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Searching for dark matter X-ray lines from the Large Magellanic Cloud with eROSITA

Jorge Terol Calvo, Marco Taoso, Andrea Caputo, Michela Negro, Marco Regis

Abstract

We perform a search for an X-ray monochromatic line arising from dark matter (DM) decay in the halo of the Large Magellanic Cloud. An emission line can be expected from two well-motivated DM candidates: sterile neturinos and axion-like particles (ALPs). We analyze the eROSITA-DE DR1 datasets in the energy range between 1 and 9 keV. No evidence for a DM line is found, and we set lower limits on the DM lifetime. We then recast these bounds into upper limits on the active-sterile neutrino mixing angle $\sin^2(2θ)$ and on the ALP to photon coupling $g_{aγ}$, for DM masses between 2 and 18 keV. These results set new strong constraints for masses below 5 keV.

Searching for dark matter X-ray lines from the Large Magellanic Cloud with eROSITA

Abstract

We perform a search for an X-ray monochromatic line arising from dark matter (DM) decay in the halo of the Large Magellanic Cloud. An emission line can be expected from two well-motivated DM candidates: sterile neturinos and axion-like particles (ALPs). We analyze the eROSITA-DE DR1 datasets in the energy range between 1 and 9 keV. No evidence for a DM line is found, and we set lower limits on the DM lifetime. We then recast these bounds into upper limits on the active-sterile neutrino mixing angle and on the ALP to photon coupling , for DM masses between 2 and 18 keV. These results set new strong constraints for masses below 5 keV.
Paper Structure (5 sections, 6 equations, 7 figures)

This paper contains 5 sections, 6 equations, 7 figures.

Table of Contents

  1. Introduction
  2. Data
  3. Line search: methodology
  4. Results
  5. Conclusions

Figures (7)

  • Figure 1: Source-exclusion mask ("cheesemask") used for the analysis. Pixels shown in black are excluded from the spectral extraction.
  • Figure 2: Count rate in the 1–9 keV energy range for all seven TMs within the extraction region defined by the cheesemask in Fig. \ref{['fig:CheeseMask']}. See text for details.
  • Figure 3: Left: Local significance $\sqrt{\rm TS}$ of line detection across the energy range studied. Dashed gray lines show the location of the instrumental background lines included in the analysis. Right: Upper limits on the the DM line flux across the energy range studied.
  • Figure 4: Data and fitted spectra for two DM line searches in the eROSITA telescope module TM3. The red dashed line corresponds to the background model, the green dotted line to the DM signal corresponding to the 95% C.L. upper limit (combining all seven TMs) and the blue solid line to their sum, i.e. the total fitted model. Left and right panels refer to the search of a DM line at energies $E=1.206$ keV and $E=4.325$ keV, respectively.
  • Figure 5: Lower limits on the DM lifetime, $\tau_{\rm DM}$, as a function of the DM mass, $m_{\rm DM}$, for a two body decay process with one photon in the final state. In purple we show the limits derived in this paper using LMC observations from eROSITA DR1. In gray we show previously derived lower limits from other X-ray observations including NuSTAR Roach:2022lgo, XMM-Newton Foster:2021ngm, Chandra Horiuchi:2013noa and Suzaku Loewenstein:2008yi.
  • ...and 2 more figures