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Title: Modeling the He II Transverse Proximity Effect: Constraints on Quasar Lifetime and Obscuration

Abstract

The He II transverse proximity effect - enhanced He II Lyα transmission in a background sightline caused by the ionizing radiation of a foreground quasar - offers a unique opportunity to probe the emission properties of quasars, in particular the emission geometry (obscuration, beaming) and the quasar lifetime. Building on the foreground quasar survey published in Schmidt et al., we present a detailed model of the He II transverse proximity effect, specifically designed to include light travel time effects, finite quasar ages, and quasar obscuration. Here, we post-process outputs from a cosmological hydrodynamical simulation with a fluctuating He ii ultraviolet background model, with the added effect of the radiation from a single bright foreground quasar. We vary the age t age and obscured sky fractions Ω obsc of the foreground quasar, and explore the resulting effect on the He ii transverse proximity effect signal. Fluctuations in intergalactic medium density and the ultraviolet background, as well as the unknown orientation of the foreground quasar, result in a large variance of the He II Lyα transmission along the background sightline. We develop a fully Bayesian statistical formalism to compare far-ultraviolet He ii Lyα transmission spectra of the background quasars to our models,more » and extract joint constraints on t age and Ω obsc for the six Schmidt et al. foreground quasars with the highest implied He II photoionization rates. Our analysis suggests a bimodal distribution of quasar emission properties, whereby one foreground quasar, associated with a strong He II transmission spike, is relatively old (22 Myr) and unobscured (Ω obsc < 35%), whereas three others are either younger than 10 Myr or highly obscured (Ω obsc > 70%).« less

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4];  [5]; ORCiD logo [6]
  1. Univ. of California, Santa Barbara, CA (United States). Dept. of Physics; Max-Planck-Inst. für Astronomie, Heidelberg (Germany); Univ. of Heidelberg (IMPRS-HD), Heidelberg (Germany). International Max Planck Research School for Astronomy and Cosmic Physics
  2. Univ. of California, Santa Barbara, CA (United States). Dept. of Physics; Max-Planck-Inst. für Astronomie, Heidelberg (Germany)
  3. Max-Planck-Inst. für Astronomie, Heidelberg (Germany); Univ. Potsdam, Golm (Germany). Inst. für Physik und Astronomie
  4. Univ. of California, Santa Barbara, CA (United States). Dept. of Physics
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  6. Univ. of Edinburgh, Scotland (United Kingdom). The Royal Observatory, Inst. for Astronomy
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP) (SC-25)
OSTI Identifier:
1493259
Grant/Contract Number:  
AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 861; Journal Issue: 2; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS

Citation Formats

Schmidt, Tobias M., Hennawi, Joseph F., Worseck, Gábor, Davies, Frederick B., Lukić, Zarija, and Oñorbe, Jose. Modeling the He II Transverse Proximity Effect: Constraints on Quasar Lifetime and Obscuration. United States: N. p., 2018. Web. doi:10.3847/1538-4357/aac8e4.
Schmidt, Tobias M., Hennawi, Joseph F., Worseck, Gábor, Davies, Frederick B., Lukić, Zarija, & Oñorbe, Jose. Modeling the He II Transverse Proximity Effect: Constraints on Quasar Lifetime and Obscuration. United States. doi:10.3847/1538-4357/aac8e4.
Schmidt, Tobias M., Hennawi, Joseph F., Worseck, Gábor, Davies, Frederick B., Lukić, Zarija, and Oñorbe, Jose. Tue . "Modeling the He II Transverse Proximity Effect: Constraints on Quasar Lifetime and Obscuration". United States. doi:10.3847/1538-4357/aac8e4. https://www.osti.gov/servlets/purl/1493259.
@article{osti_1493259,
title = {Modeling the He II Transverse Proximity Effect: Constraints on Quasar Lifetime and Obscuration},
author = {Schmidt, Tobias M. and Hennawi, Joseph F. and Worseck, Gábor and Davies, Frederick B. and Lukić, Zarija and Oñorbe, Jose},
abstractNote = {The He II transverse proximity effect - enhanced He II Lyα transmission in a background sightline caused by the ionizing radiation of a foreground quasar - offers a unique opportunity to probe the emission properties of quasars, in particular the emission geometry (obscuration, beaming) and the quasar lifetime. Building on the foreground quasar survey published in Schmidt et al., we present a detailed model of the He II transverse proximity effect, specifically designed to include light travel time effects, finite quasar ages, and quasar obscuration. Here, we post-process outputs from a cosmological hydrodynamical simulation with a fluctuating He ii ultraviolet background model, with the added effect of the radiation from a single bright foreground quasar. We vary the age tage and obscured sky fractions Ωobsc of the foreground quasar, and explore the resulting effect on the He ii transverse proximity effect signal. Fluctuations in intergalactic medium density and the ultraviolet background, as well as the unknown orientation of the foreground quasar, result in a large variance of the He II Lyα transmission along the background sightline. We develop a fully Bayesian statistical formalism to compare far-ultraviolet He ii Lyα transmission spectra of the background quasars to our models, and extract joint constraints on tage and Ωobsc for the six Schmidt et al. foreground quasars with the highest implied He II photoionization rates. Our analysis suggests a bimodal distribution of quasar emission properties, whereby one foreground quasar, associated with a strong He II transmission spike, is relatively old (22 Myr) and unobscured (Ωobsc < 35%), whereas three others are either younger than 10 Myr or highly obscured (Ωobsc > 70%).},
doi = {10.3847/1538-4357/aac8e4},
journal = {The Astrophysical Journal (Online)},
number = 2,
volume = 861,
place = {United States},
year = {2018},
month = {7}
}

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