7.1 keV sterile neutrino constraints from X-ray observations of 33 clusters of galaxies with Chandra ACIS (original) (raw)
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An X-ray Spectroscopic Search for Dark Matter in the Perseus Cluster with Suzaku
We present the results from deep Suzaku observations of the central region of the Perseus cluster. Bulbul et al. (2014) reported the detection by XMM-Newton instruments of an unidentified X-ray emission line at an energy around 3.5keV in spectra for the Perseus and other clusters. They argued for a possibility of the decay of sterile neutrino, a dark matter candidate. We examine Suzaku X-ray Imaging Spectrometer (XIS) spectra of the Perseus cluster for evidence in the 3.5keV line and other possible dark matter features in the 2-6keV energy band. In order to search for and constrain a weak line feature with the XIS, observations of the Crab nebula are used to evaluate the system's effective area. We found no line feature at the claimed position with a systematic line flux upper limit at a half (1.5eV in line equivalent width) of the claimed best-fit value by Bulbul et al. We discuss this inconsistency in terms of instrumental calibration errors and modeling of continuum emission. Future prospects for high-energy resolution spectroscopy with ASTRO-H are presented.
X-ray lines from dark matter: the good, the bad, and the unlikely
Journal of Cosmology and Astroparticle Physics, 2014
We consider three classes of dark matter (DM) models to account for the recently observed 3.5 keV line: metastable excited state DM, annihilating DM, and decaying DM. We study two examples of metastable excited state DM. The first, millicharged composite DM, has both inelasticity and photon emission built in, but with a very constrained parameter space. In the second example, up-scattering and decay come from separate sectors and is thus less constrained. The decay of the excited state can potentially be detectable at direct detection experiments. However we find that CMB constraints are at the border of excluding this as an interpretation of the DAMA signal. The annihilating DM interpretation of the X-ray line is found to be in tension with CMB constraints.
Search for Photon-Linelike Signatures from Dark Matter Annihilations with H.E.S.S
Physical Review Letters, 2013
Gamma-ray line signatures can be expected in the very-high-energy (E > 100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily distinguishable from astrophysical -ray sources that in most cases produce continuous spectra that span over several orders of magnitude in energy. Using data collected with the H.E.S.S. -ray instrument, upper limits on linelike emission are obtained in the energy range between 500GeVand500 GeV and 500GeVand25 TeV for the central part of the Milky Way halo and for extragalactic observations, complementing recent limits obtained with the Fermi-LAT instrument at lower energies. No statistically significant signal could be found. For monochromatic -ray line emission, flux limits of ð2 Â 10 À7 -2 Â 10 À5 Þ m À2 s À1 sr À1 and ð1 Â 10 À8 -2 Â 10 À6 Þ m À2 s À1 sr À1 are obtained for the central part of the Milky Way halo and extragalactic observations, respectively. For a DM particle mass of 1 TeV, limits on the velocity-averaged DM annihilation cross section hvi ! reach $10 À27 cm 3 s À1 , based on the Einasto parametrization of the Galactic DM halo density profile. PACS numbers: 95.35.+d, 95.85.Pw Introduction.-In the last few years, imaging atmospheric Cherenkov telescopes have been used to search for dark matter (DM) signals in very-high-energy (VHE; E > 100 GeV) rays [1-10]. Objects with large predicted DM density, like the Galactic center (GC), the central Galactic halo region (CGH), dwarf galaxies, or centers of nearby galaxies were studied. All such searches concentrated on the detection of rays produced in decays of secondary particles-mostly neutral mesons-in the process of DM self-annihilation or decay (see, e.g., Refs. [11,). The broad energy distribution of such rays is continuous and therefore more difficult to distinguish from -ray emission from astrophysical (particle accelerating) sources, as opposed to spectral features, which would pose a much more striking evidence for a DM-induced -ray signal. The most prominent spectral feature is a -ray line (note, however, that VHE -ray line features may also arise due to unshocked e þ =e À winds created by pulsars [13]), which, for DM self-annihilation into =Z (and m ) m Z ), is expected at an energy at or close to the DM particle mass, E % m . For a decay ! X of a DM particle with m ) m X , E % m =2. Such annihilations or decays are, however, loop
Decaying dark matter in dwarf spheroidal galaxies: Prospects for x-ray and gamma-ray telescopes
Physical Review D
Dwarf spheroidal galaxies are dark matter dominated systems, and as such, ideal for indirect dark matter searches. If dark matter decays into high-energy photons in the dwarf galaxies, they will be a good target for current and future generations of X-ray and gamma-ray telescopes. By adopting the latest estimates of density profiles of dwarf galaxies in the Milky Way, we revise the estimates dark matter decay rates in dwarf galaxies; our results are more robust, but weaker than previous estimates. Applying these results, we study the detectability of dark matter decays with X-ray and very-high-energy gamma-ray telescopes, such as eROSITA, XRISM, Athena, HAWC, and CTA. Our projection shows that all of these X-ray telescopes will be able to critically assess the claim of the 7 keV sterile neutrino decays from stacked galaxy clusters and nearby galaxies. For TeV decaying dark matter, we can constrain its lifetime to be longer than ∼10 27-10 28 s. We also make projections for future dwarf galaxies that would be newly discovered with the Vera Rubin Observatory Legacy Survey of Space and Time, which will further improve the expected sensitivity to dark matter decays both in the keV and PeV mass ranges.
Dwarf galaxy annihilation and decay emission profiles for dark matter experiments
2014
Gamma-ray searches for dark matter annihilation and decay in dwarf galaxies rely on an understanding of the dark matter density profiles of these systems. Conversely, uncertainties in these density profiles propagate into the derived particle physics limits as systematic errors. In this paper we quantify the expected dark matter signal from 20 Milky Way dwarfs using a uniform analysis of the most recent stellar-kinematic data available. Assuming that the observed stellar populations are equilibrium tracers of spherically-symmetric gravitational potentials that are dominated by dark matter, we find that current stellar-kinematic data can predict the amplitudes of annihilation signals to within a factor of a few for the ultra-faint dwarfs of greatest interest. On the other hand, the expected signal from several classical dwarfs (with high-quality observations of large numbers of member stars) can be localized to the ~20% level. These results are important for designing maximally sensitive searches in current and future experiments using space and ground-based instruments.
Physical Review D, 2020
Local dwarf spheroidal galaxies (dSphs) are nearby dark-matter dominated systems, making them excellent targets for searching for gamma rays from particle dark matter interactions. If dark matter annihilates or decays directly into two gamma rays (or a gamma ray and a neutral particle), a monochromatic spectral line is created. At TeV energies, no other processes are expected to produce spectral lines, making this a very clean indirect dark matter search channel. With the development of event-by-event energy reconstruction, we can now search for spectral lines with the High Altitude Water Cherenkov (HAWC) Observatory. HAWC is a wide field of view survey instrument located in central Mexico that observes gamma rays from <1 TeV to >100 TeV. In this work we present results from a recent search for spectral lines from local, dark matter dominated dwarf galaxies using 1038 days of HAWC data. We also present updated limits on several continuum channels that were reported in a previous publication. Our gamma-ray spectral line limits are the most constraining obtained so far from 20 TeV to 100 TeV.
Physical Review D, 2007
We present upper limits on line emission in the Cosmic X-ray background (CXB) that would be produced by decay of sterile neutrino dark matter. We employ the spectra of the unresolved component of the CXB in the Chandra Deep Fields North and South obtained with the Chandra CCD detector in the E = 0.8 − 9 keV band. The expected decay flux comes from the dark matter on the lines of sight through the Milky Way galactic halo. Our constraints on the sterile neutrino decay rate are sensitive to the modeling of the Milky Way halo. The highest halo mass estimates provide a limit on the sterile neutrino mass of ms < 2.9 keV in the Dodelson-Widrow production model, while the lowest halo mass estimates provide the conservative limit of ms < 5.7 keV (2σ). We also discuss constraints from a short observation of the softer (E < 1 keV) X-ray background with a rocket-borne calorimeter by McCammon and collaborators.
Direct x-ray constraints on sterile neutrino warm dark matter
Physical Review D, 2006
Warm dark matter (WDM) might more easily account for small scale clustering measurements than the heavier particles typically invoked in Lambda cold dark matter (LCDM) cosmologies. In this paper, we consider a Lambda WDM cosmology in which sterile neutrinos nu_s, with a mass m_s of roughly 1-100 keV, are the dark matter. We use the diffuse X-ray spectrum (total minus resolved point source emission) of the Andromeda galaxy to constrain the rate of sterile neutrino radiative decay: nu_s -> nu_{e,mu,tau} + gamma. Our findings demand that m_s < 3.5 keV (95% C.L.) which is a significant improvement over the previous (95% C.L.) limits inferred from the X-ray emission of nearby clusters, m_s < 8.2 keV (Virgo A) and m_s < 6.3 keV (Virgo A + Coma).