1andrea caliandro search of optimized cuts for pulsar detection andrea caliandro - infn bari dc2...
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1Andrea Caliandro
Search of Optimized Cuts for Search of Optimized Cuts for
Pulsar DetectionPulsar DetectionAndrea Caliandro - INFN Bari
DC2 CloseOut
May 31 2006
Goddard Space Flight Center
2Andrea Caliandro
Summary Summary
Have been searched the best ROI & Energy band that maximize the probability for a point source to be periodic
– Parameter considered• Sky position• Flux• Observation Time
For this work a sample of 900 pulsars and diffuse emission have been simulated 15 times
– Each simulation is characterized by a value of flux attributed to all the pulsars and by the Observation time
• PSR flux: 1e-6, 0.3e-6, 1e-7, 0.3e-7, 1e-8 ph/cm2s• ObsTime: 1 Week, 2Week, 4Week
Finally this search has been tested on the DC2 sky– All the radio loud PSR in the pulsarDB have been analyzed
3Andrea Caliandro
Sky SimulationSky Simulation
AntiCenter Lateral Center Center Lateral
(2,-2) (6, 2) (10, 6)
• Is taken into account the strip of sky |b|<10
• This strip is subdivided in 9 regions– Center2-2, Center2_6, Center 6_10
– Lateral2-2, Lateral2_6, Lateral6_10
– Anticenter2-2, Anticenter2_6, Anticenter6_10
• In each region there are 100 psr uniformly distributed
– In this way the statistic is the same for each region
– This is not a simulation of a real pulsar population
• Diffuse emission simulation
– Galactic diffuse emission
– Extragalactic diffuse emission
• gtorbsim parameter– Pointing strategy: SLEWING
– Rocking angle = 35°
4Andrea Caliandro
Pulsar SimulationPulsar Simulation
• 2 peaks pulse shape– Phase position, width and height are random
• There is just the constrain for the peak distance to be more than 0.3 phase
• P = 1s, Pdot = 0s/s, Pddot = 0s/s2
– These choices are just to simplify the analysis, but do not affect the result
(Nel and De Jager,1995)• b = 1
• E0 = 10GeV
• g is a random number distributed as e gaussian N(1.4, 0.2)
– These choices are based on the data of the Gamma-ray Pulsars (Nel, De Jager 1995) and how I have chosen the Energy band to investigate
– See next slide
ScienceTools: CelestialSource/Pulsar
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Energy cutEnergy cut: Energy band from the selected
Emin value to the maximum observable Energy (200GeV)
(gtselect)
Binning: 20 MeV 50 MeV100 MeV200 MeV400 MeV600 MeV 1 GeV 10 GeV
Binning:0.25° 2°0.50° 3°0.75° 4°1° 6°1.5° 8°
ROIROI: Disk with Radius R
centerd on the source(gtselect)
Base AnalysisBase Analysis
Emin (MeV)
Rad
ius
(Deg
rees
)
Histogram by Cuts
Emin (keV)
• For each source are selected a series of ROI and Energy cut
• For each of these selection are calculated the Htest and the relative
probability (PHtest)
6Andrea Caliandro
Htest Algorithm Htest Algorithm
4312 pNpepb Np
n
1)( 312 HqeHqHw Hq
)44(max 2
201
mZH m
m
For N>=100 m=20
For N<100 m=N/5
bHeaPHtest 2eHdHecPHtest
HbneHwPHtest )(
Probability that H could be greater of the found value P(>H)
For H<=23
For 23<H<50
For N < 100
If H>=3030)30( nbewPHtest
For N < 20HbnePHtest 15.1
If H>=252515.1 nbePHtest
For N < 10: 1PHtest
84 ePHtest For H>=50
(De Jager et al. 1989)
7Andrea Caliandro
Single Pulsar Histograms
Histograms & Distributions Histograms & Distributions • From the Single Pulsar Histograms
– Htest & PHtest histograms
• Are obtained, for each value of PSR flux & Observation Time (i.e. for each simulation) and relative to each Region of the sky
– Mean Htest & PHtest Histograms– Simply the normalized sum of the Single
Pulsar Histogram
– Distribution of the Max Htest Values– Taken by each Htest Single Pulsar
Histogram» See next slides
– Distribution of the Minimum PHtest Values– Taken by each PHtest Single Pulsar
Histogram» See next slides
– Cut Distribution for which Htest is Max– From each Single Pulsar Histogram are
taken the cuts relative to the max value» See next slides
– Cut Distribution for which PHtest is Min– From each Single Pulsar Histogram are
taken the cuts relative to the min value» See next slides
PHtestHtest
PHtest
Htest
This two histograms are
relative to PSRflux=1e-7
ObsTime=4Weeks
Region=Lateral2-2
8Andrea Caliandro
AntiCenter6_10AntiCenter2_6AntiCenter2-2
Lateral6_10Lateral2_6Lateral2-2
Center6_10
Center2_6Center2-2
AntiCenter6_10AntiCenter2_6AntiCenter2-2
Lateral6_10Lateral2_6Lateral2-2
Center6_10Center2_6Center2-2
HtestHtest
• Cut Distribution for which Htest is Maximum
• Htest Max Value Distributions
AllRegionsconsider the Regions
all together - all 900 psr
AllRegions
The plots showed in this slide are
relative to PSRflux=1e-7
ObsTime=4Weeks
9Andrea Caliandro
AntiCenter6_10AntiCenter2_6AntiCenter2-2
Lateral6_10Lateral2_6Lateral2-2
Center6_10
Center2_6Center2-2
PHtestPHtest
AllRegions
• Cut Distribution for which PHtest is Minimum
The plots showed in this slide are
relative to PSRflux=1e-7
ObsTime=4Weeks
AntiCenter6_10AntiCenter2_6AntiCenter2-2
Lateral6_10Lateral2_6Lateral2-2
Center6_10Center2_6Center2-2
• PHtest Min Value Distributions
AllRegionsconsider the Regions
all together - all 900 psr
10Andrea Caliandro
Htest
Max Value
Distribution
Cut Distribution for which Htest is Maximum
Overview on All RegionsOverview on All RegionsHtest DistributionsHtest Distributions
Flux 1e-6 ph/cm^2 sFlux 1e-6 ph/cm^2 s Flux 1e-7 ph/cm^2 sFlux 1e-7 ph/cm^2 s Flux 1e-8 ph/cm^2 sFlux 1e-8 ph/cm^2 s
(ObsTime = 4Weeks)
• Cuts Distribution:– Decreasing the Flux
• The distribution become more broad
• The peak is displaced toward high Energy
• Max Value Distribution:– Decreasing the Flux
• The distribution is less broad
• The peak is at lower values
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vs Fluencevs Fluence
Fluence (ph/cm^2)
Fluence (ph/cm^2)
Fluence (ph/cm^2)
Hte
stE
min
(M
eV)
Rad
ius
(deg
ree)
Overview on All RegionsOverview on All RegionsHtest PlotsHtest Plots
vs Fluxvs Flux
Flux (ph/cm^2s)
Flux (ph/cm^2s)
Flux (ph/cm^2s)
Hte
stE
min
(M
eV)
Rad
ius
(deg
ree)
1Week2Weeks4Weeks
By Max value Distribution
•Htest vs Flux and Fluence• Mean value of distribution
• Errors bars: right and left RMS
–Htest is proportional to the flux and the fluence
By Cuts Distribution
•Energy Cut Plots• Energy coordinate of the Peak of the distribution
• Errors bars: right and left RMS respect to the Peak
–Seems to converge towards Emin=200MeV
•Radius Plots• Radius coordinate of the Peak of the distribution
• Errors bars: right and left RMS respect to the Peak
–The peaks increase toward 1.5°
12Andrea Caliandro
PHtest
Min Value
Distribution
Cut Distribution for which PHtest is Minimum
Overview on All RegionsOverview on All RegionsPHtest DistributionsPHtest Distributions
Flux 1e-6 ph/cm^2 sFlux 1e-6 ph/cm^2 s Flux 1e-7 ph/cm^2 sFlux 1e-7 ph/cm^2 s Flux 1e-8 ph/cm^2 sFlux 1e-8 ph/cm^2 s
(ObsTime = 4Weeks)
This peak is due to the case N<100 & H>30
( see slide 6 )
• Cuts Distribution:– The behavior is the same of Htest Cuts
Distribution
– But the positions of the peak aren’t the same of Htest Cuts Distribution
This peak correspond to the case N>100 & H>50
(the best one)
13Andrea Caliandro
vs Fluencevs Fluence
Fluence (ph/cm^2)
Fluence (ph/cm^2)
Fluence (ph/cm^2)
PH
test
(l
og
10)
Em
in (
MeV
)R
adiu
s (d
egre
e)
Overview on All RegionsOverview on All RegionsPHtest PlotsPHtest Plots
vs Fluxvs Flux
Flux (ph/cm^2s)
Flux (ph/cm^2s)
Flux (ph/cm^2s)
PH
test
(l
og
10)
Em
in (
MeV
)R
adiu
s (d
egre
e)
1Week2Weeks4Weeks
By Min value Distribution
•PHtest vs Flux and Fluence• Mean value of distribution
• Errors bars: standard RMS
–There is a smooth step starting at 2E-2ph/cm2 ending at 3E-1ph/cm2
By Cuts Distribution
•Energy Cut Plots• Energy coordinate of the Peak of the distribution
• Errors bars: right and left RMS respect to the Peak
–For low fluence is convenient to cut at Energy greater of 200MeV
–For high fluence cut aren’t needed
•Radius Plots• Radius coordinate of the Peak of the distribution
• Errors bars: right and left RMS respect to the Peak
–Radius decrease until 0.25°
14Andrea Caliandro
Diffuse HtestDiffuse Htest
Htest Htest PHtestPHtest
Relative CalculationRelative Calculation
• The described analysis has been performed on the Diffuse Data file alone
– Related to each psr sky position, the Htest & PHtest histograms are builded
– The Distributions are calculated in two different way
• Absolute Calculation– The max value is taken from
each Htest histogram
– The min value is taken from each PHtest histogram
• Relative Calculation– From the Htest and PHtest
histograms is taken the value relative to the Best Cut for the corresponding pulsar
Absolute CalculationAbsolute Calculation
Diffuse Distribution example for the simulation with ObsTime = 4Weeks
and psr Flux = 1e-6
15Andrea Caliandro
PHtest with Diffuse linePHtest with Diffuse lineAllRegionsAllRegions
Diffuse Relative CalculationDiffuse Relative CalculationDiffuse Absolute CalculationDiffuse Absolute Calculation
• Absolute Calculation– The PHtest on the Diffuse is
independent from the fluence
– We can say that a source is a pulsar with good significance if log10(PHtest)<-2.5
• Relative Calculation– The PHtest on the Diffuse is not
constant but increase with the fluence
– PHtest values under the dotted line means pulsar with good significance
– above ~6E-2ph/cm2 the PHtest value of pulsar are all good
16Andrea Caliandro
PHtest Center Regions PHtest Center Regions Center2_6Center2_6Center2-2Center2-2 Center6_10Center6_10
over ~1E-1ph/cm2 the PHtest value of pulsar are all good
17Andrea Caliandro
PHtest Lateral Regions PHtest Lateral Regions Lateral2_6Lateral2_6Lateral2-2Lateral2-2 Lateral6_10Lateral6_10
over ~4E-2ph/cm2 the PHtest value of pulsar are all good
18Andrea Caliandro
PHtest Anticenter Regions PHtest Anticenter Regions AntiCenter2_6AntiCenter2_6AntiCenter2-2AntiCenter2-2 AntiCenter6_10AntiCenter6_10
over ~5E-2ph/cm2 the PHtest value of pulsar are all good
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First ConclusionsFirst Conclusions
Max Htest value in Cut Histogram not always correspond to Minimum PHtest value– Infact the distribution are different
• See slide 10 & 12
Cuts Distribution are too broad to determine a precice value for Energy cut and Radius of the ROI as function of the fluence and the position in the sky region– For low fluence are necessary Energy cut above 100 or
200MeV
– For high fluence to have a good PHtest value is enough to take radius not greater than 1.5° or 2°
By the PHtest performed on the diffuse we can say that in first approximation a source is a pulsar with good significance if log10(PHtest)<-2.5 – We have also seen that the application of the best cut
increase this value in function of the fluence
20Andrea Caliandro
DC2 Pulsar AnalysisDC2 Pulsar Analysis
C
en
ter2
-2
C
en
ter2
_6
Ce
nte
r6_
10
An
tiC
en
ter2
-2
An
tiC
en
ter2
_6
An
tiC
en
ter6
_1
0
L
ate
ral2
-2
La
tera
l2_
6
La
tera
l6_
10
E
xte
rna
l
• Best cuts have been searched for all the pulsar in the DC2pulsarDB
• DC2pulsarDB and LATsourceCatalog have been compared
– 40 pulsars have been found in the LATsourceCatalog
– In this way we also obtain a flux estimation for these pulsars
• A different analysis has been performed for pulsars with and without flux estimation
• Distribution of pulsar population in the sky
– About 90% of the pulsar population is in the Central and Lateral Region with |b|<6
21Andrea Caliandro
DC2 psr with Flux estimation DC2 psr with Flux estimation
The best ROI radius for all pulsars but 3 is less than 2°
Below 1ph/cm2 the Energy cut are broadly distributed from Emin=50MeV to Emin=1GeV
Above 1ph/cm2 there is a concentration of pulsars without Energy cut
Considering the threshold at log10(PHtest)=-2.5 we lost 6 pulsars
22Andrea Caliandro
Pulsar not in LAT catalogPulsar not in LAT catalog
• Distribution of PHtest
– There are 23 pulsars below the threshold of log10(PHtest)=-2.5
• 15 have the best possible value of the PHtest
• Distribution of Cuts
– Most of the pulsars have the best ROI radius <2°
– and No Energy cut
23Andrea Caliandro
Some Light CurveSome Light Curve
Rad=0.75Emin=200Log(P)=-6.8Nevt=2098
Rad=0.5Emin=50Log(P)=-6.3Nevt=100
Rad=8Emin=200Log(P)=-4.4Nevt=30413
Rad=0.25Emin=20Log(P)=-7.4Nevt=158
Rad=0.25Emin=20Log(P)=-7.4Nevt=143
Rad=0.75Emin=100Log(P)=-6.6Nevt=2223Rad=0.5
Emin=400Log(P)=-2.6Nevt=632
Rad=0.25Emin=20Log(P)=-2.9Nevt=269
Maybe a trick of the
simulators?
24Andrea Caliandro
ConclusionsConclusions
Appling the search of the Energy cut and the ROI radius that minimize the PHtest value we have found 23 pulsars that aren’t in the LATsourceCatalog– The cut found are not standard cut
• Most of the psr have a best radius <-2°
• Most of the psr have not Energy cut
– Maybe could be useful to build a Science Tools that make this search
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