Transcript DC2 pulsars analysis: a population point-of-view

DC2 pulsars analysis:
Gamma-ray Large Area Space
Telescope
a population point-of-view
Massimiliano Razzano
(INFN - Pisa)
LAT DC2 Closeout Meeting
(GSFC, May 31-June 2 2006)
06/02/2006
M.Razzano - DC II Closeout Meeting
Outline
•Analysis overview;
•Scripting in Python: the pyPulsar tool;
•Cuts and thresholds;
•The EGRET pulsars;
•Detecting pulsars in the LAT source catalog;
•The flux distribution;
•The brightest MSP;
•Beyond the LAT source catalog;
•Conclusions and DC2 follow-up
Analysis overview
•I will present an analysis to detect pulsars with radio counterparts in the D4;
•An automatic procedure for testing the periodicity of pulsars has been conducted to
find high-confidence identification;
•More detailed analysis on some pulsars (e.g. EGRET pulsars or MSP pulsars);
•The basic characteristics of the detected pulsars have been derived;
A preliminary note:
Yes, I was involved in the DC2 pulsars generation…but….
1. We put a lot of pulsars in the DC2 sky…
2. DC2 pulsar truth is on my PC in some obscure directory with some obscure name…
3. It is almost impossible to me to remember names like PSR XYZM+IJKF12345…
4. Through hypnosis Julie and Seth forced me to forget everything…
Believe me…by doing this analysis, I completely ignored the DC2 truth..
Why scripting? Why Python?
•Scripts are very useful to create some automatized analysis (see also
D.Smith’s talk);
•Scripts allow to perform the basic data reduction in automatic way (applying
cuts, barycentering, etc…);
•Scripts can be done using bash/tcsh shell or using scripting languages like
Python
For these analysis a set of Python scripts have been developed
•With Python more complex operations can be done easily (e.g. parsing);
•A lot of Python extension are availabe (e.g. pyROOT, pyFits, sihyppo);
•See www.python.org for much informations about Python;
Python scripting: pyPulsar
pyPulsar is a set of Python classes and
scripts for doing pulsar analysis
pyAnScripts
(scripts for various
pulsar-related
analysis)
pyGtTools
(classes for interfacing with
LAT Pulsar Science Tools)
•pyGtBary
•pyGtPsearch
•pyGtEphcomp
pyPulsar
(class for managing data
and analysis of a pulsar)
•pyGtPhase
•pyGtSelect
LAT Pulsar Tools
Analysis
results
Python scripting: pyPulsar (II)
•A list of pulsar is given in input (extracted from D4, from
coincidences with LAT Source catalog, etc…);
•For every pulsar the ROI is selected and FT1 barycentered;
•Periodicity test is applied (here only Chi2) and phase
assigned;
•The output file contain chance probability of the periodicity
test;
•Plots of detected pulsars and determination of population
parameters (e.g. using ROOT macro);
About cuts and thresholds…
•For each pulsar an specific selection in ROI, energy, etc. can be done;
•For each pulsar list the analysis was performed for 2 energy ranges and with
corresponding selection of the ROI according to the PSF;
What is the threshold for pulsar
detection?
After some tests and some discussions I
decided to use a more “conservative”
detection limits, according to the EGRET
pulsars papers
Energy
Radius of ROI
E>100MeV
3°
E>1GeV
1°
Energy
c2 chance probability
Reference
No detection
P > 2 x10-3
The same as below
Low-confidence detection
10-9 < P < 2 x10-3
Limit of B0656+14 (Ramanamurthy
et al. 1996)
High-confidence detection
P < 10-9
Limit of B1951+32 (Ramanamurthy
et al. 1995)
The EGRET pulsars
Vela
The first exercise is the
analysis of the EGRET
pulsars, testing
periodicity and
recovering lightcurve
Seeing that pulsars does pulse….
Geminga
Crab
E>100MeV
ROI with R=3°
Periodic
at C.L. >
99.99%
E>100MeV
ROI with R=3°
Periodic
at C.L. >
99.99%
E>100MeV
ROI with R=3°
Periodic
at C.L. >
99.99%
All-sky count
map of the
simulation of
55 days for
DC2
E>200MeV
ROI with
R=3°
Periodic at
C.L. >
99.99%
E>100 MeV
ROI with
R=1°
Periodic at
C.L. >
06/02/2006
E>300MeV
ROI of
R=1.5°
Periodic at
C.L. >
99.99%
M.Razzano - DC II Closeout Meeting
Pulsars in the LAT source catalog?
As first step a search for coincidence between LAT sources and pulsars in D4
Radius dependent on energy (LAT_Cat_v2)
49 pulsars found
Pulsars in the Lat catalog: summary
The first step is the analysis for E>100MeV
Low confidence
High confidence
No detection
13
Low confid.
14
High confid.
22
Pulsars in the Lat catalog: populations
Youngest non-MSP have age≈103 y
(Vela & Crab) and B≈5x1012 G
1014G
age≈108
Oldest non-MSP have
& Crab) and B≈2x1011 G
103yr
y (Vela
Low confidence
Low confidence
109G
High confidence
High confidence
Name
RA
Dec
period
pdot
PSR_J1955p2149
298,98
21,82
0,00169861
1,87E-20
PSR_J0904m5008
136,07
-50,14
0,00231079
3,94E-20
PSR_J1659m5022
254,98
-50,37
0,00262529
7,64E-21
PSR_J0717m1235
109,45
-12,59
0,00329634
7,23E-21
PSR_J1735m5757
263,96
-57,96
0,00689783
3,36E-20
PSR_J1745m0952
266,28
-9,876
0,0193763
9,50E-20
4 MSP detected at high confidence
and 1 at low confidence
(B<109gauss, age>109y)
PSR J0904-5008, the brightest MSP
In the LAT Catalog its
flux is 1.7 x 10-7
ph/cm2/s
Fit with power-law +
exponential cutoff
a=1.01±0.01
Ecut=37,1±1,3 GeV
Phase curve after
periodicity test
Period=2,31 ms
Pulsars in the LAT catalog: DC fluxes
Low confidence
An interesting plot is the LogN-LogS
(see D.J.Thompson ’03)
High confidence
Slope=-1.04±0.19
The low coincidence show a
change of slope.
Various possible origins
(background,
geometry,luminosity
distributions)
The high confidence pulsars
follow a similar distribution
Beyond the LAT catalog: Summary(I)
•The next step is the scan on the entire D4 database. First for E>100MeV
•We expect to find more pulsars since there is the help of the periodicity signature
Low conf
High conf
E>100MeV
No detection
42
Low confid.
26
High confid.
29
Beyond the LAT catalog: Summary(I)
•Then I repeat the scan for E>1GeV
•The pulsar detected will be different because of many reasons (different
ROI,different spectra of pulsars, etc…)
Low conf
High conf
E>1GeV
No detection
38
Low confid.
34
High confid.
25
The number of high+low is increased. In order
to have a final sum we must make an OR of
the results at 2 energies
Beyond the LAT catalog:population
E>100MeV
After merging E100MeV and E1GeV results
No detection
14
Low confid.
51
High confid.
32
E>1GeV
More MSP at E>1GeV
Find the
differences….
(Spectral shape)
Conclusions and DC2 follow-up
•LAT pulsars will be a big amount, then an automatic system for pre-analysis should be
very useful;
•Python could be a good candidate, pyPulsar is under development: available in CVS
(/users/razzano/pyPulsar);
•The LAT sensitivity will permit study of different sub-population of pulsars: this was the
case of DC2;
•At least 4 MSP can be detected during DC2 in the LAT source catalog;
•At E < 10-7 ph/cm2/s the logN-logS shows a change in slope: it will be the same with real
data?
•By scanning the D4 32 high-confidence pulsars have been found: why discrepancies with
other analyses? Most probably differences in putting threshold and in cuts;
•Detection is very sensitive to cuts and threshold: study of optimal cuts is strongly needed;
•Explore other test statistics, in particular the H-test: try different strategies for detecting
more pulsars;
Special thanks to Dave, Patrizia, Alice, Isabelle, Gottfried and
the other people of PSR group for the very interesting
discussions and suggestions !