1Andrea Caliandro Search of Optimized Cuts for Pulsar Detection Andrea Caliandro - INFN Bari DC2 CloseOut May Goddard Space Flight Center

2Andrea CaliandroSummary 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/cm 2 s 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 Simulation AntiCenter LateralCenter CenterLateral (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 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/s 2 –These choices are just to simplify the analysis, but do not affect the result (Nel and De Jager,1995) b = 1 E 0 = 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

5Andrea Caliandro Energy cut Energy cut: Energy band from the selected Emin value to the maximum observable Energy (200GeV) (gtselect) Binning: 20 MeV 50 MeV 100 MeV 200 MeV 400 MeV 600 MeV 1 GeV 10 GeV Binning: 0.25°2° 0.50° 3° 0.75°4° 1°6° 1.5°8° ROI ROI: Disk with Radius R centerd on the source (gtselect) Base Analysis Emin (MeV) Radius (Degrees) 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 For N>=100 m=20 For N<100 m=N/5 Probability that H could be greater of the found value P(>H) For H<=23 For 23<H<50 For N < 100 If H>=30 For N < 20 If H>=25 For N < 10: For H>=50 (De Jager et al. 1989)

7Andrea Caliandro Single Pulsar Histograms 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 PHtest Htest PHtest Htest This two histograms are relative to PSRflux=1e -7 ObsTime=4Weeks Region=Lateral2-2

8Andrea Caliandro AntiCenter6_10 AntiCenter2_6 AntiCenter2-2 Lateral6_10 Lateral2_6 Lateral2-2 Center6_10 Center2_6 Center2-2 AntiCenter6_10 AntiCenter2_6 AntiCenter2-2 Lateral6_10 Lateral2_6 Lateral2-2 Center6_10 Center2_6 Center2-2 Htest Cut Distribution for which Htest is Maximum Htest Max Value Distributions AllRegions consider 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_10 AntiCenter2_6 AntiCenter2-2 Lateral6_10 Lateral2_6 Lateral2-2 Center6_10 Center2_6 Center2-2 PHtest AllRegions Cut Distribution for which PHtest is Minimum The plots showed in this slide are relative to PSRflux=1e -7 ObsTime=4Weeks AntiCenter6_10 AntiCenter2_6 AntiCenter2-2 Lateral6_10 Lateral2_6 Lateral2-2 Center6_10 Center2_6 Center2-2 PHtest Min Value Distributions AllRegions consider the Regions all together - all 900 psr

10Andrea Caliandro Htest Max Value Distribution Cut Distribution for which Htest is Maximum Overview on All Regions Htest Distributions Flux 1e-6 ph/cm^2 s Flux 1e-7 ph/cm^2 s Flux 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

11Andrea Caliandro vs Fluence Fluence (ph/cm^2) Htest Emin (MeV) Radius (degree) Overview on All Regions Htest Plots vs Flux Flux (ph/cm^2s) Htest Emin (MeV) Radius (degree) 1Week 2Weeks 4Weeks 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 Regions PHtest Distributions Flux 1e-6 ph/cm^2 s Flux 1e-7 ph/cm^2 s Flux 1e-8 ph/cm^2 s (ObsTime = 4Weeks) This peak is due to the case N 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 Fluence Fluence (ph/cm^2) PHtest (log10) Emin (MeV) Radius (degree) Overview on All Regions PHtest Plots vs Flux Flux (ph/cm^2s) PHtest (log10) Emin (MeV) Radius (degree) 1Week 2Weeks 4Weeks 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/cm 2 ending at 3E-1ph/cm 2 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 Htest HtestPHtest Relative 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 Calculation Diffuse Distribution example for the simulation with ObsTime = 4Weeks and psr Flux = 1e -6

15Andrea Caliandro PHtest with Diffuse line PHtest with Diffuse line AllRegions Diffuse Relative Calculation Diffuse 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 -2 ph/cm 2 the PHtest value of pulsar are all good

16Andrea Caliandro PHtest Center Regions Center2_6 Center2-2 Center6_10 over ~1E -1 ph/cm 2 the PHtest value of pulsar are all good

17Andrea Caliandro PHtest Lateral Regions Lateral2_6 Lateral2-2 Lateral6_10 over ~4E -2 ph/cm 2 the PHtest value of pulsar are all good

18Andrea Caliandro PHtest Anticenter Regions AntiCenter2_6 AntiCenter2-2 AntiCenter6_10 over ~5E -2 ph/cm 2 the PHtest value of pulsar are all good

19Andrea Caliandro First 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 Analysis Center2-2 Center2_6 Center6_10 AntiCenter2-2 AntiCenter2_6 AntiCenter6_10 Lateral2-2 Lateral2_6 Lateral6_10 External 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 The best ROI radius for all pulsars but 3 is less than 2° Below 1ph/cm 2 the Energy cut are broadly distributed from Emin=50MeV to Emin=1GeV Above 1ph/cm 2 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 catalog Distribution of PHtest –There are 23 pulsars below the threshold of log10(PHtest)= 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 Curve Rad=0.75 Emin=200 Log(P)=-6.8 Nevt=2098 Rad=0.5 Emin=50 Log(P)=-6.3 Nevt=100 Rad=8 Emin=200 Log(P)=-4.4 Nevt=30413 Rad=0.25 Emin=20 Log(P)=-7.4 Nevt=158 Rad=0.25 Emin=20 Log(P)=-7.4 Nevt=143 Rad=0.75 Emin=100 Log(P)=-6.6 Nevt=2223 Rad=0.5 Emin=400 Log(P)=-2.6 Nevt=632 Rad=0.25 Emin=20 Log(P)=-2.9 Nevt=269 Maybe a trick of the simulators?

24Andrea CaliandroConclusions 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