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Title: HOW TO SEARCH FOR ISLANDS OF NEUTRAL HYDROGEN IN THE z ∼ 5.5 IGM

Abstract

Observations of the Lyman-alpha (Lyα) forest may allow reionization to complete as late as z ∼ 5.5, provided the ionization state of the intergalactic medium (IGM) is sufficiently inhomogeneous at these redshifts. In this case, significantly neutral islands may remain among highly ionized gas with the ionized regions allowing some transmission through the Lyα forest. This possibility has the important virtue that it is eminently testable with existing Lyα forest data. In particular, we describe three observable signatures of significantly neutral gas in the z ∼ 5.5 IGM. We use mock quasar spectra produced from numerical simulations of reionization to develop these tests. First, we quantify how the abundance and length of absorbed regions in the forest increase with the volume-averaged neutral fraction in our reionization model. Second, we consider stacking the transmission profile around highly absorbed regions in the forest. If and only if there is significantly neutral gas in the IGM, absorption in the damping wing of the Lyα line will cause the transmission to recover slowly as one moves from absorbed to transmitted portions of the spectrum. Third, the deuterium Lyβ line should imprint a small but distinctive absorption feature slightly blueward of absorbed neutral regions inmore » the Lyβ forest. We show that these tests can be carried out with existing Keck HIRES spectra at z ∼ 5.5, with the damping wing being observable for 〈x{sub H} {sub I}〉≳0.05 and the deuterium feature observable with additional high-resolution spectra for 〈x{sub H} {sub I}〉≳0.2.« less

Authors:
;  [1]
  1. Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104 (United States)
Publication Date:
OSTI Identifier:
22364340
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 799; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; COMPUTERIZED SIMULATION; COSMOLOGY; DEUTERIUM; HYDROGEN; INTERGALACTIC SPACE; LYMAN LINES; QUASARS; RESOLUTION; TRANSMISSION; UNIVERSE

Citation Formats

Malloy, Matthew, and Lidz, Adam. HOW TO SEARCH FOR ISLANDS OF NEUTRAL HYDROGEN IN THE z ∼ 5.5 IGM. United States: N. p., 2015. Web. doi:10.1088/0004-637X/799/2/179.
Malloy, Matthew, & Lidz, Adam. HOW TO SEARCH FOR ISLANDS OF NEUTRAL HYDROGEN IN THE z ∼ 5.5 IGM. United States. https://doi.org/10.1088/0004-637X/799/2/179
Malloy, Matthew, and Lidz, Adam. Sun . "HOW TO SEARCH FOR ISLANDS OF NEUTRAL HYDROGEN IN THE z ∼ 5.5 IGM". United States. https://doi.org/10.1088/0004-637X/799/2/179.
@article{osti_22364340,
title = {HOW TO SEARCH FOR ISLANDS OF NEUTRAL HYDROGEN IN THE z ∼ 5.5 IGM},
author = {Malloy, Matthew and Lidz, Adam},
abstractNote = {Observations of the Lyman-alpha (Lyα) forest may allow reionization to complete as late as z ∼ 5.5, provided the ionization state of the intergalactic medium (IGM) is sufficiently inhomogeneous at these redshifts. In this case, significantly neutral islands may remain among highly ionized gas with the ionized regions allowing some transmission through the Lyα forest. This possibility has the important virtue that it is eminently testable with existing Lyα forest data. In particular, we describe three observable signatures of significantly neutral gas in the z ∼ 5.5 IGM. We use mock quasar spectra produced from numerical simulations of reionization to develop these tests. First, we quantify how the abundance and length of absorbed regions in the forest increase with the volume-averaged neutral fraction in our reionization model. Second, we consider stacking the transmission profile around highly absorbed regions in the forest. If and only if there is significantly neutral gas in the IGM, absorption in the damping wing of the Lyα line will cause the transmission to recover slowly as one moves from absorbed to transmitted portions of the spectrum. Third, the deuterium Lyβ line should imprint a small but distinctive absorption feature slightly blueward of absorbed neutral regions in the Lyβ forest. We show that these tests can be carried out with existing Keck HIRES spectra at z ∼ 5.5, with the damping wing being observable for 〈x{sub H} {sub I}〉≳0.05 and the deuterium feature observable with additional high-resolution spectra for 〈x{sub H} {sub I}〉≳0.2.},
doi = {10.1088/0004-637X/799/2/179},
url = {https://www.osti.gov/biblio/22364340}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 2,
volume = 799,
place = {United States},
year = {2015},
month = {2}
}