Effective Opacity of the Intergalactic Medium from Galaxy Spectra Analysis. (arXiv:2005.09667v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+Monzon_J/0/1/0/all/0/1">Jose S. Monzon</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Prochaska_J/0/1/0/all/0/1">J. Xavier Prochaska</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lee_K/0/1/0/all/0/1">Khee-Gan Lee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chisholm_J/0/1/0/all/0/1">John Chisholm</a>
We measure the effective opacity ($tau_{eff}$) of the Intergalactic Medium
(IGM) from the composite spectra of 281 Lyman-Break Galaxies (LBGs) in the
redshift range $2 lesssim z lesssim 3$. Our spectra are taken from the COSMOS
Lyman-Alpha Mapping And Tomographic Observations (CLAMATO) survey derived from
the Low Resolution Imaging Spectrometer (LRIS) on the W.M. Keck I telescope. We
generate composite spectra in two redshift intervals and fit them with spectral
energy distribution (SED) models composed of simple stellar populations.
Extrapolating these SED models into the Ly$alpha$ forest, we measure the
effective Ly$alpha$ opacity ($tau_{eff}$) in the $2.02 leq z leq 2.44$
range. At $z = 2.22$, we estimate $tau_{eff} = 0.159 pm 0.001$ from a
power-law fit to the data. These measurements are consistent with estimates
from quasar analyses at $z<2.5$ indicating that the systematic errors
associated with normalizing quasar continua are not substantial. We provide a
Gaussian Processes model of our results and previous $tau_{eff}$ measurements
that describes the steep redshift evolution in $tau_{eff}$ from $z = 1.5 – 4$.
We measure the effective opacity ($tau_{eff}$) of the Intergalactic Medium
(IGM) from the composite spectra of 281 Lyman-Break Galaxies (LBGs) in the
redshift range $2 lesssim z lesssim 3$. Our spectra are taken from the COSMOS
Lyman-Alpha Mapping And Tomographic Observations (CLAMATO) survey derived from
the Low Resolution Imaging Spectrometer (LRIS) on the W.M. Keck I telescope. We
generate composite spectra in two redshift intervals and fit them with spectral
energy distribution (SED) models composed of simple stellar populations.
Extrapolating these SED models into the Ly$alpha$ forest, we measure the
effective Ly$alpha$ opacity ($tau_{eff}$) in the $2.02 leq z leq 2.44$
range. At $z = 2.22$, we estimate $tau_{eff} = 0.159 pm 0.001$ from a
power-law fit to the data. These measurements are consistent with estimates
from quasar analyses at $z<2.5$ indicating that the systematic errors
associated with normalizing quasar continua are not substantial. We provide a
Gaussian Processes model of our results and previous $tau_{eff}$ measurements
that describes the steep redshift evolution in $tau_{eff}$ from $z = 1.5 – 4$.
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