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Title: A sensitive search for unknown spectral emission lines in the diffuse X-ray background with XMM-Newton

Abstract

The Standard Model of particle physics can be extended to include sterile (right-handed) neutrinos or axions to solve the dark matter problem. Depending upon the mixing angle between active and sterile neutrinos, the latter have the possibility to decay into monoenergetic active neutrinos and photons in the keV-range while axions can couple to two photons. We have used data taken with the X-ray telescope XMM-Newton for the search of line emissions. We used pointings with high exposures and expected dark matter column densities with respect to the dark matter halo of the Milky Way. The posterior predictive p-value analysis has been applied to locate parameter space regions which favour additional emission lines. In addition, upper limits of the parameter space of the models have been generated such that the preexisting limits have been significantly improved.

Authors:
;  [1];  [2]
  1. Institut für Experimentalphysik, Universität Hamburg, Luruper Chaussee 149, D-22761 Hamburg (Germany)
  2. Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg (Germany)
Publication Date:
OSTI Identifier:
22676150
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2017; Journal Issue: 06; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; AXIONS; DENSITY; EMISSION; KEV RANGE; MILKY WAY; MIXING ANGLE; NONLUMINOUS MATTER; PARTICLE DECAY; PHOTONS; SPACE; STANDARD MODEL; STERILE NEUTRINOS; TELESCOPES; X RADIATION

Citation Formats

Gewering-Peine, A., Horns, D., and Schmitt, J.H.M.M., E-mail: alexander.gewering-peine@desy.de, E-mail: dieter.horns@desy.de, E-mail: jschmitt@hs.uni-hamburg.de. A sensitive search for unknown spectral emission lines in the diffuse X-ray background with XMM-Newton. United States: N. p., 2017. Web. doi:10.1088/1475-7516/2017/06/036.
Gewering-Peine, A., Horns, D., & Schmitt, J.H.M.M., E-mail: alexander.gewering-peine@desy.de, E-mail: dieter.horns@desy.de, E-mail: jschmitt@hs.uni-hamburg.de. A sensitive search for unknown spectral emission lines in the diffuse X-ray background with XMM-Newton. United States. doi:10.1088/1475-7516/2017/06/036.
Gewering-Peine, A., Horns, D., and Schmitt, J.H.M.M., E-mail: alexander.gewering-peine@desy.de, E-mail: dieter.horns@desy.de, E-mail: jschmitt@hs.uni-hamburg.de. Thu . "A sensitive search for unknown spectral emission lines in the diffuse X-ray background with XMM-Newton". United States. doi:10.1088/1475-7516/2017/06/036.
@article{osti_22676150,
title = {A sensitive search for unknown spectral emission lines in the diffuse X-ray background with XMM-Newton},
author = {Gewering-Peine, A. and Horns, D. and Schmitt, J.H.M.M., E-mail: alexander.gewering-peine@desy.de, E-mail: dieter.horns@desy.de, E-mail: jschmitt@hs.uni-hamburg.de},
abstractNote = {The Standard Model of particle physics can be extended to include sterile (right-handed) neutrinos or axions to solve the dark matter problem. Depending upon the mixing angle between active and sterile neutrinos, the latter have the possibility to decay into monoenergetic active neutrinos and photons in the keV-range while axions can couple to two photons. We have used data taken with the X-ray telescope XMM-Newton for the search of line emissions. We used pointings with high exposures and expected dark matter column densities with respect to the dark matter halo of the Milky Way. The posterior predictive p-value analysis has been applied to locate parameter space regions which favour additional emission lines. In addition, upper limits of the parameter space of the models have been generated such that the preexisting limits have been significantly improved.},
doi = {10.1088/1475-7516/2017/06/036},
journal = {Journal of Cosmology and Astroparticle Physics},
number = 06,
volume = 2017,
place = {United States},
year = {Thu Jun 01 00:00:00 EDT 2017},
month = {Thu Jun 01 00:00:00 EDT 2017}
}
  • We present an all-sky catalog of diffuse O VII and O VIII line intensities, extracted from archival XMM-Newton observations. This catalog supersedes our previous catalog, which covered the sky between l = 120 Degree-Sign and l = 240 Degree-Sign . We attempted to reduce the contamination from near-Earth solar wind charge exchange (SWCX) emission by excluding times of high solar wind proton flux from the data. Without this filtering, we were able to extract measurements from 1868 observations. With this filtering, nearly half of the observations became unusable, and only 1003 observations yielded measurements. The O VII and O VIIImore » intensities are typically {approx}2-11 and {approx}<3 photons cm{sup -2} s{sup -1} sr{sup -1} (line unit, L.U.), respectively, although much brighter intensities were also recorded. Our data set includes 217 directions that have been observed multiple times by XMM-Newton. The time variation of the intensities from such directions may be used to constrain SWCX models. The O VII and O VIII intensities typically vary by {approx}<5 and {approx}<2 L.U. between repeat observations, although several intensity enhancements of >10 L.U. were observed. We compared our measurements with models of the heliospheric and geocoronal SWCX. The heliospheric SWCX intensity is expected to vary with ecliptic latitude and solar cycle. We found that the observed oxygen intensities generally decrease from solar maximum to solar minimum, both at high ecliptic latitudes (which is as expected) and at low ecliptic latitudes (which is not as expected). The geocoronal SWCX intensity is expected to depend on the solar wind proton flux incident on the Earth and on the sightline's path through the magnetosheath. The intensity variations seen in directions that have been observed multiple times are in poor agreement with the predictions of a geocoronal SWCX model. We found that the oxygen lines account for {approx}40%-50% of the 3/4 keV X-ray background that is not due to unresolved active galactic nuclei, in good agreement with a previous measurement. However, we found that this fraction is not easily explainable by a combination of SWCX emission and emission from hot plasma in the halo. We also examined the correlations between the oxygen intensities and Galactic longitude and latitude. We found that the intensities tend to increase with longitude toward the inner Galaxy, possibly due to an increase in the supernova rate in that direction or the presence of a halo of accreted material centered on the Galactic center. The variation of intensity with Galactic latitude differs in different octants of the sky, and cannot be explained by a single simple plane-parallel or constant-intensity halo model.« less
  • We present measurements of the Galactic halo's X-ray emission for 110 XMM-Newton sight lines selected to minimize contamination from solar wind charge exchange emission. We detect emission from few million degree gas on {approx}4/5 of our sight lines. The temperature is fairly uniform (median = 2.22 Multiplication-Sign 10{sup 6} K, interquartile range = 0.63 Multiplication-Sign 10{sup 6} K), while the emission measure and intrinsic 0.5-2.0 keV surface brightness vary by over an order of magnitude ({approx}(0.4-7) Multiplication-Sign 10{sup -3} cm{sup -6} pc and {approx}(0.5-7) Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} deg{sup -2}, respectively, with median detections of 1.9more » Multiplication-Sign 10{sup -3} cm{sup -6} pc and 1.5 Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} deg{sup -2}, respectively). The high-latitude sky contains a patchy distribution of few million degree gas. This gas exhibits a general increase in emission measure toward the inner Galaxy in the southern Galactic hemisphere. However, there is no tendency for our observed emission measures to decrease with increasing Galactic latitude, contrary to what is expected for a disk-like halo morphology. The measured temperatures, brightnesses, and spatial distributions of the gas can be used to place constraints on models for the dominant heating sources of the halo. We provide some discussion of such heating sources, but defer comparisons between the observations and detailed models to a later paper.« less
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