Brent M. Smith
Hubble Space Telescope Wide Field Camera 3 Observations of Escaping Lyman Continuum Radiation from Galaxies and Weak AGN at Redshifts z ∼ 2.3–4.1
Smith, Brent M.; Windhorst, Rogier A.; Jansen, Rolf A.; Cohen, Seth H.; Jiang, Linhua; Dijkstra, Mark; Koekemoer, Anton M.; Bielby, Richard; Inoue, Akio K.; MacKenty, John W.; O’Connell, Robert W.; Silk, Joseph I.
Authors
Rogier A. Windhorst
Rolf A. Jansen
Seth H. Cohen
Linhua Jiang
Mark Dijkstra
Anton M. Koekemoer
Richard Bielby
Akio K. Inoue
John W. MacKenty
Robert W. O’Connell
Joseph I. Silk
Abstract
We present observations of escaping Lyman Continuum (LyC) radiation from 34 massive star-forming galaxies (SFGs) and 12 weak AGN with reliably measured spectroscopic redshifts at $z\simeq 2.3\mbox{--}4.1$. We analyzed Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) mosaics of the Early Release Science (ERS) field in three UVIS filters to sample the rest-frame LyC over this redshift range. With our best current assessment of the WFC3 systematics, we provide $1\sigma $ upper limits for the average LyC emission of galaxies at $\langle z\rangle $ = 2.35, 2.75, and 3.60 to ~28.5, 28.1, and 30.7 mag in image stacks of 11–15 galaxies in the WFC3/UVIS F225W, F275W, and F336W, respectively. The LyC flux of weak AGN at $\langle z\rangle $ = 2.62 and 3.32 are detected at 28.3 and 27.4 mag with S/Ns of ~2.7 and 2.5 in F275W and F336W for stacks of 7 and 3 AGN, respectively, while AGN at $\langle z\rangle $ = 2.37 are constrained to gsim27.9 mag at $1\sigma $ in a stack of 2 AGN. The stacked AGN LyC light profiles are flatter than their corresponding non-ionizing UV continuum profiles out to radii of $r\lesssim 0\buildrel{\prime\prime}\over{.} 9$, which may indicate a radial dependence of porosity in the ISM. With synthetic stellar SEDs fit to UV continuum measurements longward of ${\rm{Ly}}\alpha $ and IGM transmission models, we constrain the absolute LyC escape fractions to ${f}_{\mathrm{esc}}^{\mathrm{abs}}\simeq {22}_{-22}^{+44}$% at $\langle z\rangle $ = 2.35 and lesssim55% at $\langle z\rangle $ = 2.75 and 3.60, respectively. All available data for galaxies, including published work, suggests a more sudden increase of ${f}_{\mathrm{esc}}$ with redshift at $z\simeq 2$. Dust accumulating in (massive) galaxies over cosmic time correlates with increased H i column density, which may lead to reducing ${f}_{\mathrm{esc}}$ more suddenly at $z\lesssim 2$. This may suggest that SFGs collectively contributed to maintaining cosmic reionization at redshifts $z\gtrsim 2\mbox{--}4$, while AGN likely dominated reionization at $z\lesssim 2$.
Citation
Smith, B. M., Windhorst, R. A., Jansen, R. A., Cohen, S. H., Jiang, L., Dijkstra, M., …Silk, J. I. (2018). Hubble Space Telescope Wide Field Camera 3 Observations of Escaping Lyman Continuum Radiation from Galaxies and Weak AGN at Redshifts z ∼ 2.3–4.1. Astrophysical Journal, 853(2), Article 191. https://doi.org/10.3847/1538-4357/aaa3dc
Journal Article Type | Article |
---|---|
Acceptance Date | Dec 18, 2017 |
Online Publication Date | Feb 5, 2018 |
Publication Date | Feb 1, 2018 |
Deposit Date | Feb 22, 2018 |
Publicly Available Date | Feb 22, 2018 |
Journal | Astrophysical Journal |
Print ISSN | 0004-637X |
Publisher | American Astronomical Society |
Peer Reviewed | Peer Reviewed |
Volume | 853 |
Issue | 2 |
Article Number | 191 |
DOI | https://doi.org/10.3847/1538-4357/aaa3dc |
Public URL | https://durham-repository.worktribe.com/output/1366084 |
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Copyright Statement
© 2018. The American Astronomical Society. All rights reserved.
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