Erratum to “Observations of the Sagittarius dwarf galaxy by the HESS experiment and search for a dark matter signal” [Astropart. Phys. 29(1) (2008) 55–62]

Abstract

Observations of the Sagittarius dwarf spheroidal (Sgr dSph) galaxy were carried out with the H.E.S.S. array of four imaging air Cherenkov telescopes in June 2006. A total of 11 hours of high quality data are available after data selection. There is no evidence for a very high energy γ-ray signal above the energy threshold at the target position. A 95% C.L. flux limit of 3.6 × 10 −12 cm −2 s −1 above 250 GeV has been derived. Constraints on the velocity-weighted cross section σv are calculated in the framework of Dark Matter particle annihilation using realistic models for the Dark Matter halo profile of Sagittarius dwarf galaxy. Two different models have been investigated encompassing a large class of halo types. A 95% C.L. exclusion limit on σv of the order of 2 × 10 −25 cm 3 s −1 is obtained for a core profile in the 100 GeV -1 TeV neutralino mass range.

Leptonic dark matter annihilation in the evolving universe: constraints and implications

“…In our model, in the absence of DM annihilation but with X-ray only, the ionization fraction and the IGM temperature till z ≈ 6 are O(10 −3 ) and O(100) K respectively 4 . If the DM annihilation is taken into account as an energy source, the cosmic ionization fraction will have a higher plateau (of the order O(10 −3 )) during the evolution history.…”

“…It is found that the global 21 cm signal for the models with DM annihilation differs somewhat from the "standard" scenario without DM annihilation. Due to the rise of the IGM temperature 4 Note that the ionization fraction seems to be lower than that derived according to observations of Lyα forest and the WMAP measurement of the electron scattering optical depth [76]. In this work we only adopt a simple description of the ordinary reionization precess and do not intend to give good description to Lyα forest and WMAP data.…”

“…with the energy loss rate b(E e , z) ≈ 2.67 × 10 −17 (1 + z) 4 (E e /GeV) 2 GeV s −1 . Finally the differential Klein-Nishina cross section F KN (ǫ, E e , E) in Eq.…”

“…Recently, observations of the cosmic ray (CR) positron fraction by the PAMELA experiment [1], the total electron and positron spectra by the ATIC [2] experiment, the PPB-BETS [3] experiment, the HESS [4,5] experiment and the Fermi [6] experiment all show interesting excesses when compared with the expectations of the conventional astrophysical background.…”

Gamma rays from blazars

“…Vary rapid variations of the γ-ray flux, with inferred doubling time-scales down to few minutes, have been observed in several blazars (both BL Lacs and FSRQ), most notably PKS 2155-304 [43], Mkn 501 [44], BL Lac [45], PKS 1222+21 [46], IC 310 ( [47] although the precise classification of this source is still matter of debate) and, last but not least, 3C279 (at GeV energies by pointed observations with Fermi/LAT, [48]). Such small timescales directly imply, via the standard causality argument, very compact emission regions, with radii not exceeding r < ct var δ ≈ FIGURE 1.…”