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Gamma-rays from Dark Matter Mini-Spikes in Andromeda Galaxy M31

Gamma-rays from Dark Matter Mini-Spikes in Andromeda Galaxy M31. Mattia Fornasa and Marco Taoso. based on astro-ph/0703757 by M. Fornasa, M. Taoso and G.Bertone. 2nd IDAPP 2days Meeting - Giovedì 3 maggio 2007. Introduction. Evidences for Dark Matter (DM) WMAP measurement ( W m =0.25)

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Gamma-rays from Dark Matter Mini-Spikes in Andromeda Galaxy M31

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  1. Gamma-rays from Dark Matter Mini-Spikes in Andromeda Galaxy M31 Mattia Fornasa and Marco Taoso based on astro-ph/0703757 by M. Fornasa, M. Taoso and G.Bertone 2nd IDAPP 2days Meeting - Giovedì 3 maggio 2007

  2. Introduction • Evidences for Dark Matter (DM) • WMAP measurement (Wm=0.25) • rotation curves of galaxies • the “bullet” cluster • Open Problems • DM nature • DM interactions • DM formation mechanism • Detection techniques • signals from colliders • direct detection • indirect detection of annihilation • products such as neutrinos, antiprotons or gamma-rays Chandra photo album: X-ray image of 1E0657-558 3 Maggio 2007 M. Fornasa and M.Taoso

  3. Introduction Our work is focused on indirect detection: we are looking for gamma-rays from DM annihilation in high-density regions in the sky (1) • search for a signal from the Galactic Center • HESS reported an excess of gamma-rays • no possible interpretation as DM annihilation HESS collaboration, astro-ph/0610509 3 Maggio 2007 M. Fornasa and M.Taoso

  4. Introduction • Intermediate Mass Black Holes (IMBHs) • located in mini-halos in the Galactic smooth DM profile • necessity to consider an extragalactic source (M31) G. Bertone, astro-ph/ 0603148 High-energy, point-like, unknown gamma-rays sources in a 3° region around Andromeda would be a clear and unquestionable signal for DM annihilations around IMBHs 3 Maggio 2007 M. Fornasa and M.Taoso

  5. Intermediate Mass Black Holes (IMBHs) • mass from 20 M to 106 M • no one actually ever “detected” an • Intermediate Mass Black Hole • Evidences for IMBHs: • Ultra Luminous X-ray • sources (ULXs) • extrapolation of M-s • relation of SMBHs to • globular clusters • IMBHs would provide • massive seeds for the • growth of SMBHs G. Bertone, astro-ph/ 0603148 Miller, Colbert, astro-ph/0308402 3 Maggio 2007 M. Fornasa and M.Taoso

  6. Intermediate Mass Black Holes (IMBHs) G. Bertone, astro-ph/ 0603148 3 Maggio 2007 M. Fornasa and M.Taoso

  7. Spike formation at the Galactic center Galactic halo density profile is supposed to be a Navarro-Frenk-White (NFW): (3) From a power-law density profile, a “spike” can form with a new slope: G. Bertone, astro-ph/ 0603148 (4) (5) 3 Maggio 2007 M. Fornasa and M.Taoso

  8. Spike formation at the Galactic center Ullio, Zhao, Kamionkowski, astro-ph/0101481 G. Bertone, astro-ph/ 0603148 From a NFW (g=-1) the final spike has gsp=-7/3 (6) (7) 3 Maggio 2007 M. Fornasa and M.Taoso

  9. Spike formation at the Galactic center • Arguments against spikes formation: • off-center black hole formation • gravitational interaction with stars • merger effects • “loss-cone”, DM that falls inside rSchw G. Bertone, astro-ph/ 0603148 Ullio, Zhao, Kamionkowski, astro-ph/0101481 Merritt, Milosavljevic, Verde, Jimenez astro-ph/0201376 3 Maggio 2007 M. Fornasa and M.Taoso

  10. IMBHs catalogue (Bertone, Zentner, Silk) • Focusing on astro-ph/0509565 by G. Bertone, • A. Zentner and J. Silk: • initial catalogue of IMBHs • merging tree • selection of unmerged mini-halos • no baryonic content and the BH lays in the center G. Bertone, astro-ph/ 0603148 Bertone, Zentner, Silk, Astro-ph/0509565 3 Maggio 2007 M. Fornasa and M.Taoso

  11. IMBHs catalogue for Andromeda • How IMBHs are characterized: • realization ID • Black Hole Mass [M] • IMBH distance from the center of the Galaxy [kpc] • rsp [kpc] • r(rsp) [M/kpc3] G. Bertone, astro-ph/ 0603148 Andromeda IMBHs are 65.2±14.5 per realization, with an average mass of 1.54·105M and an average distance from M31 center of 32.3 kpc. 3 Maggio 2007 M. Fornasa and M.Taoso

  12. Annihilation Flux (8) To compute the differential energy spectrum a particular model of physics beyond the SM is needed: G. Bertone, astro-ph/ 0603148 (9) (10) 3 Maggio 2007 M. Fornasa and M.Taoso

  13. Differential energy spectrum • FPS (Fornengo-Pieri-Scopel) • MSSM is assumed and the DM candidate is the lightest neutralino • focused on hadronization of b quarks • fit from simulated data, using standard package as PYTHIA • (x=E/mc) (10) (a, b, c, d, e)=(-1.5, 0.37, -16.05, 18.01, -19.50) G. Bertone, astro-ph/ 0603148 • Kretzer Fragmentation Functions (www.pv.infn.it/%7Eradici/FFdatabase) • DM candidate is again a neutralino • photon production from a p0 resulting from quarks b (11) 3 Maggio 2007 M. Fornasa and M.Taoso

  14. Differential energy spectrum • BBEG (Bergstrom-Bringmann-Eriksson-Gustafsson) • DM candidate from Universal Extra-Dimension, • what is called B(1) • contribution of primary photons from charged leptons is no longer neglected (B(1)B(1)gl+l-) (12) G. Bertone, astro-ph/ 0603148 3 Maggio 2007 M. Fornasa and M.Taoso

  15. Detection of IMBHs with ACTs • mc=1 TeV and sv=3·10-26 cm3s-1 • Eth=100 GeV • typical ACT angular resolution is 0.1° • typical ACT effective area is 3·104 m2 • exposure time is 100 hours 3 Maggio 2007 M. Fornasa and M.Taoso

  16. Detection of IMBHs with ACTs (13) • Origin of background: • EGRET: (14) • Hadronic and electronic: (15) (16) 3 Maggio 2007 M. Fornasa and M.Taoso

  17. Detection of IMBHs with ACTs ACT sensitivity for a 5s detection results 1.6·10-12 cm-2s-1, higher than the brightest bins of the previous sky map. 3 Maggio 2007 M. Fornasa and M.Taoso

  18. Detection of IMBHs with ACTs Number of IMBHs over ACT sensitivity is 5.2 ± 3.1 for mc=1 TeV 3 Maggio 2007 M. Fornasa and M.Taoso

  19. Detection of IMBHs with GLAST • mc=150 GeV and the energy threshold is 10 MeV • GLAST angular resolution is expected to be 3° (from 10 MeV to 500 MeV), 0.5° (from 500 MeV to 4 GeV) and 0.15° (above 4 GeV) • a selection is made and only high-energy photons (above 4 GeV) are considered • extragalactic background • hadronic and electronic backgrounds are absent • the effective area times the exposition time is roughly 8·109 cm2s • the resulting sensitivity for a 2 months period is • 1.1·10-10cm-2s-1 3 Maggio 2007 M. Fornasa and M.Taoso

  20. Detection of IMBHs with GLAST Number of IMBHs over GLAST sensitivity is 17.1 ± 5.8 for mc=150 GeV 3 Maggio 2007 M. Fornasa and M.Taoso

  21. Detection of IMBHs with GLAST 3 Maggio 2007 M. Fornasa and M.Taoso

  22. Conclusions • fluxes from DM annihilations in mini-halos around IMBHs • that populate the Andromeda Galaxy have been computed • detection with an ACT is very challenging, due to the • hadron background • the scenario with GLAST is more promising, even if the • best angular resolution is achieved only after a strict selection • (very high-energy photons) • the picture is that of isolated, point-like, bright sources • in a region 3° wide around the Andromeda center 3 Maggio 2007 M. Fornasa and M.Taoso

  23. Differential energy spectrum • FPS (Fornengo-Pieri-Scopel) • MSSM is assumed and the DM candidate is a neutralino • focused only on the main channel (hadronization of b quarks) • fit from simulated data, using standard package as PYTHIA (x=E/mc) • differential spectrum for t leptons hadronization is presented too (see later) (17) (a, b, c, d, e)=(-1.31, 6.94, -4.93, -0.51, -4.53) (a, b, c, d, e)=(-1.5, 0.37, -16.05, 18.01, -19.50) • Kretzer Fragmentation Functions • DM candidate is again a neutralino • FF is the probability to have an hadron h with xQ2 from a parton • p with Q2 3 Maggio 2007 M. Fornasa and M.Taoso

  24. Differential energy spectrum • focused on the photon production from a p0 resulting from • quarks b (i.e. p=b, h=p0) • a flat spectrum for photons from pions is assumed (18) (19) • BBEG (Bergstrom-Bringmann-Eriksson-Gustafsson) • differential spectrum is calculated for a DM candidate from • Universal Extra-Dimension, what is called B(1) • contribution of primary photons from charged leptons is • no longer neglected (B(1)B(1)gl+l-) (20) 3 Maggio 2007 M. Fornasa and M.Taoso

  25. Differential energy spectrum From now on, only the FPS parametrization will be used 3 Maggio 2007 M. Fornasa and M.Taoso

  26. Differential energy spectrum (20) (21) 3 Maggio 2007 M. Fornasa and M.Taoso

  27. Exclusion Plot • Solid line: all realizations with at least one detectable IMBH • Dashed line: 20 realizations over 200 with at least one detectable IMBH 3 Maggio 2007 M. Fornasa and M.Taoso

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