Dawn K. Erb et al 2018 ApJL 862 L10
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88670
Deposited By: Tony Diaz
Deposited On:09 Aug 2018 14:59
Last Modified:16 Nov 2021 00:28

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