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Title: A New Measurement of the Temperature–density Relation of the IGM from Voigt Profile Fitting

Abstract

We decompose the Lyman-α (Lyα) forest of an extensive sample of 75 high signal-to-noise ratio and high-resolution quasar spectra into a collection of Voigt profiles. Absorbers located near caustics in the peculiar velocity field have the smallest Doppler parameters, resulting in a low-b cutoff in the b- distribution set primarily by the thermal state of the intergalactic medium (IGM). We fit this cutoff as a function of redshift over the range 2.0 ≤ z ≤ 3.4, which allows us to measure the evolution of the IGM temperature-density (T = T 0(ρ/ρ 0) γ-1) relation parameters T 0 and γ. We calibrate our measurements against mock Lyα forest data generated using 26 hydrodynamic simulations with different thermal histories from the THERMAL suite, also encompassing different values of the IGM pressure smoothing scale. We adopt a forward-modeling approach and self-consistently apply the same algorithms to both data and simulations, propagating both statistical and modeling uncertainties via Monte Carlo. The redshift evolution of T 0 (γ) shows a suggestive peak (dip) at z = 2.9 (z = 3). Our measured evolution of T 0 and γ is generally in good agreement with previous determinations in the literature. Both the peak in the evolutionmore » of T 0 at z = 2.8, as well as the high temperatures T 0 ≃ 15,000-20,000 K that we observe at 2.4 < z < 3.4, strongly suggest that a significant episode of heating occurred after the end of H I reionization, which was most likely the cosmic reionization of He II.« less

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [5];  [6];  [7]
  1. Max-Planck-Inst. für Astronomie, Heidelberg (Germany); Univ. of Heidelberg, Heidelberg (Germany). International Max Planck Research School for Astronomy & Cosmic Physics
  2. Max-Planck-Inst. für Astronomie, Heidelberg (Germany); Univ. of Heidelberg, Heidelberg (Germany). International Max Planck Research School for Astronomy & Cosmic Physics; Univ. of California, Santa Barbara, CA (United States). Physics Dept.
  3. Max-Planck-Inst. für Astronomie, Heidelberg (Germany); Univ. of California, Santa Barbara, CA (United States). Physics Dept.
  4. Max-Planck-Inst. für Astronomie, Heidelberg (Germany)
  5. Saint Michaels College, Colchester, VT (United States). Dept. of Chemistry and Physics
  6. Max-Planck-Inst. für Astronomie, Heidelberg (Germany); Kavli Inst. for Cosmology and Inst. of Astronomy, Cambridge (United Kingdom); Inst. of Astronomy, Cambridge (United Kingdom)
  7. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
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:
1493263
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: 865; Journal Issue: 1; Journal ID: ISSN 1538-4357
Publisher:
Institute of Physics (IOP)
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; cosmology: observations; dark ages, reionization, first stars; intergalactic medium; quasars: absorption lines

Citation Formats

Hiss, Hector, Walther, Michael, Hennawi, Joseph F., Oñorbe, José, O’Meara, John M., Rorai, Alberto, and Lukić, Zarija. A New Measurement of the Temperature–density Relation of the IGM from Voigt Profile Fitting. United States: N. p., 2018. Web. doi:10.3847/1538-4357/aada86.
Hiss, Hector, Walther, Michael, Hennawi, Joseph F., Oñorbe, José, O’Meara, John M., Rorai, Alberto, & Lukić, Zarija. A New Measurement of the Temperature–density Relation of the IGM from Voigt Profile Fitting. United States. doi:10.3847/1538-4357/aada86.
Hiss, Hector, Walther, Michael, Hennawi, Joseph F., Oñorbe, José, O’Meara, John M., Rorai, Alberto, and Lukić, Zarija. Wed . "A New Measurement of the Temperature–density Relation of the IGM from Voigt Profile Fitting". United States. doi:10.3847/1538-4357/aada86. https://www.osti.gov/servlets/purl/1493263.
@article{osti_1493263,
title = {A New Measurement of the Temperature–density Relation of the IGM from Voigt Profile Fitting},
author = {Hiss, Hector and Walther, Michael and Hennawi, Joseph F. and Oñorbe, José and O’Meara, John M. and Rorai, Alberto and Lukić, Zarija},
abstractNote = {We decompose the Lyman-α (Lyα) forest of an extensive sample of 75 high signal-to-noise ratio and high-resolution quasar spectra into a collection of Voigt profiles. Absorbers located near caustics in the peculiar velocity field have the smallest Doppler parameters, resulting in a low-b cutoff in the b- distribution set primarily by the thermal state of the intergalactic medium (IGM). We fit this cutoff as a function of redshift over the range 2.0 ≤ z ≤ 3.4, which allows us to measure the evolution of the IGM temperature-density (T = T0(ρ/ρ0)γ-1) relation parameters T 0 and γ. We calibrate our measurements against mock Lyα forest data generated using 26 hydrodynamic simulations with different thermal histories from the THERMAL suite, also encompassing different values of the IGM pressure smoothing scale. We adopt a forward-modeling approach and self-consistently apply the same algorithms to both data and simulations, propagating both statistical and modeling uncertainties via Monte Carlo. The redshift evolution of T 0 (γ) shows a suggestive peak (dip) at z = 2.9 (z = 3). Our measured evolution of T 0 and γ is generally in good agreement with previous determinations in the literature. Both the peak in the evolution of T 0 at z = 2.8, as well as the high temperatures T0 ≃ 15,000-20,000 K that we observe at 2.4 < z < 3.4, strongly suggest that a significant episode of heating occurred after the end of H I reionization, which was most likely the cosmic reionization of He II.},
doi = {10.3847/1538-4357/aada86},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 865,
place = {United States},
year = {2018},
month = {9}
}

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Cited by: 7 works
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Figures / Tables:

Figure 1 Figure 1: KODIAQ and UVES Ly$α$ forest sightlines used in this work. The sample is described in § 2. Sightlines from the KODIAQ sample are marked in red and UVES sightlines are marked in blue. The corresponding QSO redshifts are marked as colored points. DLAs and bad regions that weremore » excluded are shown as gaps. The blue vertical lines show the bins that will be used for the cutoff fitting analysis. Gray regions are not used because of lower coverage.« less

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