Probing the Milky Way’s Dark Matter Halo for the 3.5 keV Line. (arXiv:2008.02283v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Sicilian_D/0/1/0/all/0/1">Dominic Sicilian</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cappelluti_N/0/1/0/all/0/1">Nico Cappelluti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bulbul_E/0/1/0/all/0/1">Esra Bulbul</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Civano_F/0/1/0/all/0/1">Francesca Civano</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Moscetti_M/0/1/0/all/0/1">Massimo Moscetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reynolds_C/0/1/0/all/0/1">Christopher S. Reynolds</a>
We present a comprehensive search for the 3.5 keV line, using $sim$51 Ms of
archival Chandra observations peering through the Milky Way’s Dark Matter Halo
from across the entirety of the sky, gathered via the Chandra Source Catalog
Release 2.0. We consider the data’s radial distribution, organizing
observations into four data subsets based on angular distance from the Galactic
Center. All data is modeled using both background-subtracted and
background-modeled approaches to account for the particle instrument
background, demonstrating statistical limitations of the currently-available
$sim$1 Ms of particle background data. A non-detection is reported in the
total data set, allowing us to set an upper-limit on 3.5 keV line flux and
constrain the sterile neutrino dark matter mixing angle. The upper-limit on
sin$^2$(2$theta$) is $2.58 times 10^{-11}$, corresponding to the upper-limit
on 3.5 keV line flux of $2.34 times 10^{-7}$ ph s$^{-1}$ cm$^{-2}$, which is
marginally consistent with several prior detections but is closely consistent
with recently-set constraints. Non-detections are reported in all radial data
subsets, allowing us to constrain the spatial profile of 3.5 keV line
intensity, which does not conclusively differ from Navarro-Frenk-White
predictions. Thus, while offering heavy constraints, we do not entirely rule
out the sterile neutrino dark matter scenario or the more general decaying dark
matter hypothesis for the 3.5 keV line. We have also used the non-detection of
any unidentified emission lines across our continuum to further constrain the
sterile neutrino parameter space.
We present a comprehensive search for the 3.5 keV line, using $sim$51 Ms of
archival Chandra observations peering through the Milky Way’s Dark Matter Halo
from across the entirety of the sky, gathered via the Chandra Source Catalog
Release 2.0. We consider the data’s radial distribution, organizing
observations into four data subsets based on angular distance from the Galactic
Center. All data is modeled using both background-subtracted and
background-modeled approaches to account for the particle instrument
background, demonstrating statistical limitations of the currently-available
$sim$1 Ms of particle background data. A non-detection is reported in the
total data set, allowing us to set an upper-limit on 3.5 keV line flux and
constrain the sterile neutrino dark matter mixing angle. The upper-limit on
sin$^2$(2$theta$) is $2.58 times 10^{-11}$, corresponding to the upper-limit
on 3.5 keV line flux of $2.34 times 10^{-7}$ ph s$^{-1}$ cm$^{-2}$, which is
marginally consistent with several prior detections but is closely consistent
with recently-set constraints. Non-detections are reported in all radial data
subsets, allowing us to constrain the spatial profile of 3.5 keV line
intensity, which does not conclusively differ from Navarro-Frenk-White
predictions. Thus, while offering heavy constraints, we do not entirely rule
out the sterile neutrino dark matter scenario or the more general decaying dark
matter hypothesis for the 3.5 keV line. We have also used the non-detection of
any unidentified emission lines across our continuum to further constrain the
sterile neutrino parameter space.
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