Search for ultralight scalar dark matter with NANOGrav pulsar timing arrays. (arXiv:1904.09143v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Kato_R/0/1/0/all/0/1">Ryo Kato</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Soda_J/0/1/0/all/0/1">Jiro Soda</a>
An ultralight scalar field is a candidate for the dark matter. The ultralight
scalar dark matter with mass around $10^{-23},{rm eV}$ induces oscillations
of the pulse arrival time in the sensitive frequency range of the pulsar timing
arrays. We search for the ultralight scalar dark matter using the North
American Nanohertz Observatory for Gravitational Waves 11-year Data Set. As a
result of the Bayesian analysis, no significant evidence for the presence of
the ultralight scalar dark matter is found. Therefore, the 95% confidence
upper limit is given to the signal induced by the ultralight scalar dark
matter. In comparison with the published Bayesian upper limits on the amplitude
of the ultralight scalar dark matter obtained by Bayesian analysis using the
Parkes Pulsar Timing Array 12-year data set (Porayko et al. 2018), we find
three times stronger upper limit in the frequency range from $10^{-8.34}$ to
$10^{-8.19},{ rm Hz}$ which corresponds to the mass range from
$9.45times10^{-24}$ to $1.34times10^{-23},{rm eV}$. In terms of the energy
density of the dark matter, we find that the energy density near the Earth is
less than $7,{rm GeV/cm^3}$ in the range from $10^{-8.55}$ to $10^{-8.01},{
rm Hz}$ (from $5.83times10^{-24}$ to $2.02times10^{-23},{rm eV}$). The
strongest upper limit on the the energy density is given by $2,{rm GeV/cm^3}$
at a frequency $10^{-8.28},{ rm Hz}$ (corresponding to a mass
$1.09times10^{-23},{rm eV}$). We also confirm that the existence of the
signal induced by the ultralight scalar dark matter can not be excluded if the
solar system ephemeris error is not included in the model of the observation
data. Moreover, if we analyze noises other than the signal of the ultralight
scalar dark matter in advance, we find that the noise of the pulsar PSR
J1909-3744 becomes smaller as expected but the noise of the other pulsars
becomes larger.
An ultralight scalar field is a candidate for the dark matter. The ultralight
scalar dark matter with mass around $10^{-23},{rm eV}$ induces oscillations
of the pulse arrival time in the sensitive frequency range of the pulsar timing
arrays. We search for the ultralight scalar dark matter using the North
American Nanohertz Observatory for Gravitational Waves 11-year Data Set. As a
result of the Bayesian analysis, no significant evidence for the presence of
the ultralight scalar dark matter is found. Therefore, the 95% confidence
upper limit is given to the signal induced by the ultralight scalar dark
matter. In comparison with the published Bayesian upper limits on the amplitude
of the ultralight scalar dark matter obtained by Bayesian analysis using the
Parkes Pulsar Timing Array 12-year data set (Porayko et al. 2018), we find
three times stronger upper limit in the frequency range from $10^{-8.34}$ to
$10^{-8.19},{ rm Hz}$ which corresponds to the mass range from
$9.45times10^{-24}$ to $1.34times10^{-23},{rm eV}$. In terms of the energy
density of the dark matter, we find that the energy density near the Earth is
less than $7,{rm GeV/cm^3}$ in the range from $10^{-8.55}$ to $10^{-8.01},{
rm Hz}$ (from $5.83times10^{-24}$ to $2.02times10^{-23},{rm eV}$). The
strongest upper limit on the the energy density is given by $2,{rm GeV/cm^3}$
at a frequency $10^{-8.28},{ rm Hz}$ (corresponding to a mass
$1.09times10^{-23},{rm eV}$). We also confirm that the existence of the
signal induced by the ultralight scalar dark matter can not be excluded if the
solar system ephemeris error is not included in the model of the observation
data. Moreover, if we analyze noises other than the signal of the ultralight
scalar dark matter in advance, we find that the noise of the pulsar PSR
J1909-3744 becomes smaller as expected but the noise of the other pulsars
becomes larger.
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