Download Analysis of the Unidentified EGRET Source 3EG J1835+5918

Dark Matter Search with the MAGIC Telescope: Analysis of the Unidentified EGRET Source 3EG J1835+5918
Candidato: Fabio Zandanel
Relatore: Prof. Mosè Mariotti
Correlatore: Dott. Michele Doro
Summary
The Dark Matter paradigm ●
Detection of gamma rays from ground
●
Data Analysis
●
3EG J1835+5918 Analysis
●
Discussion
●
2
Universe content: Dark Matter
Universe content: only about 4% is accounted of baryonic matter
~4% dark baryons
~0.4% luminous matter
about 23% of the Universe energy­
matter density is accounted of non­baryonic collisionless and dissipation­free (i.e. cold) dark matter
~73% dark energy
3
Universe content: Dark Matter
Universe content: only about 4% is accounted of baryonic matter
~4% dark baryons
~0.4% luminous matter
about 23% of the Universe energy­
matter density is accounted of non­baryonic collisionless and dissipation­free (i.e. cold) dark matter
Evidences for the dark matter existence:
~73% dark energy
CMB anisotropies
galaxies rotational curves
“bullet” clustering
4
Universe content: Dark Matter
Universe content: only about 4% is accounted of baryonic matter
~4% dark baryons
~0.4% luminous matter
about 23% of the Universe energy­
matter density is accounted of non­baryonic collisionless and dissipation­free (i.e. cold) dark matter
Evidences for the dark matter existence:
CMB anisotropies
galaxies rotational curves
“bullet” clustering
~73% dark energy
two possible DM candidates:
supersymmetric neutralino
Kaluza­Klein particle
5
Gamma rays from DM annihilation
In many scenarios direct annihilation in two photons is severely suppressed, but a continuum gamma spectrum is expected from the decay of secondary neutral pions
gamma rays flux from DM annihilation:
  E∝∫ 2 x dV
6
Gamma rays from DM annihilation
In many scenarios direct annihilation in two photons is severely suppressed, but a continuum gamma spectrum is expected from the decay of secondary neutral pions
gamma rays flux from DM annihilation:
  E∝∫ 2 x dV
a detectable gamma rays flux is expected from regions where strong enhancements in the DM density are present, i.e. where strong gravitational field are present
7
Gamma rays from DM annihilation
In many scenarios direct annihilation in two photons is severely suppressed, but a continuum gamma spectrum is expected from the decay of secondary neutral pions
gamma rays flux from DM annihilation:
  E∝∫ 2 x dV
a detectable gamma rays flux is expected from regions where strong enhancements in the DM density are present, i.e. where strong gravitational field are present
Galactic Center
Dwarf Spheroidal Intermediate Mass Black­Holes
8
The IMBHs Scenario
Bertone, Zentner, Silk Phys.Rew.D 2005
“A New Signature of Dark Matter Annihilations: Gamma­Rays from Intermediate­Mass Black Holes”
During the evolution of halos, intermediate mass black holes formed at high redshift are found not to suffer merging and to grow adiabatically
A number of them (100­1000) can be remained wandering undisturbed in the Galactic Halo Onto them, DM could have had the time to accrete and produce very peaked distribution (“mini­spike”)
The large density implies a large annihilation rate: they could be very bright gamma sources
9
Gamma rays flux from mini­spikes
gamma spectrum prefactor dependence of per annihilation
mass and particle physics
radial profile
central core
10
Gamma rays flux from mini­spikes
gamma spectrum prefactor dependence of per annihilation
mass and particle physics
power low spectrum
spectral index ­1.5
exponential cut­off
radial profile
central core
The flux final dependence from the particle physics parameters is:
2/ 7 −9/ 7
 v  m
11
Gamma rays flux from mini­spikes
gamma spectrum prefactor dependence of per annihilation
mass and particle physics
power low spectrum
spectral index ­1.5
exponential cut­off
radial profile
central core
The flux final dependence from the particle physics parameters is:
2/ 7 −9/ 7
 v  m
Advantages with respect to other scenarios:
IMBHs position: less background
IMBHs do not suffer merging that could destroy the DM spike
small dependence from particle physics parameters
12
Unidentified EGRET Sources
After 10 years, still ~100 EGRET sources are unidentified
Normal to search for IMBHs in Unidentified EGRET Sources
Selection can be performed:
– steady emission
– spectral index compatible with ­1.5
– high galactic latitude
Different sources should have:
same spectra
same spectral index
same cut­off at DM mass
If observed, they would constitute a smoking gun signature for DM
13
Summary
The Dark Matter paradigm ●
Detection of gamma rays from ground
●
Data Analysis
●
3EG J1835+5918 Analysis
●
Discussion
●
14
Observation Technique
Space­borne experiments detect directly gamma rays gamma ray
photons are only about 0.1% of the cosmic rays Ch
er
en
Ground­based telescopes detect the Cherenkov light produced by air showers
ko
vl
i gh
t
electromagnetic
air shower
~ 1o
~ 10 km
background
hadronic showers
~ 120 m
15
Observation Technique
Space­borne experiments detect directly gamma rays gamma ray
Ch
er
en
Ground­based telescopes detect the Cherenkov light produced by air showers
ko
vl
i gh
t
electromagnetic
air shower
~ 1o
~ 10 km
EGRET telescope supported by the CGRO satellite
~ 120 m
16
Observation Technique
Ground­based telescopes detect the Cherenkov light produced by air showers
gamma ray
Ch
er
en
Imaging
Atmospheric
Cherenkov
Telescopes
ko
vl
i gh
t
electromagnetic
air shower
~ 120 m
~ 1o
~ 10 km
Cherenkov photons focused on a pixelled camera
typically elliptic images
images analysis
17
Observation Technique
Ground­based telescopes detect the Cherenkov light produced by air showers
gamma ray
Ch
er
en
Imaging
Atmospheric
Cherenkov
Telescopes
ko
vl
i gh
t
electromagnetic
air shower
~ 120 m
~ 1o
~ 10 km
Image parametrization
Hillas/Image parameters
intensity
orientation
shape
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The MAGIC Telescope
La Palma (2225 m a.s.l.)
Major
Atmospheric
Gamma­ray
Imaging
Cherenkov
field of view: 3.5°
angular resolution: 0.1°
energy range: 60 GeV – 10 TeV
energy resolution: 20 – 30%
flux sensitivity: 2% Crab flux ~ 1o
fast repositioning (< 40 sec)
17 m parabolic reflector multilevel trigger
Largest single­dish
577 PMTs camera
2 GHz MuX FADC
Lowest energy threshold
19
Summary
The Dark Matter paradigm ●
Detection of gamma rays from ground
●
Data Analysis
●
3EG J1835+5918 Analysis
●
Discussion
●
20
Analysis Chain
ON data
OFF data
Monte Carlo data
Calibration:
Data Sample reduction
Signal detection
Source Position reconstruction
Flux/Upper Limits calculation
charge
number of photons
Image “cleaning”:
Hillas/Image parameters calculation: image Hillas
parametrization parameters
21
Analysis Chain
ON data
OFF data
Monte Carlo data
Data Sample reduction
Signal detection
Source Position reconstruction
Flux/Upper Limits calculation
Background Rejection: gamma­hadron separation
gamma hadrons
Random Forest
For each event a global parameter Hadronness:
real number spanning from 0 to 1
0
gamma­like event
1
hadron­like event Hadronness cut: rejection hadron­like events
22
Analysis Chain
ON data
OFF data
Monte Carlo data
Data Sample reduction
Signal detection
Source Position reconstruction
Flux/Upper Limits calculation
Alpha distribution: Hadronness cut
Excess events
gamma events are characterized by small Alpha values
Background events
hadronic events have a random Alpha distribution
23
Analysis Chain
ON data
OFF data
Monte Carlo data
Data Sample reduction
Signal detection
Source Position reconstruction
Flux/Upper Limits calculation
Alpha distribution: Hadronness cut
Excess events
gamma events are characterized by small Alpha values
Background events
hadronic events have a random Alpha distribution
24
Analysis Chain
ON data
OFF data
Monte Carlo data
Data Sample reduction
Signal detection
Source Position reconstruction
Flux/Upper Limits calculation
Alpha distribution: Hadronness cut
a source is detected if the signal significance is greater then 5
25
Analysis Chain
ON data
OFF data
Monte Carlo data
Data Sample reduction
Signal detection
Source Position reconstruction
Flux/Upper Limits calculation
Source Position Reconstruction: bi­dimensional plot of the most probable source position in the sky
If the source was correctly pointed, the excesses must be in the pointed position 26
Analysis Chain
ON data
OFF data
Monte Carlo data
SIGNAL
NO SIGNAL
Data Sample reduction
Signal detection
Source Position reconstruction
Flux/Upper Limits calculation
Differential Flux = F  E
Flux Upper Limit
N   E
N   E = excess events
A eff  T eff
Teff = effective time N  E min , E max  95 %
f 0
〈 A eff  E min , E max , 〉 T eff
Aeff = effective area N95%: number of observable events (95% confidence level)
27
Summary
The Dark Matter paradigm ●
Detection of gamma rays from ground
●
Data Analysis
●
3EG J1835+5918 Analysis
●
Discussion
●
28
The source: 3EG J1835+5918
3EG J1835 was selected within the Unidentified EGRET Sources: no explanation for its emission
“observed” in X­ray but no association
If there is a mini­
spike signal, it would become well­visible within 30 hours of observation 29
3EG J1835+5918 Data Sample
Observation Period: 22/06/2006 – 03/07/2006
Data Sample: 31.5 hours ON data
26 hours ON 5.5 hours OFF data
5.5 hours OFF
exclusion of ~5 hours of ON data due to a mis­pointing (technical problem)
Unfortunately operating conditions:
~5 hours of ON data lost
few OFF hours
bad background estimation
technical trigger problem sensitivity loss
30
3EG J1835+5918 Data Sample
Observation Period: 22/06/2006 – 03/07/2006
Data Sample: 31.5 hours ON data
26 hours ON 5.5 hours OFF data
5.5 hours OFF
exclusion of ~5 hours of ON data due to a mis­pointing (technical problem)
Unfortunately operating conditions:
~5 hours of ON data lost
few OFF hours
technical trigger problem the chips connecting the trigger levels convert the signal from 8 pixels
31
3EG J1835+5918 Data Sample
Observation Period: 22/06/2006 – 03/07/2006
Data Sample: 31.5 hours ON data
26 hours ON 5.5 hours OFF data
5.5 hours OFF
exclusion of ~5 hours of ON data due to a mis­pointing (technical problem)
Unfortunately operating conditions:
~5 hours of ON data lost
few OFF hours
technical trigger problem the chips connecting the trigger levels convert the signal from 8 pixels
overheating problem
some chips burnt
trigger region lost
inhomogeneous events distribution 32
3EG J1835+5918 Data Inhomogeneity
Center of Gravity events distribution
 ­distribution
Expected: symmetric for rotations around the camera center and almost flat
Expected: flat  ­distribution
120­300 GeV
33
3EG J1835+5918 Data Inhomogeneity
Center of Gravity events distribution
 ­distribution
Expected: symmetric for rotations around the camera center and almost flat
Expected: flat  ­distribution
120­300 GeV
34
3EG J1835+5918 Data Inhomogeneity
Center of Gravity events distribution
 ­distribution
Expected: flat  ­distribution
Expected: symmetric for rotations around the camera center and almost flat
the effect is less visible at higher energies
300­700 GeV
35
3EG J1835+5918 Data Inhomogeneity
The action was to take out the camera regions affected by the chips­burnt problem
30% camera lost
180°<  <240° & 280°<  <325°
36
Test Analysis on Crab Nebula
Crab Nebula data sample:
2.5 hours ON data (04/01/2005)
2.7 hours OFF data (08/01/2005)
taking in good operating conditions
In order to test how a 30% of camera lost can affect the analysis
two independent analysis
normal Crab cut Crab: on which was applied the ­cut

 ­cut
37
Test Analysis on Crab Nebula
Crab Nebula data sample:
2.5 hours ON data (04/01/2005)
2.7 hours OFF data (08/01/2005)
taking in good operating conditions
In order to test how a 30% of camera lost can affect the analysis
two independent analysis
normal Crab cut Crab: on which was applied the ­cut

 ­cut
38
Test Analysis on Crab Nebula
Crab Nebula data sample:
2.5 hours ON data (04/01/2005)
2.7 hours OFF data (08/01/2005)
taking in good operating conditions
In order to test how a 30% of camera lost can affect the analysis
two independent analysis
normal Crab cut Crab: on which was applied the ­cut

 ­cut
39
Test Analysis on Crab Nebula
Crab Nebula data sample:
2.5 hours ON data (04/01/2005)
2.7 hours OFF data (08/01/2005)
taking in good operating conditions
In order to test how a 30% of camera lost can affect the analysis
two independent analysis
normal Crab cut Crab: on which was applied the ­cut

~30% of excess events lost correct source position reconstruction
correct flux estimation
an analysis is possible according to these conclusions
40
Signal Detection No signal detection
the significances were never greater then ~2
3EG J1835+5918 has not been observed with significant detection above 120 GeV
41
Source Position Reconstruction The source position reconstruction showed initially an astonishing result:
above 300 GeV the “sky­analysis” showed an empty sky
between 120 and 300 GeV, excesses off­center were found
[120­300 GeV]
excesses
significances
significances
42
Source Position Reconstruction The source position reconstruction showed initially an astonishing result:
above 300 GeV the “sky­analysis” showed an empty sky
between 120 and 300 GeV, excesses off­center were found
Crab Nebula Example ­ [300­700 GeV]
excesses
significances
significances
43
Source Position Reconstruction The source position reconstruction showed initially an astonishing result:
above 300 GeV the “sky­analysis” showed an empty sky
between 120 and 300 GeV, excesses off­center were found
Sky Map [120­300 GeV]:
serendipity discovery?
wrong EGRET source position?
“fake source”?
Image parameters re­calculation with respect to the excesses position:
no signal detection, significances never greater than ~1 , probably the 
analysis at these energies are dominated by systematic errors
How it is possible?
44
Why a Fake Source? Great inhomogeneities could create fake sources:
the 3EG J1835+5918 data sample have inhomogeneity problems
at low energies these problems are very strong
at energies above 300 GeV, the inhomogeneities are almost negligible
120­300 GeV:
very strong inhomogeneities in addition of the camera regions lost
45
Upper Limits Calculation Upper Limits on the 3EG J1835+5918 emission:
f 0 [ 181 GeV ] =2.9∗10−10 ph cm−2 s −1 TeV −1 ⇒ 0.129 C.U.
f 0 [ 403GeV ] =3.3∗10−12 ph cm−2 s−1 TeV −1 ⇒ 0.012 C.U.
f 0 [ 1196 GeV ]=2.5∗10
−13
−2
ph cm s
−3
f0 is given in “Crab Unit”: 1C.U.=1.5∗10
−1
 
E
GeV
TeV
−2.58
−1
⇒0.014 C.U.
very high
“good”
ph cm−2 s −1 TeV −1
“the signal is below f0”
“the signal presence above f0 probability is of 5%”
“if there were a signal above f0, a detection would be possible” 46
Upper Limits Calculation Upper Limits on the 3EG J1835+5918 emission:
−10
−2 −1
−1
f 0 [ 181 GeV ] =2.9∗10 ph cm s TeV ⇒ 0.129 C.U.
−12
−2 −1
−1
f 0 [ 403GeV ] =3.3∗10 ph cm s TeV ⇒ 0.012 C.U.
f 0 [ 1196 GeV ]=2.5∗10
−13
−2
ph cm s
−1
TeV
−1
⇒0.014 C.U.
very high
“good”
It is possible to set an upper limit on the dark matter mass
47
“DM Mass Upper Limit” Supposing the 3EG J1835 to be an IMBH:
mDM< 800 GeV
only a speculative result!
48
Summary
The Dark Matter paradigm ●
Detection of gamma rays from ground
●
Data Analysis
●
3EG J1835+5918 Analysis
●
Discussion
●
49
Discussion No signal detection was reached
A fake signal was found at low energies [120­300 GeV] due to the strong inhomogeneities, but:
Important: as the inhomogeneities could be able to create a fake signal, they could also be able to board a true source with a faint signal!!!
3EG J1835+5918 was not observed, but in the energy range 120­300 GeV this could be due to data peculiarities and another observation of this source is desirable!
50
Conclusions The 3EG J1835+5918 was not detected, but at energies below 300 GeV this could be do to data peculiarities
software improvements: there is the necessity of a “sky­analysis” code that must be able to avoid fake results due to inhomogeneities
another observation of the 3EG J1835+5918 is necessary
other Unidentified EGRET Sources are good IMBH candidates
waiting next generation space­born experiments results (AGILE, GLAST)
waiting MAGIC II...
51
Outlook: the MAGIC TelescopeS
MAGIC II
a clone of the first telescope at 85 m of distance ~ 1o
MAGIC II will be operating in early 2008
Stereoscopic view
time coincidence constraints between two instruments
lowering of the energy threshold (~30 GeV)
increase in sensitivity of a factor 2
52
53
Gammas from DM Annihilation
   
0
  Z 
gamma lines
supersymmetric neutralino:
  f f bb
continuum gammas from hadronization:
0
 
B 1 B 1   
gamma lines
Kaluza­Klein particle:
+ ­
B 1 B 1  l l 
and secondary gammas via cascading decays of final states and qq

semihadronic decays of leptons
gamma lines are severely suppressed or give a very low flux!
54
Gamma Spectrum per annihilation
It is necessary to specify the gamma spectrum per annihilation dN/dE
G.Bertone, A.R.Zentner & J.Silk,
Phys.Rev. D72 (2005) 103517
55
IMBHs Main evidence for their existence
Ultra Luminous X­ray objects
Two scenarios: remnants of Population collapse of primordial gas
III or “first” stars in early­forming halos
gammas from mini­
spikes
56
Atmospheric Showers Electromagnetic Showers
Hadronic Showers
57
Atmospheric Showers Electromagnetic Showers
Hadronic Showers
58
Cherenkov Effect 1
cos=
 n
59
Cherenkov Radiation 60
IACT Technique Basic Idea: observe gamma rays studying the images formed on the telescope camera from the Cherenkov flashes (coming from air showers) when focused on a plane
IACTs transform the arrival directions of Cherenkov photons in points that form a shower image on the focal (camera) plane
Photons coming from the perpendicular direction with respect to the telescope plane are focused on the camera center
Photons incident with an angle are focused on a distance

 ∝
61
Detection Technique IACT (Imaging Atmospheric Cherenkov Telescopes) imaging Cherenkov
technique Cherenkov photons ~ 1o
image on telescope camera
typical elliptic shape
62
Detection Technique IACT (Imaging Atmospheric Cherenkov Telescopes) imaging Cherenkov
technique Cherenkov photons head
~ 1o
image on telescope camera
typical elliptic shape
63
Detection Technique IACT (Imaging Atmospheric Cherenkov Telescopes) imaging Cherenkov
technique Cherenkov photons head
~ 1o
tail
image on telescope camera
typical elliptic shape
64
Detection Technique IACT (Imaging Atmospheric Cherenkov Telescopes) imaging Cherenkov
technique images analysis
~ 1o
Intensity: primary particle energy
65
Detection Technique IACT (Imaging Atmospheric Cherenkov Telescopes) imaging Cherenkov
technique gamma event images analysis
image points toward the camera center
~ 1o
Intensity: primary particle energy
random events direction
hadronic event
Orientation: incoming direction
66
Detection Technique IACT (Imaging Atmospheric Cherenkov Telescopes) imaging Cherenkov
technique gamma event images analysis
elliptic shape
very compact
~ 1o
Intensity: primary particle energy
Orientation: incoming direction
roundish shape
fragmentation
hadronic event
Shape: primary particle nature
67
Image Parameters images analysis images Hillas (1985) parametrization parameters
image
moments
~ 1o
Main Image Parameters:
Alpha: angle between major axis and the center of gravity­camera center direction
Size: total number of collected photons
68
False Source Plot False Source Method:
camera divided in N*N region
for each region the image parameters are re­calculated with respect to the center of the respective bin
an Alpha plot is then obtained
results plotted in a bi­dimensional plot
69
Source Position Reconstruction
Skymap
bi­dimensional plot of the most probable source position in the sky
The Disp method:
Disp: distance between the image center and the unknown source position (along the major axis)
Source Position Reconstruction
Skymap
bi­dimensional plot of the most probable source position in the sky
The Disp method:
Disp: distance between the image center and the unknown source position (along the major axis)
two possible solution
Source Position Reconstruction
Skymap
bi­dimensional plot of the most probable source position in the sky
The Disp method:
Disp: distance between the image center and the unknown source position (along the major axis)
two possible solution
head­tail discriminator
Source Position Reconstruction
Skymap
bi­dimensional plot of the most probable source position in the sky
The Disp method:
Disp: distance between the image center and the unknown source position (along the major axis)
two possible solution
head­tail discriminator
Skymap and False Source Plot Skymap
120­300 GeV
False Source Plot
74
Skymap and False Source Plot Skymap
300­700 GeV
False Source Plot
75