Slide1 : Gamma-rays from Dark Matter
Mini-Spikes in Andromeda
Galaxy M31 Mattia Fornasa and Marco Taoso 2nd IDAPP 2days Meeting - Giovedì 3 maggio 2007 based on astro-ph/0703757 by M. Fornasa, M. Taoso and G.Bertone
Slide2 :
Introduction
M. Fornasa and M.Taoso 3 Maggio 2007 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
Slide3 :
Introduction
M. Fornasa and M.Taoso 3 Maggio 2007 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
Slide4 :
Introduction
M. Fornasa and M.Taoso 3 Maggio 2007 Intermediate Mass Black Holes (IMBHs)
located in mini-halos in the Galactic smooth DM profile
necessity to consider an extragalactic source (M31) 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 G. Bertone,
astro-ph/
0603148
Slide5 : G. Bertone,
astro-ph/
0603148
Intermediate Mass Black Holes (IMBHs)
M. Fornasa and M.Taoso 3 Maggio 2007 mass from 20 M to 106 M
no one actually ever 'detected' an
Intermediate Mass Black Hole Miller, Colbert, astro-ph/0308402 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
Slide6 : G. Bertone,
astro-ph/
0603148
Intermediate Mass Black Holes (IMBHs)
M. Fornasa and M.Taoso 3 Maggio 2007
Slide7 : G. Bertone,
astro-ph/
0603148
Spike formation at the Galactic center
M. Fornasa and M.Taoso 3 Maggio 2007 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: (4) (5)
Slide8 : G. Bertone,
astro-ph/
0603148
Spike formation at the Galactic center
M. Fornasa and M.Taoso 3 Maggio 2007 Ullio, Zhao, Kamionkowski,
astro-ph/0101481 (6) (7) From a NFW (g=-1) the final spike has gsp=-7/3
Slide9 : G. Bertone,
astro-ph/
0603148
Spike formation at the Galactic center
M. Fornasa and M.Taoso 3 Maggio 2007 Arguments against spikes formation:
off-center black hole formation
gravitational interaction with stars
merger effects
'loss-cone', DM that falls inside rSchw Ullio, Zhao, Kamionkowski,
astro-ph/0101481 Merritt, Milosavljevic, Verde, Jimenez
astro-ph/0201376
Slide10 : G. Bertone,
astro-ph/
0603148
IMBHs catalogue (Bertone, Zentner, Silk)
M. Fornasa and M.Taoso 3 Maggio 2007 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 Bertone, Zentner, Silk,
Astro-ph/0509565
Slide11 : G. Bertone,
astro-ph/
0603148
IMBHs catalogue for Andromeda
M. Fornasa and M.Taoso 3 Maggio 2007 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] Andromeda IMBHs are 65.2±14.5 per realization,
with an average mass of 1.54·105 M and
an average distance from M31 center of 32.3 kpc.
Slide12 : G. Bertone,
astro-ph/
0603148
Annihilation Flux
M. Fornasa and M.Taoso 3 Maggio 2007 (8) To compute the differential energy spectrum a particular model of physics beyond the SM is needed: (9) (10)
Slide13 : G. Bertone,
astro-ph/
0603148
M. Fornasa and M.Taoso 3 Maggio 2007 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) (a, b, c, d, e)=(-1.5, 0.37, -16.05, 18.01, -19.50) (10)
Differential energy spectrum
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)
Slide14 : G. Bertone,
astro-ph/
0603148
M. Fornasa and M.Taoso 3 Maggio 2007 (12)
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-)
Slide15 :
M. Fornasa and M.Taoso 3 Maggio 2007
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
Slide16 :
M. Fornasa and M.Taoso 3 Maggio 2007
Detection of IMBHs with ACTs (13) (14) Origin of background:
EGRET: Hadronic and electronic: (16) (15)
Slide17 :
M. Fornasa and M.Taoso 3 Maggio 2007
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.
Slide18 :
M. Fornasa and M.Taoso 3 Maggio 2007
Detection of IMBHs with ACTs Number of IMBHs over ACT sensitivity is
5.2 ± 3.1 for mc=1 TeV
Slide19 :
M. Fornasa and M.Taoso 3 Maggio 2007
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
Slide20 :
M. Fornasa and M.Taoso 3 Maggio 2007
Detection of IMBHs with GLAST Number of IMBHs over GLAST sensitivity is
17.1 ± 5.8 for mc=150 GeV
Slide21 :
M. Fornasa and M.Taoso 3 Maggio 2007
Detection of IMBHs with GLAST
Slide22 :
M. Fornasa and M.Taoso 3 Maggio 2007
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
Slide23 :
M. Fornasa and M.Taoso 3 Maggio 2007
Differential energy spectrum 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 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) (a, b, c, d, e)=(-1.5, 0.37, -16.05, 18.01, -19.50) (a, b, c, d, e)=(-1.31, 6.94, -4.93, -0.51, -4.53) (17)
Slide24 : 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) M. Fornasa and M.Taoso 3 Maggio 2007
Differential energy spectrum 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)
Slide25 : M. Fornasa and M.Taoso 3 Maggio 2007
Differential energy spectrum From now on, only the FPS parametrization will be used
Slide26 : M. Fornasa and M.Taoso 3 Maggio 2007
Differential energy spectrum (20) (21)
Slide27 : M. Fornasa and M.Taoso 3 Maggio 2007
Exclusion Plot Solid line: all realizations with at least one detectable IMBH
Dashed line: 20 realizations over 200 with at least one detectable IMBH