skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A New Precision Measurement of the Small-scale Line-of-sight Power Spectrum of the Ly α Forest

Abstract

We present a new measurement of the Lyα forest power spectrum at 1.8 < z < 3.4 using 74 Keck/HIRES and VLT/UVES high-resolution, high-signal-to-noise-ratio quasar spectra. We developed a custom pipeline to measure the power spectrum and its uncertainty, which fully accounts for finite resolution and noise and corrects for the bias induced by masking missing data, damped Lyα absorption systems, and metal absorption lines. Our measurement results in unprecedented precision on the small-scale modes $$k\gt 0.02\,{\rm{s}}\,{\mathrm{km}}^{-1}$$, inaccessible to previous SDSS/BOSS analyses. It is well known that these high-k modes are highly sensitive to the thermal state of the intergalactic medium, but contamination by narrow metal lines is a significant concern. We quantify the effect of metals on the small-scale power and find a modest effect on modes with $$k\lt 0.1\,{\rm{s}}\,{\mathrm{km}}^{-1}$$. As a result, by masking metals and restricting to $$k\lt 0.1\,{\rm{s}}\,{\mathrm{km}}^{-1}$$, their impact is completely mitigated. We present an end-to-end Bayesian forward-modeling framework whereby mock spectra with the same noise, resolution, and masking as our data are generated from Lyα forest simulations. These mock spectra are used to build a custom emulator, enabling us to interpolate between a sparse grid of models and perform Markov chain Monte Carlo fits. Our results agree well with BOSS on scales $$k\lt 0.02\,{\rm{s}}\,{\mathrm{km}}^{-1}$$, where the measurements overlap. The combination of the percent-level low-k precision of BOSS with our 5%–15% high-k measurements results in a powerful new data set for precisely constraining the thermal history of the intergalactic medium, cosmological parameters, and the nature of dark matter. Lastly, the power spectra and their covariance matrices are provided as electronic tables.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [5]; ORCiD logo [6]; ORCiD logo [7]
  1. Univ. of California, Santa Barbara, CA (United States). Physics Dept.; Max-Planck-Inst. fur Astronomie, Heidelberg (Germany); Univ. of Heidelberg (Germany). International Max Planck Research School for Astronomy & Cosmic Physics
  2. Univ. of California, Santa Barbara, CA (United States). Physics Dept.; Max Planck Inst. fur Astronomie, Heidelberg (Germany)
  3. Max Planck Inst. fur Astronomie, Heidelberg (Germany); Univ. of Heidelberg (Germany). International Max Planck Research School for Astronomy & Cosmic Physics
  4. Max Planck Inst. fur Astronomie, Heidelberg (Germany)
  5. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  6. Cambridge Inst. of Astronomy, Cambridge (United Kingdom)
  7. Saint Michael's College, Colchester, VT (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory-National Energy Research Scientific Computing Center
Sponsoring Org.:
USDOE Office of Science (SC); National Aeronautic and Space Administration (NASA); National Science Foundation (NSF)
OSTI Identifier:
1524339
Grant/Contract Number:  
AC02-05CH11231; NNX10AE84G; NNx16AF52G
Resource Type:
Accepted Manuscript
Journal Name:
The Astrophysical Journal (Online)
Additional Journal Information:
Journal Name: The Astrophysical Journal (Online); Journal Volume: 852; 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

Citation Formats

Walther, Michael, Hennawi, Joseph F., Hiss, Hector, Oñorbe, Jose, Lee, Khee-Gan, Rorai, Alberto, and O’Meara, John. A New Precision Measurement of the Small-scale Line-of-sight Power Spectrum of the Ly α Forest. United States: N. p., 2017. Web. doi:10.3847/1538-4357/aa9c81.
Walther, Michael, Hennawi, Joseph F., Hiss, Hector, Oñorbe, Jose, Lee, Khee-Gan, Rorai, Alberto, & O’Meara, John. A New Precision Measurement of the Small-scale Line-of-sight Power Spectrum of the Ly α Forest. United States. doi:10.3847/1538-4357/aa9c81.
Walther, Michael, Hennawi, Joseph F., Hiss, Hector, Oñorbe, Jose, Lee, Khee-Gan, Rorai, Alberto, and O’Meara, John. Thu . "A New Precision Measurement of the Small-scale Line-of-sight Power Spectrum of the Ly α Forest". United States. doi:10.3847/1538-4357/aa9c81. https://www.osti.gov/servlets/purl/1524339.
@article{osti_1524339,
title = {A New Precision Measurement of the Small-scale Line-of-sight Power Spectrum of the Ly α Forest},
author = {Walther, Michael and Hennawi, Joseph F. and Hiss, Hector and Oñorbe, Jose and Lee, Khee-Gan and Rorai, Alberto and O’Meara, John},
abstractNote = {We present a new measurement of the Lyα forest power spectrum at 1.8 < z < 3.4 using 74 Keck/HIRES and VLT/UVES high-resolution, high-signal-to-noise-ratio quasar spectra. We developed a custom pipeline to measure the power spectrum and its uncertainty, which fully accounts for finite resolution and noise and corrects for the bias induced by masking missing data, damped Lyα absorption systems, and metal absorption lines. Our measurement results in unprecedented precision on the small-scale modes $k\gt 0.02\,{\rm{s}}\,{\mathrm{km}}^{-1}$, inaccessible to previous SDSS/BOSS analyses. It is well known that these high-k modes are highly sensitive to the thermal state of the intergalactic medium, but contamination by narrow metal lines is a significant concern. We quantify the effect of metals on the small-scale power and find a modest effect on modes with $k\lt 0.1\,{\rm{s}}\,{\mathrm{km}}^{-1}$. As a result, by masking metals and restricting to $k\lt 0.1\,{\rm{s}}\,{\mathrm{km}}^{-1}$, their impact is completely mitigated. We present an end-to-end Bayesian forward-modeling framework whereby mock spectra with the same noise, resolution, and masking as our data are generated from Lyα forest simulations. These mock spectra are used to build a custom emulator, enabling us to interpolate between a sparse grid of models and perform Markov chain Monte Carlo fits. Our results agree well with BOSS on scales $k\lt 0.02\,{\rm{s}}\,{\mathrm{km}}^{-1}$, where the measurements overlap. The combination of the percent-level low-k precision of BOSS with our 5%–15% high-k measurements results in a powerful new data set for precisely constraining the thermal history of the intergalactic medium, cosmological parameters, and the nature of dark matter. Lastly, the power spectra and their covariance matrices are provided as electronic tables.},
doi = {10.3847/1538-4357/aa9c81},
journal = {The Astrophysical Journal (Online)},
number = 1,
volume = 852,
place = {United States},
year = {2017},
month = {12}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record

Save / Share: