Fermi Gamma-ray Haze via Dark Matter and Millisecond Pulsars Dmitry Malyshev, Ilias Cholis, Joseph Gelfand CCPP, NYU arxiv: 1002.0587
Gamma-ray haze via DM and MSPs Gamma-ray haze data Dobler et al. arxiv:0910.4583 This is the gamma-ray overdensity that remains after subtracting these templates from the Fermi data
Gamma-ray haze via DM and MSPs Possibilities to consider: 1. Dark Matter annihilation 2. IA supernovae electrons 3. Millisecond pulsars pulsed gamma-rays and e+e-
Gamma-ray haze via DM and MSPs Compare the luminosities in the Milky Way halo Gamma-ray haze: ∼ 10 38 erg / s 1. Dark Matter 2. IA supernovae 3. Millisecond pulsars
Gamma-ray haze via DM and MSPs Compare the luminosities in the Milky Way halo Gamma-ray haze: ∼ 10 38 erg / s 1. Dark Matter: ∼ 2 × 10 37 erg / s freeze out cross section � σ v � 0 = 3 . 0 × 10 − 26 cm 3 s − 1 mass 300 GeV Einasto profile local DM density ρ DM = 0 . 4 GeVcm − 3 We need either large boost factors or prompt gamma-ray emission
Gamma-ray haze via DM and MSPs Compare the luminosities in the Milky Way halo Gamma-ray haze: ∼ 10 38 erg / s 1. Dark Matter: ∼ 2 × 10 37 erg / s 2. IA supernovae: < 10 37 erg / s Based on 1A SNe rate in the halo (Sullivan et al. 2006) 5 × 10 − 14 yr − 1 M − 1 ⊙ and average SNe output in electrons necessary to account for high energy cosmic rays (Kobayashi et al. 2004) 10 48 erg
Gamma-ray haze via DM and MSPs Compare the luminosities in the Milky Way halo Gamma-ray haze: ∼ 10 38 erg / s 1. Dark Matter: ∼ 2 × 10 37 erg / s 2. IA supernovae: < 10 37 erg / s 3. Millisecond pulsars: < 10 39 erg / s For a population of 50 000 pulsars in the Milky Way halo with average spin-down luminosity for 8 MSPs observed by Fermi (Abdo et al. 2009) 2 × 10 34 erg / s
Gamma-ray haze via DM and MSPs Pulsed gamma-rays from 47 Tuc MSPs are similar to low energy part in the gamma-ray haze spectrum. Thus we can expect that the low energy part can be explained by a population of Milky Way halo MSPs ? DM ? MSPs in the Milky Way halo. The high energy part of the gamma-haze spectrum is more difficult to explain. 47 Tuc MSPs Abdo et al. 2009 Dobler et al. 2009
Gamma-ray haze via DM and MSPs Fermi Haze Template (|l| " 15, -30 " b " -10) 7 Total Total DM W + W - , M ! =300 GeV DM W + W - , Prompt # Milky Way Halo MSPs 6 DM W + W - , ICS off ISRF × 10 constant Intensity (10 -20 erg/sec/Hz/cm 2 /sr) Haze Data E 2 Intensity (GeV cm -2 sec -1 sr -1 ) MSPs pulsed # , P # =5.6 × 10 37 erg s -1 v = 23 GHz 5 MSPs ICS off ISRF, P e ± =2.7 × 10 38 erg s -1 4 1e-06 M ! =300 GeV 3 MSP e+e- ICS 2 1 Pulsed gammas 0 DM prompt gammas 5 10 15 20 25 30 35 1e-07 Latitudinal Radial Distance from GC (degrees) Both gamma-ray haze and DM e+e- ICS x10 WMAP haze are OK 0.1 1 10 100 1000 Energy (GeV) In this model we need 30 000 MSPs in Milky Way halo with average spin-down energy conversion efficiencies = 0 . 1 η γ = 0 . 5 η e ±
Gamma-ray haze via DM and MSPs MSPs pulsed gammas and DM to W+W- prompt gammas Fermi Haze Template (|l| " 15, -30 " b " -10) 7 Total Total DM W + W - , M ! =300 GeV, B.F.=3 DM W + W - , Prompt # constant 6 Haze Data DM W + W - , ICS off ISRF × 10 Intensity (10 -20 erg/sec/Hz/cm 2 /sr) 5 v = 23 GHz E 2 Intensity (GeV cm -2 sec -1 sr -1 ) MSPs pulsed # , P # =1.3 × 10 38 erg s -1 4 M ! =300 GeV, B.F.=3 1e-06 DM prompt gammas 3 2 Pulsed gammas 1 0 5 10 15 20 25 30 35 Latitudinal Radial Distance from GC (degrees) 1e-07 DM e+e- ICS x10 WMAP haze: No 0.1 1 10 100 1000 Energy (GeV) Gamma-ray haze: OK with DM BF = 3 Here we need 60 000 MSPs in Milky Way halo with η γ = 0 . 1
Gamma-ray haze via DM and MSPs MSPs pulsed gammas and DM e+e- annihilation 7 Total Fermi Haze Template (|l| " 15, -30 " b " -10) XDM e ± , M ! =1.2 TeV, B.F.=100 Total constant 6 Haze Data XDM e ± , ICS off ISRF Intensity (10 -20 erg/sec/Hz/cm 2 /sr) XDM e ± , FSR × 100 5 v = 23 GHz E 2 Intensity (GeV cm -2 sec -1 sr -1 ) MSPs pulsed # , P # =3.4 × 10 37 erg s -1 4 M ! =1.2 TeV, B.F.=100 1e-06 3 2 DM e+e- ICS 1 DM FSR x100 0 5 10 15 20 25 30 35 Latitudinal Radial Distance from GC (degrees) 1e-07 Pulsed gammas WMAP haze: OK 0.1 1 10 100 1000 Energy (GeV) Gamma-ray haze: OK with DM BF = 100 In this case we need 20 000 MSPs in Milky Way halo with η γ = 0 . 1
Gamma-ray haze via DM and MSPs Conclusions 1. In DM models with one type of DM particles we need an astrophysical source of gamma-rays in the Milky Way halo 2. Millisecond pulsars is the most plausible such source 3. We need about 20 000 - 60 000 MSPs in the Milky Way stellar halo. 4. To fit the WMAP haze we need either • leptonically annihilating DM with BF ~ 100 or • significant e+e- emission from MSPs (about 50% of spin-down)
Recommend
More recommend
