Optimized dark matter searches in deep observations of Segue 1 with MAGIC

Abstract

We present the results of stereoscopic observations of the satellite galaxy Segue 1 with the MAGIC Telescopes, carried out between 2011 and 2013. With almost 160 hours of good-quality data, this is the deepest observational campaign on any dwarf galaxy performed so far in the very high energy range of the electromagnetic spectrum. We search this large data sample for signals of dark matter particles in the mass range between 100 GeV and 20 TeV. For this we use the full likelihood analysis method, which provides optimal sensitivity to characteristic gamma-ray spectral features, like those expected from dark matter annihilation or decay. In particular, we focus our search on gamma-rays produced from different final state Standard Model particles, annihilation with internal bremsstrahlung, monochromatic lines and box-shaped signals. Our results represent the most stringent constraints to the annihilation cross-section or decay lifetime obtained from observations of satellite galaxies, for masses above few hundred GeV. In particular, our strongest limit (95% confidence level) corresponds to a ∼ 500 GeV dark matter particle annihilating into τ+τ−, and is of order ⟨σannv⟩ ≃ 1.2 × 10−24 cm3 s−1 — a factor ∼ 40 above the ⟨σannv⟩ ≃ thermal value.

A White Paper on keV sterile neutrino Dark Matter

“…Limits on the DM decay width with gauge bosons in the final state were derived in [363] from an analysis of the diffuse gamma-ray emission using Fermi-LAT data, in [361] from observations of the dwarf galaxy Segue 1 using the MAGIC telescopes, and in [364] from Fermi-LAT observations of several nearby galaxies and clusters. Besides, limits from antiprotons were derived in [365,366] from the non-observation of an excess in the antiproton-toproton fraction measured by the PAMELA experiment [367].…”

Optimized Dark Matter Searches in Deep Observations of Segue 1 with MAGIC

“…Then, by the means of the Kolmogorov-Smirnov statistics (K-S), we compare the energy distribution of events from each of the modeling zones (individually and combined) to that from the OFF region. The modeling region(s) providing the highest K-S probability is (are) selected, and its (smoothed) measured differential energy distribution is used as the background model in the full likelihood (for more details, refer to [36]). The statistical and systematic uncertainties introduced by this procedure in our final results are estimated by comparing the limits obtained using the selected modeling region(s) with those that we would obtain if the average of all four zones was used instead.…”

Constraints on Dark Matter with Gamma-Ray Experiments and Future Observational Strategies

“…As baryons collapse and move to the center they increase the gravitational potential, which in turn forces the FIGURE 1 | Comparison of constraints on the DM annihilation cross section for the bb (Left) and τ τ (Right) channels [25] with previously published constraints from LAT analysis of the Milky Way halo (3σ limit) [26], 112 h of observations of the Galactic Center with H.E.S.S. [27], and 157.9 h of observations of Segue 1 with MAGIC [28]. These limits have been found to be fairly insensitive to the assumed DM density profile [25].…”

“…The analysis of the Fermi Collaboration [22] using 5 years of data and the Pass 7 event selections [23] and the on-going analysis with 6.5 year of data and the Pass 8 event selections [24] confirm the excess but confirm also that when all the uncertainties on the excess morphology and spectrum related to the modeling of the various components of gamma-ray emission in that region, in particular in the distribution of interstellar gas along the line of sight, in the low latitude emission from the Fermi bubbles, and in the abundance of cosmic ray sources in the innermost Galaxy are considered the spectrum varies significantly and it is not possible FIGURE 2 | Comparison of Fermi-LAT constraints on the DM annihilation cross section for the τ τ channel [25] with Antares [29], IceCube-DeepCore [30] and MAGIC [28]. to discriminate between the different hypotesis.…”

“…However, uncertainties in the structure of the Galactic DM distribution can significantly enlarge the best-fit regions of σ v channel, and m DM . Figure 2 shows a comparison of constraints on the DM annihilation cross section for the τ τ channel [25] with Antares [29], IceCube-DeepCore [30] and MAGIC [28]. One can see that the Fermi limits are the best limits below 2 TeV.…”