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Sterile neutrino dark matter bounds from galaxies of the Local Group  [PDF]
Shunsaku Horiuchi,Philip J. Humphrey,Jose Onorbe,Kevork N. Abazajian,Manoj Kaplinghat,Shea Garrison-Kimmel
Physics , 2013, DOI: 10.1103/PhysRevD.89.025017
Abstract: We show that the canonical oscillation-based (non-resonant) production of sterile neutrino dark matter is inconsistent at $>99$% confidence with observations of galaxies in the Local Group. We set lower limits on the non-resonant sterile neutrino mass of $2.5$ keV (equivalent to $0.7$ keV thermal mass) using phase-space densities derived for dwarf satellite galaxies of the Milky Way, as well as limits of $8.8$ keV (equivalent to $1.8$ keV thermal mass) based on subhalo counts of $N$-body simulations of M 31 analogues. Combined with improved upper mass limits derived from significantly deeper X-ray data of M 31 with full consideration for background variations, we show that there remains little room for non-resonant production if sterile neutrinos are to explain $100$% of the dark matter abundance. Resonant and non-oscillation sterile neutrino production remain viable mechanisms for generating sufficient dark matter sterile neutrinos.
Swift observation of Segue 1: constraints on sterile neutrino parameters in the darkest galaxy  [PDF]
N. Mirabal
Physics , 2010, DOI: 10.1111/j.1745-3933.2010.00963.x
Abstract: Some extensions of standard particle physics postulate that dark matter may be partially composed of weakly interacting sterile neutrino particles that have so far eluded detection. We use a short (~5 ks) archival X-ray observation of Segue 1 obtained with the X-ray Telescope (XRT) onboard the Swift satellite to exclude the presence of sterile neutrinos in the 1.6 - 14 keV mass range down to a flux limit of 6 x 10^{-12} erg cm-2 s-1 within 67 pc of its centre. With an estimated mass-to-light ratio of ~3400 Msun/Lsun, Segue 1 is the darkest ultrafaint dwarf galaxy currently measured. Spectral analysis of the Swift XRT data fails to find any non-instrumental spectral feature possibly connected with the radiative decay of a dark matter particle. Accordingly, we establish upper bounds on the sterile neutrino parameter space based on the non-detection of emission lines in the spectrum. The present work provides the most sensitive X-ray search for sterile neutrinos in a region with the highest dark matter density yet measured.
The role of the eROSITA all-sky survey in searches for sterile neutrino dark matter  [PDF]
Fabio Zandanel,Christoph Weniger,Shin'ichiro Ando
Physics , 2015, DOI: 10.1088/1475-7516/2015/09/060
Abstract: We investigate for the first time the potential of angular auto- and cross-correlation power spectra in identifying sterile neutrino dark matter in the cosmic X-ray background. We take as reference the performance of the soon-to-be-launched eROSITA satellite. The main astrophysical background sources against sterile neutrino decays are active galactic nuclei, galaxies powered by X-ray binaries, and clusters of galaxies. While sterile neutrino decays are always subdominant in the auto-correlation power spectra, they can be efficiently enhanced when cross-correlating with tracers of the dark matter distribution such as galaxies in the 2MASS catalogues. We show that the planned four-years eROSITA all-sky survey will provide a large enough photon statistics to potentially yield very stringent constraints on the decay lifetime, enabling to firmly test the recently claimed 3.56-keV X-ray line found towards several clusters and galaxies and its decaying dark matter interpretation. However, we also show that in order to fully exploit the potential of eROSITA for dark matter searches, it is vital to overcome the shot-noise limitations inherent to galaxy catalogues as tracers for the dark matter distribution.
Improved limits on sterile neutrino dark matter from full-sky observations by the Fermi-GBM  [PDF]
Shunsaku Horiuchi,Kenny C. Y. Ng,Jennifer M. Gaskins,Miles Smith,Robert Preece
Physics , 2015,
Abstract: For the first time, we use the Gamma-ray Burst Monitor (GBM) on-board the Fermi satellite to search for sterile neutrino decay lines in the energy range 10-25 keV corresponding to sterile neutrino mass range 20-50 keV. This energy range has been out of reach of traditional X-ray satellites such as Chandra, Suzaku, XMM-Newton, and gamma-ray satellites such as INTEGRAL. Furthermore, the extremely wide field of view of the GBM opens a large fraction of the Milky Way dark matter halo to be probed. We start with 1601 days worth of GBM data, implement stringent data cuts, and perform two simple line search analyses on the reduced data: in the first, the line flux is limited without background modeling, and in the second, the background is modeled as a power-law. We find no significant excess lines in both our searches. We set new limits on sterile neutrino mixing angles, improving on previous limits by approximately an order of magnitude. Better understanding of detector and astrophysical backgrounds, as well as detector response, can further improve the limit.
Resonantly-Produced 7 keV Sterile Neutrino Dark Matter Models and the Properties of Milky Way Satellites  [PDF]
Kevork N. Abazajian
Physics , 2014, DOI: 10.1103/PhysRevLett.112.161303
Abstract: Sterile neutrinos produced through a resonant Shi-Fuller mechanism are arguably the simplest model for a dark matter interpretation origin of the recent unidentified X-ray line seen toward a number of objects harboring dark matter. Here, I calculate the exact parameters required in this mechanism to produce the signal. The suppression of small scale structure predicted by these models is consistent with Local Group and high-$z$ galaxy count constraints. Very significantly, the parameters necessary in these models to produce the full dark matter density fulfill previously determined requirements to successfully match the Milky Way Galaxy's total satellite abundance, the satellites' radial distribution and their mass density profile, or "too big to fail problem." I also discuss how further precision determinations of the detailed properties of the candidate sterile neutrino dark matter can probe the nature of the quark-hadron transition, which takes place during the dark matter production.
STERILE NEUTRINOS AS A SOLUTION TO ALL NEUTRINO ANOMALIES  [PDF]
Juha T. Peltoniemi
Physics , 1995,
Abstract: The sterile neutrino solutions to different irregular results and observations in neutrino physics are studied. It is pointed out that introducing sterile neutrinos helps to solve simultaneously the observed anomalies. It is argued that sterile neutrinos can solve the conflict between dark matter neutrinos, LSND result and supernova nucleosynthesis. Other supernova constraints for sterile neutrinos are revised. Possibilities to avoid the big bang nucleosynthesis constraints for sterile neutrinos are explored. It is claimed that sterile neutrinos can solve the crisis in big bang nucleosynthesis. It is pointed out that sterile neutrinos can provide a consistent explanation to the anomalies observed at Karmen. It is argued that sterile neutrinos are valid dark matter candidates. It is claimed that the conversions to sterile states are consistent solutions to both the solar and the atmospheric neutrino problems, and cannot be ruled out by cosmological or astrophysical arguments. Models for the masses and the interactions of sterile neutrinos are reviewed.
Next decade of sterile neutrino studies  [PDF]
Alexey Boyarsky,Dmytro Iakubovskyi,Oleg Ruchayskiy
Physics , 2013, DOI: 10.1016/j.dark.2012.11.001
Abstract: We review the status of sterile neutrino dark matter and discuss astrophysical and cosmological bounds on its properties as well as future prospects for its experimental searches. We argue that if sterile neutrinos are the dominant fraction of dark matter, detecting an astrophysical signal from their decay (the so-called 'indirect detection') may be the only way to identify these particles experimentally. However, it may be possible to check the dark matter origin of the observed signal unambiguously using its characteristic properties and/or using synergy with accelerator experiments, searching for other sterile neutrinos, responsible for neutrino flavor oscillations. We argue that to fully explore this possibility a dedicated cosmic mission - an X-ray spectrometer - is needed.
Sterile neutrino production in models with low reheating temperatures
Yaguna, Carlos E.
High Energy Physics - Phenomenology , 2007, DOI: 10.1088/1126-6708/2007/06/002
Abstract: By numerically solving the appropriate Boltzmann equations, we study the production of sterile neutrinos in models with low reheating temperatures. We take into account the production in oscillations as well as in direct decays and compute the sterile neutrino primordial spectrum, the effective number of neutrino species, and the sterile neutrino contribution to the mass density of the Universe as a function of the mixing and the reheating parameters. It is shown that sterile neutrinos with non-negligible mixing angles do not necessarily lead to $N_\nu\sim 4$ and that sterile neutrinos may have the right relic density to explain the dark matter of the Universe. If dark matter consists of sterile neutrinos produced in oscillations, X-rays measurements set a strong limit on the reheating temperature, $\tr\gtrsim 7\mev$. We also point out that the direct decay opens up a new production mechanism for sterile neutrino dark matter where cosmological constraints can be satisfied.
Sterile Neutrino and Accelerating Universe  [PDF]
P. Q. Hung
Physics , 2000,
Abstract: If all three neutrino oscillation data were to be confirmed in the near future, it is probable that one might need a sterile neutrino, in addition to the three active ones. This sterile neutrino, nu_S, would be very light with mass m_{nu_S} less than or equal to 1 eV or even with m_{\nu_S} approximately 10^{-3} eV according to some scenarios. Why would it be so light? On another front, recent cosmological observations and analyses appear to indicate that the present universe is flat and accelerating, and that the present energy density is dominated by a ``dark variety'', with rho_V approximately (10^{-3}eV)^4. Is it a constant? Is there a link between these apparently unrelated phenomena?
Tidal Disruption of Satellite Galaxies in a Semi-Analytic Model of Galaxy Formation  [PDF]
Bruno M. B. Henriques,Peter A. Thomas
Physics , 2009, DOI: 10.1111/j.1365-2966.2009.16151.x
Abstract: We introduce a new physical recipe into the De Lucia and Blaizot version of the Munich semi-analytic model built upon the Millennium dark matter simulation: the tidal stripping of stellar material from satellite galaxies during mergers. To test the significance of the new physical process we apply a Monte Carlo Markov Chain parameter estimation technique constraining the model with the $K$-band luminosity function, $B-V$ colours and the black hole-bulge mass relation. The differences in parameter correlations, and in the allowed regions in likelihood space, reveal the impact of the new physics on the basic ingredients of the model, such as the star-formation laws, feedback recipes and the black hole growth model. With satellite disruption in place, we get a model likelihood four times higher than in the original model, indicating that the new process seems to be favoured by observations. This is achieved mainly due to a reduction in black hole growth that produces a better agreement between the properties of central black holes and host galaxies. Compared to the best-fit model without disruption, the new model removes the excess of dwarf galaxies in the original recipe with a more modest supernova heating. The new model is now consistent with the three observational data sets used to constrain it, while significantly improving the agreement with observations for the distribution of metals in stars. Moreover, the model now follows the build up of intra-cluster light.
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