The experiment to detect the global epoch of reionization signature (EDGES)
collaboration reported the detection of a line at 78~MHz in the sky-averaged
spectrum due to neutral hydrogen (HI) 21-cm hyperfine absorption of cosmic
microwave background photons at redshift $z\sim17$. This requires that the spin
temperature of HI be coupled to the kinetic temperature of the gas at this
redshift through scattering of Lyman-$\alpha$ photons emitted by massive stars.
To explain the experimental result, star-formation needs to be sufficiently
efficient at $z\sim17$ and this can be used to constrain models in which
small-scale structure formation is suppressed (DMF), either due to dark matter
free-streaming or non-standard inflationary dynamics. We combine simulations of
structure formation with a simple recipe for star-formation to investigate
whether these models emit enough Lyman-$\alpha$ photons to reproduce the
experimental signal for reasonable values of the star-formation efficiency,
$f_\star$. We find that a thermal warm dark matter (WDM) model with mass
$m_WDM\sim4.3\,keV$ is consistent with the timing of the
signal for $f_2\%$. The exponential growth of structure around
$z17$ in such a model naturally generates a sharp onset of the absorption.
A model with $m_WDM\sim3\,keV$ requires higher star-formation
efficiency, $f_\star\sim6\%$, which is a factor of few above predictions of
current star-formation models and observations of satellites in the Milky Way.
However, uncertainties in the process of star-formation at these redshifts do
not allow to derive strong constrains on such models using 21-cm absorption
line. The onset of the 21-cm absorption is generally slower in DMF than in cold
dark matter models, unless some process significantly suppresses star formation
in halos with circular velocity below $20$~km~s$^-1$.
%0 Generic
%1 leo2019constraining
%A Leo, Matteo
%A Theuns, Tom
%A Baugh, Carlton M.
%A Li, Baojiu
%A Pascoli, Silvia
%D 2019
%K library
%T Constraining structure formation using EDGES
%U http://arxiv.org/abs/1909.04641
%X The experiment to detect the global epoch of reionization signature (EDGES)
collaboration reported the detection of a line at 78~MHz in the sky-averaged
spectrum due to neutral hydrogen (HI) 21-cm hyperfine absorption of cosmic
microwave background photons at redshift $z\sim17$. This requires that the spin
temperature of HI be coupled to the kinetic temperature of the gas at this
redshift through scattering of Lyman-$\alpha$ photons emitted by massive stars.
To explain the experimental result, star-formation needs to be sufficiently
efficient at $z\sim17$ and this can be used to constrain models in which
small-scale structure formation is suppressed (DMF), either due to dark matter
free-streaming or non-standard inflationary dynamics. We combine simulations of
structure formation with a simple recipe for star-formation to investigate
whether these models emit enough Lyman-$\alpha$ photons to reproduce the
experimental signal for reasonable values of the star-formation efficiency,
$f_\star$. We find that a thermal warm dark matter (WDM) model with mass
$m_WDM\sim4.3\,keV$ is consistent with the timing of the
signal for $f_2\%$. The exponential growth of structure around
$z17$ in such a model naturally generates a sharp onset of the absorption.
A model with $m_WDM\sim3\,keV$ requires higher star-formation
efficiency, $f_\star\sim6\%$, which is a factor of few above predictions of
current star-formation models and observations of satellites in the Milky Way.
However, uncertainties in the process of star-formation at these redshifts do
not allow to derive strong constrains on such models using 21-cm absorption
line. The onset of the 21-cm absorption is generally slower in DMF than in cold
dark matter models, unless some process significantly suppresses star formation
in halos with circular velocity below $20$~km~s$^-1$.
@misc{leo2019constraining,
abstract = {The experiment to detect the global epoch of reionization signature (EDGES)
collaboration reported the detection of a line at 78~MHz in the sky-averaged
spectrum due to neutral hydrogen (HI) 21-cm hyperfine absorption of cosmic
microwave background photons at redshift $z\sim17$. This requires that the spin
temperature of HI be coupled to the kinetic temperature of the gas at this
redshift through scattering of Lyman-$\alpha$ photons emitted by massive stars.
To explain the experimental result, star-formation needs to be sufficiently
efficient at $z\sim17$ and this can be used to constrain models in which
small-scale structure formation is suppressed (DMF), either due to dark matter
free-streaming or non-standard inflationary dynamics. We combine simulations of
structure formation with a simple recipe for star-formation to investigate
whether these models emit enough Lyman-$\alpha$ photons to reproduce the
experimental signal for reasonable values of the star-formation efficiency,
$f_\star$. We find that a thermal warm dark matter (WDM) model with mass
$m_\mathrm{WDM}\sim4.3\,\mathrm{keV}$ is consistent with the timing of the
signal for $f_\star \lesssim 2\%$. The exponential growth of structure around
$z\sim 17$ in such a model naturally generates a sharp onset of the absorption.
A model with $m_\mathrm{WDM}\sim3\,\mathrm{keV}$ requires higher star-formation
efficiency, $f_\star\sim6\%$, which is a factor of few above predictions of
current star-formation models and observations of satellites in the Milky Way.
However, uncertainties in the process of star-formation at these redshifts do
not allow to derive strong constrains on such models using 21-cm absorption
line. The onset of the 21-cm absorption is generally slower in DMF than in cold
dark matter models, unless some process significantly suppresses star formation
in halos with circular velocity below $\sim 20$~km~s$^{-1}$.},
added-at = {2019-09-11T17:39:50.000+0200},
author = {Leo, Matteo and Theuns, Tom and Baugh, Carlton M. and Li, Baojiu and Pascoli, Silvia},
biburl = {https://www.bibsonomy.org/bibtex/233d7bb3d836366fda7ef53f856855e9b/gpkulkarni},
description = {Constraining structure formation using EDGES},
interhash = {992d4c4d2b025aa81087b539e2858ea8},
intrahash = {33d7bb3d836366fda7ef53f856855e9b},
keywords = {library},
note = {cite arxiv:1909.04641Comment: 19 pages, 3 figures. Prepared for submission to JCAP},
timestamp = {2019-09-11T17:39:50.000+0200},
title = {Constraining structure formation using EDGES},
url = {http://arxiv.org/abs/1909.04641},
year = 2019
}