Correlations in the three-dimensional Lyman-alpha forest contaminated by high column density absorbers. Rogers, K. K., Bird, S., Peiris, H. V., Pontzen, A., Font-Ribera, A., & Leistedt, B. ArXiv e-prints, 1711:arXiv:1711.06275, November, 2017.
Correlations in the three-dimensional Lyman-alpha forest contaminated by high column density absorbers [link]Paper  abstract   bibtex   
Correlations measured in 3D in the Lyman-alpha forest are contaminated by the presence of the damping wings of high column density (HCD) absorbing systems of neutral hydrogen (HI; having column densities \$N({\textbackslash}mathrm\{HI\}) {\textgreater} 1.6 {\textbackslash}times 10{\textasciicircum}\{17\}{\textbackslash},{\textbackslash}mathrm\{atoms\}{\textbackslash},{\textbackslash}mathrm\{cm\}{\textasciicircum}\{-2\}\$), which extend significantly beyond the redshift-space location of the absorber. We measure this effect as a function of the column density of the HCD absorbers and redshift by measuring 3D flux power spectra in cosmological hydrodynamical simulations from the Illustris project. Survey pipelines exclude regions containing the largest damping wings. We find that, even after this procedure, there is a scale-dependent correction to the 3D Lyman-alpha forest flux power spectrum from residual contamination. We model this residual using a simple physical model of the HCD absorbers as linearly biased tracers of the matter density distribution, convolved with their Voigt profiles and integrated over the column density distribution function. We recommend the use of this model over existing models used in data analysis, which approximate the damping wings as top-hats and so miss shape information in the extended wings. The simple linear Voigt model is statistically consistent with our simulation results for a mock residual contamination up to small scales (\$k {\textless} 1{\textbackslash},h{\textbackslash},{\textbackslash}mathrm\{Mpc\}{\textasciicircum}\{-1\}\$), even though it cannot account for the effect of the highest column density absorbers (which are in any case preferentially removed from survey data) on the smallest scales (e.g., \$k {\textgreater} 0.4{\textbackslash},h{\textbackslash},{\textbackslash}mathrm\{Mpc\}{\textasciicircum}\{-1\}\$ for small DLAs; \$N({\textbackslash}mathrm\{HI\}) {\textbackslash}sim 10{\textasciicircum}\{21\}{\textbackslash},{\textbackslash}mathrm\{atoms\}{\textbackslash},{\textbackslash}mathrm\{cm\}{\textasciicircum}\{-2\}\$). Our model is appropriate for an accurate analysis of the baryon acoustic oscillations feature and it is additionally essential for reconstructing the full shape of the 3D flux power spectrum, assuming that the highest column density absorbers are removed.
@article{rogers_correlations_2017,
	title = {Correlations in the three-dimensional {Lyman}-alpha forest contaminated by high column density absorbers},
	volume = {1711},
	url = {http://adsabs.harvard.edu/abs/2017arXiv171106275R},
	abstract = {Correlations measured in 3D in the Lyman-alpha forest are contaminated 
by the presence of the damping wings of high column density (HCD)
absorbing systems of neutral hydrogen (HI; having column densities
\$N({\textbackslash}mathrm\{HI\}) {\textgreater} 1.6 {\textbackslash}times
10{\textasciicircum}\{17\}{\textbackslash},{\textbackslash}mathrm\{atoms\}{\textbackslash},{\textbackslash}mathrm\{cm\}{\textasciicircum}\{-2\}\$), which extend significantly
beyond the redshift-space location of the absorber. We measure this
effect as a function of the column density of the HCD absorbers and
redshift by measuring 3D flux power spectra in cosmological
hydrodynamical simulations from the Illustris project. Survey pipelines
exclude regions containing the largest damping wings. We find that, even
after this procedure, there is a scale-dependent correction to the 3D
Lyman-alpha forest flux power spectrum from residual contamination. We
model this residual using a simple physical model of the HCD absorbers
as linearly biased tracers of the matter density distribution, convolved
with their Voigt profiles and integrated over the column density
distribution function. We recommend the use of this model over existing
models used in data analysis, which approximate the damping wings as
top-hats and so miss shape information in the extended wings. The simple
linear Voigt model is statistically consistent with our simulation
results for a mock residual contamination up to small scales (\$k {\textless}
1{\textbackslash},h{\textbackslash},{\textbackslash}mathrm\{Mpc\}{\textasciicircum}\{-1\}\$), even though it cannot account for the effect
of the highest column density absorbers (which are in any case
preferentially removed from survey data) on the smallest scales (e.g.,
\$k {\textgreater} 0.4{\textbackslash},h{\textbackslash},{\textbackslash}mathrm\{Mpc\}{\textasciicircum}\{-1\}\$ for small DLAs; \$N({\textbackslash}mathrm\{HI\}) {\textbackslash}sim
10{\textasciicircum}\{21\}{\textbackslash},{\textbackslash}mathrm\{atoms\}{\textbackslash},{\textbackslash}mathrm\{cm\}{\textasciicircum}\{-2\}\$). Our model is appropriate
for an accurate analysis of the baryon acoustic oscillations feature and
it is additionally essential for reconstructing the full shape of the 3D
flux power spectrum, assuming that the highest column density absorbers
are removed.},
	journal = {ArXiv e-prints},
	author = {Rogers, Keir K. and Bird, Simeon and Peiris, Hiranya V. and Pontzen, Andrew and Font-Ribera, Andreu and Leistedt, Boris},
	month = nov,
	year = {2017},
	keywords = {Astrophysics - Cosmology and Nongalactic Astrophysics},
	pages = {arXiv:1711.06275},
}

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